Half-bridge power converter with pre-charging circuit

• US 10,536,087 B1
• Filed: 10/11/2018
• Issued: 01/14/2020
• Est. Priority Date: 10/11/2018
• Status: Active Grant

• Current Assignee: Tdk-Lambda Americas Incorporated (TDK Corporation)
• Original Assignee: Tdk-Lambda Americas Incorporated (TDK Corporation)
• Inventors: He, Jin, Hilburn, Del
• Primary Examiner(s): Zhang, Jue
• Assistant Examiner(s): Singh, David A.
• Application Number:
  US16/157,604
• Time in Patent Office: 460 Days
• Field of Search: 363 17, 363 2102, 363 2103, 363 98
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 1/0048 Circuits or arrangements for reducing losses using snubbers H02M1/34
• CPC Class Codes: H02M 1/0085 Partially controlled bridges
• 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 1/088 for the simultaneous control of series or parallel connected semiconductor devices
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters
• CPC Class Codes: H02M 1/40 Means for preventing magnetic saturation
• CPC Class Codes: H02M 3/07 using capacitors charged and discharged alternately by semiconductor devices with control electrode , e.g. charge pumps
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• 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 3/3376 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/4811 having auxiliary actively switched resonant commutation circuits connected to intermediate DC voltage or between two push-pull branches
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H02M 7/4818 with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits
• 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

A half-bridge power converter includes a transformer dividing the half-bridge power converter into a primary side and a secondary side. Disposed on the first side is a first capacitor bank and a second capacitor bank in series with the first capacitor hank, and also a bootstrap capacitor configured to be charged by current flowing through a charging current flowpath. The charging current flowpath extends at least through a pre-charging circuit located on the primary side, the pre-charging circuit being configured to reduce a voltage imbalance between the first capacitor bank and the second capacitor bank. The half-bridge power converter also includes a discharging current flowpath that extends at least through a primary winding of the transformer and the pre-charging circuit.

Claims

1. A half-bridge power converter comprising:

a transformer dividing the half-bridge power converter into a primary side and a secondary side;

a first capacitor bank and a second capacitor bank in series with the first capacitor bank, wherein the first capacitor bank and the second capacitor bank are located on the primary side;

a bootstrap capacitor on the primary side, wherein the bootstrap capacitor is configured to be charged by current flowing through a charging current flowpath that extends at least through a pre-charging circuit located on the primary side, wherein the pre-charging circuit reduces a voltage imbalance between the first capacitor bank and the second capacitor bank; and

a discharging current flowpath that extends at least through a primary winding of the transformer and the pre-charging circuit.

2. The half-bridge power converter of claim 1, wherein the charging current flowpath passes through the bootstrap capacitor.

3. The half-bridge power converter of claim 2, wherein the charging current flowpath passes through a bootstrap resistor and a bootstrap diode.

4. The half-bridge power converter of claim 1, further comprising a blocking capacitor connected between a primary winding of the transformer and the pre-charging circuit.

5. The half-bridge power converter of claim 4, wherein the blocking capacitor has a higher capacitance than the first capacitor bank and the second capacitor bank, and wherein the blocking capacitor has a higher capacitance than the bootstrap capacitor.

6. The half-bridge power converter of claim 1, wherein the pre-charging circuit further comprises:

a pre-charge resistor in series with a primary winding of the transformer; and

a pre-charge switching device connected to the pre-charge resistor.

7. The half-bridge power converter of claim 6, wherein the pre-charge switching device is an N-channel MOSFET, and wherein the pre-charge resistor is connected to a drain of the N-channel MOSFET.

8. The half-bridge power converter of claim 7, further comprising:

a gate pull-down resistor connected between a gate of the N-channel MOSFET and a primary ground.

9. The half-bridge power converter of claim 1, further comprising:

a high-side switching device;

a low-side switching device; and

a driver IC chip connected to the high-side switching device and the low side switching device to control a set of switching cycles of the half-bridge power converter;

wherein the pre-charging circuit is located in parallel with the low-side switching device.

10. The half-bridge power converter of claim 1, further comprising:

a pair of synchronous rectification devices disposed on the secondary side of the of the half-bridge power converter, wherein each of the pair of synchronous rectification devices has an equal power rating.

11. An apparatus comprising:

a power supply providing a first power level;

a half-bridge power converter electrically coupled to the power supply, wherein the half-bridge power converter includes;

a transformer dividing the half-bridge power converter into a primary side and a secondary side;

a first capacitor bank and a second capacitor bank in series with the first capacitor bank, wherein the first capacitor bank and the second capacitor bank are located on the primary side;

a bootstrap capacitor on the primary side, wherein the bootstrap capacitor is configured to be charged by current flowing through a charging current flowpath that extends at least through a pre-charging circuit located on the primary side, wherein the pre-charging circuit reduces a voltage imbalance between the first capacitor bank and the second capacitor bank; and

a discharging current flowpath that extends at least through a primary winding of the transformer and the pre-charging circuit;

a resistive load connected to the half-bridge power converter, wherein the half-bridge power converter provides the resistive load with a second power level that differs from the first power level.

12. The apparatus of claim 11, wherein the charging current flowpath passes through the bootstrap capacitor.

13. The apparatus of claim 12, wherein the charging current flowpath passes through a bootstrap resistor and a bootstrap diode.

14. The apparatus of claim 11, wherein the half-bridge power converter further comprises a blocking capacitor connected between a primary winding of the transformer and the pre-charging circuit, wherein the blocking capacitor has a higher capacitance than the first capacitor bank and the second capacitor bank, and wherein the blocking capacitor has a higher capacitance than the bootstrap capacitor.

15. The apparatus of claim 11, wherein the pre-charging circuit further comprises:

a pre-charge resistor in series with a primary winding of the transformer; and

a pre-charge switching device connected to the first pre-charge resistor.

16. The apparatus of claim 15, wherein the pre-charge switching device is an N-channel MOSFET, and wherein the first pre-charge resistor is connected to a drain of the N-channel MOSFET.

17. The apparatus of claim 16, further comprising:

a gate pull-down resistor connected between a gate of the N-channel MOSFET and a primary ground.

18. The apparatus of claim 11, further comprising:

a high-side switching device;

a low-side switching device; and

a driver IC chip connected to the high-side switching device and the low side switching device to control a set of switching cycles of the half-bridge power converter;

wherein the pre-charging circuit is located in parallel with the low-side switching device.

19. The apparatus of claim 11, further comprising:

a pair of synchronous rectification devices disposed on the secondary side of the of the half-bridge power converter, wherein each of the pair of synchronous rectification devices has an equal power rating.

20. A method for starting a half-bridge power converter, the method comprising:

activating a pre-charge switching device for a charging interval duration, wherein the pre-charge switching device is located on a primary side of the half-bridge power converter;

supplying a current through a charging current flowpath for the charging interval duration to charge a bootstrap capacitor located on the primary side;

wherein the bootstrap capacitor is configured to be charged by current flowing through the charging current flowpath that extends at least through the pre-charge switching device located on the primary side, wherein the pre-charge switching device reduces a voltage imbalance between a first capacitor bank and a second capacitor bank;

deactivating the pre-charge switching device after the charging interval duration; and

alternately activating a high-side switching device and a low-side switching device, wherein the high-side switching device and the low-side switching device are located on the primary side; and

wherein the high-side switching device is activated a least in part using the charge on the bootstrap capacitor.

21. The method of claim 20, further comprising:

delaying for a transition delay before the step of alternately activating the high-side switching device and the low-side switching device.

22. The method of claim 20, wherein the current supplied through the charging current flowpath charges a bootstrap capacitor in the charging current flowpath.

23. The method of claim 20;

further comprising;

discharging a second capacitor bank through a discharging current flowpath for the charging interval duration, wherein the discharging current flowpath passes through the pre-charge switching device.