Power feedback power factor correction scheme for multiple lamp operation
First Claim
1. A ballast circuit for a parallel operation of at least one lamp, each of said at least one lamp having a ballasting capacitor, said circuit operating in high frequency cycles, said circuit comprising:
- one or more power transistors to generate a resonant inductor current;
a LLC resonant converter comprising a resonant inductor, an output transformer having magnetizing inductance, and at least one resonant capacitor, a part of said LLC resonant converter forming a resonant tank circuit for generating a first voltage;
said output transformer providing galvanic isolation for generating a second voltage, said resonant inductor being disposed between said output transformer on its first side and said one resonant capacitor on its second; and
said at least one lamp having a third voltage via said ballasting capacitor.
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Accused Products
Abstract
A ballast circuit for a single or multiple lamp parallel operation where at each lamp a condition may be controlled such that the amplitude of a resonant inductor current and an output voltage are almost constant in the steady state. The inventive circuit consists of a half-bridge of a DC storage capacitor, a DC blocking capacitor, power transistors which alternatively switch on and off and having 50% duty ratio, and an LLC resonant converter having a resonant inductor and one or more resonant capacitors. The inventive circuit consists of an output transformer providing galvanic isolation for a double path type power feedback scheme. The output transformer produces magnetizing inductance utilized for power feedback circuit optimization and is inserted right after the resonant inductor of the half-bridge circuit.
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Citations
15 Claims
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1. A ballast circuit for a parallel operation of at least one lamp, each of said at least one lamp having a ballasting capacitor, said circuit operating in high frequency cycles, said circuit comprising:
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one or more power transistors to generate a resonant inductor current;
a LLC resonant converter comprising a resonant inductor, an output transformer having magnetizing inductance, and at least one resonant capacitor, a part of said LLC resonant converter forming a resonant tank circuit for generating a first voltage;
said output transformer providing galvanic isolation for generating a second voltage, said resonant inductor being disposed between said output transformer on its first side and said one resonant capacitor on its second; and
said at least one lamp having a third voltage via said ballasting capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A ballast circuit for a parallel operation of multiple lamps, each of the lamps having a ballasting capacitor, said circuit comprising:
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a power feedback circuit; and
a LLC resonant converter comprising a resonant inductor connected on one side to an output transformer having magnetizing inductance, and connected on the other side to at least one resonant capacitor, a part of said LLC resonant converter forming a resonant tank circuit for generating a first voltage, said resonant tank circuit allowing said power feedback circuit to produce reasonable power factor in said input current of the ballast circuit for differing number of said multiple lamps and keeping a DC bus voltage under 220 Volts for said differing number of said multiple lamps.
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Specification