Methods and apparatus for a resonant converter

• US 7,889,519 B2
• Filed: 01/12/2007
• Issued: 02/15/2011
• Est. Priority Date: 01/12/2006
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Leitermann, Olivia, Rivas, Juan M., Pilawa-Podgurski, Robert C. N., Sagneri, Anthony D., Perreault, David J., Han, Yehui
• Primary Examiner(s): Assouad; Patrick J
• Assistant Examiner(s): HERNANDEZ, MANUEL J
• Application Number:
  US11/622,571
• Publication Number:
  US 20070171680A1
• Time in Patent Office: 1,495 Days
• Field of Search: 363/21.02, 363/39, 363/40, 323/222, 323/282, 323/351
• US Class Current: 363/21.02
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 1/34 Snubber circuits
• CPC Class Codes: H02M 3/005 using Cuk converters
• CPC Class Codes: H02M 3/155 using semiconductor devices only
• CPC Class Codes: H02M 3/1557 Single ended primary inductor converters [SEPIC]
• CPC Class Codes: H02M 3/335 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

Methods and apparatus for a dc-dc converter for operating at substantially fixed switching frequency, the converter including a rectifier, and a resonant inverter coupled to the rectifier, the resonant inverter including a switch and a reactive network having first, second, third and fourth energy storage elements, wherein an impedance magnitude at the output of the switch due to the reactive network has minima at dc and at a frequency near a second harmonic of the switching frequency.

Claims

1. A dc-dc converter for operating at substantially fixed switching frequency across a range of voltage conversion ratios and output powers, the dc-dc converter comprising:

a rectifier; and

a resonant inverter coupled to the rectifier, the resonant inverter including a switch and a reactive network having exactly four energy storage elements, wherein an impedance magnitude at the output of the switch due to the reactive network has minima at dc and at a frequency near a second harmonic of the switching frequency.

2. The dc-dc converter of claim 1, wherein an impedance of the reactive network and loading by the rectifier shape a voltage across the switch such that a frequency content dominantly comprises dc, the fundamental of the switching frequency, and the third harmonic of the switching frequency.

3. The dc-dc converter of claim 1, wherein an impedance of the reactive network and loading by the rectifier shape the switch voltage to provide substantially zero-voltage switching of the switch.

4. The dc-dc converter of claim 3, wherein the impedance of the reactive network and loading by the rectifier further shape the switch voltage to a quasi-trapezoidal waveform having a peak value of less than three times the dc input voltage during steady-state operation.

5. The dc-dc converter of claim 1, further including first and second dc input terminals, wherein switch includes first and second terminals, wherein the four energy storage elements includes first, second third, and fourth energy storage elements, wherein the first energy storage element is a first capacitance coupled between the first and second switch terminals, the second energy storage element is a first inductor having a first end connected to the first dc input terminal and a second end coupled to the switch first terminal, a direct connection from the second dc input terminal to the switch second terminal, a series connection of a second inductor corresponding to the third energy storage element and a second capacitor corresponding to the fourth energy storage element having a first end connected to the switch first terminal and a second end connected to the switch second terminal, wherein the series connection of the second inductor and the second capacitor is resonant near the second harmonic of the dc-dc converter switching frequency.

6. The dc-dc converter of claim 5, further including first and second dc output terminals, a rectifying device having a first and second terminal where the second terminal is connected to the first dc output terminal, a third inductor corresponding to a fifth energy storage element having a first terminal connected to the switch first terminal and a second terminal connected to the rectifying device first terminal, a third capacitor corresponding to a sixth energy storage element having a first terminal connected to the rectifying device first terminal and a second terminal connected to the switch second terminal, a direct connection from the switch second terminal to the second dc output terminal.

7. The dc-dc converter of claim 6, wherein the first capacitance is composed entirely of the switch parasitic capacitance.

8. The dc-dc converter of claim 6, wherein the third capacitance is composed entirely of the rectifying device parasitic capacitance.

9. The dc-dc converter of claim 1, wherein the converter provides a path for dc current from the converter input to the converter output and delivers a fraction of the total converted power at dc.

10. The dc-dc converter of claim 1, wherein the output of the converter is regulated by on-off modulation of the power stage.

11. The dc-dc converter of claim 1, wherein the switching control is implemented by driving the inverter switch with a resonant gate drive scheme.

12. The dc-dc converter of claim 1, wherein relative magnitudes of impedance Z_ds at the fundamental and the third harmonic of the switching frequency form a ratio greater than one determining a maximum voltage across the switch of less than or equal to 2.4 times the input voltage.

13. A dc-dc converter for operation at a single switching frequency for variable output power, the dc-dc converter comprising:

a rectifier; and

a dc input having first and second terminals; and

a resonant inverter, the resonant inverter including a switch having first and second terminals, wherein the second switch terminal is connected to the second terminal of the dc input; and

a reactive network having two magnetic elements and two capacitive elements, wherein said reactive network provides;

a dc path from the first dc input terminal to the first switch terminal;

a capacitance between first and second switch terminals; and

a path from the first switch terminal to the second switch terminal having low impedance near two times said switching frequency.

14. The dc-dc converter of claim 13, wherein said resonant network provides waveshaping of the voltage across the terminals of the inverter switch such that said voltage has a quasi-trapezoidal waveform providing near-zero turn-off and turn-on conditions for the switch.

15. A method for providing a dc-dc converter for operating at substantially fixed switching frequency across a range of voltage conversion ratios and powers, comprising:

providing a rectifier; and

coupling a resonant inverter to the rectifier, the resonant inverter including a switch and a reactive network having exactly four energy storage elements, wherein an impedance magnitude at the output of the switch due to the reactive network has minima at dc and at a frequency near a second harmonic of the switching frequency.

16. The method claim 15, further including providing an impedance of the reactive network and loading by the rectifier to shape a voltage across the switch such that the frequency content dominantly comprises dc, the fundamental of the switching frequency, and the third harmonic of the switching frequency.

17. The method of claim 15, wherein an impedance of the reactive network and loading by the rectifier shape the switch voltage to provide substantially zero-voltage switching of the switch.

18. The method of claim 17, wherein the impedance of the reactive network and loading by the rectifier further shape the switch voltage to a quasi-trapezoidal waveform having a peak value of less than three times the dc input voltage during steady-state operation.

19. The method of claim 15, further including providing first and second dc input terminals, wherein switch includes first and second terminals, wherein the four energy storage elements includes first, second third, and fourth energy storage elements, wherein the first energy storage element is a first capacitance coupled between the first and second switch terminals, the second energy storage element is a first inductor having a first end connected to the first dc input terminal and a second end coupled to the switch first terminal, a direct connection from the second dc input terminal to the switch second terminal, a series connection of a second inductor corresponding to the third energy storage element and a second capacitor corresponding to the fourth energy storage element having a first end connected to the switch first terminal and a second end connected to the switch second terminal, wherein the series connection of the second inductor and the second capacitor is resonant near the second harmonic of the dc-dc converter switching frequency.

20. The method of claim 19, further including providing first and second dc output terminals, a rectifying device having a first and second terminal where the second terminal is connected to the first dc output terminal, a third inductor corresponding to a fifth energy storage element having a first terminal connected to the switch first terminal and a second terminal connected to the rectifying device first terminal, a third capacitor corresponding to a sixth energy storage element having a first terminal connected to the rectifying device first terminal and a second terminal connected to the switch second terminal, a direct connection from the switch second terminal to the second dc output terminal.

21. The method of claim 15, wherein the converter provides a path for dc current from the converter input to the converter output and delivers a fraction of the total converted power at dc.

22. The method of claim 15, wherein the first capacitance is composed entirely of the switch parasitic capacitance.

23. A dc-dc converter comprising:

a rectifier; and

a resonant inverter coupled to the rectifier, the resonant inverter including;

a switch activated at a fixed switching frequency and a fixed duty ratio across a range of output powers; and

a reactive network for providing near zero-voltage switching turn on of said switch, said reactive network having two zeros and two poles, wherein a first one of the two zeros is at dc and a second one of the two zeros is located in relation to the second harmonic of said switching frequency.

24. The dc-dc converter of claim 23, wherein control of the average converter output is obtained by on/off control of the converter.

25. The dc-dc converter of claim 23, wherein a first one of the two poles is located in relation to the switching frequency and a second one of the two poles is located in relation to the third harmonic of the switching frequency.