Accelerated commutation for passive clamp isolated boost converters

• US 6,452,815 B1
• Filed: 05/24/2001
• Issued: 09/17/2002
• Est. Priority Date: 02/22/2001
• Status: Expired due to Term

• Current Assignee: Ford Motor Company
• Original Assignee: Ford Motor Company
• Inventors: Zhu, Lizhi, Lai, Jih-Sheng, Lee, Fred C.
• Primary Examiner(s): Han, Jessica
• Application Number:
  US09/865,099
• Time in Patent Office: 481 Days
• Field of Search: 363/17, 363/24, 363/25, 363/26, 363/39, 363/40, 363/49, 363/56.02, 363/56.05, 363/56.06, 363/56.08, 363/98, 363/127, 363/132, 363/133, 361/91.7
• US Class Current: 363/17
• CPC Class Codes: H02M 1/34 Snubber circuits
• CPC Class Codes: H02M 1/342 Active non-dissipative snubbers
• CPC Class Codes: H02M 1/348 Passive dissipative snubbers
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33584 Bidirectional converters
• CPC Class Codes: H02M 3/33592 having a synchronous rectifier circuit or a synchronous freewheeling circuit at the secondary side of an isolation transformer
• CPC Class Codes: H02M 3/337 in push-pull configuration H02M3/33576 takes precedence; with self-oscillating arrangements H02M3/3382, H02M3/3385
• 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

This invention is an efficient and cost effective bi-directional DC/DC converter that can effectively reduce the switch voltage stress (such as a semiconductor) with an accelerated commutation circuit, and thus allowing a low-cost passive clamp circuit to be used. Specifically, the invention is a method and system to accelerate commutation for passive-clamped isolated boost converters, which can also be a boost mode in a bi-directional DC/DC converter. A primary circuit has a snubber comprising a diode, a capacitor and an energy dissipater (such as a resistor or small buck converter). The primary circuit can be a “full bridge converter” or a “push-pull converter” or an “L-type converter” configuration. The commutation of the present invention protects the primary circuit switches from voltage spikes during switching conditions. The present invention can shorten a secondary circuit by turning on at least two switches on the secondary circuit simultaneously for a minimal calibratable period while primary circuit diagonal switches turn off. The present invention also has a means to allow a smooth transition between a choke current and a primary current. Primary current increases linearly through the snubber circuit during circuit startup, thus protecting the primary circuit controllers.

Claims

1. A system to accelerate commutation for passive-clamped isolated boost converters comprising:

a current source;

a primary circuit comprising at least one pair of switches;

a secondary circuit comprising at least two pairs of diagonal switches;

a transformer connected to the primary circuit and the secondary circuit; and

the primary circuit further comprising a snubber comprising a diode, a capacitor and an energy dissipater, whereby the primary circuit switches are protected from voltage spikes during switching conditions.

2. The system of claim 1 wherein the switches are semiconductor switches.

3. The system of claim 1 wherein the switches comprise anti-paralleled diodes.

4. The system of claim 1 wherein the energy dissipater is a resistor.

5. The system of claim 1 wherein the energy dissipater is a small buck converter.

6. The system of claim 1 wherein the primary circuit is in a full-bridge configuration.

7. The system of claim 1 wherein the primary circuit is in a push-pull configuration.

8. The system of claim 1 wherein the primary circuit is in an L-type configuration.

9. The system of claim 1 wherein the primary circuit is accelerated by a system to shorten the secondary circuit of the transformer and switching voltage spikes are routed into the snubber on the primary circuit.

10. The system of claim 9 wherein the system to short the secondary circuit comprises a system to turn on at least two bottom switches on the secondary circuit simultaneously for a minimal calibratable period while primary circuit diagonal switches turn off, whereby the primary circuit current can be transferred to the secondary circuit quickly and reduce a voltage spike due to primary current and transformer leakage interaction.

11. The system of claim 1 wherein the system is one directional.

12. The system of claim 1 wherein the system is bi-directional.

13. The system of claim 1 wherein the snubber further comprises a means to allow a smooth transition between a choke current and a primary current.

14. A method for accelerating commutation for passive clamp isolated boost converter circuit comprised of a transformer connected to a primary circuit, and a secondary circuit, comprising the steps of:

bypassing at least one pair of diagonal primary circuit switches during switching;

shorting the secondary circuit; and

snubbing the primary circuit using a diode, a capacitor and a means for dissipating energy, whereby primary circuit switches are protected from voltage spikes in a switching condition.

15. The method of claim 14 wherein the switches are semiconductor switches.

16. The method of claim 14 wherein the switches comprise anti-paralleled diodes.

17. The method of claim 14 wherein the means for dissipating energy uses a resistor.

18. The method of claim 14 wherein the means for dissipating energy uses a small buck converter.

19. The method of claim 14 wherein the step of shortening the secondary circuit comprises the step of turning on at least two switches on the secondary circuit simultaneously for a minimal calibratable period.

20. The method of claim 14 wherein the method is one directional.

21. The method of claim 14 wherein the system is bi-directional.

22. The method of claim 14 wherein snubbing the primary circuit further comprises the step of allowing a smooth transition between a choke current and a primary current.