Control circuit for resonant converters

• US 4,897,775 A
• Filed: 02/24/1988
• Issued: 01/30/1990
• Est. Priority Date: 06/16/1986
• Status: Expired due to Fees

• Current Assignee: Electronic Power Conditioning Incorporated (Schneider Electric SE)
• Original Assignee: Robert F. Frijouf
• Inventors: Klaassens, J. Ben
• Primary Examiner(s): Wong, Peter S.
• Assistant Examiner(s): Sterrett, Jeffrey
• Application Number:
  US07/161,422
• Time in Patent Office: 706 Days
• Field of Search: 363/28, 363/96, 363/136, 363/137, 363/160, 363/164, 363/173
• US Class Current: 363/96
• CPC Class Codes: H02M 7/758 with automatic control of output waveform or frequency
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

An improved control circuits is disclosed for use with a resonant converter having a resonant circuit and a first and a second plurality of switches for transferring electrical power between first and second terminals. The improved control circuit comprises a power transfer control or an outer control loop and a resonant circuit control or an inner control loop with the resonant circuit control having a predictor circuit. The power transfer control regulates the electrical power transferred between the first and second terminals through selective conduction of the first and second plurality of switches for selectively initiating oscillation of the resonant circuit to provide resonant pulses of the resonant circuit. A predictor circuit instantaneously monitors the operation of the resonant converter and instantaneously and continuously predicts prior to the completion of each resonant portion when the initiation of conduction of one of the switches will produce a resonant portion having a final waveform in conformity with a pre-established standard. The resonant circuit control compares an output of the predictor circuit to the pre-established standard for initiating conduction of the switches within each resonant portion to conform each resonant portion to the pre-established standard.

Claims

1. An improved resonant converter for transferring electrical power between first terminal means and second terminal means, comprising in combination:

a resonant circuit including a capacitor and an inductor;

a first and a second plurality of switch means interconnecting said resonant circuit with the first and second terminal means, respectively;

a control circuit comprising outer control means and inner control means having a predictor circuit for controlling said resonant circuit;

said outer control means selectively actuating said switch means for selectively initiating resonant portions in said resonant circuit to transfer electrical power between the first and second terminal means;

sensor means for instantaneously monitoring the operation of the resonant converter;

means connecting said sensor means to said predictor circuit for predicting the final waveform of each resonant portion prior to the completion of the resonant portion; and

said inner control means comparing an output of said predictor circuit to a pre-established standard for initiating conduction of one of said switch means within each resonant portion to conform each of resonant portion to said pre-established standard.

2. An improved resonant converter for transferring electrical power between first terminal means and second terminal means, comprising in combination:

a series resonant circuit including a capacitor and an inductor;

a first and a second plurality of switch means interconnecting said resonant circuit with the first and second terminal means, respectively;

a control circuit comprising outer control means and inner control means having a predictor circuit for controlling said resonant circuit;

said outer control means selectively actuating said switch means for selectively initiating resonant portions in said resonant circuit to transfer electrical power between the first and second terminal means;

sensor means for instantaneously monitoring the voltage on the first and second terminal means and the voltage and current in said resonant circuit;

means connecting said sensor means to said predictor circuit for instantaneously and continuously predicting prior to the completion of the resonant portion when the initiation of conduction of one of said switch means will produce a resonant portion having a final waveform in conformity with said pre-established standard; and

said inner control means comparing an output of said predictor circuit to a pre-established standard for initiating conduction of said one of said switch means within each resonant portion to conform each resonant portion to said pre-established standard.

3. An improved resonant converter as set forth in claim 2, wherein said resonant circuit control mean initiates conduction of said one of said switch means to produce a resonant portion having a substantially constant value of energy in each resonant portion.

4. An improved resonant converter as set forth in claim 2, wherein said resonant circuit control mean initiates conduction of said one of said switch means to limit the voltage on said capacitor below a pre-established voltage level.

5. An improved resonant converter as set forth in claim 2, wherein said resonant circuit control mean initiates conduction of said one of said switch means to limit the current in said resonant circuit below a pre-established current level.

6. An improved resonant converter for transferring electrical power between first terminal means and second terminal means, comprising in combination:

a resonant circuit including a capacitor and an inductor;

a first and a second plurality of switch means interconnecting said resonant circuit with the first and second terminal means, respectively;

a control circuit comprising outer control means and inner control means having a predictor circuit for controlling said resonant circuit;

said outer control means selectively actuating said switch means for selectively initiating resonant portions in said resonant circuit to transfer electrical power between the first and second terminal means;

sensor means for instantaneously monitoring the operation of the resonant converter;

means connecting said sensor means to said inner control means for predicting the final waveform of each of the resonant portion prior to the completion of the resonant portion; and

said inner control means comparing the predicted output of the final waveform of each resonant portion to a pre-established standard for initiating conduction of one of said switch means within each resonant portion to quantize the energy transferred in each resonant portion to be at said pre-established standard.

7. An improved resonant converter for transferring electrical power between first terminal and second terminal means, comprising in combination:

a series resonant circuit including a capacitor and an inductor;

a first and a second plurality of switch means interconnecting said resonant circuit with the first and second terminal means, respectively;

a control circuit resonant comprising outer control means and inner control means having a predictor circuit for controlling said resonant circuit;

said outer control means selectively actuating said switch means for selectively initiating oscillation of said resonant circuit to control the transfer of electrical power between the first and second terminal means;

said oscillation of said resonant circuit comprising a first resonant portion wherein a resonant current flows in a first direction and a second resonant portion wherein a resonant current flows in a second direction;

said inner control means initiating conduction of one of said switch means within each resonant portion to define a first duration of each resonant portion wherein electrical power is transferred from one of the terminal means to said resonant circuit and to define a second duration of each resonant portion wherein electrical power is transferred to one of the terminal means from said resonant circuit;

sensor means for instantaneously monitoring the operation of the resonant converter;

means connecting said sensor means to said predictor circuit to initiate calculating at the commencement of each resonant portion and to predict the final waveform of each resonant portion prior to the completion of the respective resonant portion; and

said inner control means comparing an output of said predictor circuit to a pre-established standard for controlling the time of initiation of conduction of one of said switch means within each resonant portion to provide a constant transfer of energy within each resonant portion.

8. An improved control circuit for a high frequency series resonant converter, the resonant converter having a capacitor connected in series with an inductor with a first and a second plurality of unidirectional switch means respectively interconnecting the series resonant circuit to first and second terminal means, the resonant converter having outer control means for selectively actuating said first and second plurality of unidirectional switch means for selectively initiating alternate polarity high frequency resonant current pulses in said series resonant circuit to transfer of electrical power between the first and second terminal means;

the improvement comprising;

inner control means having a predictor circuit for instantaneously monitoring the operation of the resonant converter to instantaneously predict the final waveform of each of said high frequency resonant current pulses prior to the completion of the respective high frequency resonant current pulse; and

said inner control means selectively actuating at least one of said first and second plurality of unidirectional switch means within each of said high frequency resonant current pulses to alter the voltage applied to the series resonant circuit by the first and second terminal means to conform each of said high frequency resonant current pulses to be in accordance with a pre-established standard.

9. An improved resonant converter as set forth in claim 8, wherein said resonant circuit control mean initiates conduction of said one of said switch means to produce a resonant portion having a substantially constant value of energy in each resonant portion.

10. An improved resonant converter as set forth in claim 8, wherein said resonant circuit control mean initiates conduction of said one of said switch means to limit the voltage on said capacitor below a pre-established voltage level.

11. An improved resonant converter as set forth in claim 8, wherein said resonant circuit control mean initiates conduction of said one of said switch means to limit the current in said resonant circuit below a pre-established current level.

12. An improved resonant converter for transferring electrical power between input terminal means and output terminal means, comprising:

a resonant circuit including a capacitor and an inductor;

a first and a second plurality of switch means interconnecting said resonant circuit with the input terminal means and the output terminal means;

power sensor means for sensing the power transfered by said resonant converter between the input terminal means and the output terminal means;

outer control means including a power reference signal and a power comparator;

said power reference signal establishing the desired power transfer between the input terminal means and the output terminal means;

means connecting said power sensor means and said power reference signal to said output comparator for providing a power comparator output;

means connecting said power comparator output from said power comparator to said outer control means for selectively actuating said first and said second plurality of switch means to initiate oscillation in said resonant circuit to transfer electrical power between the input and the output terminal means in accordance with said power reference signal;

said oscillation of said resonant circuit having a first resonant portion wherein a resonant current flows toward said resonant capacitor of said resonant circuit and having a second resonant portion wherein a resonant current flows away from said resonant capacitor of said resonant circuit;

inner control means being able to initiate conduction of one of said switch means within each of said resonant portions for dividing each of said resonant portions into a first duration and a second duration;

said first duration of each of said resonant portions transfering electrical power from said resonant circuit to one of the input and output terminal means;

said second duration of each of said resonant portions transfering electrical power from one of the input and output terminal means to said resonant circuit;

resonant sensor means for instantaneously monitoring the operation of the resonant circuit;

said inner control means further comprising a resonant reference signal, a predictor circuit and a resonant comparator;

said resonant reference signal establishing a desired standard of energy transfer through said resonant circuit for each of said resonant portions;

means connecting said resonant sensor means to said predictor circuit for initiating calculation at the commencement of each of said resonant portions to predicting the final quantity of energy of each of said resonant portions prior to the completion of the respective resonant portion;

means connecting said predictor circuit and said resonant reference signal to said resonant comparitor for comparing a predicted output from said predictor circuit to said resonant reference signal;

means connecting said comparator means to activate said inner control means for initiating the conducting of one of said switch means within each of said resonant portions to vary the relative magnitudes of said first and second durations in each of said resonant portions; and

said variation of the relative magnitudes of said first and second durations conforming the quantity of energy transferred in each of said resonant portions with said desired standard of energy transfer for each resonant portion thereby producing a uniform transfer of energy for each of said resonant portions of oscillation of said resonant circuit.