Power efficiency improvement of an audio amplifier by adaptive control of a charge pump

• US 9,329,613 B2
• Filed: 01/03/2013
• Issued: 05/03/2016
• Est. Priority Date: 01/06/2012
• Status: Expired due to Fees

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Ting, Chia-Din
• Primary Examiner(s): Elahee, MD S
• Application Number:
  US13/733,595
• Publication Number:
  US 20130177175A1
• Time in Patent Office: 1,216 Days
• Field of Search: 381/120, 327/536, 330/297
• US Class Current: 1/1
• 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 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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;

a clock generator connected to the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal and sixth signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, respectively;

a detector connected to the first bonding pad, configured to operably detect a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator configured to operably provide 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, configured to operably compare the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

2. The charge pump of claim 1, 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.

3. The charge pump of claim 1, 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.

4. The charge pump of claim 3, 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.

5. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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 switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal and sixth signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, respectively;

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.

6. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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;

a clock generator connected to the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal and sixth signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, respectively; and

a seventh switch connected between the first bonding pad and the ground terminal, controlled by a seventh signal provided by the clock generator;

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.

7. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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;

a clock generator connected to the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal and sixth signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, respectively;

a seventh switch connected between the input terminal and the second bonding pad, controlled by a seventh signal determined by a clock signal and a mode select signal by the clock generator;

a detector connected to the first and second bonding pads, configured to operably detect a first voltage of the first bonding pad during a second mode of the charge pump to generate a second voltage, and detect 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 configured to operably provide 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, configured to operably compare 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.

8. The charge pump of claim 7, 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.

9. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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;

a clock generator connected to the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal and sixth signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch, respectively; and

a seventh switch connected between the input terminal and the second bonding pad, controlled by a seventh signal determined by a clock signal and a mode select signal by the clock generator;

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.

10. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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;

a clock generator connected to the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal, sixth signal and seventh signal according to a clock signal and a mode select signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch, respectively;

a detector connected to the first bonding pad, configured to operably detect a first voltage of the first bonding pad to generate a second voltage related to the first voltage;

a reference voltage generator configured to operably provide 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, configured to operably compare the second voltage with the reference voltage to turn off the first switch when the second voltage becomes greater than the reference voltage.

11. The charge pump of claim 10, wherein during a first operation state of a first mode of the charge pump, the first switch, the second switch and the third switch are turned on and the fourth switch, the fifth switch, the sixth switch and the seventh switch 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.

12. 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 configured to operably receive an input voltage;

a first output terminal connected to a first output capacitor, configured to operably provide a positive voltage;

a second output terminal connected to a second output capacitor, configured to operably provide 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 switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch, configured to operably generate first signal, second signal, third signal, fourth signal, fifth signal, sixth signal and seventh signal according to a clock signal and a mode select signal to control the first switch, the second switch, the third switch, the fourth switch, the fifth switch, the sixth switch and the seventh switch, respectively;

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