Mixed mode regulation controller for a resonant power converter

• US 5,051,880 A
• Filed: 12/29/1989
• Issued: 09/24/1991
• Est. Priority Date: 12/29/1989
• Status: Expired due to Fees

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Harm, Charles E., Timm, Kenneth J.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): STERRETT, JEFFREY L
• Application Number:
  US07/459,038
• Time in Patent Office: 634 Days
• Field of Search: 363/17, 363/26, 363/97, 363/98, 363/132, 363/134, 363/49
• US Class Current: 363/49
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• 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

Frequency variation in a resonant zero voltage switching (ZVS) power converter is combined with supplemental duty cycle modulation to obtain voltage regulation and to narrow the required frequency band needed for regulation of a given output load. These two regulation processes are applied simultaneously to the power switch control in order to accommodate a wider range of regulated load. Hence in the alternative, for a given load range a smaller frequency range is needed than would be the case if frequency variation alone is used.

The regulation control circuit includes both a duty cycle modulator and a frequency modulator each being responsive to an error signal responsive to a differential between an output voltage of the converter and a reference voltage. Each individual modulator has its own transfer function; one transfer function being kHz/volt the other transfer function being % duty cycle/volt. The regulation control circuit output is a rectangular pulse type signal that contains both elements of frequency modulation and duty cycle modulation.

Claims

1. A resonant power converter, comprising:

a power switching circuit interconnecting an input to an output,

control circuitry for regulating an output of the power switching circuit by controlling switching in the power switching circuit, including;

an error signal generator for establishing a desired output signal level and generating an error signal proportionate to a difference between an actual output signal level and the desired output signal level;

a frequency generator responsive to the error signal for generating a frequency signal whose frequency is responsive to the error signal;

a duty cycle generator responsive to the error signal and to the frequency signal for generating a duty cycle modulated pulse signal whose frequency is established by the frequency signal with the duty cycle pulse signal generated at the frequency established and controlled in response to the error signal;

drive circuitry for driving the power switching circuitry in response to the duty cycle modulated signal;

error boundary limit circuitry for inverting the error signal applied to the frequency generator and the duty cycle generator with defined limits, at start up of the resonant power converter and including;

an amplifier circuit responsive to the error signal generator to produce an inverted error signal, and

a feedback circuit operative for retaining the inverted error signal output of the amplifier within specified limits.

2. A resonant power converter, comprising:

an input and an output;

a power switch for coupling energy between the input and the output;

a sensing circuit for quantifying a deviation of a voltage at the output from a regulation value and generating an error signal;

drive circuitry for driving the power switch, including;

a frequency modulator generating a periodic waveform responsive to the error signal of the sensing circuit;

a duty cycle modulator responsive to the error signal of the sensing circuit to generate a signal level and to the periodic waveform of the frequency modulator;

means for combining the outputs of the frequency modulator and the duty cycle modulator to generate a power switch drive signal which is simultaneously frequency and duty cycle modulated by adjusting the signal level relative to the periodic waveform, and

control circuitry for establishing a frequency of operation and a specified duty cycle at start up of the resonant power converter including a limiter circuit operative for inverting the error signal output of the sensing circuit.

3. A resonant power converter as claimed in claim 2, and further including:

circuitry for dividing a switch drive signal into two signals of opposite polarity.