Inverter power supply with single discharge path
First Claim
1. An inverter power supply for driving an electrical device comprising:
- a DC voltage supply providing a DC voltage;
a transformer having a primary winding, a secondary winding, and a feedback winding;
an L-C resonant circuit comprising a capacitor and said primary winding;
a self-excited oscillator comprising a series connection of said L-C resonant circuit, a parallel arrangement of a resistor and a diode, and a switching element across said DC supply, said switching element being alternately turned on and off to generate a high frequency voltage across said primary winding, a high frequency feedback voltage across said feedback winding and a resulting output AC voltage across said secondary winding, said output AC voltage being applied to a load circuit of said device;
a biasing capacitor to be charged by a current from said DC voltage, said biasing capacitor being connected in series with said feedback winding to provide an offset voltage which is additive to said high frequency feedback voltage developed across said feedback winding to give a bias voltage applied to a control terminal of said switching element so as to alternately turn on and off said switching element for driving said self-excited oscillator;
a current sensor which senses a current flowing through said switching element and provides a first level signal indicative of the sensed current;
a single discharge path extending across said biasing capacitor and not through said switching element;
switching means consisting of a bipolar transistor inserted in said single discharge path to turn on, upon said first level signal exceeding a threshold level, to discharge said biasing capacitor to a level for maintaining said offset voltage at a constant level during continued oscillation of said L-C resonant circuit.
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Accused Products
Abstract
An inverter power supply having a DC source, a transformer having a primary winding, a secondary winding, and a feedback winding, an L-C resonant circuit of a capacitor and the primary winding, and a self-excited oscillator. The oscillator includes an L-C resonant circuit and an FET connected in series with the primary winding across the DC source to generate a high frequency voltage across the primary winding, a feedback voltage across the feedback winding and a resulting output AC voltage across the secondary winding. A biasing capacitor is connected in parallel with a series combination of the L-C resonant circuit and the FET across the DC source to be charged thereby. The biasing capacitor is also connected in series with the feedback winding to provide an offset voltage which is additive to the feedback winding to give a bias voltage applied to a gate of the FET so as to alternately turn on and off the FET for driving the self-excited oscillator. A current sensor is provided to sense a current flowing through FET and gives a first level signal indicative of the sensed current being fed to the resonant circuit. Extending across the biasing capacitor is a single discharge path which does not go through the FET. A switching transistor is inserted in the single discharge path and is caused to turn on, upon the first level signal exceeding a threshold level, to discharge the biasing capacitor to a level for maintaining the offset voltage at a constant level during continued oscillation of the L-C resonant circuit.
27 Citations
10 Claims
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1. An inverter power supply for driving an electrical device comprising:
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a DC voltage supply providing a DC voltage; a transformer having a primary winding, a secondary winding, and a feedback winding; an L-C resonant circuit comprising a capacitor and said primary winding; a self-excited oscillator comprising a series connection of said L-C resonant circuit, a parallel arrangement of a resistor and a diode, and a switching element across said DC supply, said switching element being alternately turned on and off to generate a high frequency voltage across said primary winding, a high frequency feedback voltage across said feedback winding and a resulting output AC voltage across said secondary winding, said output AC voltage being applied to a load circuit of said device; a biasing capacitor to be charged by a current from said DC voltage, said biasing capacitor being connected in series with said feedback winding to provide an offset voltage which is additive to said high frequency feedback voltage developed across said feedback winding to give a bias voltage applied to a control terminal of said switching element so as to alternately turn on and off said switching element for driving said self-excited oscillator; a current sensor which senses a current flowing through said switching element and provides a first level signal indicative of the sensed current; a single discharge path extending across said biasing capacitor and not through said switching element; switching means consisting of a bipolar transistor inserted in said single discharge path to turn on, upon said first level signal exceeding a threshold level, to discharge said biasing capacitor to a level for maintaining said offset voltage at a constant level during continued oscillation of said L-C resonant circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification