POWER EFFICIENCY IMPROVEMENT OF AN AUDIO AMPLIFIER BY ADAPTIVE CONTROL OF A CHARGE PUMP

• US 20130177175A1
• Filed: 01/03/2013
• Published: 07/11/2013
• Est. Priority Date: 01/06/2012
• Status: Active Grant

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: TING, Chia-Din
• Granted Patent: US 9,329,613 B2
• Time in Patent Office: Days
• US Class Current: 381/120
• CPC Class Codes: G05F 3/02 Regulating voltage or current
• CPC Class Codes: H03G 1/0094 using switched capacitors
• CPC Class Codes: H03G 3/20 Automatic control H03G3/005 takes precedence; combined with volume compression or expansion H03G7/00

Abstract

A control circuit and method for an audio amplifier detect a signal for driving a speaker to control the switching frequency and the operation mode of a charge pump in the audio amplifier, to improve power efficiency of the audio amplifier. Preferably, a digital interface is further used to test the magnitude of the output signal of the audio amplifier, to reduce the costs of analog test. The charge pump has fewer switches and thus saves costs and die area of an integrated circuit. The control method needs only two phase control for the charge pump to generate a positive voltage and a negative voltage, and thus simplifies the operation of the circuit.

Claims

1. A control circuit for an audio amplifier including a power stage to generate an output signal according to a signal at an input terminal thereof for driving one or more speakers, the control circuit comprising:

a charge pump connected to the power stage, operative to convert an input voltage into a variable positive voltage and a variable negative voltage for supplying to the power stage to generate the output signal; and

an adaptive frequency and voltage controller connected to the charge pump, operative to detect a level of a signal related to the output signal to generate a clock signal and a mode select signal for the charge pump, thereby determining a switching frequency and an operation mode of the charge pump.

2. The control circuit of claim 1, wherein the adaptive frequency and voltage controller detects a level of the output signal to generate the clock signal and the mode select signal.

3. The control circuit of claim 1, wherein the adaptive frequency and voltage controller detects a level of a signal at an input terminal of the power stage to generate the clock signal and the mode select signal.

4. The control circuit of claim 1, further comprising an amplitude level setting circuit connected to the adaptive frequency and voltage controller, operative to provide a plurality of reference voltages to the adaptive frequency and voltage controller, wherein the plurality of reference voltages are compared with the signal related to the output signal to identify the level of the signal related to the output signal.

5. The control circuit of claim 1, wherein the adaptive frequency and voltage controller comprises a design-for-test circuit operative to test the output signal for identifying whether a magnitude of the output signal is correct.

6. The control circuit of claim 1, wherein the charge pump comprises:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad and the second bonding pad for a second flying capacitor connected therebetween;

an input terminal receiving the input voltage;

a first output terminal connected to a first output capacitor, providing the positive voltage;

a second output terminal connected to a second output capacitor, providing the negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the third bonding pad and the ground terminal;

a fourth switch connected between the first bonding pad and the first output terminal;

a fifth switch connected between the second bonding pad and the first output terminal;

a sixth switch connected between the third bonding pad and the second output terminal; and

a clock generator connected to the adaptive frequency and voltage controller and the first through sixth switches, operative to generate first through sixth signals according to the clock signal and the mode select signal to control the first through sixth switches, respectively.

7. The control circuit of claim 6, wherein the charge pump further comprises:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

8. The control circuit of claim 7, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off; and

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and the sixth switches are turned on.

9. The control circuit of claim 7, wherein the charge pump further comprises a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

10. The control circuit of claim 9, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first through fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

11. The control circuit of claim 6, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off; and

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and sixth switches are turned on.

12. The control circuit of claim 6, wherein the charge pump further comprises a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

13. The control circuit of claim 12, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first through fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

14. The control circuit of claim 6, wherein the charge pump further comprises a seventh switch connected between the input terminal and the second bonding pad, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

15. The control circuit of claim 14, wherein the charge pump further comprises:

a detector connected to the first and second bonding pads, detecting a first voltage of the first bonding pad during a second mode of the charge pump to generate a second voltage, and detecting a third voltage of the second bonding pad during a first mode of the charge pump to generate the second voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the seventh switch during the first mode of the charge pump when the second voltage becomes greater than the reference voltage, and to turn off the first switch during the second mode of the charge pump when the second voltage becomes greater than the reference voltage.

16. The control circuit of claim 15, wherein during a first operation state of the first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of the second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth, seventh switches are turned off and the second, fourth and sixth switches are turned on.

17. The control circuit of claim 14, wherein during a first operation state of a first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth, seventh switches are turned off and the second, fourth and sixth switches are turned on.

18. The control circuit of claim 1, wherein the charge pump comprises:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad connected to a second flying capacitor;

an input terminal receiving the input voltage;

a first output terminal connected to a first output capacitor, providing the positive voltage;

a second output terminal connected to a second output capacitor, providing the negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the first bonding pad and the first output terminal;

a fourth switch connected between the first bonding pad and the ground terminal;

a fifth switch connected between the second bonding pad and the second output terminal;

a sixth switch connected between the second bonding pad and the third bonding pad;

a seventh switch connected between the first bonding pad and the third bonding pad; and

a clock generator connected to the adaptive frequency and voltage controller and the first through seventh switches, operative to generate first through seventh signals according to the clock signal and the mode select signal to control the first through seventh switches, respectively.

19. The control circuit of claim 18, wherein the charge pump further comprises:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

20. The control circuit of claim 19, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

21. The control circuit of claim 18, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

22. A control method for an audio amplifier including a power stage to generate an output signal according to a signal at an input terminal thereof for driving one or more speakers, the control method comprising:

A.) converting an input voltage into a variable positive voltage and a variable negative voltage by a charge pump for supplying to the power stage to generate the output signal; and

B.) detecting a level of a signal related to the output signal for generating a clock signal and a mode select signal to determine a switching frequency and an operation mode of the charge pump.

23. The control method of claim 22, wherein the step B comprises detecting a level of the output signal to generate the clock signal and the mode select signal.

24. The control method of claim 22, wherein the step B comprises detecting a level of the signal at the input terminal of the power stage to generate the clock signal and the mode select signal.

25. The control method of claim 22, wherein the step B comprises providing a plurality of reference voltages to be compared with the signal related to the output signal to identify the level of the signal related to the output signal.

26. The control method of claim 22, further comprising testing the output signal to identify whether a magnitude of the output signal is correct.

27. The control method of claim 22, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

disabling a first flying capacitor;

connecting a first terminal and a second terminal of a second flying capacitor to a first output capacitor and a ground terminal, respectively; and

supplying the input voltage to the first terminal of the second flying capacitor to charge the second flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

disabling the first flying capacitor; and

connecting the first and second terminals of the second flying capacitor to the ground terminal and a second output capacitor, respectively, to make the second flying capacitor charge the second output capacitor, thereby generating the negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting a second terminal of the first flying capacitor to the first terminal of the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

28. The control method of claim 27, wherein the step of disabling the first flying capacitor comprises making a short circuit between the first and second terminals of the first flying capacitor or floating the first terminal of the first flying capacitor.

29. The control method of claim 27, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

30. The control method of claim 29, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

31. The control method of claim 27, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

32. The control method of claim 31, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

33. The control method of claim 22, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a first terminals of a second flying capacitor, respectively;

connecting a second terminal of the second flying capacitor to a ground terminal; and

supplying the input voltage to the first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the second flying capacitor, respectively; and

connecting the second terminal of the second flying capacitor to a second output capacitor to charge the second output capacitor, thereby generating the negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting a second terminal of the first flying capacitor to the first terminal of the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

34. The control method of claim 33, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

35. The control method of claim 34, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

36. The control method of claim 33, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

37. The control method of claim 36, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

38. The control method of claim 22, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a ground terminal, respectively;

disabling a second flying capacitor whose second terminal is grounded; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and a second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating the negative voltage; and

disabling the second flying capacitor;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting the second terminal of the first flying capacitor to the first terminal of the second flying capacitor; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the second flying capacitor;

during a second operation state of the second mode of the charge pump, connecting the first and second terminals of the first flying capacitor to the first output capacitor and the ground terminal, respectively and connecting the first terminal of the second flying capacitor to the first output capacitor, to make the first and second flying capacitors charge the first output capacitor, thereby generating the positive voltage; and

during a third operation state of the second mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating the negative voltage; and

disabling the second flying capacitor.

39. The control method of claim 38, wherein the step of disabling the second flying capacitor comprises floating the first terminal of the second flying capacitor.

40. The control method of claim 38, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

41. The control method of claim 40, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

42. The control method of claim 38, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

43. The control method of claim 42, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

44. A charge pump comprising:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad and the second bonding pad for a second flying capacitor connected therebetween;

an input terminal receiving an input voltage;

a first output terminal connected to a first output capacitor, providing a positive voltage;

a second output terminal connected to a second output capacitor, providing a negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the third bonding pad and the ground terminal;

a fourth switch connected between the first bonding pad and the first output terminal;

a fifth switch connected between the second bonding pad and the first output terminal;

a sixth switch connected between the third bonding pad and the second output terminal; and

a clock generator connected to the first through sixth switches, operative to generate first through sixth signals to control the first through sixth switches, respectively.

45. The charge pump of claim 44, further comprising:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

46. The charge pump of claim 45, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off;

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and sixth switches are turned on.

47. The charge pump of claim 45, further comprising a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal provided by the clock generator.

48. The charge pump of claim 47, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, fourth and fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

49. The charge pump of claim 44, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off;

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and sixth switches are turned on.

50. The charge pump of claim 44, further comprising a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal provided by the clock generator.

51. The charge pump of claim 50, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, fourth and fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

52. The charge pump of claim 44, wherein the charge pump further comprises a seventh switch connected between the input terminal and the second bonding pad, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

53. The charge pump of claim 52, wherein the charge pump further comprises:

a detector connected to the first and second bonding pads, detecting a first voltage of the first bonding pad during a second mode of the charge pump to generate a second voltage, and detecting a third voltage of the second bonding pad during a first mode of the charge pump to generate the second voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the seventh switch during the first mode of the charge pump when the second voltage becomes greater than the reference voltage, and to turn off the first switch during the second mode of the charge pump when the second voltage becomes greater than the reference voltage.

54. The charge pump of claim 53, wherein during a first operation state of the first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of the second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

55. The charge pump of claim 52, wherein during a first operation state of a first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

72. The control method of claim 54, wherein the step of disabling the second flying capacitor comprises floating the first terminal of the second flying capacitor.

73. The control method of claim 54, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

74. The control method of claim 73, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

75. The control method of claim 54, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

76. The control method of claim 75, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

56. A charge pump comprising:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad connected to a second flying capacitor;

an input terminal receiving an input voltage a first output terminal connected to a first output capacitor, providing a positive voltage;

a second output terminal connected to a second output capacitor, providing a negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the first bonding pad and the first output terminal;

a fourth switch connected between the first bonding pad and the ground terminal;

a fifth switch connected between the second bonding pad and the second output terminal;

a sixth switch connected between the second bonding pad and the third bonding pad;

a seventh switch connected between the first bonding pad and the third bonding pad; and

a clock generator connected to the first through seventh switches, operative to generate first through seventh signals according to the clock signal and the mode select signal to control the first through seventh switches, respectively.

57. The charge pump of claim 56, further comprising:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

58. The charge pump of claim 57, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

59. The charge pump of claim 56, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

60. A control method for a charge pump, comprising:

during a first operation state of a first mode of the charge pump, performing steps of;

disabling a first flying capacitor;

connecting a first terminal and a second terminal of a second flying capacitor to a first output capacitor and a ground terminal, respectively; and

supplying an input voltage to the first terminal of the second flying capacitor to charge the second flying capacitor and the first output capacitor, thereby generating a positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

disabling the first flying capacitor; and

connecting the first and second terminals of the second flying capacitor to the ground terminal and a second output capacitor, respectively, to make the second flying capacitor charge the second output capacitor, thereby generating a negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting the second terminal of the first flying capacitor to the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

61. The control method of claim 60, wherein the step of disabling the first flying capacitor comprises making a short circuit between the first and second terminals of the first flying capacitor or floating the first terminal of the first flying capacitor.

62. The control method of claim 60, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

63. The control method of claim 62, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

64. The control method of claim 60, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

65. The control method of claim 64, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

66. A control method for a charge pump, comprising:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a first terminal of a second flying capacitor, respectively;

connecting a second terminal of the second flying capacitor to a ground terminal; and

supplying an input voltage to the first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating a positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the first terminal of the second flying capacitor, respectively; and

connecting the second terminal of the second flying capacitor to a second output capacitor to charge the second output capacitor, thereby generating a negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting a second terminal of the first flying capacitor to the first terminal of the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

67. The control method of claim 66, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

68. The control method of claim 67, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

69. The control method of claim 66, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

70. The control method of claim 69, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

71. A control method for a charge pump, comprising steps of:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a ground terminal, respectively;

disabling the second flying capacitor whose second terminal is grounded; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the first output capacitor, thereby generating a positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and a second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating a negative voltage; and

disabling the second flying capacitor;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting the second terminal of the first flying capacitor to a first terminal of the second flying capacitor; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the second flying capacitor;

during a second operation state of the second mode of the charge pump, connecting the first and second terminals of the first flying capacitor to the first output capacitor and the ground terminal, respectively and connecting the first terminal of the second flying capacitor to the first output capacitor, to make the first flying capacitor and the second flying capacitor charge the first output capacitor, thereby generating the positive voltage; and

during a third operation state of the second mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating the negative voltage; and

disabling the second flying capacitor.

77. A control circuit for an audio amplifier including a power stage to generate an output signal according to a signal at an input terminal thereof for driving one or more speakers, and a gain setting circuit to provide a setting signal to control a gain of the power stage, the control circuit comprising:

a charge pump connected to the power stage, operative to convert an input voltage into a variable positive voltage and a variable negative voltage for supplying to the power stage to generate the output signal;

an adaptive voltage controller connected to the charge pump, operative to detect a level of a signal related to the output signal to generate a mode select signal for the charge pump, thereby determining an operation mode of the charge pump; and

a switching frequency controller connected to the charge pump, operative to generate a clock signal according to the setting signal for the charge pump, thereby determining a switching frequency of the charge pump.

78. The control circuit of claim 77, wherein the adaptive voltage controller detects a level of the output signal to generate the mode select signal.

79. The control circuit of claim 77, wherein the adaptive voltage controller detects a level of a signal at an input terminal of the power stage to generate the mode select signal.

80. The control circuit of claim 77, further comprising an amplitude level setting circuit connected to the adaptive voltage controller, operative to provide a plurality of reference voltages to the adaptive voltage controller, wherein the plurality of reference voltages are compared with the signal related to the output signal to identify the level of the signal related to the output signal.

81. The control circuit of claim 77, wherein the adaptive voltage controller comprises a design-for-test circuit operative to test the output signal for identifying whether a magnitude of the output signal is correct.

82. The control circuit of claim 77, wherein the charge pump comprises:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad and the second bonding pad for a second flying capacitor connected therebetween;

an input terminal receiving the input voltage;

a first output terminal connected to a first output capacitor, providing the positive voltage;

a second output terminal connected to a second output capacitor, providing the negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the third bonding pad and the ground terminal;

a fourth switch connected between the first bonding pad and the first output terminal;

a fifth switch connected between the second bonding pad and the first output terminal;

a sixth switch connected between the third bonding pad and the second output terminal; and

a clock generator connected to the adaptive voltage controller, the switching frequency controller and the first through sixth switches, operative to generate first through sixth signals according to the clock signal and the mode select signal to control the first through sixth switches, respectively.

83. The control circuit of claim 82, wherein the charge pump further comprises:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

84. The control circuit of claim 83, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off; and

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and sixth switches are turned on.

85. The control circuit of claim 83, wherein the charge pump further comprises a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

86. The control circuit of claim 85, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first through fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

87. The control circuit of claim 82, wherein during a first operation state of a first mode of the charge pump, the first, third, fourth and fifth switches are turned on and the second and sixth switches are turned off;

during a second operation state of the first mode of the charge pump, the first, third, fourth and fifth switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth and sixth switches are turn off; and

during a second operation state of the second mode of the charge pump, the first, third and fifth switches are turned off and the second, fourth and sixth switches are turned on.

88. The control circuit of claim 82, wherein the charge pump further comprises a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

89. The control circuit of claim 88, wherein during a first operation state of a first mode of the charge pump, the first, third and fourth switches are turned on and the second, fifth, sixth and seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first through fifth switches are turned off and the sixth and seventh switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth and seventh switches are turned off and the second, fourth and sixth switches are turn on.

90. The control circuit of claim 82, wherein the charge pump further comprises a seventh switch connected between the input terminal and the second bonding pad, controlled by a seventh signal determined by the clock signal and the mode select signal by the clock generator.

91. The control circuit of claim 90, wherein the charge pump further comprises:

a detector connected to the first and second bonding pads, detecting a first voltage of the first bonding pad during a second mode of the charge pump to generate a second voltage, and detecting a third voltage of the second bonding pad during a first mode of the charge pump to generate the second voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the seventh switch during the first mode of the charge pump when the second voltage becomes greater than the reference voltage, and to turn off the first switch during the second mode of the charge pump when the second voltage becomes greater than the reference voltage.

93. The control circuit of claim 90, wherein during a first operation state of the first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of the second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth, seventh switches are turned off and the second, fourth and sixth switches are turned on.

92. The control circuit of claim 91, wherein during a first operation state of a first mode of the charge pump, the first, second, fourth and sixth switches are turned off and the third, fifth and seventh switches are turned on;

during a second operation state of the first mode of the charge pump, the first, third, fourth, fifth and seventh switches are turned off and the second and sixth switches are turned on;

during a first operation state of a second mode of the charge pump, the first, third and fifth switches are turned on and the second, fourth, sixth and seventh switches are turned off; and

during a second operation state of the second mode of the charge pump, the first, third, fifth, seventh switches are turned off and the second, fourth and sixth switches are turned on.

94. The control circuit of claim 77, wherein the charge pump comprises:

a first bonding pad and a second bonding pad for a first flying capacitor connected therebetween;

a third bonding pad connected to a second flying capacitor;

an input terminal receiving the input voltage a first output terminal connected to a first output capacitor, providing the positive voltage;

a second output terminal connected to a second output capacitor, providing the negative voltage;

a first switch connected between the input terminal and the first bonding pad;

a second switch connected between the second bonding pad and a ground terminal;

a third switch connected between the first bonding pad and the first output terminal;

a fourth switch connected between the first bonding pad and the ground terminal;

a fifth switch connected between the second bonding pad and the second output terminal;

a sixth switch connected between the second bonding pad and the third bonding pad;

a seventh switch connected between the first bonding pad and the third bonding pad; and

a clock generator connected to the adaptive voltage controller, the switching frequency controller and the first through seventh switches, operative to generate first through seventh signals according to the clock signal and the mode select signal to control the first through seventh switches, respectively.

95. The control circuit of claim 94, wherein the charge pump further comprises:

a detector connected to the first bonding pad, detecting a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator providing a variable reference voltage for controlling the positive voltage or the negative voltage; and

a comparator connected to the detector and the reference voltage generator, comparing the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

96. The control circuit of claim 95, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first through third switches, and the sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

97. The control circuit of claim 94, wherein during a first operation state of a first mode of the charge pump, the first through third switches are turned on and the fourth through seventh switches are turned off;

during a second operation state of the first mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on;

during a first operation state of a second mode of the charge pump, the first and sixth switches are turned on and the second, third, fourth, fifth and seventh switches are turned off;

during a second operation state of the second mode of the charge pump, the first, fourth, fifth and sixth switches are turned off and the second, third and seventh switches are turned on; and

during a third operation state of the second mode of the charge pump, the first, second, third, sixth and seventh switches are turned off and the fourth and fifth switches are turned on.

98. A control method for an audio amplifier including a power stage to generate an output signal according to a signal at an input terminal thereof for driving one or more speakers, and a gain setting circuit to provide a setting signal to control a gain of the power stage, the control method comprising:

A.) converting an input voltage into a variable positive voltage and a variable negative voltage by a charge pump for supplying to the power stage to generate the output signal;

B.) detecting a level of a signal related to the output signal for generating a mode select signal to determine an operation mode of the charge pump; and

C.) generating a clock signal according to the setting signal to determine a switching frequency of the charge pump.

99. The control method of claim 98, wherein the step B comprises detecting a level of the output signal to generate the mode select signal.

100. The control method of claim 98, wherein the step B comprises detecting a level of the signal at the input terminal of the power stage to generate the mode select signal.

101. The control method of claim 98, wherein the step B comprises providing a plurality of reference voltages to be compared with the signal related to the output signal to identify the level of the signal related to the output signal.

102. The control method of claim 98, further comprising testing the output signal to identify whether a magnitude of the output signal is correct.

103. The control method of claim 98, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

disabling a first flying capacitor;

connecting a first terminal and a second terminal of a second flying capacitor to a first output capacitor and a ground terminal, respectively; and

supplying the input voltage to the first terminal of the second flying capacitor to charge the second flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

disabling the first flying capacitor; and

connecting the first and second terminals of the second flying capacitor to the ground terminal and a second output capacitor, respectively, to make the second flying capacitor charge the second output capacitor, thereby generating the negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting a second terminal of the first flying capacitor to the first terminal of the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

104. The control method of claim 103, wherein the step of disabling the first flying capacitor comprises making a short circuit between the first and second terminals of the first flying capacitor or floating the first terminal of the first flying capacitor.

105. The control method of claim 103, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

106. The control method of claim 105, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

107. The control method of claim 103, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

108. The control method of claim 107, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

109. The control method of claim 98, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a first terminal of a second flying capacitor, respectively;

connecting a second terminal of the second flying capacitor to a ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the second flying capacitor, respectively; and

connecting the second terminal of the second flying capacitor to a second output capacitor to charge the second output capacitor, thereby generating the negative voltage;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting a second terminal of the first flying capacitor to the first terminal of the second flying capacitor and the first output capacitor;

connecting the second terminal of the second flying capacitor to the ground terminal; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor, the second flying capacitor and the first output capacitor, thereby generating the positive voltage; and

during a second operation state of the second mode of the charge pump, performing steps of;

connecting the first terminal of the first flying capacitor to the first output capacitor;

connecting the second terminal of the first flying capacitor and the first terminal of the second flying capacitor to the ground terminal; and

connecting the second terminal of the second flying capacitor to the second output capacitor to charge the second output capacitor, thereby generating the negative voltage.

110. The control method of claim 109, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

111. The control method of claim 110, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

112. The control method of claim 110, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

113. The control method of claim 112, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

114. The control method of claim 98, wherein the step A comprises:

during a first operation state of a first mode of the charge pump, performing steps of;

connecting a first terminal and a second terminal of a first flying capacitor to a first output capacitor and a ground terminal, respectively;

disabling the second flying capacitor whose second terminal is grounded; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the first output capacitor, thereby generating the positive voltage;

during a second operation state of the first mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and a second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating the negative voltage; and

disabling the second flying capacitor;

during a first operation state of a second mode of the charge pump, performing steps of;

connecting the second terminal of the first flying capacitor to the first terminal of the second flying capacitor; and

supplying the input voltage to a first terminal of the first flying capacitor to charge the first flying capacitor and the second flying capacitor;

during a second operation state of the second mode of the charge pump, connecting the first and second terminals of the first flying capacitor to the first output capacitor and the ground terminal, respectively and connecting the first terminal of the second flying capacitor to the first output capacitor, to make the first and second flying capacitors charge the first output capacitor, thereby generating the positive voltage; and

during a third operation state of the second mode of the charge pump, performing steps of;

connecting the first and second terminals of the first flying capacitor to the ground terminal and the second output capacitor, respectively, to make the first flying capacitor charge the second output capacitor, thereby generating the negative voltage; and

disabling the second flying capacitor.

115. The control method of claim 114, wherein the step of disabling the second flying capacitor comprises floating the first terminal of the second flying capacitor.

116. The control method of claim 114, further comprising, during the first operation state of the first mode of the charge pump, detecting the positive voltage and stopping supplying the input voltage when the positive voltage becomes greater than a target value.

117. The control method of claim 116, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.

118. The control method of claim 114, further comprising, during the first operation state of the second mode of the charge pump, detecting a voltage at the first terminal of the first flying capacitor and stopping supplying the input voltage when the voltage at the first terminal of the first flying capacitor becomes greater than a target value.

119. The control method of claim 118, further comprising adjusting the target value to adjust the positive voltage or the negative voltage.