HYSTERETIC-MODE PULSE FREQUENCY MODULATED (HM-PFM) RESONANT AC TO DC CONVERTER

• US 20140160805A1
• Filed: 12/19/2012
• Published: 06/12/2014
• Est. Priority Date: 12/07/2012
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Oh, InHwan, Sims, Nicholas A.
• Granted Patent: US 9,391,524 B2
• Time in Patent Office: Days
• US Class Current: 363/21.02
• CPC Class Codes: H02M 1/08 Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 1/4241 using a resonant converter
• CPC Class Codes: H02M 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 7/217 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

The disclosed embodiments provide an AC/DC power converter that converts an AC input voltage into a DC output voltage. This AC/DC power converter includes an input rectifier stage which rectifies an AC input voltage into a first rectified voltage. The AC/DC power converter also includes a switching resonant stage which is directly coupled to the output of the input rectifier stage. The switching resonant stage converts the rectified voltage into a first high frequency AC voltage of a first amplitude. This AC/DC power converter additionally includes a transformer which is coupled to the output of the switching resonant stage and is configured to down-convert the first high frequency AC voltage into a second high frequency AC voltage of a second amplitude. Furthermore, the AC/DC power converter includes an output rectifier stage which is coupled to the output of the transformer, wherein the output rectifier stage rectifies the second high frequency AC voltage into a DC output voltage.

Claims

1. An AC/DC power converter for converting an AC input voltage into a DC output voltage, comprising:

an input rectifier stage which rectifies an AC input voltage into a first rectified voltage;

a switching resonant stage directly coupled to the output of the input rectifier stage, wherein the switching resonant stage converts the rectified voltage into a first high frequency AC voltage of a first amplitude;

a transformer coupled to the output of the switching resonant stage and configured to down-convert the first high frequency AC voltage into a second high frequency AC voltage of a second amplitude; and

an output rectifier stage coupled to the output of the transformer, wherein the output rectifier stage rectifies the second high frequency AC voltage into a DC output voltage.

2. The AC/DC power converter of claim 1, further comprising a controller coupled between the primary winding of the transformer and the input of the switching resonant stage.

3. The AC/DC power converter of claim 2, wherein the controller receives a primary voltage associated with the primary winding of the transformer as a feedback input signal and generates one or more control signals which drive the switching resonant stage.

4. The AC/DC power converter of claim 3, wherein the primary voltage is the first high frequency AC voltage.

5. The AC/DC power converter of claim 3, further comprising a rectifier circuit configured to convert the primary voltage into a rectified primary voltage.

6. The AC/DC power converter of claim 5, wherein the controller further comprises a first comparator of a first reference voltage and a second comparator of a second reference voltage, wherein the first reference voltage and the second reference voltage define a range of variation for the rectified primary voltage.

7. The AC/DC power converter of claim 6, wherein the controller further comprises a logic module coupled to the outputs of the first comparator and the second comparator:

wherein if the rectified primary voltage is greater than the first reference voltage, the logic module selects a first driving frequency to generate the one or more control signals; and

wherein if the rectified primary voltage is less than the second reference voltage, the logic module selects a second driving frequency to generate the one or more control signals.

8. The AC/DC power converter of claim 7, wherein the first driving frequency is associated with a first gain of the switching resonant stage, wherein the second driving frequency is associated with a second gain of the switching resonant stage;

and wherein the first gain is less than the second gain.

9. The AC/DC power converter of claim 7, wherein the first driving frequency is greater than the second driving frequency.

10. The AC/DC power converter of claim 3, wherein the controller receives the first rectified voltage as a feed-forward input signal.

11. The AC/DC power converter of claim 10, wherein the controller includes a feed-forward synchronization module which is configured to synchronize the one or more control signals with the first rectified voltage.

12. The AC/DC power converter of claim 1, wherein the switching resonant stage further comprises:

a switching stage which comprises one or more switches; and

a resonant stage which is coupled to the output of the switching stage.

13. The AC/DC power converter of claim 12, wherein the resonant stage further comprises an LLC resonant tank which comprises two inductors and a single capacitor.

14. The AC/DC power converter of claim 13, wherein one or both of the two inductors is integrated with the transformer to form an integrated transformer.

15. The AC/DC power converter of claim 1, wherein the AC/DC power converter does not use a pre-regulator (PFC) stage between the input rectifier stage and the switching resonant stage.

16. A power supply, comprising:

an AC power connector; and

an AC/DC power converter coupled to the AC power connector and configured to convert an AC input voltage to a DC output voltage;

wherein the AC/DC power converter further comprises;

an input rectifier stage which rectifies an AC input voltage into a first rectified voltage;

a switching resonant stage directly coupled to the output of the input rectifier stage, wherein the switching resonant stage converts the rectified voltage into a first high frequency AC voltage of a first amplitude;

a transformer coupled to the output of the switching resonant stage and configured to down-convert the first high frequency AC voltage into a second high frequency AC voltage of a second amplitude; and

an output rectifier stage coupled to the output of the transformer, wherein the output rectifier stage rectifies the second high frequency AC voltage into a DC output voltage.

17. The power supply of claim 16, wherein the AC/DC power converter further comprises a controller coupled between the primary winding of the transformer and the input of the switching resonant stage.

18. The power supply of claim 17, wherein the controller receives a primary voltage associated with the primary winding of the transformer as a feedback input signal and generates one or more control signals which drive the switching resonant stage.

19. The power supply of claim 18, wherein the primary voltage is the first high frequency AC voltage.

20. The power supply of claim 18, wherein the AC/DC power converter further comprises a rectifier circuit configured to convert the primary voltage into a rectified primary voltage.

21. The power supply of claim 20, wherein the controller further comprises a first comparator of a first reference voltage and a second comparator of a second reference voltage, wherein the first reference voltage and the second reference voltage define a range of variation for the rectified primary voltage.

22. The power supply of claim 21, wherein the controller further comprises a logic module coupled to the outputs of the first comparator and the second comparator:

wherein if the rectified primary voltage is greater than the first reference voltage, the logic module selects a first driving frequency to generate the one or more control signals; and

wherein if the rectified primary voltage is less than the second reference voltage, the logic module selects a second driving frequency to generate the one or more control signals.

23. The power supply of claim 22, wherein the first driving frequency is associated with a first gain of the switching resonant stage, wherein the second driving frequency is associated with a second gain of the switching resonant stage;

and wherein the first gain is less than the second gain.

24. The power supply of claim 22, wherein the first driving frequency is greater than the second driving frequency.

25. The power supply of claim 18, wherein the controller receives the first rectified voltage as a feed-forward input signal.

26. The power supply of claim 25, wherein the controller includes a feed-forward synchronization module which is configured to synchronize the one or more control signals with the first rectified voltage.

27. The power supply of claim 16, wherein the switching resonant stage of the AC/DC power converter further comprises:

a switching stage which comprises one or more switches; and

a resonant stage which is coupled to the output of the switching stage.

28. The power supply of claim 27, wherein the resonant stage further comprises an LLC resonant tank which comprises two inductors and a single capacitor.

29. The power supply of claim 28, wherein one or both of the two inductors is integrated with the transformer to form an integrated transformer.

30. The power supply of claim 16, wherein the AC/DC power converter does not use a pre-regulator (PFC) stage between the input rectifier stage and the switching resonant stage.

31. A system that converts an AC input voltage into a DC output voltage, comprising:

an input rectifier stage which rectifies an AC input voltage into a first rectified voltage;

a switching resonant stage directly coupled to the output of the input rectifier stage, wherein the switching resonant stage converts the rectified voltage into a first high frequency AC voltage of a first amplitude;

a transformer coupled to the output of the switching resonant stage and configured to down-convert the first high frequency AC voltage into a second high frequency AC voltage of a second amplitude; and

an output rectifier stage coupled to the output of the transformer, wherein the output rectifier stage rectifies the second high frequency AC voltage into a DC output voltage.