Zero voltage switching half bridge resonant converter

• US 4,814,962 A
• Filed: 05/27/1988
• Issued: 03/21/1989
• Est. Priority Date: 05/27/1988
• Status: Expired due to Term

• Current Assignee: Lineage Power Corporation (GE Aerospace)
• Original Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Inventors: Magalhaes, Frank M., Walk, Ralph, Ziesse, Norman G., Ostapiak, Roman
• Primary Examiner(s): Beha, Jr., William H.
• Application Number:
  US07/199,963
• Time in Patent Office: 298 Days
• Field of Search: 363/17, 363/16, 363/98, 363/132
• US Class Current: 363/16
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• 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

A DC to DC converter combines a half-bridge inverter with a resonant rectifier through a series LC circuit which conducts power at substantially a single frequency. Energy stored in the parasitic capacitors of the two power switches are transferred from one parasitic capacitor to the other in order to enhance efficiency of operation. The transfer is controlled by controlling the relative phase between the voltage and current in the inverter section.

Claims

1. In combination:

An inverter circuit, including input means for accepting a high voltage DC input;

a resonant rectifier having a resistive component of input impedance that increases with increasing power and including a significant reactive impedance for providing a substantial impedance transformation and, connected to rectify an output of the inverter circuit,

the inverter including;

a first switch,

a first capacitor shunting the first switch,

a first diode shunting the first switch,

a second switch,

a second capacitor shunting the second switch,

a second diode shunting the second switch,

the first and second switch being connected in series with each other and across the input means,

a series LC circuit connected to couple a circuit node between the first and second switches to the resonant rectifier, and having an inductive reactance over an operating frequency range of the inverter, and further having large inductive and capacitive reactive impedances close in value to each other so that a relatively small frequency change produces a large impedance variation,

drive means for biasing the first and second switches alternately conductive at a switching frequency above a resonant frequency of the LC series circuit.

2. The combination as defined in claim 1 wherein

the first and second switch are controlled to have common nonconducting intervals during which charge is transferred from one of the first and second capacitors to another one of the first and second capacitors.

3. The combination as defined in claim 1 wherein a resistive component of input impedance of the resonant rectifier is substantially invariant to changes in frequency within the operating range of the inverter.

4. The combination as defined in claim 1 and further including regulation circuitry comprising

means for comparing an output voltage of the rectifier with a reference voltage and generating an error voltage, and

means for varying a frequency of operation of the inverter in response to the error voltage.

5. In combination:

A switching circuit comprising;

input means for accepting a DC voltage,

a first switch and a second switch having a common circuit and node conenction connected in a series connection and the series connection connected across the input means,

a first diode and a first capacitor each shunting the first switch,

a second diode and a second capacitor each shunting the second switch,

an LC circuit comprising inductance and capacitance connected in series and connected to a circuit node common to the first and second switch, and inductive and capacitive reactances having substantial values close in value to one another whereby a limited frequency change produces a substantial reactance change,

an output network for coupling the tuned circuit to a load to be energized and including resonant rectification means which is adapted to present a substantially linear impedance to the tuned circuit, and having sufficient inductive and capacitive reactance for providing a substantial impedance transformation,

means for alternately driving the first and second switch into conduction at a frequency above a resonant frequency of the series LC circuit and providing controlled intervals of simultaneous nonconduction of the first and second switch between each alternate interval of conduction, each nonconduction interval sufficient to allow a capacitor associated with one switch to discharge into a capacitor associated with another switch.

6. The combination as defined in claim 5 and further including

means for regulating an output voltage applied to the load comprising

a comparator for comparing the output voltage to a reference voltage and generating an error voltage and

means for controlling a frequency of the means for alternately driving in response to the error voltage.

7. The combination as defined in claim 5 whereby a resistive component at input impedance of the rectification means increases with increasing power applied to the load.

8. The combination as defined in claim 5 wherein a current output at the common switch node is constrained to be substantially sinusoidal.

9. A high frequency converter circuit comprising:

a half bridge configured inverter including first and second active switches, each including a shunt diode and a shunt capacitance, connected in series and alternately enabled conducting for switching an applied DC voltage with an interspersed controlled dead time between conducting intervals,

a resonant rectifier including a rectifying diode and including sufficient associated reactive elements for producing a substantial impedance transformation and operative for rectifying a substantially single frequency signal without creating ringing transients,

a tuned reactive circuit including series connected inductive and capacitive elements resonant at a frequency below a switching frequency of the inverter and operative for coupling energy from a node between the first and second active switches of the inverter to the rectifier at substantially a single frequency and constraining a current waveform of an output of the inverter switches to lag the voltage wave form across the first and second active switches, and further having substantial inductive and capacitive reactance close in value to one another so that a slight frequency change produces a substantial impedance change.

10. A high frequency converter circuit as defined in claim 9 wherein an input impedance of the resonant rectifier is substantially invariant to changes in frequency within the operating range of the converter.

11. A high frequency converter circuit as defined in claim 10 wherein a resistive component of an input impedance of the resonant rectifier increases with increasing power applied to the load.

12. In combination:

an inverter circuit comprising;

means for accepting a high DC voltage input,

a bridge type voltage switching arrangement for inverting the high DC voltage input to a pulsed voltage,

means for driving the bridge type switching arrangement within a preselected frequency range,

a resonant rectifier circuit comprising;

means for accepting a load to be energized,

at least a rectifying diode,

a rectifier input including a reactive shunt component operative for insuring a resistive input impedance,

the resonant rectifier circuit having two operative frequency poles with resistive impedance maxima located at opposite ends of a bandwidth of operation of the inverter and further having its resistive component of input impedance vary directly with power applied to the rectifier input,

a series LC circuit coupling the bridge type voltage switching arrangement to the rectifier input and operative to interact with the input impedance of the rectifier to form a variable voltage divider and being tuned to be resonant at a frequency below an operating frequency of the means for driving,

means for generating an error signal in response to a deviation of a voltage at the means for accepting a load from a regulated value, and

means responsive to the error signal for varying an operating frequency of the means for driving.

13. A combination as claimed in claim 12 wherein the resonant rectifier includes reactive impedance operative for providing a substantial impedance transformation of voltage applied to the rectifier input.

14. A DC to DC converter comprising:

a half bridge inverter in which each power swtich includes a shunt diode and a shunt capacitance, the shunt diode being operative to prevent reverse voltages across each power switch,

a resonant rectifier in which waveform shaping inhibits ringing across the rectifying diodes, and the reactive components define two frequency response poles related to the converter operating frequency so that an input impedance of the rectifier includes an input resistance substantially independent of frequency within the operating frequency.

a reactive circuit, inductive at the operating frequency, connected in series with the input impedance of the resonant rectifier and coupling each power switch of the half bridge inverter to the resonant rectifier, and

voltage regulation circuitry operative for varying a frequency of operation of the converter in order to vary an impedance of the reactive circuit and control a voltage applied to the input impedance of the rectifier.

15. A DC to DC converter as defined in claim 14 wherein the reactive circuit comprises:

a series LC circuit having large inductive and capacitive reactive impedances close in value to each other so that a relatively small frequency change produces a large impedance variation.

16. A DC to DC converter as defined in claim 14 wherein the power switches are enabled alternately conducting with an intervening non-conduction interval sufficient to allow a shunt capacitance associated with one power switch to discharge into a shunt capacitance associated with another power switch.

17. A DC to DC converter as defined in claim 14 wherein the voltage regulation circuitry includes:

means for comparing an output voltage of the resonant rectifier with a reference voltage and generating an error voltage, and

means for varying frequency of switching of the power switches in response to the error voltage.