Variable-frequency variable-input-voltage converter with minimum frequency limit

• US 5,764,495 A
• Filed: 12/31/1996
• Issued: 06/09/1998
• Est. Priority Date: 05/01/1996
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Faulk, Richard A.
• Primary Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US08/775,615
• Time in Patent Office: 525 Days
• Field of Search: 363/16, 363/20, 363/21, 363/97, 363/131, 363/163, 363/165, 323/301, 323/303
• US Class Current: 363/21.13
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/33507 with automatic control of the output voltage or current, e.g. flyback converters H02M3/33561, H02M3/33569 take precedence
• CPC Class Codes: H02M 3/33576 having at least one active switching element at the secondary side of an isolation transformer

Abstract

A variable-input-voltage variable-switching-frequency power converter with a minimum frequency limit. The switching frequency never goes below a certain minimum while the converter is on. Thus switching frequency is dependent on input voltage, for input voltages in one range, and is NOT dependent on input voltage, for input voltages in another range.

Claims

1. A power conversion method, comprising the steps of:

(a.) repeatedly switching a transistor to switch an input voltage, which varies over a voltage range of at least 3;

1, onto an inductance, while

keeping the frequency of said switching step substantially fixed whenever said input voltage falls within a first range of magnitudes, and

varying the frequency of said switching step in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;

wherein said magnitudes of said second range are all greater than said magnitudes of said first range; and

(b.) coupling power out from said inductance to provide an output of converted power.

2. The method of claim 1, wherein said step of coupling power out uses a secondary inductance which is magnetically coupled to said inductance.

3. The method of claim 1, wherein said output of converted power is used to provide power to a computer system.

4. The method of claim 1, wherein said output of converted power is used to provide power to an electrical storage and recharging system.

12. The method of claim 1, wherein said transistor is a field-effect-transistor.

27. The power conversion method of claim 1, wherein said input voltage is a substantially unfiltered full-wave rectified voltage.

28. The power conversion method of claim 1, wherein the frequency of said switching step increases with said input voltage, whenever said input voltage falls within said second range of magnitudes.

29. The power conversion method of claim 1, wherein the frequency of said switching is substantially fixed at a frequency which is above the audible range whenever said input voltage falls within said first range of magnitudes.

5. A power converter circuit, comprising:

a transformer having primary and secondary windings;

a controllable switch connected to vary current, from an input voltage connection, through said primary winding;

wherein said input voltage varies substantially continuously;

a power output connection operatively connected to draw power from said secondary winding of said transformer; and

control logic operatively connected to control switching of said switch in a control relationship wherein

the frequency of said switching is substantially fixed whenever said input voltage falls within a first range of magnitudes, and

the frequency of said switching is varied in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;

wherein said magnitudes of said second range are all greater than said magnitudes of said first range.

6. The circuit of claim 5, wherein said power output connections are configured to provide power to a computer system.

7. The circuit of claim 5, wherein said power output connections are configured to provide power to an electrical storage and recharging system.

13. The circuit of claim 5, wherein said controllable switch is a field-effect-transistor.

14. The circuit of claim 5, wherein said control logic comprises a first controller operatively connected to said secondary winding of said transformer and a second controller operatively connected to said primary winding of said transformer;

wherein said first controller operates as a master in a master-slave relationship with said second controller.

15. The circuit of claim 5, wherein said control logic comprises a first controller operatively connected to said secondary winding of said transformer and a second controller operatively connected to said primary winding of said transformer;

wherein said first controller communicates with said second controller through a pulse transformer which is separate from said first transformer.

16. The circuit of claim 5, wherein said control logic on said secondary winding of said transformer is operatively connected through a first diode to a second diode, the combination of which is used to control the frequency of said switching.

30. The power conversion circuit of claim 5, wherein said input voltage is a substantially unfiltered full-wave rectified voltage.

31. The power conversion circuit of claim 5, wherein the frequency of said switching step increases with said input voltage, whenever said input voltage falls within said second range of magnitudes.

32. The power conversion circuit of claim 5, wherein the frequency of said switching is substantially fixed at a frequency which is above the audible range whenever said input voltage falls within said first range of magnitudes.

8. A power converter circuit, comprising:

a transformer having primary and secondary windings;

a controllable switch connected to vary current, from an input voltage connection, through said primary winding;

wherein said input voltage varies substantially continuously;

a power output connection operatively connected to draw power from said secondary winding of said transformer; and

secondary-side control logic operatively connected to draw power from said secondary winding of said transformer, and configured to control switching of said switch in a control relationship wherein

the frequency of said switching is substantially fixed whenever said input voltage falls within a first range of magnitudes, and

the frequency of said switching is varied in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;

wherein said magnitudes of said second range are all greater than said magnitudes of said first range.

9. The circuit of claim 8, wherein said power output connections are configured to provide power to a computer system.

10. The circuit of claim 8, wherein said power output connections are configured to provide power to an electrical storage and recharging system.

17. The circuit of claim 8, wherein said controllable switch is a field-effect-transistor.

18. The circuit of claim 8, wherein said secondary-side control logic of said transformer operates as a master in a master-slave relationship with a primary-side control logic operatively connected to draw power from said primary winding of said transformer.

19. The circuit of claim 8, wherein said secondary-side control logic is operatively connected through a first diode to a second diode, the combination of which are used to control the frequency of said switching.

33. The power conversion circuit of claim 8, wherein said input voltage is a substantially unfiltered full-wave rectified voltage.

34. The power conversion circuit of claim 8, wherein the frequency of said switching step increases with said input voltage, whenever said input voltage falls within said second range of magnitudes.

35. The power conversion circuit of claim 8, wherein the frequency of said switching is substantially fixed at a frequency which is above the audible range whenever said input voltage falls within said first range of magnitudes.

11. A computer system, comprising:

memory, and a microprocessor operatively connected to read and write said memory;

a graphics controller connected to said microprocessor;

a video display connected to said graphics controller;

a transformer having primary and secondary windings;

a controllable switch connected to vary current, from an input voltage connection, through said primary winding;

wherein said input voltage varies substantially continuously;

a power output connection operatively connected to draw power from said secondary winding of said transformer; and

control logic operatively connected to control switching of said switch in a control relationship wherein

the frequency of said switching is substantially fixed whenever said input voltage falls within a first range of magnitudes, and

the frequency of said switching is varied in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;

wherein said magnitudes of said second range are all greater than said magnitudes of said first range.

20. The system of claim 11, wherein said controllable switch is a field-effect-transistor.

21. The system of claim 11, wherein said control logic on said secondary winding of said transformer operates as a master in a master-slave relationship with a control logic on said primary winding operatively connected to draw power from said primary winding of said transformer.

22. The system of claim 11, wherein said control logic circuit on said secondary winding is operatively connected through a first diode to a second diode, the combination of which is used to control the frequency of said switching.

36. The computer system of claim 11, wherein said input voltage is a substantially unfiltered full-wave rectified voltage.

37. The computer system of claim 11, wherein the frequency of said switching step increases with said input voltage, whenever said input voltage falls within said second range of magnitudes.

38. The computer system of claim 11, wherein the frequency of said switching is substantially fixed at a frequency which is above the audible range whenever said input voltage falls within said first range of magnitudes.

23. A power conversion circuit, comprising:

means for repeatedly switching a transistor to switch an input voltage, which varies over a voltage range of at least 3;

1, onto an inductance, while

keeping the frequency of said switching substantially fixed whenever said input voltage falls within a first range of magnitudes, and

varying the frequency of said switching in dependence on said input voltage, whenever said input voltage falls within a second range of magnitudes;

wherein said magnitudes of said second range are all greater than said magnitudes of said first range; and

means for coupling power out from said inductance to provide an output of converted power.

24. The power conversion circuit of claim 23, wherein a secondary inductance is magnetically coupled to said inductance.

25. The power conversion circuit of claim 23, wherein said output of converted power is used to provide power to a computer system.

26. The power conversion circuit of claim 23, wherein said output of converted power is used to provide power to an electrical storage and recharging system.

39. The power conversion circuit of claim 23, wherein said input voltage is a substantially unfiltered full-wave rectified voltage.

40. The power conversion circuit of claim 23, wherein the frequency of said switching step increases with said input voltage, whenever said input voltage falls within said second range of magnitudes.

41. The power conversion circuit of claim 23, wherein the frequency of said switching is substantially fixed at a frequency which is above the audible range whenever said input voltage falls within said first range of magnitudes.