Hysteretic-mode pulse frequency modulated (HM-PFM) resonant AC to DC converter

• US 9,391,524 B2
• Filed: 12/19/2012
• Issued: 07/12/2016
• Est. Priority Date: 12/07/2012
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Oh, InHwan, Sims, Nicholas A.
• Primary Examiner(s): Zhang, Jue
• Application Number:
  US13/720,811
• Publication Number:
  US 20140160805A1
• Time in Patent Office: 1,301 Days
• Field of Search: 363/21.02, 363/21.03
• US Class Current: 1/1
• 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 that rectifies an AC input voltage into a first rectified voltage;

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

a transformer coupled to an 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;

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

a controller including a first comparator of a first reference voltage and a second comparator of a second reference voltage;

wherein the controller includes a logic circuit coupled to outputs of the first and the second comparators and to a rectifier circuit, the recifier circuit configured to convert a primary voltage associated with a primary winding of the transformer into a rectified primary voltage;

wherein the controller receives the rectified primary voltage and, in response, generates one or more control signals to drive the switching resonant stage;

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

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

2. The AC/DC power converter of claim 1, wherein the primary voltage is the first high frequency AC voltage.

3. The AC/DC power converter of claim 1, wherein the first reference voltage and the second reference voltage define a range of variation for the rectified primary voltage.

4. The AC/DC power converter of claim 1, 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.

5. The AC/DC power converter of claim 1, wherein the first driving frequency is greater than the second driving frequency.

6. The AC/DC power converter of claim 1, wherein the controller receives the rectified primary voltage as a feed-forward input signal.

7. The AC/DC power converter of claim 6, wherein the controller includes a feed-forward synchronization circuit that is configured to synchronize the one or more control signals with the rectified primary voltage.

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

a switching stage that includes one or more switches; and

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

9. The AC/DC power converter of claim 8, wherein the resonant stage further comprises an LLC resonant tank that includes two inductors and a single capacitor.

10. The AC/DC power converter of claim 9, wherein one or both of the two inductors is integrated with the transformer to form an integrated transformer.

11. 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.

12. 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 the AC input voltage into a first rectified voltage;

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

a transformer coupled to an 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;

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

a controller including a first comparator of a first reference voltage and a second comparator of a second reference voltage;

wherein the controller includes a logic circuit coupled to outputs of the first and the second comparators and to a rectifier circuit, the rectifier circuit configured to convert a primary voltage associated with a primary winding of the transformer into a rectified primary voltage;

wherein the controller receives the rectified primary voltage and, in response, generates one or more control signals to drive the switching resonant stage;

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

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

13. The power supply of claim 12, wherein the primary voltage is the first high frequency AC voltage.

14. The power supply of claim 12, wherein the first reference voltage and the second reference voltage define a range of variation for the rectified primary voltage.

15. The power supply of claim 12, 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.

16. The power supply of claim 12, wherein the first driving frequency is greater than the second driving frequency.

17. The power supply of claim 12, wherein the controller receives the rectified primary voltage as a feed-forward input signal.

18. The power supply of claim 17, wherein the controller includes a feed-forward synchronization circuit that is configured to synchronize the one or more control signals with the rectified primary voltage.

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

a switching stage that includes one or more switches; and

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

20. The power supply of claim 19, wherein the resonant stage further comprises an LLC resonant tank that includes two inductors and a single capacitor.

21. The power supply of claim 20, wherein one or both of the two inductors is integrated with the transformer to form an integrated transformer.

22. The power supply of claim 12, wherein the AC/DC power converter does not use a pre-regulator (PFC) stage between the input rectifier stage and the switching resonant stage.

23. 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 an output of the input rectifier stage, wherein the switching resonant stage converts the first rectified voltage into a first high frequency AC voltage of a first amplitude;

a transformer coupled to an 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;

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

a controller including a first comparator of a first reference voltage and a second comparator of a second reference voltage;

wherein the controller includes a logic circuit coupled to outputs of the first and the second comparators and to a rectifier circuit, the rectifier circuit configured to convert a primary voltage associated with a primary winding of the transformer into a rectified primary voltage;

wherein the controller receives the rectified primary voltage and, in response, generates one or more control signals to drive the switching resonant stage;

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

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