US 4,893,227 AGranted

Push pull resonant flyback switchmode power supply converter

AssigneeVenus Scientific Inc.

InventorsGeorge C. Gallios, Charles Lien, Remo Stella, Wendell Boucher

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Abstract

A flyback converter high voltage power supply which includes two switches operating in push pull fashion to provide alternate polarity energy pulses to a load. A main component of the power supply is a transformer, the primary winding of which is divided into halves. The secondary may be also be split into halves, or may be configured without a split so long as the secondary and rectifier combination result in full wave rectification. The first of the two switches couples an input voltage across the first primary half to store energy in the magnetic core during a first time interval, and at the end of the first time interval disconnects the first primary half from the input voltage. During a second time interval, the energy stored in the magnetic core during the first time interval is delivered to the load via the secondary winding. The second of the two switches similarly couples the input voltage across the second primary half to store energy in the magnetic core during a third time interval, and then disconnects the second primary half from the input voltage at the beginning of the fourth time interval. During the fourth time interval, the energy stored in the magnetic core is again transferred to the load via the secondary. A duty factor modulator is used to control the switching of the first and second switches to vary the length of the time intervals in response to variations in the load and input voltage.

Claims22

Dependent claims

A push pull resonant flyback switchmode power supply converter for supplying power to a load, comprising:

(a) a transformer having a primary and a secondary, said primary comprising first and second primary halves with an equal number of primary turns;
(b) first switch means for coupling an input voltage of an input power supply across said first primary half during a first series of time intervals to store energy from said input power supply in the form of current in the inductance of said primary without resonance and for disconnecting said first primary half from said input voltage during a second series of time intervals during which the current in the inductance of said primary is transferred to said secondary, said secondary having an inductance and a parallel stray capacitance, the energy stored in the form of voltage in said stray capacitance being transferred in the form of current to the inductance of said secondary by parallel resonance, the current in the inductance of said secondary being delivered to said load when the voltage across said stray capacitance resonates to a predetermined level which is greater than said input voltage;
(c) second switch means for coupling said input voltage of said input power supply across said second primary half during a third series of time intervals to store energy from said input power supply in the form of current in the inductance of said primary without resonance and for disconnecting said second primary half from said input voltage during a fourth series of time intervals during which the current in the inductance of said primary is transferred to said secondary, the energy stored in the form of voltage in the stray capacitance of said secondary being transferred in the form of current to the inductance of said secondary by parallel resonance, the current in the inductance of said secondary being delivered to said load when the voltage across said stray capacitance resonates to said predetermined level which is greater than said input voltage;
(d) pulse width modulating means for controlling the switching of said first and second switch means to vary the length and frequency of said time intervals in response to variations in the load and in said input voltage;
and
(e) means for synchronizing said pulse width modulating means to the frequency of said time intervals as required by the resonant frequency of the parallel stray capacitance and inductance of said secondary.

3 more elements

A method of supplying high voltage to a load using a resonant flyback circuit with a main power stage comprising a transformer having a primary and a secondary, said primary formed of first and second primary halves with an equal number of primary windings, said method comprising repeating a switching interval, which interval comprises the steps of:

(a) switching an input voltage of an input power supply across said first primary half during a first time interval to store energy from said input power supply in the form of current in the inductance of said primary without resonance;
(b) disconnecting said first primary half from said input voltage during second a time interval during which the current in the inductance of said primary is transferred to said secondary, said secondary having an inductance and a parallel stray capacitance, the energy stored in the form of voltage in said stray capacitance being transferred in the form of current to the inductance of said secondary by parallel resonance, the current in the inductance of said secondary being delivered to the load when the voltage across said stray capacitance resonates to a predetermined level which is greater than said input voltage;
(c) switching said input voltage of said input power supply across said second primary half during a third time interval to store energy from said input power supply in the form of current in the inductance of said primary without resonance;
(d) disconnecting said second primary half from said input voltage during a fourth time interval during which the current in the inductance of said primary is transferred to said secondary, the energy stored in the form of voltage in the stray capacitance being transferred in the form of current to the inductance of said secondary by parallel resonance, the current in the inductance of said secondary being delivered to the load when the voltage across said stray capacitance resonates to said predetermined level which is greater than said input voltage;
(e) controlling the duration and frequency of the switching and disconnecting of steps (a) through (d) in response to variations in the load and in said input voltage;
and
(f) controlling the frequency of the switching set forth in steps (a) through (d) to synchronism the controlling of the switching with the time intervals as required by the resonant frequency of the stray capacitance and inductance of said secondary.

4 more elements

Dependencies are inferred from the claim text.