Loss and noise reduction in power converters

Abstract

An apparatus includes (a) switching power conversion circuitry including an inductive element connected to deliver energy via a unidirectional conducting device from an input source to a load during a succession of power conversion cycles, and circuit capacitance that can resonate with the inductive element during a portion of the power conversion cycles to cause a parasitic oscillation, and (b) clamp circuitry connected to trap energy in the inductive element and reduce the parasitic oscillation.

1. Apparatus comprising:
 switching power conversion apparatus for converting power from an input source for delivery to a load comprising an inductive element connected to deliver energy via a unidirectional conducting device from said input source to said load during a succession of power conversion cycles,  
 circuit capacitance which can resonate with said inductive element during a potion of said power conversion cycle to cause a parasitic oscillation unrelated to the power conversion process, and  
 clamp circuitry configured to trap energy in the inductive element and prevent said parasitic oscillation.  
 
     
     
       2. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a unipolar, non-isolated boost converter comprising a shunt switch. 
     
     
       3. The apparatus of  claim 2  in which the shunt switch is controlled to cause the power conversion to occur in a discontinuous mode. 
     
     
       4. The apparatus of  claim 1  in which the clamp circuitry is configured to trap the energy in the inductor in a manner that is essentially non-dissipative. 
     
     
       5. The apparatus of  claim 1  in which the clamp circuitry comprises elements configured to trap the energy by short-circuiting the inductor during a controlled time period. 
     
     
       6. The apparatus of  claim 1  in which the inductive element comprises a choke. 
     
     
       7. The apparatus of  claim 1  in which the inductive element comprises a transformer. 
     
     
       8. The apparatus of  claim 5  in which the elements comprise a second switch connected effectively in parallel with the inductor. 
     
     
       9. The apparatus of  claim 8  in which the second switch is connected directly in parallel with the inductor. 
     
     
       10. The apparatus of  claim 8  in which the second switch is inductively coupled in parallel with the inductor. 
     
     
       11. The apparatus of  claim 8  in which the second switch comprises a field effect transistor in series with a diode. 
     
     
       12. The apparatus of  claim 8  wherein said power conversion apparatus is  comprises a unipolar, non-isolated boost converter comprising a shunt switch and a switch controller, said switch controller controlling the timing of a power delivery period during which said shunt switch is open and a shunt period during which the shunt switch is closed. 
     
     
       13. The apparatus of  claim 12  in which the shunt switch is controlled to cause the power conversion to occur in a discontinuous mode. 
     
     
       14. The apparatus of  claim 12  in which the second switch is opened for a period before the shunt switch is closed in order to discharge parasitic capacitances in the apparatus. 
     
     
       15. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a unipolar, isolated, single-ended forward converter. 
     
     
       16. The apparatus of  claim 15  wherein said power conversion apparatus is  comprises a buck converter. 
     
     
       17. The apparatus of  claim 15  wherein said power conversion apparatus is  comprises a flyback converter. 
     
     
       18. The apparatus of  claim 15  wherein said single-ended forward converter is  comprises a zero-current switching converter. 
     
     
       19. The apparatus of  claim 15  wherein said single-ended forward converter is  comprises a PWM converter. 
     
     
       20. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a bipolar, non-isolated, boost converter. 
     
     
       21. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a bipolar, non-isolated boost converter. 
     
     
       22. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a bipolar, non-isolated buck converter. 
     
     
       23. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a bipolar, non-isolated boost converter. 
     
     
       24. The apparatus of  claim 1  wherein said power conversion apparatus is  comprises a bipolar, isolated buck converter. 
     
     
       25. In a power converter which converts power from an input source for delivery to a load during a succession of power conversion cycles and which comprises an inductive element connected to deliver power via a unidirectional conducting device from said input source to said load and a circuit capacitance which can resonate with said inductive element during a portion of said power conversion cycle to cause a parasitic oscillation unrelated to the power conversion process,
 a method for preventing said parasitic oscillations comprising  
 providing clamp circuitry for trapping energy in the inductive element during a portion of the power conversion cycle.  
 
     
     
       26. The method of  claim 25  also including releasing the energy from the inductor essentially non-dissipatively. 
     
     
       27. The method of  claim 17  wherein the trapping of energy comprises short-circuiting the inductive element during a controlled time period. 
     
     
       28. The method of  claim 27  in which the short-circuiting is done by a second switch connected effectively in parallel with the inductive element. 
     
     
       29. The apparatus of  claim 28  also including opening the second switch for a portion of the power conversion cycle in order to discharge parasitic capacitances. 
     
     
       30. Apparatus comprising
   switching power conversion apparatus for converting power from an input source for delivery to a load comprising an inductive element connected to deliver energy from said input source to said load during a succession of power conversion cycles,        clamp circuitry configured to hold energy in the inductive element, and        control circuitry configured to regulate the on and off periods of the clamp circuitry such that the clamp circuitry is configured to carry a reverse current flowing in the inductor and is turned off at a time when a remaining current is flowing in the inductor, wherein the remaining current has a level that is at least a substantial portion of a peak value of the reverse current.      
     
     
       31. The apparatus of  claim 30  wherein the remaining current is used to charge or discharge parasitic capacitances.  
     
     
       32. A method comprising:
   providing power conversion circuitry having an inductive element connected to deliver power from an input source to a load during a succession of power conversion cycles;        providing clamp circuitry for holding energy in the inductive element during a portion of the power conversion cycle;        providing control circuitry for controlling the on and off times of the clamp circuitry,        configuring the on and off times of the clamp circuitry to hold energy in the inductive element during the on time of the clamp and to release a substantial portion of the held energy during the off time of the clamp.      
     
     
       33. The method of  claim 32  wherein the release of the held energy is used to charge or discharge parasitic capacitances.  
     
     
       34. A method comprising:
   providing power conversion circuitry having an inductive element connected to deliver power from an input source to a load during a succession of power conversion cycles;        providing clamp circuitry for conducting a current flowing in the inductive element during a portion of the power conversion cycle;        providing control circuitry for controlling the on and off times of the clamp circuitry;        configuring the on and off times of the clamp circuitry to carry a reverse current flowing in the inductor and to turn off the clamp circuitry before the reverse current flowing in the inductor decays essentially to zero.      
     
     
       35. The method of  claim 34  wherein the reverse current flowing in the inductor is used to charge or discharge parasitic capacitances during the off time of the clamp.