DC-DC CONVERTER CIRCUIT

• US 20110285370A1
• Filed: 05/09/2011
• Published: 11/24/2011
• Est. Priority Date: 05/07/2010
• Status: Active Grant

• Current Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Original Assignee: STMicroelectronics SRL (STMicroelectronics NV)
• Inventors: GRITTI, Giovanni
• Granted Patent: US 8,570,011 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• 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 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/1588 comprising at least one synchronous rectifier element H02M3/1582, H02M3/1584 take precedence
• 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

An embodiment of a voltage conversion unit is proposed. The voltage conversion unit comprises a switching DC-DC converter including an input terminal for receiving an input voltage from a source, a control terminal adapted to receive a pulse width modulated driving signal oscillating at a first frequency, and an output terminal for providing to a load an output voltage generated from the input voltage according to the driving signal. The voltage conversion unit further comprises a switching control unit configured to receive the output voltage and a reference voltage and to set a duty cycle of the driving signal based on a comparison between the output voltage and the reference voltage. The switching DC-DC converter and the switching control unit form a feedback loop having a loop gain defining a corresponding operating bandwidth of the voltage conversion unit. The load is configured to drain a current pulse train having a second frequency; the values of the first and second frequencies are such to cause the occurrence of beat oscillations at frequencies comprised within the operating bandwidth. The switching control unit comprises means for reducing the beat oscillations by increasing the loop gain at least for a frequency interval comprised within the operating bandwidth.

Claims

1. A voltage conversion unit comprising:

a switching DC-DC converter including an input terminal for receiving an input voltage from a source, a control terminal adapted to receive a pulse width modulated driving signal oscillating at a first frequency, and an output terminal for providing to a load an output voltage generated from the input voltage according to the driving signal, and

a switching control unit configured to receive the output voltage and a reference voltage and to set a duty cycle of the driving signal based on a comparison between the output voltage and the reference voltage, the switching DC-DC converter and the switching control unit forming a feedback loop having a loop gain defining a corresponding operating bandwidth of the voltage conversion unit, wherein the load is configured to drain a current pulse train having a second frequency, the values of the first and second frequencies being such to cause the occurrence of beat oscillations at frequencies comprised within the operating bandwidth; and

wherein the switching control unit comprises means for reducing an amplitude of the beat oscillations by increasing the loop gain at least for a frequency interval comprised within the operating bandwidth.

2. The voltage conversion unit of claim 1, wherein the switching control unit comprises:

a feedback unit adapted to receive the output voltage and the reference voltage and to generate a comparison voltage based on the difference between the output voltage and the reference voltage, and

a driving signal generator unit adapted to receive the comparison signal and to generate the driving signal based on the comparison voltage.

3. The voltage conversion unit of claim 2, wherein the feedback unit comprises an operational amplifier having a non-inverting input terminal for receiving the reference voltage, an inverting input terminal coupled to the output terminal of the switching DC-DC converter and an output terminal coupled to the driving signal generator for providing the comparison voltage.

4. The voltage conversion unit of claim 3, wherein the feedback unit further comprises a first passive network and a second passive network, wherein:

the first passive network has a first terminal coupled to the output of the switching DC-DC converter for receiving the output voltage and a second terminal coupled to the inverting input terminal of the operational amplifier, and

the second passive network has a first terminal coupled to the inverting input terminal of the operational amplifier and a second terminal coupled to the output terminal of the operational amplifier.

5. The voltage conversion unit of claim 4, wherein the means for reducing the beat oscillations includes means for varying the impedance of at least one among the first and the second passive networks.

6. The voltage conversion unit of claim 5, wherein the means for reducing the beat oscillations comprises means for increasing the loop gain by increasing the impedance of the second passive network and/or decreasing the impedance of the first passive network.

7. The voltage conversion unit of claim 4, wherein the second passive network comprises

a first capacitor having a first terminal coupled to the non-inverting input terminal of the operational amplifier and a second terminal coupled to the output terminal of the operational amplifier;

a second capacitor having a first terminal coupled to the second terminal of the first capacitor and a second terminal coupled to a first terminal of a resistor, the resistor having a second terminal coupled to the inverting input terminal of the operational amplifier, wherein the means for reducing the beat oscillations includes an additional capacitor having a first terminal coupled to the first terminal of the resistor and a second terminal coupled to the inverting input terminal of the operational amplifier.

8. The voltage conversion unit of claim 1, wherein the load is a central processing unit or a graphic processor unit.

9. The voltage conversion unit of claim 1, wherein both the first and second frequencies are of the order of magnitude of the hundreds of kHz.

10. A power supply, comprising:

an output node;

a circuit node operable to receive an interference signal having a first frequency;

a converter circuit operable to generate a regulated output signal at the output node and to switch at a second frequency; and

a feedback circuit coupled to the output node and to the converter circuit and operable to generate a compensation signal having a third frequency that is approximately equal to a difference between the first and second frequencies.

11. The power supply of claim 10 wherein the interference signal comprises a current signal.

12. The power supply of claim 10 wherein the interference signal comprises a load signal.

13. The power supply of claim 10 wherein the regulated output signal comprises a regulated output voltage.

14. The power supply of claim 10, further comprising:

an input node;

wherein the converter circuit comprises an inductor having a first node and having a second node coupled to the output node; and

wherein the converter circuit is operable to couple the first node of the inductor to and to uncouple the first node of the inductor from the input node at the second frequency.

15. The power supply of claim 10, further comprising:

first and second input nodes;

wherein the converter circuit comprises an inductor having a first node and having a second node coupled to the output node; and

wherein the converter circuit is operable to alternately couple the first node of the inductor to the first and second input nodes at the second frequency.

16. The power supply of claim 10 wherein the feedback circuit comprises:

an operational amplifier having an input node and an output node;

a first capacitor coupled between the input and output nodes;

a resistor and second capacitor serially coupled between the input and output nodes; and

a third capacitor coupled in electrical parallel with the resistor.

17. The power supply of claim 10 wherein the first frequency is in a range of approximately 0-2 MHz.

18. The power supply of claim 10 wherein the second frequency is in a range of approximately 0-2 MHz.

19. The power supply of claim 10 wherein the third frequency is in a range of approximately 0-100 KHz.

20. The power supply of claim 10 wherein the converter circuit and feedback circuit form a loop having a unity-gain frequency that is approximately one tenth of the second frequency.

21. The power supply of claim 10 wherein:

the converter circuit and feedback circuit form a loop having a unity-gain frequency; and

the loop has a zero at a frequency that is less than the unity-gain frequency.

22. The power supply of claim 10 wherein:

the converter circuit and feedback circuit form a loop having a unity-gain frequency; and

the loop has two zeros at a frequency that is less than the unity-gain frequency.

23. The power supply of claim 10 wherein the converter circuit is operable to switch at a duty cycle that is related to the compensation signal.

24. The power supply of claim 10 wherein the output node and the circuit node comprise a same node.

25. The power supply of claim 10 wherein:

the converter circuit and feedback circuit form a loop having a unity-gain frequency; and

the loop has two poles at a frequency that is less than the unity-gain frequency.

26. The power supply of claim 10 wherein the converter circuit comprises a single phase.

27. The power supply of claim 10 wherein the converter circuit comprises multiple phases.

28. A system, comprising:

a power supply, including;

an output node;

a circuit node operable to receive an interference signal having a first frequency;

a converter circuit operable to generate a regulated output signal at the output node and to switch at a second frequency; and

a feedback circuit coupled to the output node and to the converter circuit and operable to generate a compensation signal having a third frequency that is approximately equal to a difference between the first and second frequencies; and

a load coupled to the output node.

29. The system of claim 28 wherein:

the output node and the circuit node comprise the same node; and

the load is operable to generate the interference signal at the output node.

30. The system of claim 28 wherein the load is operable to generate the interference signal by periodically changing a current that the load draws from the power supply.

31. The system of claim 28 wherein the load is operable to generate the interference signal by periodically changing a magnitude of a current that the load draws from the power supply.

32. The system of claim 28 wherein the load comprises an integrated circuit.

33. The system of claim 28 wherein the load comprises a processor.

34. The system of claim 28 wherein a portion of the power supply and the load are disposed on a same integrated-circuit die.

35. The system of claim 28 wherein a portion of the power supply and the load are disposed on different integrated-circuit dies.

36. A method, comprising:

generating a regulated output signal at an output node by coupling a first input signal to the output node at a first frequency and at a duty cycle;

receiving an interference signal having a second frequency; and

compensating the regulated output signal at a third frequency that is approximately equal to a difference between the first and second frequencies.

37. The method of claim 36 wherein the regulated output signal comprises a regulated output voltage.

38. The method of claim 36 wherein generating the regulated output signal comprises coupling the input signal to the output node via an inductor.

39. The method of claim 36 wherein generating the regulated output signal comprises alternately coupling the output node to the first input signal and to a second input signal.

40. The method of claim 36 wherein generating the regulated output signal comprises alternately coupling the output node to the first input signal and to ground.

41. The method of claim 36 wherein receiving the interference signal comprises receiving the interference signal at the output node.

42. The method of claim 36 wherein the interference signal comprises an interference current.

43. The method of claim 36, further comprising generating the interference signal with a load that is coupled to the output node.

44. The method of claim 36 wherein compensating the regulated output signal comprises varying the duty cycle at the third frequency.