Regulated self-oscillating resonant converter with current feedback
First Claim
1. A self-oscillating resonant converter for at least one discharge lamp which during normal operation exhibits lamp operating parameters of lamp voltage, lamp current and lamp power, wherein the converter comprises a half-bridge inverter including two field effect transistors and an output node between said transistors, a gate driving circuit for controlling said field effect transistors, and a linear core transformer having a load winding through which load current passes, the load winding having one end connected to the output node,characterized in that the transformer includes a control winding, andthe converter further comprises means for controlling the gate driving circuit during the normal operating state of the lamp to vary the oscillating frequency so as to maintain one of the lamp operating parameters constant, said means including a feedback and regulation circuit connected to and producing an AC control current in said control winding.
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Accused Products
Abstract
Lamp voltage or current obtained from a self-oscillating converter is stabilized by a feedback circuit. Gates of the switching transistors are connected to output windings of a current transformer whose input current winding is in series with the resonant load lamp circuit. The lamp voltage or current is sensed, and the resulting signal is used to control current through an auxiliary control winding on the current transformer. Preferably, two opposite conductivity type control transistors are connected in parallel across the control winding, and low-pass filtered DC signals corresponding to the lamp voltage or current bias the control transistors.
38 Citations
23 Claims
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1. A self-oscillating resonant converter for at least one discharge lamp which during normal operation exhibits lamp operating parameters of lamp voltage, lamp current and lamp power, wherein the converter comprises a half-bridge inverter including two field effect transistors and an output node between said transistors, a gate driving circuit for controlling said field effect transistors, and a linear core transformer having a load winding through which load current passes, the load winding having one end connected to the output node,
characterized in that the transformer includes a control winding, and the converter further comprises means for controlling the gate driving circuit during the normal operating state of the lamp to vary the oscillating frequency so as to maintain one of the lamp operating parameters constant, said means including a feedback and regulation circuit connected to and producing an AC control current in said control winding.
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2. A self-oscillating resonant converter for at least one discharge lamp which during normal operation exhibits lamp operating parameters of lamp voltage, lamp current and lamp power, wherein the converter comprises a half-bridge inverter including two field effect transistors and an output node between said transistors, a gate driving circuit for controlling said field effect transistors, and a linear core transformer having a load winding through which load current passes, the load winding having one end connected to the output node,
characterized in that the transformer includes a control winding, and the converter further comprises means for controlling the gate driving circuit to vary the oscillating frequency so as to maintain one of the lamp operating parameters constant, said means including a feedback and regulation circuit connected to and producing an AC control current in said control winding, and the feedback and regulation circuit include means for sensing the lamp voltage, and the control current is responsive to the sensed voltage.
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16. A self-oscillating resonant converter for at least one discharge lamp which during normal operation exhibits lamp operating parameters of lamp voltage, lamp current and lamp power, wherein the converter comprises a half-bridge inverter including two field effect transistors and an output node between said transistors, a gate driving circuit for controlling said field effect transistors, and a linear core transformer having a load winding through which load current passes, the load winding having one end connected to the output node,
characterized in that the transformer includes a control winding, and the converter further comprises means for controlling the gate driving circuit to vary the oscillating frequency so as to maintain one of the lamp operating parameters constant, said means including a feedback and regulation circuit connected to and producing an AC control current in said control winding, the feedback and regulation circuit include means for sensing the lamp current, and the control current is responsive to the sensed current, wherein said feedback and regulation circuit includes a first rectifying and filtering circuit for providing a first unidirectional voltage having a first polarity, and a unidirectional current control circuit responsive to said first unidirectional voltage, said unidirectional current control circuit comprises a first control transistor having a current path, the first control transistor being connected across the control winding to permit current to pass through the control winding in one direction, and said feedback and regulation circuit comprises a second control transistor connected across the control winding to permit current to pass through the control winding in a direction opposite the one direction.
Specification