Frequency limited resonant regulator useful in, for example, a half-bridge inverter

• US 4,729,085 A
• Filed: 12/29/1986
• Issued: 03/01/1988
• Est. Priority Date: 12/29/1986
• Status: Expired due to Term

• Current Assignee: RCA Corporation
• Original Assignee: RCA Corporation
• Inventors: Truskalo, Walter
• Primary Examiner(s): BEHA JR, WILLIAM
• Application Number:
  US06/946,867
• Time in Patent Office: 428 Days
• Field of Search: 363/16, 363/17, 363/25, 363/56, 363/79, 363/80, 363/98, 363/75, 323/248
• US Class Current: 363/56.02
• CPC Class Codes: H02M 3/3376 with automatic control of output voltage or current
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

In a resonant regulator power supply, a resonant circuit is coupled to a source of alternating input voltage that is controllable in operating frequency. A power transformer primary winding is coupled across the capacitive element of the resonant circuit for generating an output voltage across a secondary winding. A control circuit varies the operating frequency in a negative feedback loop to regulate the output voltage on the positive slope of the frequency characteristic curve. A frequency limiting circuit prevents the operating frequency from passing through the resonance frequency of the resonant circuit.

Claims

1. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage; and

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including means for developing a first sense voltage representative of an inductive voltage developed by said inductive element and means for developing a second sense voltage representative of a capacitive voltage developed by said capacitive element.

2. A power supply according to claim 1 wherein normal operation is in a range of said operating frequency that is below said resonance frequency.

3. A power supply according to claim 1 wherein normal operation is in a range of said operating frequency that is below said resonance frequency.

4. A power supply according to claim 1 wherein said first sense voltage developing means comprises a sense winding magnetically coupled to said inductive element.

5. A power supply according to claim 1 wherein said second sense voltage developing means includes a transformer having a first winding coupled to said capacitive element and having a second winding for developing said second sense voltage.

6. A power supply according to claim 5 wherein said first sense voltage developing means comprises a sense winding magnetically coupled to said inductive element.

7. A power supply according to claim 1 wherein said output supply voltage generating means includes a power transformer having a first winding coupled to said capacitive element, a second winding for generating said output supply voltage, and a third winding for developing said second sense voltage.

8. A power supply according to claim 7 wherein said first sense voltage developing means comprises a sense winding magnetically coupled to said inductive element.

9. A power supply according to claim 1 wherein said frequency limiting circuit includes means responsive to said first and second sense voltages for developing a third sense voltage indicative of a difference between said inductive and capacitive voltages.

10. A power supply according to claim 9 wherein said third sense voltage comprises the algebraic sum of said first and second sense voltages such that a magnitude of said third sense voltage is indicative of the closeness of said operating frequency to said resonance frequency.

11. A power supply according to claim 10 wherein a first polarity of said third sense voltage is indicative of said operating frequency being one of a below-resonance frequency and an above-resonance frequency.

12. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage, including means for generating, in accordance with said negative feedback loop, a first frequency control signal that varies in a given manner as said operating frequency approaches said resonance frequency from a given direction; and

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including means for generating a second frequency control signal that varies in a manner opposite that of said first control signal as said operating frequency approaches said resonance frequency from said given direction.

13. A power supply according to claim 12 wherein said control circuit includes means for supplying said first frequency control signal to said source of alternating input voltage when said operating frequency is within a given frequency range that is on one side of said resonance frequency and for supplying said second frequency control signal when said operating frequency is within a given limit of said resonance frequency.

14. A power supply according to claim 12 wherein said frequency limiting circuit substitutes said second frequency control signal when said operating frequency is within a given limit of said resonance frequency.

15. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage, including a first amplifier for amplifying a negative feedback voltage representative of said output supply voltage; and

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including means coupled to said resonant circuit for generating first and second AC signals and means including a second amplifier responsive to said first and second AC signals for generating a frequency sense voltage that is indicative of the closeness of said operating frequency to said resonance frequency.

16. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage, including a first amplifier for amplifying a negative feedback voltage representative of said output supply voltage; and

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including a second amplifier having a gain that is substantially greater than that of said first amplifier for amplifying a frequency sense voltage that is indicative of the closeness of said operating frequency to said resonance frequency.

17. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage, including a first amplifier for amplifying a negative feedback voltage representative of said output supply voltage;

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including a second amplifier from amplifying a frequency sense voltage that is indicative of the closeness of said operating frequency to said resonance frequency; and

means for combining outputs of said first and second amplifiers, wherein a magnitude of the output of said first amplifier tends to vary in a given sense when said operating frequency varies in a first direction, whereas a magnitude of the output of said second amplifier tends to vary in an opposing sense.

18. A resonant regulator power supply, comprising:

a source of alternating input voltage, controllable in operating frequency;

a resonant circuit coupled to and excited by said source and having associated therewith a resonance frequency, said resonant circuit including an inductive element and a capacitive element;

means coupled to said resonant circuit for generating an output supply voltage;

a control circuit coupled to said source and responsive to said output supply voltage for varying said operating frequency in a negative feedback loop to regulate said output supply voltage, including a first amplifier for amplifying a negative feedback voltage representative of said output supply voltage;

a frequency limiting circuit coupled to said resonant circuit for preventing said operating frequency from passing through said resonance frequency, including a second amplifier for amplifying a frequency sense voltage that is indicative of the closeness of said operating frequency to said resonance frequency; and

a switching arrangement coupled to the two amplifiers for preventing said source of alternating input voltage from responding to said frequency sense voltage when said operating frequency is within a first range of frequencies on one side of said resonance frequency and for preventing said source from responding to said negative feedback voltage when said operating frequency is within a given limit of said resonance frequency.

19. A power supply according to claim 18 wherein said switching arrangement comprises first and second diodes series coupled with respective outputs of said first and second amplifiers, said frequency sense voltage blocking conduction of said first diode when said operating frequency approaches said resonance frequency to within said given limit.