Process for operating a switching power supply

• US 7,309,975 B2
• Filed: 05/15/2006
• Issued: 12/18/2007
• Est. Priority Date: 05/16/2005
• Status: Expired due to Fees

• Current Assignee: Eltam Ein Hashofet
• Original Assignee: Eltam Ein Hashofet
• Inventors: Erez, Eran, Fishbein, Omri
• Primary Examiner(s): Laxton; Gary L
• Application Number:
  US11/433,574
• Publication Number:
  US 20060255776A1
• Time in Patent Office: 582 Days
• Field of Search: 323/222, 323/223, 323/225, 323/259, 323/266, 323/268, 323/271, 323/282, 323/285, 323/344
• US Class Current: 323/259
• CPC Class Codes: H02M 1/0012 Control circuits using digital or numerical techniques in DC/DC converters H02M3/157, H02M3/33515; in DC-AC converters H02M7/53873
• CPC Class Codes: H02M 3/1582 Buck-boost converters H02M3/1584 takes precedence

Abstract

There is provided a process for operating a switch mode power supply circuit (Switcher) connectable to a load, the circuit having a first buck switch, a second boost switch and an inductor in a buck boost circuit, the process including applying input voltage to the circuit, selectively activating each of the buck switch and boost switch, and selectively limiting the ON-time of the buck switch, for accelerating discharge of the inductor.

Claims

1. A process for operating a switch-mode power factor correction (PFC) circuit connectable to a load, said circuit including a first buck switch, a second boost switch and an inductor in a buck boost circuit, said process comprising:

selectively applying input voltage to the PFC circuit, said input voltage being a rectified AC wave, and

activating both of said buck switch and boost switch near zero current of said inductor, while limiting ON-time of the buck switch, for accelerating discharge of said inductor,

wherein the buck switch ON-time (t_buck) and boost switch ON-time (t_boost), the PFC circuit input voltage (Vin) and the PFC circuit output voltage (Vo) conform with the equation;

(t_buck=t_boost)/t_boost=Vin/Vo.

2. The process as claimed in claim 1, wherein during portions of the input voltage wave, each switch ON-time is controlled to facilitate smooth transition between operation modes of the PFC circuit.

3. The process claimed in claim 1 wherein, said buck switch ON-time is gradually reduced and said boost switch ON-time is gradually increased to facilitate smooth efficient transition from buck operation mode to buck-boost/Modified Boost operation mode and from boost operation mode to buck-boost/Modified Boost operation mode of the PFC circuit.

4. The process claimed in claim 1 wherein, said buck switch ON-time is gradually increased and said boost switch ON-time is gradually reduced to facilitate smooth transition from buck-boost/Modified Boost operation mode to boost operation mode and from buck-boost/Modified Boost operation mode to buck operation mode of the PFC circuit.

5. The process as claimed in claim 1, wherein during a discontinuous-critical-current mode (DCCM), the current is limited by controlling the charge time of the inductor.

6. The process as claimed in claim 1, further comprising activating a short term circuit shutoff during a development period of a voltage surge and deactivating said shutoff following a fading of the voltage surge.

7. The process as claimed in claims 1, further comprising reducing power delivered to the load for protection against overheating.

8. The process as claimed in claim 1, further comprising providing a circuit shutoff effected by comparison of a short-term mean value of a load voltage to a long-term mean value of a load voltage, for protection against short circuit.

9. The process as claimed in claim 1, wherein power delivered by the PFC circuit is limited to a predetermined maximum.

10. The process as claimed in claim 1, wherein the buck switch ON-time limitation secures the PFC circuit output voltage control.

11. The process as claimed in claim 1, wherein the buck switch ON-time limitation secures the PFC circuit input current control.

12. The process as claimed in claim 1, wherein Vin and Vo represent instantaneous values.

13. The process as claimed in claim 1, wherein Vin and Vo represent mean values.

14. A process for operating a switch-mode power factor correction (PFC) circuit connectable to a load, said circuit including a first buck switch, a second boost switch and an inductor in a buck boost circuit, said process comprising:

selectively applying input voltage to the circuit, said input voltage is a rectified AC wave, and activating both of said buck switch and boost switch near zero current of said inductor, while limiting the ON-time of the buck switch, in order to accelerate discharge of said inductor, wherein said buck switch ON-time (t_buck) and said boost switch ON-time (t_boost) obey the equation t_buck-t_boost=k t_boost;

k being a real number preferably selectable between approximately 2 to approximately 6 and t_boost=(2LPin/V²in_rms) g(k,Vin,Vo);

L being the inductance of said inductor;

Pin being the PFC input power;

V²in_rms being the squared rms value of the PFC input voltage, and g(k,Vin,Vo) being a correction factor, which is a function of the PFC circuit input voltage (Vin) and output voltage (Vo) with said k as a parameter.

15. The process as claimed in claim 14, wherein said correction factor g(k,Vin,Vo) obeys the equation g(k,Vin,Vo)=(m²(1+k)+m)/(m(1+k)²−

k²) where m=Vin/ Vo.

16. The process as claimed in claim 15, wherein said correction factor g(k,Vin,Vo) constitutes a set of linear functions of m, where m=Vin/ Vo, and each of said linear functions having at least one intersection point with the factor (m²(1+k)+m)/(m(1+k)²−

k²).

17. The process as claimed in claim 14, wherein Vin and Vo represent instantaneous values.

18. The process as claimed in claim 14, wherein Vin and Vo represent mean values.

19. The process as claimed in claim 14, wherein during portions of the input voltage wave, each switch ON-time is controlled to facilitate smooth transition between the operation modes of the PFC circuit.

20. The process as claimed in claim 14, wherein during discontinuous-critical-current mode (DCCM), the current is limited by controlling the charge time of the inductor.

21. The process as claimed in claim 14, further comprising activating a short term circuit shutoff during development period of a voltage surge and deactivating said shutoff following a fading of the voltage surge.

22. The process as claimed in claims 14, further comprising reducing power delivered to the load, for protection against overheating.

23. The process as claimed in claim 14, further comprising providing a circuit shutoff effected by comparison of a short-term mean value of a load voltage to a long-term mean value of a load voltage, for protection against short circuit.

24. The process as claimed in claim 14, wherein the power delivered by the PFC circuit is limited to a predetermined maximum.

25. The process as claimed in claim 14, wherein the buck switch ON-time limitation secures the PFC circuit output voltage control.

26. The process as claimed in claim 14, wherein the buck switch ON-time limitation secures the PFC circuit input current control.