DC/DC converter, power converter and control method thereof

• US 8,923,019 B2
• Filed: 03/22/2012
• Issued: 12/30/2014
• Est. Priority Date: 03/28/2011
• Status: Active Grant

• Current Assignee: Delta Electronics Shanghai Company Limited (Delta Electronics Incorporated)
• Original Assignee: Delta Electronics Shanghai Company Limited (Delta Electronics Incorporated)
• Inventors: Hu, Pei-Qing, Jin, Hong-Yuan, Gan, Hong-Jian, Ying, Jian-Ping
• Primary Examiner(s): Dole, Timothy J
• Assistant Examiner(s): Grubb, Matthew
• Application Number:
  US13/427,386
• Publication Number:
  US 20120250356A1
• Time in Patent Office: 1,013 Days
• Field of Search: 363/16, 363/17, 363/21.02
• US Class Current: 363/21.02
• CPC Class Codes: H02M 1/0035 using burst mode control
• 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 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H02M 3/33573 Full-bridge at primary side of an isolation transformer
• 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 DC/DC converter, a power converter and a control method thereof are disclosed, wherein the DC/DC converter includes an output circuit, a rectangular wave generator, a resonant tank, a detection unit and a control unit. The output circuit has a load. The rectangular wave generator converts an input voltage into driving pulses. The resonant tank provides a first voltage based on the driving pulses for the output circuit. The detection unit detects a signal related to a state of the load. When the state of the load is a light-load or a no-load, the control unit controls the rectangular wave generator in a hiccup mode to reduce a ratio of a work period to a stop period, or makes that number of the driving pulses within the current work period is less than the number of the driving pulses when a duty ratio is 50%.

Claims

1. A DC/DC converter comprising:

an output circuit having a load;

a rectangular wave generator for converting an input voltage into driving pulses;

a resonant tank for providing a first voltage based on the driving pulses for the output circuit;

a detection unit for detecting a signal related to a state of the load; and

a control unit for controlling the rectangular wave generator in a hiccup mode to reduce a ratio of a current work period to a stop period when the state of the load is a light-load or a no-load,

wherein the ratio of a current work period to a stop period in the light-load or the no-load is smaller than a ratio of a current work period to a stop period when the duty ratio is 50% in the light-load or the no-load wherein a working frequency of the driving pulses is higher than a resonance frequency of the resonance tank, and the duty ratio of the driving pulses is within a predetermined range, so that a voltage gain of the DC/DC converter is higher than another voltage gain under the condition of 50% duty ratio.

2. The DC/DC converter of claim 1, wherein when the state of the load is the light-load or the no-load, the control unit changes the duty ratio of the driving pulses during the current work period, and then during the stop period the control unit calculates the number of the driving pulses within the current work period and adjusts the duty ratio of the driving pulses according to the number of the driving pulses.

3. The DC/DC converter of claim 2, wherein when the state of the load is the light-load or the no-load, the control unit decreases the duty ratio of the driving pulses during the current work period;

when during the stop period the control unit determines that the number of the driving pulses within the current work period is less than or equal to the number of the driving pulses within a previous work period, the control unit keeps on decreasing the duty ratio of the driving pulses during a following work period.

4. The DC/DC converter of claim 2, wherein when the state of the load is the light-load or the no-load, the control unit decreases the duty ratio of the driving pulses during the current work period;

when during the stop period the control unit determines that the number of the driving pulses within the current work period is more than the number of the driving pulses within a previous work period, the control unit increases the duty ratio of the driving pulses during a following work period.

5. The DC/DC converter of claim 4, wherein after increasing the duty ratio of the driving pulses, when the control unit determines that the number of the driving pulses within the following work period is less than or equal to the number of the driving pulses within the current work period, the control unit keeps on increasing the duty ratio of the driving pulses during a yet following work period.

6. The DC/DC converter of claim 4, wherein after increasing the duty ratio of the driving pulses, when the control unit determines that the number of the driving pulses within the following work period is more than the number of the driving pulses within the current work period, the control unit decreases the duty ratio of the driving pulses during a yet following work period.

7. The DC/DC converter of claim 2, wherein when the state of the load is the light-load or the no-load, the control unit increases the duty ratio of the driving pulses during the current work period;

when during the stop period the control unit determines that the number of the driving pulses within the current work period is less than or equal to the number of the driving pulses within a previous work period, the control unit keeps on increasing the duty ratio of the driving pulses during a following work period.

8. The DC/DC converter of claim 2, wherein when the state of the load is the light-load or the no-load, the control unit increases the duty ratio of the driving pulses during the current work period;

when during the stop period the control unit determines that the number of the driving pulses within the current work period is more than the number of the driving pulses within a previous work period, the control unit decreases the duty ratio of the driving pulses during a following work period.

9. The DC/DC converter of claim 8, wherein after decreasing the duty ratio of the driving pulses, when the control unit determines that the number of the driving pulses within the following work period is less than or equal to the number of the driving pulses within the current work period, the control unit keeps on decreasing the duty ratio of the driving pulses during a yet following work period.

10. The DC/DC converter of claim 8, wherein after decreasing the duty ratio of the driving pulses, when the control unit determines that the number of the driving pulses within the following work period is more than the number of the driving pulses within the current work period, the control unit increases the duty ratio of the driving pulses during a yet following work period.

11. The DC/DC converter of claim 1, wherein when the state of the load is a heavy-load or a full-load, the control unit controls the rectangular wave generator in a frequency modulation mode.

12. The DC/DC converter of claim 1, wherein the rectangular wave generator comprises a switch, and the control unit controls an on/off state of the switch to output the driving pulses, wherein amplitude of the driving pulses is equal to the input voltage or the double of the input voltage.

13. The DC/DC converter of claim 12, wherein the switch is a half-bridge circuit or a full-bridge circuit.

14. The DC/DC converter of claim 1, wherein the load comprises a resistor.

15. The DC/DC converter of claim 14, wherein the output circuit further comprises a transformer and a rectifier both electrically connected to the resistor.

16. The DC/DC converter of claim 1, wherein the resonant tank is a serial resonant circuit or a parallel resonant circuit.

17. The DC/DC converter of claim 16, wherein the serial resonant circuit is a LC series resonant circuit or a LLC series resonant circuit.

18. The DC/DC converter of claim 17, wherein the LLC series resonant circuit comprises a magnetizing inductor, a resonant inductor and a resonant capacitor connected to each other in series, wherein the magnetizing inductor and the output circuit are connected in parallel.

19. The DC/DC converter of claim 18, wherein the duty ratio is less than 50% and greater than a lower limit value of the predetermined range, so that when the resonant capacitor charges, the voltage gain of the DC/DC converter is greater than said another voltage gain under the condition of 50% duty ratio.

20. The DC/DC converter of claim 18, wherein the duty ratio is greater than 50% and less than an upper limit value of the predetermined range, so that when the resonant capacitor discharges, the voltage gain of the DC/DC converter is greater than said another voltage gain under the condition of 50% duty ratio.

21. A power converter comprising:

the DC/DC converter of claim 1;

a power factor correction device electrically coupled with the DC/DC converter; and

an electromagnetic interference filter electrically coupled with the power factor correction device for receiving alternating current, wherein the electromagnetic interference filter and the power factor correction device convert the alternating current into the input voltage and provide the input voltage for the DC/DC converter.

22. The power converter of claim 21, wherein when the state of the load is the light-load or the no-load, the power factor correction device reduces the input voltage provided for the DC/DC converter.

23. The power converter of claim 21, wherein when the state of the load is the light-load or the no-load, the power factor correction device is turned off.

24. The power converter of claim 21, wherein the power factor correction device comprises:

a bridge rectifier; and

a power factor corrector electrically coupled with the bridge rectifier.

25. The power converter of claim 21, wherein the power factor correction device comprises a bridgeless power factor corrector.

26. A method of controlling a power converter, the method comprising:

(a) converting an input voltage into driving pulses;

(b) providing a first voltage based on the driving pulses for an output circuit;

(c) detecting a signal related to a state of a load; and

(d) controlling the driving pulses in a hiccup mode to reduce a ratio of a current work period to a stop period when the state of the load is a light-load or a no-load;

when the state of the load is the light-load or the no-load, controlling the driving pulses in the hiccup mode, wherein the ratio of a current work period to a stop period in the light-load or the no-load is smaller than a ratio of a current work period to a stop period when the duty ratio is 50% in the light-load or the no-load wherein step (d) comprises;

when the state of the load is the light-load or the no-load, changing a duty ratio of the driving pulses during the current work period;

then, during the stop period calculating the number of the driving pulses within the current work period, and adjusting the duty ratio of the driving pulses according to the number of the driving pulses.

27. The method of claim 26, wherein the step (d) further comprises:

when the state of the load is the light-load or the no-load, decreasing the duty ratio of the driving pulses during the current work period; and

when during the stop period it is determined that the number of the driving pulses within the current work period is less than or equal to the number of the driving pulses within a previous work period, keeping on decreasing the duty ratio of the driving pulses during a following work period.

28. The method of claim 26, wherein the step (d) further comprises:

when the state of the load is the light-load or the no-load, decreasing the duty ratio of the driving pulses during the current work period;

when during the stop period it is determined that the number of the driving pulses within the current work period is more than the number of the driving pulses within a previous work period, increasing the duty ratio of the driving pulses during a following work period.

29. The method of claim 28, wherein the step (d) further comprises:

after increasing the duty ratio of the driving pulses, when it is determined that the number of the driving pulses within the following work period is less than or equal to the number of the driving pulses within the current work period, keeping on increasing the duty ratio of the driving pulses during a yet following work period.

30. The method of claim 28, wherein the step (d) further comprises:

after increasing the duty ratio of the driving pulses, when it is determined that the number of the driving pulses within the following work period is more than the number of the driving pulses within the current work period, decreasing the duty ratio of the driving pulses during a yet following work period.

31. The method of claim 26, wherein the step (d) further comprises:

when the state of the load is the light-load or the no-load, increasing the duty ratio of the driving pulses during the current work period; and

when during the stop period it is determined that the number of the driving pulses within the current work period is less than or equal to the number of the driving pulses within a previous work period, keeping on increasing the duty ratio of the driving pulses during a following work period.

32. The method of claim 26, wherein the step (d) further comprises:

when the state of the load is the light-load or the no-load, increasing the duty ratio of the driving pulses during the current work period; and

when during the stop period it is determined that the number of the driving pulses within the current work period is more than the number of the driving pulses within a previous work period, decreasing the duty ratio of the driving pulses during a following work period.

33. The method of claim 32, wherein the step (d) further comprises:

after decreasing the duty ratio of the driving pulses, when it is determined that the number of the driving pulses within the following work period is less than or equal to the number of the driving pulses within the current work period, keeping on decreasing the duty ratio of the driving pulses during a yet following work period.

34. The method of claim 32, wherein the step (d) further comprises:

after decreasing the duty ratio of the driving pulses, when it is determined that the number of the driving pulses within the following work period is more than the number of the driving pulses within the current work period, increasing the duty ratio of the driving pulses during a yet following work period.

35. The method of claim 26, further comprising:

when the state of the load is a heavy-load or a full-load, controlling a rectangular wave generator in a frequency modulation mode.

36. The method of claim 26, wherein the step (a) further comprises:

controlling an on/off state of a switch to output the driving pulses, wherein amplitude of the driving pulses is equal to the input voltage or the double of the input voltage.

37. The method of claim 26, further comprising:

configuring an electromagnetic interference filter to receive alternating current, the electromagnetic interference filter and a power factor correction device for converting the alternating current into the input voltage and providing the input voltage.

38. The method of claim 37, further comprising:

when the state of the load is the light-load or the no-load, reducing the input voltage provided from the power factor correction device.

39. The method of claim 37, further comprising:

when the state of the load is the light-load or the no-load, turning off the power factor correction device.