Boost converter utilizing bi-directional magnetic energy transfer of coupling inductor

• US 7,161,331 B2
• Filed: 04/11/2005
• Issued: 01/09/2007
• Est. Priority Date: 04/11/2005
• Status: Active Grant

• Current Assignee: Yuan Ze University
• Original Assignee: Yuan Ze University
• Inventors: Duan, Rou-Yong, Wai, Rong-Jong
• Primary Examiner(s): Riley; Shawn
• Application Number:
  US11/102,846
• Publication Number:
  US 20060226816A1
• Time in Patent Office: 638 Days
• Field of Search: 323/222, 323/225, 323/232, 323/233
• US Class Current: 323/222
• CPC Class Codes: H02M 1/34 Snubber circuits
• CPC Class Codes: H02M 3/1552 Boost converters exploiting the leakage inductance of a transformer or of an alternator as boost inductor
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor provides a high efficiency boost DC-DC converting with above 30 times voltage boost rate, which uses a coupling inductor and low voltage switch to absorb circuit induction voltage of a passive regenerative snubber no matter if switch is turned on or off. Such that, a much higher voltage boost rate than the turn rate of transformer and wider range of switching duty cycle is obtained. A bi-directional magnetic energy path is utilized, that is, when switch is turned on the first winding of coupling inductor stores magnetic excited high current energy, and opposite magnetic flux is induced on the second winding at the same time. When switch is turned off the magnetic excited current continues and increases the voltage on the second winding. The second winding has bi-directional magnetic current induced and fully utilizes capacity of transformer'"'"'s iron core.

Claims

1. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor, comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor with a first polar point connecting to a positive end of a DC input circuit;

a passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor with a second polar point connecting said high voltage capacitor; and

a filter circuit including a filter capacitor and a rectify diode;

wherein when said semi-conductor power switch is turned on, the current stores energy in said primary winding of said coupling inductor, the voltage at said second polar point of said secondary winding is positive;

its voltage combined with the voltage of said clamping capacitor of said passive regenerative snubber, through said discharge diode of said passive regenerative snubber, charges said high voltage capacitor of said secondary circuit with a high voltage and a low current;

when said semi-conductor power switch is turned off, said clamping capacitor of said passive regenerative snubber first, through said clamping diode of its circuit, absorbs leakage induction energy of said primary winding;

when the current of said secondary winding of said coupling inductor is reversed in direction, and the voltage at the non polar point of said secondary winding of said coupling inductor is positive, and combined with other three voltages, including a positive voltage at the non polar point of said primary winding generated by a magnetic excited current of said primary winding, the DC input voltage and the voltage of said high voltage capacitor, together through said rectify diode charges said filter capacitor to maintain a stable DC output voltage;

the characteristics of the present design is that, first it has a high boost ratio with low winding ratio and lenient duty cycle control;

second, passive regenerative snubber can absorbs circuit'"'"'s induction energy, making it easier for wiring layout;

third, the energy absorbed by the clamping capacitor can be applied to boost voltage, and there is no circular current problem and further achieving the purpose of voltage clamping;

forth, all the switches and diodes can function in voltage clamping, and at the moment when switch is turned on there are no short current and high reverse-recovery current in diode;

fifth, high conversion efficiency, under no separation configuration, proper specification of the components can be subscribed according to where they are being used, that is either for low voltage large current or for high voltage low current;

sixth, simple configuration, comparing to traditional coupling inductor circuit, only two more diodes and capacitors are used but achieve much higher boost ratio with lower capacity requirements;

seventh, conversion efficiency is directly related to boost ratio, but to the size of duty cycle and if the conducting current of the switch is square wave or not;

this overcomes the bottle neck in traditional technique where the higher boost ratio is, the lower efficiency is;

eighth, coupling inductor has the same feature as transformer, where once current flows at primary winding instant output current occurs at secondary winding;

the coupling inductor functions as transformer and inductance, which dramatically reduces ripples of semi-conductor power switch and required exited inductance value, and also reduces iron core;

ninth, since exited inductance is reduced the required number of primary winding becomes less;

when large current passes the primary winding, the copper loss induced by skin effect is reduced;

tenth, violent current change can be limited to primary circuit, making it easier to control magnetic interference;

eleventh, during boosting process, DC power source provides current to output when the semi-conductor power switch is turned off;

since this part of process does not pass the switch and magnetic transfer, conversion efficiency increases;

twelfth, according to theoretical analysis and experiment, voltage withstand on semi-conductor power switch is only related to the output voltage and winding ratio of coupling inductor;

this feature is well suited to power conversion equipments with large range of input power sources.

2. A boost converter of claim 1, wherein said semi-conductor power switch of primary circuit has a character of low conduction loss for low voltage and high current.

3. A boost converter of claim 1, wherein said coupling inductor of primary circuit and secondary circuit is a double winding transformer with high magnetic excited current and wide air gaps;

by utilizing the different turn ratios of said transformer to control the range of voltages and currents, lower voltage side has less turns of winding and larger current, and higher voltage side is vise versa.

4. A boost converter of claim 1, wherein said passive regenerative snubber absorbs both circuit induction energy and the leakage induction energy of said primary winding of said coupling inductor;

where the absorbed energy can be used to boost voltage, and when said semi-conductor switch is turned on, further provides a current passage for said coupling inductor of said secondary circuit;

this is different from traditional coupling induction configuration and the key in providing bi-directional magnetic passage; and

a higher leakage induction of said primary winding of said coupling inductor will reduces induction voltage of said secondary winding;

by utilizing said passive regenerative snubber plus increased conducting time of said semi-conductor power switch, a constant output voltage can be maintained;

thus, in the present design a transform with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method where traditional two separated windings will fulfill the purpose.

5. A boost converter of claim 1, wherein said clamping diode of said passive regenerative snubber is further connects to said semi-conductor power switch and said clamping capacitor, which withstands the same voltage that said semi-conductor power switch withstands, therefore, a low voltage low conduction loss Schottky diode can be used.

6. A boost converter of claim 1, wherein said discharge diode of said passive regenerative snubber connects to said clamping capacitor and said filter circuit, when its reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and withstands a lower voltage than the output voltage without additional snubber installed;

normally, lower withstand diode'"'"'s specification is, lower conducting voltage is, thus Schottky diode with low voltage low conducting loss can be used.

7. A boost converter of claim 1, wherein when reverse voltage of said rectify diode of said filter circuit is higher than the difference between the output voltage and the voltage of said clamping capacitor of said passive regenerative snubber, said discharge diode of said passive regenerative snubber starts to conduct and withstands a lower voltage than the output voltage without additional snubber;

where said diode and discharge diode of said passive regenerative snubber compensate each other and function as voltage damper at the same time.

8. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor having a first polar point defined as the place connecting to a positive end of a DC input circuit;

a passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a filter circuit including a filter capacitor and a rectify diode;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor having a second polar point defined as the place connecting said filter circuit;

when said semi-conductor power switch of said primary circuit is turned on, the current stores energy in said primary winding of said coupling inductor, the voltage at said second polar point of said secondary winding is positive;

its voltage combined with the voltage of said high voltage capacitor of said secondary circuit charges said filter capacitor of said filter circuit;

when the semi-conductor power switch is turned off, the non polar point of said secondary winding of the coupling inductor has a positive voltage which, through said clamping diode and said discharge diode of said passive regenerative snubber, charges said high voltage capacitor, at the same time, the leakage induction current of said primary winding of said coupling inductor, through said clamping diode, charges said clamping capacitor of said passive regenerative snubber;

when the voltage of said clamping capacitor rises above the voltage of said semi-conductor power switch, the current of a reverse bias of said clamping diode stops and the voltage of said clamping capacitor discharges to said high voltage capacitor of said secondary circuit through said discharge diode;

the characteristic of the present design is that the voltage of said high voltage capacitor of said secondary circuit comes exclusively from said secondary winding of said coupling inductor, and the DC input voltage and the voltage of said primary winding do not charge to said filter circuit in series;

hence it has a low voltage boost ratio, high clamping voltage;

however, after increasing duty cycle to maintain fixed output voltage, effective current of said semi-conductor power switch can be reduced, that is, the switching loss and the current withstood can be reduced;

in addition, it has high boosting ratio, easy wiring layout and the energy absorbed by the capacitor of the passive regenerative snubber can be applied to boost voltage, all the switches and diodes achieve clamping function, high conversion rate, simple configuration, efficiency is not directly related to boosting ratio, small induction spike, induction interference is easy dealt with and suitable to large range of input voltage.

9. A boost converter of claim 8, wherein said semi-conductor power switch of said primary circuit has a characteristic of low conduction loss for low voltage and high current.

10. A boost converter of claim 8, wherein said coupling inductor is a double winding transformer with high magnetic excited current and wide air gaps, by utilizing the different turn ratios of said transformer to coordinate voltages and currents, such that a low voltage side has less turns of winding and large current, and a high voltage side is vise versa.

11. A boost converter of claim 8, wherein said passive regenerative snubber can absorb both circuit induction energy and the leakage induction energy of said primary winding of said coupling inductor, where the absorbed energy can be used to boost voltage;

when said semi-conductor switch is turned on, it further provides a current passage for said coupling inductor of said secondary circuit;

this is different from traditional coupling induction configuration and the key in providing bi-directional magnetic passage; and

a higher leakage induction of said primary winding of said coupling inductor will reduces the induction voltage of said secondary winding;

by using said passive regenerative snubber and increasing conducting time of said semi-conductor power switch, a constant output voltage can be maintained;

thus, in the present design a transformer with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method while traditional two separated windings will fulfill the purpose.

12. A boost converter of claim 8, wherein said clamping diode of said passive regenerative snubber connects to said semi-conductor power switch and said clamping capacitor, which withstands the same voltage that said semi-conductor power switch withstands;

therefore, a low voltage low conduction loss Schottky diode can be used.

13. A boost converter of claim 8, wherein said discharge diode of said passive regenerative snubber connects to said clamping capacitor and said filter circuit, when its reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and withstands a lower voltage than the output voltage without additional snubber installed;

normally, lower withstand diode'"'"'s specification is, lower conducting voltage is.

14. A boost converter of claim 8, wherein when reverse voltage of said rectify diode of said filter circuit is higher than the difference between the output voltage and the voltage of said clamping capacitor of said passive regenerative snubber, said discharge diode of said passive regenerative snubber starts to conduct and withstands a lower voltage than the output voltage without additional snubber installed;

where said diode and discharge diode of said passive regenerative snubber compensate each other, and avoiding the problem of reverse-recovery current of the diode too high.

22. A boost converter of claim 8, wherein when the reverse voltage of said rectify diode of said filter circuit is higher than the difference between the output voltage and the voltage of said clamping capacitor of said passive regenerative snubber, said discharge diode of said first passive regenerative snubber starts to conduct and withstand a lower voltage than output voltage without additional snubber installed, where this diode and the discharge diode of said passive regenerative snubber compensate each other and function as voltage clamper to avoid the problem of reverse-recovery current of the diode too high.

15. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor having a first polar point defined as the place connecting to a positive end of a DC input circuit;

a first passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor having a second polar point defined as the place connecting said high voltage capacitor;

a filter circuit including a filter capacitor and a rectify diode;

when said semi-conductor power switch of said primary circuit is turned on, the current stores the energy in said primary winding of said coupling capacitor and the voltage of said polar point of said secondary winding of said coupling inductor is positive;

its voltage combined with the voltage of said clamping capacitor of said first passive regenerative snubber in series, through said discharging diode of said first passive regenerative snubber, charges the high voltage capacitor of said secondary circuit by high voltage and low current;

when said semi-conductor power switch is turned off, said clamping capacitor of said first passive regenerative snubber, through its clamping diode, first absorbs the leakage induction energy of said primary winding of said coupling inductor;

when the current of said secondary winding of said coupling inductor reverses in direction, the voltage of its non polar point is positive, combined with the positive voltage at the non polar point of said primary winding generated by a magnetic excited current of said primary winding, the DC input voltage and the voltage of said high voltage capacitor of said secondary circuit together, through said rectify diode of said filter circuit, charges said filter capacitor to maintain a stable DC output voltage;

the characteristic of the design is that the primary winding directly absorbs the spike current and then, when the switch is turned on, it uses this energy to charge the high voltage capacitor of the secondary circuit;

in addition, it has high boosting ratio, easy wiring layout and the energy absorbed by the capacitor of the passive regenerative snubber can be applied to boost voltage, all the switches and diodes achieve clamping function, high conversion rate, simple configuration, efficiency is not directly related to boosting ratio, small induction spike, induction interference is easy dealt with and suitable to large range of input voltage.

16. A boost converter of claim 15, wherein a second passive regenerative snubber is added to absorb current spike evenly and boost voltage by regenerative method;

said second passive regenerative snubber comprising a clamping diode, a discharge diode and a clamping capacitor, working as the same as said first passive regenerative snubber.

17. A boost converter of claim 15, wherein said semi-conductor power switch of said primary circuit has a characteristic of low conduction loss for low voltage and high current.

18. A boost converter of claim 15, wherein said coupling inductor is a double winding transformer with high magnetic excited current and wide air gaps;

by utilizing said different turn ratios of said transformer to control the range of voltages and currents, where a lower voltage side has less turns of winding and larger current, and a higher voltage side is vise versa.

19. A boost converter of claim 15, wherein said passive regenerative snubber can absorb circuit induction energy and the leakage induction energy of said primary winding of said coupling inductor, where the absorbed energy can be used to boost voltage;

when said semi-conductor switch is turned on, it further provides a current passage for said coupling inductor of said secondary circuit, where a higher leakage induction of said primary winding of said coupling inductor will reduces the induction voltage of said secondary winding;

by using said passive regenerative snubber and increasing conducting time of the semi-conductor power switch a constant output voltage can be maintained;

thus, in the present design a transformer with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method while traditional two separated windings will fulfill the purpose.

20. A boost converter of claim 15, wherein said clamping diode of said passive regenerative snubber connects to said semi-conductor power switch and said clamping capacitor to withstand the same voltage that said semi-conductor power switch withstands;

therefore, a low voltage low conduction loss Schottky diode can be used.

21. A boost converter of claim 15, wherein said discharge diode of said passive regenerative snubber connects to said clamping capacitor and said filter circuit;

when the reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and withstand a lower voltage than the output voltage without additional snubber installed;

normally, the lower withstand a diode has, the lower turn-on voltage is.

23. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor having a first polar point defined as the place connecting to the positive end of a DC input circuit;

a first passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a filter circuit including a filter capacitor and a rectify diode;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor having a second polar point defined as the place connecting said filter circuit;

when said semi-conductor power switch of said primary circuit is turned on, the current stores the energy in said primary winding of said coupling capacitor and the voltage of said polar point of said secondary winding of said coupling inductor is positive, and the voltage of said secondary winding combined with the voltage of said high voltage capacitor of said secondary winding charges said filter capacitor of said filter circuit;

when said semi-conductor power switch is turned off, the voltage at the non polar point of said secondary winding is positive, and this voltage charges said high voltage capacitor through said clamping diode and said discharging diode of said first passive regenerative snubber;

at the same time, the leakage induction current of said primary winding of said coupling inductor charges said clamping capacitor of said first passive regenerative snubber through said clamping diode;

when the voltage at the positive end of said clamping capacitor rises above the voltage of said semi-conductor power switch, the reverse bias of said clamping diode stops and the voltage of said clamping capacitor charges said high voltage capacitor of said secondary circuit through said discharging diode;

the characteristic of the present design is that the voltage of said high voltage capacitor of said secondary circuit comes exclusively from said secondary winding of said coupling inductor, and the DC input voltage and the voltage of said primary winding cancel each other and do not charge to the filter circuit in series;

hence it has a low voltage boost ratio, high clamping voltage;

however, after increasing duty cycle to maintain fixed output voltage, effective current of said semi-conductor power switch can be reduced, that is, the switching loss and the current withstood can be reduced;

in addition, it has high boosting ratio, easy wiring layout and the energy absorbed by the capacitor of the passive regenerative snubber can be applied to boost voltage, all the switches and diodes achieve clamping function, high conversion rate, simple configuration, efficiency is not directly related to boosting ratio, small induction spike, induction interference is easy dealt with and suitable to large range of input voltage.

24. A boost converter of claim 23, wherein a second passive regenerative snubber is added to absorb current spike evenly and boost voltage by regenerative method;

said second passive regenerative snubber comprising a clamping diode, a discharge diode and a clamping capacitor, working as the same as said first passive regenerative snubber.

25. A boost converter of claim 23, wherein said semi-conductor power switch of said primary circuit has a characteristic of low conduction loss for low voltage and high current.

26. A boost converter of claim 23, wherein said coupling inductor is a double winding transformer with high magnetic excited current and wide air gaps;

by utilizing said different turn ratios of said transformer to control the range of voltages and currents, where a lower voltage side has less turns of winding and larger current, and a higher voltage side is vise versa.

27. A boost converter of claim 23, wherein said first passive regenerative snubber can absorb circuit induction energy and the leakage induction energy of said primary winding of said coupling inductor, where the absorbed energy can be used to boost voltage;

and when said semi-conductor switch is turned on, it further provides a current passage for the coupling inductor of secondary circuit;

this is different from traditional coupling induction configuration and the key in providing bi-directional magnetic passage; and

a higher leakage induction of said primary winding of said coupling inductor will reduces the induction voltage of said secondary winding;

by using said first passive regenerative snubber and increasing conducting time of said semi-conductor power switch, a constant output voltage can be maintained;

thus, in the present design a transformer with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method where traditional two separated windings will fulfill the purpose.

28. A boost converter of claim 23, wherein said clamping diode of said first passive regenerative snubber connects to said semi-conductor power switch and said clamping capacitor to withstand the same voltage that said semi-conductor power switch withstands;

hence, a low voltage low conduction loss Schottky diode can be used.

29. A boost converter of claim 23, wherein said discharge diode of said first passive regenerative snubber connects to said clamping capacitor and said filter circuit;

when the reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and withstands a lower voltage than the output voltage without additional snubber installed;

normally, the lower withstand a diode has, the lower turn-on voltage is.

30. A boost converter of claim 23, wherein when the reverse voltage of said rectify diode of said filter circuit is higher than the difference between the DC output voltage and the voltage of said clamping capacitor of said first passive regenerative snubber, said discharge diode of said first passive regenerative snubber starts to conduct and withstands a lower voltage than output voltage without additional snubber installed;

this diode and said discharge diode of said passive regenerative snubber compensate each other and avoiding the problem of reverse-recovery current of the diode too high.

31. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor having a first polar point defined as the place connecting to the positive end of a DC input circuit;

a serially connected passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor having a second polar point defined as the place connecting said high voltage capacitor;

a filter circuit including a filter capacitor and a rectify diode;

the negative of the filter capacitor connects to the positive of said clamp capacitor of said serially connected passive regenerative snubber;

when said semi-conductor power switch of said primary circuit is turned on, the current stores the energy in said primary winding of said coupling capacitor and the voltage of said polar point of said secondary winding of said coupling inductor is positive;

the voltage of said secondary winding combined with the voltage of said high voltage capacitor of said serially connected passive regenerative snubber charges said high voltage capacitor of said secondary winding with high voltage and low current through said discharge diode of said serially connected passive regenerative snubber;

when said semi-conductor power switch is turned off, said clamp capacitor of said serially connected passive regenerative snubber first, through its clamp diode, absorbs the leakage induction energy of said primary winding of said coupling inductor;

then, when the current of said secondary winding of said coupling inductor reverses, in which the non polar point of said secondary winding is positive, this voltage combined with the positive voltage at said non polar point of said primary winding generated by a magnetic excited current of the primary winding, the DC input voltage and the voltage of said high voltage capacitor of said secondary circuit together, through said rectify diode of said filter circuit, charges said filter capacitor to maintain a stable DC output voltage;

the characteristic of the current design is that said filter capacitor of said filter circuit and said clamp capacitor of said serially connected passive regenerative snubber are connected in serial and together provide DC output;

therefore, the voltage of said filter capacitor is lower than the output DC voltage, and a capacitor with lower voltage withstand can be used;

in addition, it has high boosting ratio, easy wiring layout and the energy absorbed by the capacitor of said passive regenerative snubber can be applied to boost voltage, all the switches and diodes achieve clamping function, high conversion rate, simple configuration, efficiency is not directly related to boosting ratio, small induction spike, induction interference is easy dealt with and suitable to large range of input voltage.

32. A boost converter of claim 31, wherein said semi-conductor power switch of said primary circuit has a characteristic of low conduction loss for low voltage and high current.

33. A boost converter of claim 32, wherein said coupling inductor is a double winding transformer with high magnetic excited current and wide air gaps;

by utilizing the different turn ratios of said transformer to control the range of voltages and currents, where a lower voltage side has less turns of winding and larger current, and a higher voltage side is vise versa.

34. A boost converter of claim 31, wherein said serially connected passive regenerative snubber can absorb both circuit induction energy and the leakage induction energy of said primary winding of said coupling inductor, where the absorbed energy can be used to boost voltage;

and when said semi-conductor switch is turned on, it further provides a current passage for said coupling inductor of said secondary circuit;

this is different from traditional coupling induction configuration and the key in providing bi-directional magnetic passage; and

a higher leakage induction of said primary winding of said coupling inductor will reduces the induction voltage of said secondary winding;

by using the first passive regenerative snubber and increasing conducting time of the semi-conductor power switch, a constant output voltage can be maintained;

thus, in the present design a transformer with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method while traditional two separated windings will fulfill the purpose.

35. A boost converter of claim 31, wherein the clamping diode of said serially connected passive regenerative snubber further connects to said semi-conductor power switch and said clamping capacitor to withstand the same voltage that said semi-conductor power switch withstands;

hence, a low voltage low conduction loss Schottky diode can be used.

36. A boost converter of claim 31, wherein said discharge diode of said serially connected passive regenerative snubber connects to said clamping capacitor and said filter circuit;

when its reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and therefore it withstands a lower voltage than output voltage without additional snubber installed;

normally, the lower withstand a diode has, the lower turn-on voltage is;

a low voltage low conduction loss Schottky diode can be used.

37. A boost converter of claim 31, wherein when the reverse voltage of said rectify diode of said filter circuit is higher than the difference between the DC output voltage and the voltage of said clamping capacitor of said serially connected passive regenerative snubber, said discharge diode of said first passive regenerative snubber starts to conduct;

and therefore it withstands a lower voltage than the output voltage without additional snubber installed;

said diode and said discharge diode of said passive regenerative snubber compensate each other and avoid the problem of reverse-recovery current of the diode too high, and at the same time function as voltage clamp.

43. A boost converter of claim 31, wherein said discharge diode of said serially connected passive regenerative snubber connects to said clamping capacitor and said filter circuit;

when its reverse voltage is higher than the difference between the output voltage and the voltage of said clamping capacitor, said rectify diode of said filter circuit starts to conduct and therefore it withstands a lower voltage than the output voltage without additional snubber installed;

normally, the lower withstand a diode has, the lower turn-on voltage is.

38. A boost converter utilizing bi-directional magnetic energy transfer of coupling inductor comprising:

a primary circuit including a semi-conductor power switch and a primary winding of a coupling inductor having a first polar point defined as the place connecting to the positive end of a DC input circuit;

a serially connected passive regenerative snubber including a clamping diode, a discharge diode and a clamping capacitor;

a secondary circuit including a high voltage capacitor and a secondary winding of the coupling inductor having a second polar point defined as the place connecting said filter capacitor;

a filter circuit including a filter capacitor and a rectify diode;

the negative of the filter capacitor connects to the positive of said clamp capacitor of said serially connected passive regenerative snubber;

when said semi-conductor power switch of said primary circuit is turned on, the current stores the energy in said primary winding of said coupling capacitor and the voltage of said polar point of said secondary winding of said coupling inductor is positive;

the voltage of said secondary winding combined with the voltage of said high voltage capacitor of said secondary circuit charges said filter capacitor of said filter circuit;

when said semi-conductor power switch is turned off, the non polar point of said secondary winding of said coupling inductor is positive, its voltage charges said high voltage capacitor through said clamping diode and said discharging diode of said serially connected passive regenerative snubber;

at the same time the leakage induction current of said primary winding of said coupling inductor charges said clamping capacitor of said serially connected passive regenerative snubber through said clamping diode, and when the voltage of said clamping capacitor rises above the voltage of said semi-conductor power switch, the reverse bias on the clamping diode stops and the voltage of said clamping capacitor discharges to said high voltage capacitor of said secondary circuit through the passage of said discharging diode;

the characteristic of the current design is that said filter capacitor of said filter circuit and said clamping capacitor of said serially connected passive regenerative snubber are connected in serial and together provide the DC output;

therefore, the voltage of said filter capacitor is lower than the output DC voltage, and a capacitor with lower voltage withstand can be used;

the voltage of said high voltage capacitor of said secondary circuit comes exclusively from said secondary winding of the coupling inductor, and the DC input voltage and the voltage of said primary winding do not charge to said filter circuit in series;

hence it has a low voltage boost ratio, high clamping voltage;

however, after increasing duty cycle to maintain a fixed output voltage, effective current of said semi-conductor power switch can be reduced, that is, the switching loss and the current withstood can be reduced;

in addition, it has high boosting ratio, easy wiring layout and the energy absorbed by the capacitor of the passive regenerative snubber can be applied to boost voltage, all the switches and diodes achieve clamping function, high conversion rate, simple configuration, efficiency is not directly related to boosting ratio, small induction spike, induction interference is easy dealt with and suitable to large range of input voltage.

39. A boost converter of claim 38, wherein said semi-conductor power switch of said primary circuit has a characteristic of low conduction loss for low voltage and high current.

40. A boost converter of claim 38, wherein said coupling inductor is a double winding transformer with high magnetic excited current and wide air gaps;

by utilizing the different turn ratios of said transformer to coordinate voltages and currents, such that a low voltage side has less turns of winding and large current, and a high voltage side is vise versa.

41. A boost converter of claim 38, wherein said serially connected passive regenerative snubber not only can absorb circuit induction energy and but also the leakage induction energy of said primary winding of said coupling inductor, where the absorbed energy can be used to boost voltage, and it further provides a current passage for said coupling inductor of said secondary circuit when said semi-conductor switch is turned on;

this is different from traditional coupling induction configuration and the key in providing bi-directional magnetic passage; and

a higher leakage induction of said primary winding of said coupling inductor will reduces the induction voltage of said secondary winding;

by utilizing said passive regenerative snubber plus increased conducting time of said semi-conductor power switch, a constant output voltage can be maintained;

thus, in the present design a transformer with high induction leakage can be tolerated, and it is not limited to high coupling coefficient sandwich winding method where traditional two separated windings will fulfill the purpose.

42. A boost converter of claim 38, wherein said clamping diode of said serially connected passive regenerative snubber connects to said semi-conductor power switch and said clamping capacitor to withstand the same voltage that said semi-conductor power switch withstands;

hence a low voltage low conduction loss Schottky diode can be used.

44. A boost converter of claim 38, wherein when the reverse voltage of said rectify diode of said filter circuit is higher than the difference between the DC output voltage and the voltage of said clamping capacitor of said serially connected passive regenerative snubber, said discharge diode of said first passive regenerative snubber starts to conduct;

and therefore it withstands a lower voltage than the output voltage without additional snubber installed;

said diode and said discharge diode of said passive regenerative snubber compensate each other and avoid the problem of reverse-recovery current of the diode too high.