Pulse frequency to voltage conversion

• US 7,755,914 B2
• Filed: 03/27/2008
• Issued: 07/13/2010
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: MyPAQ Holdings Ltd. (Transpacific IP Group Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Roohparvar, Farza Bob, Telefus, Mark
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US12/079,663
• Publication Number:
  US 20080238379A1
• Time in Patent Office: 838 Days
• Field of Search: 363/16, 363/21.02, 363/21.03
• US Class Current: 363/16
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• 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 power supply apparatus and method of regulating is provided. A converter circuit includes a primary switching element and an auxiliary switching element. The auxiliary switching element is for transferring a reflected voltage signal. A transformer includes a primary and a secondary, the primary is coupled with the converter circuit. The primary and secondary each include a single winding. An output rectifier circuit is coupled with the secondary of the transformer. A resonant circuit is included in the converter circuit and is coupled with the primary. The resonant circuit includes one or more resonance capacitors that are configured for providing a transformer resonance. The transformer resonance comprises the reflected voltage signal, the capacitance of the one or more resonance capacitors and a parasitic capacitance of the transformer. The reflected voltage signal is reflected from the secondary to the primary. The resonant circuit converts a pulse train to produce a voltage potential, the voltage potential varying in proportion to an output voltage, the pulse train comprising a duty cycle proportional to a load current. A virtual output voltage feedback loop is provided. The converter circuit is responsive to a virtual output voltage reference signal in regulating an output voltage.

Claims

1. A power supply apparatus comprising:

a converter circuit comprising a primary switching element and an auxiliary switching element, the auxiliary switching element for transferring a reflected voltage signal;

a transformer comprising a primary and a secondary, the primary coupled with the converter circuit, the primary comprising a single winding and the secondary comprising a single winding;

an output rectifier circuit coupled with the secondary of the transformer; and

a resonant circuit included in the converter circuit, the resonant circuit being coupled with the primary, the resonant circuit comprising one or more resonance capacitors, the one or more resonance capacitors configured for providing a transformer resonance, the transformer resonance comprising the reflected voltage signal, the capacitance of the one or more resonance capacitors and a parasitic capacitance of the transformer, the reflected voltage signal received at the resonant circuit via the auxiliary switching element coupled to the primary, the reflected voltage signal being reflected from the secondary to the primary, the resonant circuit converting a pulse train to produce a voltage potential, the voltage potential varying in proportion to an output voltage, the pulse train comprising a duty cycle proportional to a load current.

2. The apparatus of claim 1, further comprising a virtual output voltage feedback loop, the virtual output voltage feedback loop providing an output voltage reference signal to the converter circuit via the voltage feedback circuit, the output voltage reference signal being generated from the reflected voltage signal, the output voltage reference signal being proportional to the reflected voltage signal sampled by the voltage feedback circuit, the converter circuit responsive to the output voltage reference signal in regulating the output voltage.

3. The apparatus of claim 1, further comprising a voltage feedback circuit including a voltage divider coupled with a controller and coupled with the primary for sampling the reflected voltage.

4. The apparatus of claim 1, wherein the primary switching element and the auxiliary switching element each comprise an n-type MOSFET transistor.

5. The apparatus of claim 1, wherein the first and the second resonance capacitors are coupled in parallel with the primary.

6. The apparatus of claim 1, wherein a controller includes a pulse width modulation (PWM) circuit coupled with the primary switching element.

7. The apparatus of claim 6, wherein the PWM circuit regulates a duty cycle of the primary switching element.

8. The apparatus of claim 1, wherein the converter circuit comprises a flyback converter.

9. The apparatus of claim 1, wherein the converter circuit comprises one of a forward converter, push-pull converter, half bridge converter and a full bridge converter.

10. The apparatus of claim 1, wherein the output rectifier circuit comprises one of a diode, a half-wave rectifier, and a full-wave rectifier.

11. The apparatus of claim 1, further comprising an output capacitor coupled with the output rectifier circuit.

12. The apparatus of claim 1, wherein a resonant tank of the resonant circuit includes the one or more resonance capacitors, coupled with one or more diodes, coupled with the auxiliary switching element, coupled with an inductance of the primary.

13. The apparatus of claim 12, wherein the resonant tank produces the voltage potential used to power a controller.

14. The apparatus of claim 1, wherein a charge pump comprising one more capacitors and a diode is used to store and to couple the produced voltage potential to a controller.

15. A method of regulating a power supply apparatus comprising:

generating a reflected voltage signal in a transformer comprising a primary and a secondary, the reflected voltage signal being reflected from the secondary to the primary, the primary being coupled with a converter circuit, the primary comprising a single winding and the secondary comprising a single winding;

transferring the reflected voltage signal from the primary to the converter circuit, the converter circuit comprising a primary switching element and an auxiliary switching element coupled to the primary, the auxiliary switching element for transferring the reflected voltage signal;

generating a transformer resonance with a resonant circuit included in the converter circuit, the resonant circuit being coupled with the primary, the resonant circuit comprising one or more resonance capacitors, the one or more resonance capacitors configured for providing the transformer resonance, the one or more resonance capacitors and an inductance of the transformer forming a resonant tank; and

converting a pulse train of the resonant circuit to produce a voltage potential, the voltage potential varying in proportion to an output voltage, the pulse train comprising a duty cycle proportional to a load current.

16. The method of claim 15, further comprising storing the reflected voltage in the one or more resonance capacitors and transferring the reflected voltage from the one or more resonance capacitors to a power terminal of the resonant circuit via the pulse train.

17. The method of claim 15, wherein the resonant tank increases a conversion rate of the pulse train to voltage potential conversion.

18. The method of claim 15, wherein a controller includes a pulse width modulation (PWM) circuit coupled with the primary switching element.

19. The method of claim 18, wherein the PWM circuit regulates a duty cycle of the primary switching element.

20. The method of claim 15, wherein the reflected voltage is proportional to a factor of a capacitance of a first resonance capacitor divided by a second resonance capacitor.

21. The method of claim 15, wherein the produced voltage potential is proportional to the load current.

22. The method of claim 15, wherein the transformer resonance comprises the reflected voltage signal, the capacitance of the one or more resonance capacitors and a parasitic capacitance of the transformer.

23. The method of claim 15, further comprising a virtual output voltage feedback loop, the virtual output voltage feedback loop providing an output voltage reference signal to the converter circuit via the voltage feedback circuit, the output voltage reference signal being generated from the reflected voltage signal, the output voltage reference signal being proportional to the reflected voltage signal sampled by the voltage feedback circuit, the converter circuit responsive to the output voltage reference signal in regulating the output voltage.

24. The method of claim 15, further comprising controlling a reset timing of the primary using the resonant circuit.

25. The method of claim 15, further comprising a voltage feedback circuit including a voltage divider coupled with a controller and coupled with the primary for sampling the reflected voltage.

26. The method of claim 15, wherein the primary switching element and the auxiliary switching element each comprise an n-type MOSFET transistor.

27. The method of claim 15, wherein the first and the second resonance capacitors are coupled in parallel with the primary.

28. The method of claim 15, wherein the converter circuit comprises a flyback converter.

29. The method of claim 15, wherein the converter circuit comprises one of a forward converter, push-pull converter, half bridge converter and a full bridge converter.

30. The method of claim 15, further comprising an output rectifier circuit coupled with the secondary of the transformer.

31. The method of claim 30, further comprising an output capacitor coupled with the output rectifier circuit.

32. The method of claim 15, wherein the resonant tank of the resonant circuit further includes the auxiliary switching element and one or more diodes coupled with the auxiliary switching element, the one or more diodes also coupled with the one or more resonance capacitors.

33. The method of claim 15, wherein a charge pump comprising one more capacitors and a diode is used to store and to couple the produced voltage potential to a controller.

34. The method of claim 32, wherein the resonant tank produces the voltage potential used to power a controller.

35. The method of claim 32, wherein the produced voltage potential is supplied without using an additional transformer winding in addition to a single primary winding and a single secondary winding.

36. The method of claim 32, wherein the auxiliary switching element is self-oscillating, the self-oscillating being driven by the reflected voltage and an oscillating energy of the resonant tank.

37. The method of claim 32, wherein the auxiliary switching element is driven by a controller.

38. The method of claim 32, wherein the auxiliary switching element is driven by a switch driving circuit that is external to the converter circuit.

39. A power supply apparatus comprising:

an input capacitor coupled across an input node;

a converter circuit comprising a primary switching element and an auxiliary switching element, the auxiliary switching element for transferring a reflected voltage signal, the converter circuit coupled with the input capacitor;

a transformer comprising a primary and a secondary, the primary coupled with the converter circuit, the primary comprising a single winding and the secondary comprising a single winding;

an output rectifier circuit coupled with the secondary of the transformer; and

a resonant circuit included in the converter circuit, the resonant circuit being coupled with the primary, the resonant circuit comprising one or more resonance capacitors, the one or more resonance capacitors configured for providing a transformer resonance, the transformer resonance comprising the reflected voltage signal and the capacitance of the one or more resonance capacitors, the reflected voltage signal received at the resonant circuit via the auxiliary switching element coupled to the primary, the reflected voltage signal being reflected from the secondary to the primary, the resonant circuit converting a pulse train to produce a voltage potential, the voltage potential varying in proportion to an output voltage, the pulse train comprising a duty cycle proportional to a load current.

40. The apparatus of claim 39, further comprising a virtual output voltage feedback loop, the virtual output voltage feedback loop providing an output voltage reference signal to the converter circuit via the voltage feedback circuit, the output voltage reference signal being generated from the reflected voltage signal, the output voltage reference signal being proportional to the reflected voltage signal sampled by the voltage feedback circuit, the converter circuit responsive to the output voltage reference signal in regulating the output voltage.

41. The apparatus of claim 39, further comprising a voltage feedback circuit including a voltage divider coupled with a controller and coupled with the primary for sampling the reflected voltage.