Isolated dual converter having primary side internal feedback for output regulation

• US 6,381,150 B2
• Filed: 11/19/1999
• Issued: 04/30/2002
• Est. Priority Date: 11/19/1999
• Status: Expired due to Term

• Current Assignee: Dialog Semiconductor Incorporated (Renesas Electronics Corporation)
• Original Assignee: iWatt, Inc. (Renesas Electronics Corporation)
• Inventors: Telefus, Mark D.
• Primary Examiner(s): Vu, Bao Q.
• Application Number:
  US09/444,032
• Publication Number:
  US 20020015315A1
• Time in Patent Office: 893 Days
• Field of Search: 363/15, 363/16, 363/24, 363/25, 363/26, 363/40, 363/41, 363/131
• US Class Current: 363/15
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current

Abstract

The present invention comprises an isolated dual power supply having an internal feedback loop. The dual power supply comprises a modulated switched power converter generating an internal regulated voltage output coupled to an alternating current tank. The alternating current tank has a first and a second power switch that are alternately switched ON at a 50% duty cycle. When the first switch is ON, the internal regulated voltage output is coupled to a storage capacitor and a primary winding of a transformer in the alternating current tank wherein the storage capacitor is charged and a current flows in a first direction through the primary winding. Alternatively, when the second switch is ON, the charged storage capacitor discharges and a current flows in a second direction opposite to the first direction through the primary winding. In this fashion, the transformer becomes a linear device, allowing the use of internal feedback to control the external output of the transformer.

Claims

1. A power converter, comprising:

a pulse width modulated switching power converter having a power switch for regulating an internal voltage output; and

an alternating current tank coupled to the internal voltage output, the alternating current tank having a storage capacitor and a transformer having a primary winding, a first switch that, when ON, couples the storage capacitor to the internal voltage output wherein the storage capacitor is charged and a first current flows in a first direction through the primary winding, a second switch that, when ON, permits the charged storage capacitor to discharge, wherein a second current flows in a second direction opposite to the first direction through the primary winding, and duty cycle control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and the second switch being ON when the first switch is OFF, the duty cycle control circuitry alternately switching the first and second switches at a constant duty cycle and such that the ON and OFF times of each switch are substantially equal, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch.

2. The power converter of claim 1, wherein the modulated switching power converter is a pulse width modulated boost power converter.

3. The power converter of claim 2, wherein the storage capacitor is in series with the primary winding.

4. The power converter of claim 3, wherein the storage capacitor is a resonant capacitor, the resonant capacitor and a leakage inductance of the primary winding forming a series resonant tank having a resonant frequency less than or equal to a period of the duty cycle control circuitry, whereby the first and second currents are each half-wave quasi-sinusoidal currents.

5. The power converter of claim 4, wherein the voltage across the secondary winding is regulated by adjusting the pulse width modulation of the power switch in response to sensing a peak of the first and second currents.

6. The power converter of claim 5, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the internal voltage output.

7. The power converter of claim 6, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the voltage across the secondary winding through an isolator.

8. The power converter of claim 7, wherein the isolator is an optoisolator.

9. The power converter of claim 2, wherein the storage capacitor is a resonant capacitor in parallel with the primary winding, the resonant capacitor and a leakage inductance of the primary winding forming a parallel resonant tank having a resonant frequency less than or equal to a period of the duty cycle control circuitry, whereby when the first switch is ON, a first half-wave quasi-sinusoidal voltage is impressed across the primary winding, and when the second switch is ON, a second half-wave quasi-sinusoidal voltage is impressed across the primary winding, the second half-wave quasi-sinusoidal voltage being antipodal to the first half-wave quasi-sinusoidal voltage.

10. The power converter of claim 9, wherein the voltage across the secondary winding is regulated by adjusting the pulse width modulation of the power switch in response to sensing the first and second currents.

11. The power converter of claim 1, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the internal voltage output.

12. The power converter of claim 11, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the voltage across the secondary winding through an isolator.

13. The power converter of claim 12, wherein the isolator is an optoisolator.

14. The power converter of claim 1, wherein the pulse width modulated switching power converter is a buck power converter.

15. The power converter of claim 14, wherein the storage capacitor is in series wit h the primary winding.

16. The power converter of claim 15, wherein the storage capacitor is a resonant capacitor, the resonant capacitor and a leakage inductance of the primary winding forming a series resonant tank having a resonant frequency less than or equal to a period of the duty cycle control circuitry, whereby the first and second currents are each half-wave quasi-sinusoidal currents.

17. The power converter of claim 16, wherein the voltage across the secondary winding is regulated by adjusting the pulse width modulation of the power switch in response to sensing a peak of the first and second currents.

18. The power converter of claim 17, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the internal voltage output.

19. The power converter of claim 18, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the voltage across the secondary winding through an isolator.

20. The power converter of claim 19 wherein the isolator is an optoisolator.

21. The power converter of claim 14, wherein the storage capacitor is a resonant capacitor in parallel with the primary winding, the resonant capacitor and a leakage inductance of the primary winding forming a parallel resonant tank having a resonant frequency less than or equal to a period of the duty cycle control circuitry, whereby when the first switch is ON, a first half-wave quasi-sinusoidal voltage is impressed across the primary winding, and when the second switch is ON, a second half-wave quasi-sinusoidal voltage is impressed across the primary winding, the second half-wave quasi-sinusoidal voltage being antipodal to the first half-wave quasi-sinusoidal voltage.

22. The power converter of claim 21, wherein the voltage across the secondary winding is regulated by adjusting the pulse width modulation of the power switch in response to sensing the first and second currents.

23. The power converter of claim 22, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the internal voltage output.

24. The power converter of claim 23, wherein the voltage across the secondary winding is further regulated by adjusting the pulse width modulation of the power switch in response to sensing the voltage across the secondary winding through an isolator.

25. The power converter of claim 24, wherein the isolator is an optoisolator.

26. A circuit for use in a power supply, comprising:

a power switch coupled to a voltage input;

a pulse width modulator for controlling a duty cycle of the power switch;

a diode having its anode coupled to the voltage input;

a first switch coupled to the cathode of the diode and to a voltage output;

a second switch coupled to the voltage output; and

control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and vice versa, the control circuitry alternately switching the first and second switches at a constant duty cycle, and such that the ON and OFF times of each switch are substantially equal, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch.

27. The circuit of claim 26, wherein the power switch, the diode, the pulse width modulator, the first switch, the second switch and the control circuitry are integrated on the circuit.

28. A power converter, comprising:

a pulse width modulated switching power converter having a power switch for regulating an internal voltage output;

a plurality of alternating current tanks coupled to the internal voltage output, each alternating current tank in the plurality of alternating current tanks having a storage capacitor and a transformer having a primary winding, a first switch that, when ON, couples the storage capacitor to the internal voltage output wherein the storage capacitor is charged and a first current flows in a first direction through the primary winding, a second switch that, when ON, permits the charged storage capacitor to discharge, wherein a second current flows in a second direction opposite to the first direction through the primary winding, and duty cycle control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and the second switch being ON when the first switch is OFF, the duty cycle control circuitry alternately switching the first and second switches at a constant duty cycle, and such that the ON and OFF times of each switch are substantially equal, whereby, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch; and

a clock coupled to the plurality of the alternating current tanks, wherein the first switches are switched synchronously with each other and the second switches are switched synchronously with each other.

29. The power converter of claim 28, wherein the modulated switching power converter is a boost power converter.

30. The power converter of claim 29, wherein within each of the alternating current tanks, the storage capacitor is in series with the primary winding.

31. The power converter of claim 30, wherein within each of the alternating current tanks, the storage capacitor is a resonant capacitor, the resonant capacitor and a leakage inductance of the primary winding forming a series resonant tank having a resonant frequency less than or equal to a period of the 50% duty cycle control circuitry, whereby the first and second currents are each half-wave quasi-sinusoidal currents.

32. The power converter of claim 29, wherein within each of the alternating current tanks, the storage capacitor is a resonant capacitor in parallel with the primary winding, the resonant capacitor and a leakage inductance of the primary winding forming a parallel resonant tank having a resonant frequency less than or equal to a period of the 50% duty cycle control circuitry, whereby when the first switch is ON, a first half-wave quasi-sinusoidal voltage is impressed across the primary winding, and when the second switch is ON, a second half-wave quasi-sinusoidal voltage is impressed across the primary winding, the second half-wave quasi-sinusoidal voltage being antipodal to the first half-wave quasi-sinusoidal voltage.

33. The power converter of claim 28, wherein the modulated switching power converter is a pulse width modulated buck power converter.

34. The power converter of claim 33, wherein within each of the alternating current tanks, the storage capacitor is in series with the primary winding.

35. The power converter of claim 34, wherein within each of the alternating current tanks, the storage capacitor is a resonant capacitor, the resonant capacitor and a leakage inductance of the primary winding forming a series resonant tank having a resonant frequency less than or equal to a period of the 50% duty cycle control circuitry, whereby the first and second currents are each half-wave quasi-sinusoidal currents.

36. The power converter of claim 33, wherein within each of the alternating current tanks, the storage capacitor is a resonant capacitor in parallel with the primary winding, the resonant capacitor and a leakage inductance of the primary winding forming a parallel resonant tank having a resonant frequency less than or equal to a period of the 50% duty cycle control circuitry, whereby when the first switch is ON, a first half-wave quasi-sinusoidal voltage is impressed across the primary winding, and when the second switch is ON, a second half-wave quasi-sinusoidal voltage is impressed across the primary winding, the second half-wave quasi-sinusoidal voltage being antipodal to the first half-wave quasi-sinusoidal voltage.

37. A power converter, comprising:

a first circuit stage including a modulated switching power converter having a power switch for regulating an internal voltage output; and

a second circuit stage including an alternating current tank coupled to the internal voltage output, the alternating current tank having a storage capacitor and a transformer having a primary winding, a first switch that, when ON, couples the storage capacitor to the internal voltage output wherein the storage capacitor is charged and a first current flows in a first direction through the primary winding, a second switch that, when ON, permits the charged storage capacitor to discharge, wherein a second current flows in a second direction opposite to the first direction through the primary winding, and duty cycle control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and the second switch being ON when the first switch is OFF, the duty cycle control circuitry alternately switching the first and second switches it a constant duty cycle, and such that the ON and OFF times of each switch are substantially equal, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch.

38. A circuit for use in a power supply, comprising

a first circuitry stage including:

a power switch coupled to a voltage input;

a pulse width modulator for controlling a duty cycle of the power switch;

a diode having its anode coupled to the voltage input; and

a second circuitry stage coupled to the first circuitry stage, said second circuitry stage including;

a first switch coupled to the cathode of the diode and to a voltage output;

a second switch coupled to the voltage output; and

control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and vice versa, the control circuitry alternately switching the first and second switches at a constant duty cycle, and such that the ON and OFF times of each switch are substantially equal, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch.

39. A power converter, comprising:

a first circuitry stage including a modulated switching power converter having a power switch for regulating an internal voltage output;

a second circuitry stage including a plurality of alternating current tanks coupled to the internal voltage output, each alternating current tank in the plurality of alternating current tanks having a storage capacitor and a transformer having a primary winding, a first switch that, when ON, couples the storage capacitor to the internal voltage output wherein the storage capacitor is charged and a first current flows in a first direction through the primary winding, a second switch that, when ON, permits the charged storage capacitor to discharge, wherein a second current flows in a second direction opposite to the first direction through the primary winding, and duty cycle control circuitry for alternately switching ON and OFF the first and second switches, the first switch being ON when the second switch is OFF and the second switch being ON when the first switch is OFF, the duty cycle control circuitry alternately switching the first and second switches at a constant duty cycle, and such that the ON and OFF times of each switch are substantially equal, whereby a voltage produced across a secondary winding of the transformer is regulated by modulating the power switch; and

a clock circuit coupled to the plurality of the alternating current tanks, wherein the first switches are switched synchronously with each other and the second switches are switched synchronously with each other.

40. A dual stage power converter, comprising:

a first stage modulated switching power converter having a regulated output; and

a second stage alternating current tank coupled to said output of said first stage, said second stage having a first switch and second switch that are actuated by alternately switching ON and OFF the first and second switches, the first switch being ON at approximately the same time the second switch is OFF and vice versa, and said first and second switches being actuated at a constant duty cycle.