Claims
- 1. A power supply comprising:a transformer-coupled power converter operative to convert an input direct current (DC) voltage to an intermediate DC voltage, said transformer-coupled power converter including: a transformer having at least one primary-side winding and at least one secondary-side winding; at least one pair of free-running primary-side power switches operative to generate a nearly 100% duty cycle secondary-side voltage; and at least one pair of secondary-side rectifiers operative to rectify a secondary-side current from said at least one secondary-side winding to produce said intermediate DC voltage; a buck power converter operative to produce a regulated output voltage from said intermediate DC voltage, said buck output converter including a forward buck switch in series with said at least one secondary-side winding of said transformer, and a freewheeling switch in parallel with said forward buck switch and said at least one secondary-side winding, said forward buck switch being controlled by a control signal; and a pulse width modulation (PWM) control circuit operative to monitor said regulated output voltage and to generate said control signal for said forward buck switch so as to maintain said regulated output voltage within a predetermined regulated range.
- 2. A power supply according to claim 1, wherein said transformer-coupled power converter further includes a free-running oscillator generating free-running gate signals for controlling the switching of said at least one pair of free-running primary-side power switches and a synchronization signal for synchronizing said PWM controller to said free-running gate signals.
- 3. A power supply according to claim 2, further comprising an isolating signal transmission element operative to feed said synchronization signal from said oscillator to said PWM controller.
- 4. A power supply according to claim 3, wherein said isolating signal transmission element is a signal transformer.
- 5. A power supply according to claim 3, wherein said isolating signal transmission element is an opto-coupler.
- 6. A power supply according to claim 1, wherein said freewheeling switch is a diode.
- 7. A power supply according to claim 1, wherein said freewheeling switch is a freewheeling transistor controlled by a control signal being complementary to said control signal for the forward buck switch, and wherein said PWM control circuit is operative to generate said control signal for said freewheeling transistor.
- 8. A power supply according to claim 7, wherein said PWM controller modulates leading edges of pulses composing said complementary control signals for said forward buck switch and said freewheeling transistor.
- 9. A power supply according to claim 1, wherein said PWM controller modulates leading edges of pulses composing said control signal for said forward buck switch.
- 10. A power supply according to claim 1, wherein said switches are operated using a soft-switching technique to reduce switching losses and thereby improve power supply efficiency.
- 11. A power supply according to claim 1, further comprising:a second buck power converter operative to produce a second regulated output voltage from said intermediate DC voltage in response to a second control signal; and a second PWM controller operative to monitor said second regulated output voltage and to generate said second control signal for a forward buck switch in said second buck converter so as to maintain said second regulated output voltage within a second predetermined regulated range.
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/148,164, filed Aug. 10, 1999.
US Referenced Citations (21)
Provisional Applications (1)
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Number |
Date |
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60/148164 |
Aug 1999 |
US |