High power factor isolated buck-type power factor correction converter

• US 20090290384A1
• Filed: 05/21/2008
• Published: 11/26/2009
• Est. Priority Date: 05/21/2008
• Status: Active Grant

• Current Assignee: MyPAQ Holdings Ltd. (Transpacific IP Group Limited)
• Original Assignee: Flextronics America LLC (Flextronics International Limited)
• Inventors: Jungreis, Aaron
• Granted Patent: US 8,102,678 B2
• Time in Patent Office: Days
• US Class Current: 363/17
• CPC Class Codes: H02M 1/4241 using a resonant converter
• 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
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A regulated power factor corrected power supply apparatus is provided. The apparatus includes an input rectifier circuit for receiving an input AC voltage and outputting a full-wave rectified DC voltage. A single-stage isolated buck-type converter is coupled with the input circuit. The converter circuit comprises an isolated buck-type converter circuit including an isolation transformer. An output rectifier and semiconductor tap switch are coupled to a secondary winding of the isolation transformer. The tap switch couples a larger portion of the secondary winding to an output bulk capacitor during the portions of the input sinewave half-cycle, which are low in amplitude. The tap switch enables the single-stage isolation buck-type converter to operate over a much larger portion of the input sinewave, but also allows the converter to operate at high-efficiency over the majority of the input sinewave.

Claims

1. A power converter comprising a single-stage isolated buck-type converter including an isolation transformer, the isolation transformer including a first secondary winding coupled in series with a first rectifier circuit, and a second secondary winding coupled in series with a series combination of a second rectifier circuit and a semiconductor switch, wherein the semiconductor switch is configured to turn on and off based on a parameter of an AC voltage input to the power converter, and to adjust a functional turns ratio of the isolation transformer.

2. The power converter of claim 1 wherein the isolation transformer includes a number of discrete windings coupled in series, and the semiconductor switch is configured to adaptively couple a portion of the number of discrete windings to an output bulk capacitor.

3. The power converter of claim 1 further comprising a third rectifier circuit coupled to an input of the single-stage isolated buck-type converter, wherein the third rectifier is configured to output a full-wave rectified DC voltage in response to the AC voltage input.

4. The power converter of claim 1 further comprising an electromagnetic interference filter coupled to an input of the third rectifier circuit.

5. The power converter of claim 1 wherein the AC voltage input includes the range from 90 VAC to 264 VAC.

6. The power converter of claim 1 wherein the single-stage isolated buck-type converter comprises one of the group consisting of a half-bridge converter, a full-bridge converter, a push-pull converter, and a forward converter.

7. The power converter of claim 1 wherein the single-stage isolated buck-type converter further comprises a resonant tank, and the single-stage isolated buck-type converter is configured to operate as a resonant converter.

8. The power converter of claim 7 wherein the resonant converter is configured as one of the group consisting of a series resonant circuit, a parallel resonant circuit, an LLC resonant circuit, and a series-parallel resonant circuit.

9. The power converter of claim 7 wherein the resonant converter comprises one of the group consisting of a half-bridge resonant converter, a full-bridge resonant converter, a push-pull resonant converter, and a forward resonant converter.

10. The power converter of claim 1 further comprising a second semiconductor switch, a third secondary winding, a fourth secondary winding, a third rectifier circuit, and a fourth rectifier circuit, wherein the third secondary winding is coupled in series with the third rectifier circuit, and the fourth secondary winding is coupled in series with a series combination with the second semiconductor switch and the fourth rectifier circuit, wherein the semiconductor switch, the second semiconductor switch, the first rectifier circuit, the second rectifier circuit, the third rectifier circuit, and the fourth rectifier circuit are configured to operate in a push-pull configuration so as to alternately provide a DC voltage to a first and a second output capacitor.

11. The power converter of claim 1 further comprising a second semiconductor switch coupled in series with a third rectifier circuit, wherein the second secondary winding is coupled in series with the series combination of the second semiconductor switch and the third rectifier circuit, wherein the semiconductor switch, the second semiconductor switch, the first rectifier circuit, the second rectifier circuit, and the third rectifier circuit are configured to output a full-wave rectified DC voltage output.

12. The power converter of claim 1 wherein the first secondary winding is center-tapped and coupled to an output bulk capacitor.

13. The power converter of claim 1 wherein the parameter of the AC voltage input is a line voltage input to the single-stage isolated buck-type converter.

14. A power converter comprising:

a. a first rectifier circuit configured to receive an input AC voltage and to output a full-wave rectified DC voltage;

b. a single-stage isolated buck-type converter configured to receive the full-wave rectified DC voltage as input, wherein the single-stage isolated buck-type converter includes an isolation transformer comprising a first secondary winding and a second secondary winding;

c. a second rectifier circuit coupled to the first secondary winding;

d. a third rectifier circuit coupled to the second secondary winding;

e. a tap switch coupled to an output of the third rectifier circuit, wherein the tap switch is configured to adjust a functional turns ratio of the isolation transformer; and

f. a bulk capacitor coupled to an output of the second rectifier circuit and the third rectifier circuit, wherein a voltage across the bulk capacitor is a DC voltage output of the power converter.

15. The power converter of claim 14 wherein the isolation transformer includes a number of discrete windings coupled in series, and the tap switch is configured to adaptively couple a portion of the number of discrete windings to an output bulk capacitor.

16. The power converter of claim 14 further comprising an electromagnetic interference filter coupled to an input of the first rectifier circuit.

17. The power converter of claim 14 wherein the first rectifier circuit outputs a full-wave rectified DC voltage.

18. The power converter of claim 14 wherein the AC voltage input includes the range from 90 VAC to 264 VAC.

19. The power converter of claim 14 wherein the single-stage isolated buck-type converter comprises one of the group consisting of a half-bridge converter, a full-bridge converter, a push-pull converter, and a forward converter.

20. The power converter of claim 14 wherein the single-stage isolated buck-type converter further comprises a resonant tank, and the single-stage isolated buck-type converter is configured to operate as a resonant converter.

21. The power converter of claim 20 wherein the resonant converter is configured as one of the group consisting of a series resonant circuit, a parallel resonant circuit, an LLC resonant circuit, and a series-parallel resonant circuit.

22. The power converter of claim 20 wherein the resonant converter comprises one of the group consisting of a half-bridge resonant converter, a full-bridge resonant converter, a push-pull resonant converter, and a forward resonant converter.

23. The power converter of claim 14 further comprising a second tap switch, a fourth rectifier circuit, a fifth rectifier circuit, and a second bulk capacitor, wherein the first secondary winding is coupled in series with the fourth rectifier circuit, and the second secondary winding is coupled in series with a series combination of the second tap switch and the fifth rectifier circuit, wherein the tap switch, the second tap switch, the second rectifier circuit, the third rectifier circuit, the fourth rectifier circuit, and the fifth rectifier circuit are configured to operate in a push-pull configuration so as to alternately provide a DC voltage to the bulk capacitor and the second bulk capacitor, wherein a voltage across the bulk capacitor and the second bulk capacitor coupled in series is the DC voltage output of the power converter.

24. The power converter of claim 14 further comprising a second tap switch coupled in series with a fourth rectifier circuit, wherein the secondary winding is coupled in series with a series combination of the second tap switch and the fourth rectifier circuit, wherein the tap switch, the second tap switch, the second rectifier circuit, the third rectifier circuit, and the fourth rectifier circuit are configured to output a full-wave rectified DC voltage output across the bulk capacitor.

25. The power converter of claim 14 wherein the first secondary winding is center-tapped and coupled to the bulk capacitor.

26. The power converter of claim 14 wherein the tap switch is configured to adjust the functional turns ratio according to a line voltage input to the single-stage isolated buck-type converter.

27. A power converter comprising:

a. a first rectifier circuit configured to receive an input AC voltage and to output a full-wave rectified DC voltage;

b. a first single-stage isolated buck-type converter coupled to the first rectifier including a first isolation transformer having a first primary winding and a first secondary winding, wherein the first primary winding is coupled to the first rectifier circuit and is configured to receive the full-wave rectified DC voltage;

c. a second single-stage isolated buck-type converter including a second isolation transformer having a second primary winding and a second secondary winding, wherein the second primary winding is coupled to the first rectifier circuit and is configured to receive the full-wave rectified DC voltage, further wherein when the full-wave rectified DC voltage is above a reference level both the first single-stage isolated buck-type converter and the second single-stage isolated buck-type converter are configured to operate, and when the full-wave rectified DC voltage is below the reference level the first single-stage isolated buck-type converter is configured to operate and the second single-stage isolated buck-type converter is shorted to be inoperable;

d. a second rectifier circuit coupled to the first secondary winding of the first isolation transformer;

e. a third rectifier circuit coupled to the second secondary winding of the second isolation transformer; and

f. a bulk capacitor coupled to an output of the second rectifier circuit and an output of the third rectifier circuit, wherein a voltage across the bulk capacitor is a DC voltage output of the power converter.

28. The power converter of claim 27 further comprising an electromagnetic interference filter coupled to an input of the first rectifier circuit.

29. The power converter of claim 27 wherein the AC voltage includes the range from 90 VAC to 264 VAC.

30. The power converter of claim 27 wherein the first single-stage isolated buck-type converter and the second single-stage isolated buck-type converter each comprise one of the group consisting of a half-bridge converter, a full-bridge converter, a push-pull converter, and a forward converter.

31. The power converter of claim 27 wherein the first single-stage isolated buck-type converter and the second single-stage isolated buck-type converter each further comprise a resonant tank, and the first single-stage isolated buck-type converter and the second single-stage isolated buck-type converter are each configured to operate as a resonant converter.

32. The power converter of claim 31 wherein each resonant converter is configured as one of the group consisting of a series resonant circuit, a parallel resonant circuit, an LLC resonant circuit, and a series-parallel resonant circuit.

33. The power converter of claim 31 wherein each resonant converter comprises one of the group consisting of a half-bridge resonant converter, a full-bridge resonant converter, a push-pull resonant converter, and a forward resonant converter.

34. A method of operating a power converter comprising changing a functional turns ratio of a single-stage isolated buck-type converter isolation transformer in response to a magnitude of an AC input voltage such that when the magnitude of the AC input voltage is less than a reference level, the functional turns ratio is a first ratio, and when the magnitude of the AC input voltage is equal to or greater than the reference level, the functional turns ratio is a second ratio less than the first ratio, and a DC output voltage from the single-stage isolated buck-type converter divided by the functional turns ratio is greater in magnitude than the magnitude of the AC input voltage.

35. The method of claim 34 wherein changing the functional turns ratio comprises opening or closing a tap switch coupled in series with a secondary winding on the isolation transformer.

36. The method of claim 34 wherein changing the functional turns ratio comprises shorting one of two single-stage isolated buck-type converters, wherein the two single-stage isolated buck-type converters are coupled in series and a common bulk capacitor is coupled to an output of each of the two single-stage isolated buck-type converters.

40. The method of claim 34 wherein the magnitude of the AC input voltage at which the functional turns ratio is changed is a function of an RMS value of the AC input voltage.

41. The method of claim 34 wherein the single-stage isolated buck-type converter is a resonant converter and a switching frequency is varied in response to a converter load and to an RMS value of the AC input voltage, and the switching frequency is not varied in response to an instantaneous magnitude of the AC input voltage.