CONTROL CIRCUIT AND SWITCHING POWER SUPPLY

• US 20160241145A1
• Filed: 02/12/2016
• Published: 08/18/2016
• Est. Priority Date: 02/16/2015
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: MATSUURA, Ken, LIN, Min
• Granted Patent: US 9,960,673 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter
• CPC Class Codes: H02M 1/0032 Control circuits allowing low power mode operation, e.g. in standby mode
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1563 without using an external clock H02M3/158 takes precedence
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A control circuit according to an embodiment of the present invention is configured to control a switching element of a switching power supply. The control circuit includes a comparator having a first input terminal configured to receive an output voltage of the switching power supply. The comparator has a second input terminal that is connectable to a positive terminal of a reference voltage source. The comparator has an output. The output brings the reference voltage to a first voltage while the output signal takes a first voltage level. The output brings the reference voltage to a second voltage while the output signal takes a second voltage level. The constant voltage source has a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.

Claims

1. A control circuit configured to control a switching element of a switching power supply, the control circuit comprising:

a comparator having a first input terminal configured to receive an output voltage of the switching power supply, the comparator having a second input terminal that is connectable to a positive terminal of a reference voltage source, the comparator having an output, the output brings the reference voltage to a first voltage while the output signal takes a first voltage level, the output brings the reference voltage to a second voltage while the output signal takes a second voltage level; and

a constant voltage source having a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.

2. The control circuit as claimed in claim 1, further comprising:

a level shift circuit configured to be between the output of the comparator and an input of a controller, the level shift circuit being configured to change the first voltage level or the second voltage level that is transmitted from the output of the comparator, the level shift circuit configured to supply the controller with the first voltage level changed or the second voltage changed,

wherein the controller is configured to control the switching element based on the output from the level shift circuit.

3. The control circuit as claimed in claim 2, wherein the level shift circuit comprises:

a Zener diode configured to be between the output of the comparator and the input of the controller, and

a first resistor configured to be between the input of the controller and a common ground.

4. The control circuit as claimed in claim 1, wherein the constant voltage source comprises a capacitor.

5. The control circuit as claimed in claim 2, wherein the controller is configured to perform switching a plurality of times in a period in which the output of the comparator is at the first voltage level and stop switching in a period in which the output of the comparator is at the second voltage level.

6. The control circuit as claimed in claim 2, wherein the controller is configured to turn the switching element off when a current which flows through the switching power supply becomes at least a predetermined value.

7. The control circuit as claimed in claim 1, wherein the switching power supply comprises a resonant converter.

8. A control circuit configured to control a switching element of a switching power supply having an output terminal connected to a positive terminal of a constant voltage source, the control circuit comprising:

a comparator having a first input terminal that is connectable to a negative terminal of the constant voltage source and the comparator having a second input terminal that is connectable to a reference voltage source, the comparator having an output, the output brings the reference voltage to a first voltage while the output signal takes a first voltage level, the output brings the reference voltage to a second voltage while the output signal takes a second voltage level; and

a controller configured to control the switching element based on the output of the comparator.

9. The control circuit as claimed in claim 8, wherein the constant voltage source comprises

a Zener diode that is connectable between the output terminal of the switching power supply and the first input terminal of the comparator, and

a second resistor that is connectable between the first input terminal of the comparator and the common ground.

10. The control circuit as claimed in claim 8, wherein the constant voltage source comprises a shunt regulator configured to adjust a setting voltage.

11. The control circuit as claimed in claim 8, wherein the controller is configured to perform switching a plurality of times in a period in which the output of the comparator takes a first voltage level and stop switching in a period in which the output of the comparator is at the second voltage level.

12. The control circuit as claimed in claim 8, wherein the controller is configured to turn the switching element off when a current which flows through the switching power supply becomes at least a predetermined value.

13. The control circuit as claimed in claim 8, wherein the switching power supply comprises a resonant converter.

14. A switching power supply comprising:

a control circuit configured to control a switching element of a switching power supply, the control circuit comprising;

a comparator having a first input terminal configured to receive an output voltage of the switching power supply, the comparator having a second input terminal that is connectable to a positive terminal of a reference voltage source, the comparator having an output, the output brings the reference voltage to a first voltage while the output signal takes a first voltage level, the output brings the reference voltage to a second voltage while the output signal takes a second voltage level; and

a constant voltage source having a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.

15. A switching power supply comprising:

a control circuit configured to control a switching element of a switching power supply having an output terminal connected to a positive terminal of a constant voltage source, the control circuit comprising;

a comparator having a first input terminal that is connectable to a negative terminal of the constant voltage source and the comparator having a second input terminal that is connectable to a reference voltage source, the comparator having an output, the output brings the reference voltage to a first voltage while the output signal takes a first voltage level, the output brings the reference voltage to a second voltage while the output signal takes a second voltage level; and

a controller configured to control the switching element based on the output of the comparator.

16. A control circuit configured to control a switching transistor of a switching power supply, the control circuit comprising:

a third resistor and a fourth resistor that are connected to each other to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control the switching transistor based on an output signal of the comparator,

wherein the control circuit is configured to bring the reference voltage to a first voltage while the output signal of the comparator takes a first voltage level, and the control circuit is configured to bring the reference voltage to a second voltage while the output signal of the comparator takes a second voltage level, and

the third resistor is connectable between a positive terminal of an output terminal of the switching power supply and the first input terminal of the comparator;

the control circuit further comprising;

a capacitive element that is connectable to the third resistor in parallel with each other,

wherein, where a resistance value of the third resistor is R1, a resistance value of the fourth resistor is R2, a minimum switching frequency of the switching transistor is Fmin, and a static capacitance of the capacitive element is C1, Equation (1)

17. The control circuit as claimed in claim 16, wherein the controller is configured to switch the switching transistor a plurality of times when the output of the comparator is at the first voltage level.

18. The control circuit as claimed in claim 16, wherein the controller is configured to turn the switching transistor off when a current which flows through the switching power supply becomes a predetermined value.

19. The control circuit as claimed in claim 16, wherein the switching power supply comprises a resonant converter.

20. The control circuit as claimed in claim 16, wherein the control circuit comprises a charging circuit configured to charge the capacitive element when the switching power supply is activated.

21. A switching power supply comprising:

a control circuit configured to control a switching transistor of a switching power supply, the control circuit comprising;

a third resistor and a fourth resistor that are connected to each other to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control the switching transistor based on an output signal of the comparator,

wherein the control circuit is configured to bring the reference voltage to a first voltage while the output signal of the comparator takes a first voltage level, and the control circuit is configured to bring the reference voltage to a second voltage while the output signal of the comparator takes a second voltage level, and

the third resistor is connectable between a positive terminal of an output terminal of the switching power supply and the first input terminal of the comparator;

the control circuit further comprising;

a capacitive element that is connectable to the third resistor in parallel with each other,

wherein, where a resistance value of the third resistor is R1, a resistance value of the fourth resistor is R2, a minimum switching frequency of the switching transistor is Fmin, and a static capacitance of the capacitive element is C1, Equation (1)

22. A control circuit configured to control a switching transistor of a switching power supply, the control circuit comprising:

a third resistor and a fourth resistor that are connected to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control the switching transistor based on an output signal of the comparator,

wherein the control circuit is configured to bring the reference voltage to a first voltage while the output signal of the comparator takes a first voltage level and the control circuit is configured to bring the reference voltage to a second voltage while the output signal of the comparator takes a second voltage level, and

the third resistor is connectable between a positive terminal of an output terminal of the switching power supply and the first input terminal of the comparator;

the control circuit further comprising;

a capacitive element and a switch element that are connected in parallel with the third resistor and are mutually connected in series; and

an OFF period detection circuit configured to detect that the output of the comparator continually takes the second voltage level in a period which is longer than a predetermined period,

wherein the OFF period detection circuit is configured to open the switch element and bring the reference voltage to a third voltage when the OFF period detection circuit detects that the output of the comparator continually takes the second voltage level in the period which is longer than the predetermined period.

23. The control circuit as claimed in claim 22,

wherein the OFF period detection circuit is configured to close the switch element and bring the reference voltage to the first voltage when the OFF period detection circuit detects that the output of the comparator takes the first voltage level.

24. The control circuit as claimed in claim 22,

wherein, the OFF period detection circuit is configured to open the switch element in a period which is shorter than the predetermined period and bring the reference voltage to the third voltage when the OFF period detection circuit detects that the output of the comparator continually takes the second voltage level in the period which is longer than the predetermined period;

and, after the period which is shorter than the predetermined period, to close the switch element, and bring the reference voltage to the first voltage when the output of the comparator is at the first voltage level and to the second voltage when the output of the comparator is at the second voltage level.

25. The control circuit as claimed in claim 22,

wherein the controller is configured to switch the switching transistor a plurality of times when the output of the comparator is at the first voltage level.

26. The control circuit as claimed in claim 22,

wherein the controller is configured to turn the switching transistor off when a current which flows through the switching power supply becomes the predetermined value.

27. The control circuit as claimed in claim 22,

wherein the switching power supply comprises a resonant converter.

28. The control circuit as claimed in claim 22, further comprising:

a charging circuit configured to charge the capacitive element when the switching power supply is activated.

29. A switching power supply comprising:

a control circuit configured to control a switching transistor of a switching power supply, the control circuit comprising;

a third resistor and a fourth resistor that are connected to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control the switching transistor based on an output signal of the comparator, wherein the control circuit is configured to bring the reference voltage to a first voltage while the output signal of the comparator takes a first voltage level and the control circuit is configured to bring the reference voltage to a second voltage while the output signal of the comparator takes a second voltage level, and

the third resistor is connectable between a positive terminal of an output terminal of the switching power supply and the first input terminal of the comparator;

the control circuit further comprising;

a capacitive element and a switch element that are connected in parallel with the third resistor and are mutually connected in series; and

an OFF period detection circuit configured to detect that the output of the comparator continually takes the second voltage level in a period which is longer than a predetermined period,

wherein the OFF period detection circuit is configured to open the switch element and bring the reference voltage to a third voltage when the OFF period detection circuit detects that the output of the comparator continually takes the second voltage level in the period which is longer than the predetermined period.

30. A control circuit of a switching power supply, the control circuit comprising:

a capacitive element;

a switch element that is connectable to the capacitive element; and

an output voltage detection circuit configured to compare an output voltage of the switching power supply with a predetermined value, close the switch element to charge the capacitive element when the output voltage is lower than the predetermined value, and open the switch element when the output voltage is higher than the predetermined value.

32. The control circuit as claimed in claim 30, wherein the capacitive element is connectable to an output terminal of the switching power supply.

34. The control circuit as claimed in claim 30, further comprising:

a third resistor and a fourth resistor that are connected to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control a switching transistor based on an output signal of the comparator,

wherein the reference voltage input to the second terminal of the comparator becomes a first voltage when an output of the comparator takes a first voltage level and a second voltage when the output of the comparator takes a second voltage level, and the third resistor is connectable between a positive terminal of the output terminal of the switching power supply and the first input terminal of the comparator, and the control circuit has the capacitive element connectable in parallel with the third resistor.

36. The control circuit as claimed in claim 30, further comprising:

a third resistor and a fourth resistor that are configured to voltage-divide an output voltage of the switching power supply;

an error amplifier having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the error amplifier having a second input terminal configured to receive a reference voltage; and

a controller configured to control a switching transistor based on an output voltage of the error amplifier,

wherein the capacitive element is insertable between an output terminal of the error amplifier and the first input terminal of the error amplifier.

38. The control circuit as claimed in claim 30,

wherein the output voltage detection circuit comprises a fifth resistor and a sixth resistor configured to voltage-divide an output voltage of the switching power supply;

a second comparator; and

a reference voltage source configured to supply the second comparator with the reference voltage.

40. The control circuit as claimed in claim 38,

wherein the output voltage detection circuit comprises:

a flip-flop circuit and

a signal source that is connectable to the flip-flop circuit.

31. A control circuit of a switching power supply, the control circuit comprising:

a capacitive element;

a switch element that is connectable to the capacitive element; and

an output voltage detection circuit configured to close the switch element to charge the capacitive element when the switching power supply is activated, and compare an output voltage of the switching power supply with a predetermined value to open the switch element when the output voltage is higher than the predetermined value.

33. The control circuit as claimed in claim 31, wherein the capacitive element is connectable to an output terminal of the switching power supply.

35. The control circuit as claimed in claim 31, further comprising:

a third resistor and a fourth resistor that are connected to voltage-divide an output voltage of the switching power supply;

a comparator having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the comparator having a second input terminal configured to receive a reference voltage; and

a controller configured to control a switching transistor based on an output signal of the comparator,

wherein the reference voltage received by the second terminal of the comparator becomes a first voltage when an output of the comparator takes a first voltage level and to a second voltage when the output of the comparator takes a second voltage level, and the third resistor is connectable between a positive terminal of the output terminal of the switching power supply and the first input terminal of the comparator, and the control circuit has the capacitive element connected in parallel with the third resistor.

37. The control circuit as claimed in claim 31, further comprising:

a third resistor and a fourth resistor that are configured to voltage-divide an output voltage of the switching power supply;

an error amplifier having a first input terminal configured to receive the output voltage voltage-divided by the third resistor and the fourth resistor, the error amplifier having a second input terminal configured to receive a reference voltage; and

a controller configured to control a switching transistor based on an output voltage of the error amplifier,

wherein the capacitive element is insertable between an output terminal of the error amplifier and the first input terminal of the error amplifier.

39. The control circuit as claimed in claim 31,

wherein the output voltage detection circuit comprises a fifth resistor and a sixth resistor configured to voltage-divide an output voltage of the switching power supply;

a second comparator; and

a reference voltage source configured to supply the second comparator with the reference voltage.

41. The control circuit as claimed in claim 39,

wherein the output voltage detection circuit comprises:

a flip-flop circuit and

a signal source that is connectable to the flip-flop circuit.

42. A switching power supply comprising:

a control circuit of a switching power supply,

the control circuit comprising;

a capacitive element;

a switch element that is connectable to the capacitive element; and

an output voltage detection circuit configured to compare an output voltage of the switching power supply with a predetermined value, close the switch element to charge the capacitive element when the output voltage is lower than the predetermined value, and open the switch element when the output voltage is higher than the predetermined value.

43. A switching power supply comprising:

a control circuit of a switching power supply,

the control circuit comprising;

a capacitive element;

a switch element that is connectable to the capacitive element; and

an output voltage detection circuit configured to close the switch element to charge the capacitive element when the switching power supply is activated, and compare an output voltage of the switching power supply with a predetermined value to open the switch element when the output voltage is higher than the predetermined value.