Method and apparatus for extending zero-voltage swiitching range in a DC to DC converter

• US 20090244929A1
• Filed: 03/25/2009
• Published: 10/01/2009
• Est. Priority Date: 03/26/2008
• Status: Active Grant

• Current Assignee: Enphase Energy Incorporated
• Original Assignee: Enphase Energy Incorporated
• Inventors: Fornage, Martin
• Granted Patent: US 8,873,252 B2
• Time in Patent Office: Days
• US Class Current: 363/16
• CPC Class Codes: H02M 3/335 using semiconductor devices only
• 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 7/42 Conversion of dc power input into ac power output without possibility of reversal
• CPC Class Codes: H02M 7/4807 having a high frequency intermediate AC stage
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 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

Apparatus for extending a zero voltage switching (ZVS) range during DC/DC power conversion. The apparatus comprises a DC/DC converter, operated in a quasi-resonant mode, comprising (i) a transformer, (ii) a primary switch, coupled to a primary winding of the transformer, for controlling current flow through the primary winding, and (iii) a varactor, coupled to the transformer, for accelerating a downswing in a voltage across the primary switch.

Claims

1. Apparatus for extending a zero voltage switching (ZVS) range during DC/DC power conversion, comprising:

a DC/DC converter, operated in a quasi-resonant mode, comprising (i) a transformer, (ii) a primary switch, coupled to a primary winding of the transformer, for controlling current flow through the primary winding, and (iii) a varactor, coupled to the transformer, for accelerating a downswing in a voltage across the primary switch.

2. The apparatus of claim 1, wherein a capacitance of the varactor is decreased as the voltage decreases.

3. The apparatus of claim 1, wherein the varactor is coupled to a secondary winding of the transformer.

4. The apparatus of claim 1, further comprising a voltage clamp circuit coupled across the primary switch for limiting the voltage, wherein the voltage clamp circuit comprises the varactor.

5. The apparatus of claim 1, wherein the DC/DC converter further comprises a diode and an output capacitor, wherein (i) an anode terminal of the diode is coupled to a first terminal of a secondary winding of the transformer and a first terminal of the varactor, (ii) a first terminal of the output capacitor is coupled to a cathode terminal of the diode, a second terminal of the varactor, and a first output terminal of the DC/DC converter, and (iii) a second terminal of the output capacitor is coupled to a second terminal of the secondary winding and a second output terminal of the DC/DC converter, wherein the first and the second output terminals of the DC/DC converter provide an output voltage.

6. The apparatus of claim 1, wherein the DC/DC converter further comprises an output capacitor, wherein (i) a first terminal of a secondary winding of the transformer is coupled to a first terminal of the varactor, (ii) a first terminal of the output capacitor is coupled to a second terminal of the varactor and a first output terminal of the DC/DC converter, and (iii) a second terminal of the output capacitor is coupled to a second terminal of the secondary winding and a second output terminal of the DC/DC converter, wherein the first and the second output terminals of the DC/DC converter provide an output voltage.

7. The apparatus of claim 1, wherein the DC/DC converter further comprises a diode, a capacitor, and a resistor, wherein (i) an anode terminal of the diode is coupled to a first terminal of the varactor and a drain terminal of the primary switch, (ii) a cathode terminal of the diode is coupled to a second terminal of the varactor, a first terminal of the capacitor, and a first terminal of the resistor, and (iii) a second terminal of the resistor is coupled to a second terminal of the capacitor and a source terminal of the primary switch.

8. The apparatus of claim 1, wherein the DC/DC converter further comprises a capacitor and a resistor, wherein (i) a first terminal of the varactor is coupled to a drain terminal of the primary switch, (ii) a second terminal of the varactor is coupled to a first terminal of the capacitor and a first terminal of the resistor, and (iii) a second terminal of the resistor is coupled to a second terminal of the capacitor and a source terminal of the primary switch.

9. An inverter for extending a zero voltage switching (ZVS) range during DC/AC power conversion, comprising:

a DC/DC converter for converting DC input power to DC output power, the DC/DC converter operated in a quasi-resonant mode and comprising (i) a transformer, (ii) a primary switch, coupled to a primary winding of the transformer, for controlling current flow through the primary winding, and (iii) a varactor, coupled to the transformer, for accelerating a downswing in a voltage across the primary switch; and

a DC/AC conversion module for converting the DC output power to AC output power.

10. The inverter of claim 9, wherein the varactor is coupled to a secondary winding of the transformer.

11. The inverter of claim 9, further comprising a voltage clamp circuit coupled across the primary switch for limiting the voltage, wherein the voltage clamp circuit comprises the varactor.

12. The inverter of claim 9, wherein the DC/DC converter further comprises a diode and an output capacitor, wherein (i) an anode terminal of the diode is coupled to a first terminal of a secondary winding of the transformer and a first terminal of the varactor, (ii) a first terminal of the output capacitor is coupled to a cathode terminal of the diode, a second terminal of the varactor, and a first output terminal of the DC/DC converter, and (iii) a second terminal of the output capacitor is coupled to a second terminal of the secondary winding and a second output terminal of the DC/DC converter, wherein the first and the second output terminals of the DC/DC converter provide an output voltage.

13. The inverter of claim 9, wherein the DC/DC converter further comprises an output capacitor, wherein (i) a first terminal of a secondary winding of the transformer is coupled to a first terminal of the varactor, (ii) a first terminal of the output capacitor is coupled to a second terminal of the varactor and a first output terminal of the DC/DC converter, and (iii) a second terminal of the output capacitor is coupled to a second terminal of the secondary winding and a second output terminal of the DC/DC converter, wherein the first and the second output terminals of the DC/DC converter provide an output voltage.

14. The inverter of claim 9, wherein the DC/DC converter further comprises a diode, a capacitor, and a resistor, wherein (i) an anode terminal of the diode is coupled to a first terminal of the varactor and a drain terminal of the primary switch, (ii) a cathode terminal of the diode is coupled to a second terminal of the varactor, a first terminal of the capacitor, and a first terminal of the resistor, and (iii) a second terminal of the resistor is coupled to a second terminal of the capacitor and a source terminal of the primary switch.

15. The inverter of claim 9, wherein the DC/DC converter further comprises a capacitor and a resistor, wherein (i) a first terminal of the varactor is coupled to a drain terminal of the primary switch, (ii) a second terminal of the varactor is coupled to a first terminal of the capacitor and a first terminal of the resistor, and (iii) a second terminal of the resistor is coupled to a second terminal of the capacitor and a source terminal of the primary switch.

16. A method for extending a zero voltage switching (ZVS) range during DC/DC power conversion, comprising:

deactivating a primary switch of a DC/DC converter operating in quasi-resonant mode, the primary switch for controlling current flow through a primary winding of the DC/DC converter; and

increasing a resonant frequency of a resonant circuit of the DC/DC converter during a downswing in a voltage across the primary switch to accelerate the downswing.

17. The method of claim 16, wherein the increasing a resonant frequency is caused by decreasing a capacitance of the DC/DC converter.

18. The method of claim 17, wherein the capacitance is altered by a varactor.

19. The method of claim 18, wherein the varactor is coupled to a secondary winding of the transformer.

20. The method of claim 18, further comprising limiting a spike in the voltage, wherein the limiting is performed by a voltage clamp circuit coupled across the primary switch, wherein the voltage clamp circuit comprises the varactor.