Claims
- 1. A method of regulating voltage at an output of a switching power converter, the converter comprising a switch and pulse modulating control circuitry, the pulse modulating control circuitry producing power pulses for cycling the switch ON and OFF, wherein if the switch is cycled ON and OFF according to a power pulse cycle, power is transferred from a source to a load, the method comprising:
sensing an output voltage feedback signal; comparing the sensed feedback signal to a reference at a determined time during a cycling of the switch; and regulating the output voltage by controlling turn ON and turn OFF times of the switch, in response to the output of the comparator.
- 2. The method of claim 1, wherein the comparison is accomplished by one of binary comparison logic, ternary comparison logic, and signed digital comparison logic.
- 3. The method of claim 1, wherein the determined time is determined at each cycling of the switch.
- 4. The method of claim 3, wherein the converter is a transformer-coupled power converter having an output coupled through a rectifying element, the output voltage feedback signal originates from a primary side of the converter, and the determined time is an instant at which current flowing through a secondary rectifying element is small and substantially constant from cycle to cycle of the switch.
- 5. The method of claim 1, wherein the determined time is an instant at which the output voltage feedback signal corresponds to the output voltage at the load plus a small, substantially constant voltage drop measured from cycle to cycle of the switch.
- 6. The method of claim 1, wherein the determined time is an instant at which current flowing through a secondary rectifying element is small and substantially constant from cycle to cycle of the switch.
- 7. The method of claim 1, wherein the converter is a flyback converter having a transformer flux reset point, the output voltage feedback signal is a reflected flyback voltage signal, and the determined time is a fixed backward offset time from the transformer flux reset point.
- 8. The method of claim 7, further comprising determining the transformer flux reset point using a measured or calculated value of a period of resonant oscillation of the reflected flyback voltage signal.
- 9. The method of claim 7, further comprising determining the transformer flux reset point using a point at which voltage across an auxiliary transformer winding of the converter is approximately zero.
- 10. The method of claim 7, further comprising determining the transformer flux reset point using a point at which voltage across a primary transformer winding of the converter is approximately zero.
- 11. The method of claim 1, wherein the converter is a forward converter having an output inductor, the output voltage feedback signal is a reflected voltage across an auxiliary transformer winding coupled to the output inductor, and the determined time is a fixed backward offset time from a point of flux reset of the output inductor.
- 12. The method of claim 1, wherein the converter is a direct-coupled boost converter having a rectifying element, the output voltage feedback signal corresponds to-a voltage across the switch during an OFF time, and the determined time is an instant at which current through the rectifying element is small and substantially constant from cycle to cycle of the switch.
- 13. The method of claim 1, wherein the converter is a direct-coupled buck converter having a rectifying element, the output voltage feedback signal corresponds to a differential voltage across an output inductor during an OFF time of the switch, and the determined time is an instant at which current through the rectifying element is small and substantially constant from cycle to cycle of the switch.
- 14. The method of claim 1, wherein determining the turn ON and turn OFF times of the switch in response to a present comparison is based at least in part on comparisons of the sensed feedback signal to the reference made during one or more previous switch cycles.
- 15. A method of regulating power between a source and a load, comprising:
providing a power converter, the converter comprising a switch and pulse modulating control circuitry, the pulse modulating control circuitry producing power pulses for cycling the switch ON and OFF, wherein if the switch is cycled ON and OFF according to a power pulse cycle, power is transferred from the source to the load; sensing an output voltage feedback signal originating from a primary side of the converter, the sensed feedback signal approximating an output voltage at the load; using a comparator to compare the sensed feedback signal to a reference at an instant at which the sensed feedback signal corresponds to the output voltage at the load plus a small, substantially constant voltage drop measured from cycle to cycle of the switch; and regulating the output voltage by controlling the turn ON and turn OFF times of the switch in response to an output of the comparator.
- 16. The method of claim 15, wherein the comparator is one of a binary comparator, a ternary comparator, and a signed digital comparator.
- 17. The method of claim 15, wherein the converter is a flyback converter having a transformer flux reset point, the output voltage feedback signal is a reflected flyback voltage signal, and the comparison is made at a fixed backward offset from the transformer flux reset point.
- 18. The method of claim 15, wherein the converter is a forward converter having an output inductor, the output voltage feedback signal is a reflected voltage across an auxiliary winding coupled to the output inductor, and the comparison is made at a fixed backward offset time from a point of output inductor flux reset.
- 19. The method of claim 15, wherein comparator outputs from one or more previous switch cycles are used in determining the turn ON and turn OFF times of the switch in response to a present comparator output.
- 20. A method of regulating voltage at an output of a switching power converter, comprising:
sensing an output voltage feedback signal; using a comparator to compare the sensed feedback signal to a reference; using an early/late detector to detect transitions of an output of the comparator relative to an expected transition time within a switching cycle; and regulating the output voltage by controlling the turn ON and turn OFF times of a switch in response to an output of the early/late detector.
- 21. The method of claim 20, wherein the comparator is one of a binary comparator and a ternary comparator.
- 22. The method of claim 20, wherein the expected transition time is determined at each cycling of the switch.
- 23. The method of claim 20, wherein the expected transition time is an instant at which the output voltage feedback signal corresponds to the output voltage at the load plus a small, substantially constant voltage drop measured from cycle to cycle of the switch.
- 24. The method of claim 20, wherein the expected transition time is an instant at which current flowing through a secondary rectifying element is small and substantially constant from cycle to cycle of the switch.
- 25. The method of claim 20, wherein the converter is a flyback converter having a transformer flux reset point, the output voltage feedback signal is a reflected flyback voltage signal, and the expected transition time is at a fixed backward offset time from the transformer flux reset point.
- 26. The method of claim 20, wherein early/late detector outputs from one or more previous switch cycles are used in determining the turn ON and turn OFF times of the switch in response to a present early/late detector output.
- 27. The method of claim 20, wherein the converter is a forward converter having an output inductor, the output voltage feedback signal is a reflected voltage across an auxiliary winding coupled to the output inductor, and the expected transition time is a fixed backward offset time from a point of output inductor flux reset.
- 28. The method of claim 20, wherein the converter is a direct-coupled boost converter, the output voltage feedback signal corresponds to a voltage across the switch during its OFF time, and the expected transition time is an instant at which current through a rectifying element is small and substantially constant from cycle to cycle of the switch.
- 29. The method of claim 20, wherein the converter is a direct-coupled buck converter, the output voltage feedback signal corresponds to a differential voltage across an output inductor during the OFF time of the switch, and the expected transition time is at an instant at which current through a rectifying element is small and substantially constant from cycle to cycle of the switch.
- 30. The method of claim 20, wherein the turn ON times are controlled to coincide with instants at which the voltage across the switch is a minimum.
- 31. A method of regulating voltage at an output of a switching power converter, the converter comprising a switch and pulse modulating control circuitry, the pulse modulating control circuitry producing power pulses for cycling the switch ON and OFF, wherein if the switch is cycled ON and OFF according to a power pulse cycle, power is transferred from a source to a load, the method comprising:
sensing an output voltage feedback signal originating from a primary side of the converter, the sensed feedback signal approximating an output voltage at the load; using a comparator to compare the sensed feedback signal to a reference; using an early/late detector to detect transitions of the output of the comparator relative to an instant at which the sensed feedback signal corresponds to the output voltage at the load plus a small, substantially constant voltage drop measured from cycle to cycle of the switch; and regulating the output voltage by controlling the turn ON and turn OFF times of the switch in response to an output of the early/late detector.
- 32. The method of claim 31, wherein the comparator is one of a binary comparator and a ternary comparator.
- 33. The method of claim 31, wherein early/late detector outputs from one or more previous switch cycles are used in determining one or both of the turn ON time and turn OFF time of the switch in response to a present early/late detector output.
- 34. The method of claim 31, wherein the early/late detector is one of a binary detector, a ternary detector, and a signed digital detector.
- 36. The method of claim 31, wherein the early/late detector is a binary detector, wherein the crossover of the output voltage feedback signal with a reference is signaled by the transition of the binary comparator, and monitoring whether the comparator transition occurs within a specified period of time.
- 37. The method of claim 31, the early/late detector comprising a ternary detector wherein crossover of the output voltage feedback signal with a reference is signaled by the transition of a binary comparator, the method further comprising
starting a timer at the earlier of a comparator transition time or an expected transition time, and terminating the timer upon later of the comparator transition time, the expected transition time, or a timeout of the timer,
- 38. The method of claim 1, wherein the turn ON times for the switch are controlled to coincide with instants at which the voltage across the switch is a minimum.
- 39. The method of claim 38, wherein the power converter is a flyback converter and the output voltage feedback signal is a reflected flyback voltage signal.
- 40. The method of claim 39, further comprising determining turn ON times for the switch based on a point in a switch cycle at which voltage across an auxiliary transformer winding is approximately zero.
- 42. The method of claim 39, further comprising determining turn ON times for the switch based on a point in a switch cycle at which voltage across the primary winding of the power transformer is approximately zero.
- 43. The method of claim 39, further comprising determining turn ON times for the switch based on a measured or calculated value of the period of resonant oscillation of the reflected flyback voltage signal.
RELATED APPLICATION DATA
[0001] This application claims priority to provisional application Serial No. 60/335,723, filed Nov. 29, 2001, which is fully incorporated herein by reference.
Provisional Applications (1)
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Number |
Date |
Country |
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60335723 |
Nov 2001 |
US |