US 7,453,216 B2Granted

Current resonance type inverter circuit and power controlling method

AssigneesChen Hong-Gei, Masakazu Ushijima

InventorMasakazu Ushijima

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Abstract

A high efficiency current resonance inverter circuit for a discharge lamp includes: a step-up transformer, a primary winding of the step-up transformer having a center tap being connected to a power source side, two other terminals of the primary winding being connected to collectors of two transistors, respectively, emitters of the two transistors being connected to respective terminals of a primary winding of a current transformer having a center tap, the center tap of the current transformer being connected to a ground side. A secondary winding of the current transformer is connected to bases of the two transistors to detect emitter currents of the two transistors in order to detect a resonance current, thereby performing oscillation. When the current resonance inverter circuit is used for a discharge lamp, the need for a conventional collector resonance inverter circuit is eliminated.

Claims24

Dependent claims

A current resonance inverter circuit for a discharge lamp comprising:

a step-up transformer;
and
a current transformer,
a primary winding of said step-up transformer having a center tap being connected to a power source, two other terminals of said primary winding being connected to collectors of two transistors, respectively, emitters of said two transistors being connected to respective terminals of a primary winding the current transformer,
the current transformer having a center tap, said center tap of said current transformer being connected to a ground side, a secondary winding of said current transformer being connected to bases of said two transistors to detect emitter currents of said two transistors in order to detect a resonance current, thereby performing oscillation,
further comprising a secondary side circuit of said step-up transformer including:
an inductor with a predetermined leakage inductance value which occurs from said secondary winding;
said discharge lamp of said secondary winding;
a distributed capacitor of said secondary winding;
a capacitor for adjusting a resonance frequency;
and
a capacitor for handling stray capacitance generated in the vicinity of said discharge lamp,
wherein the distributed capacitor, the capacitor for adjusting the resonance frequency, and the capacitor for handling stray capacitance form a secondary side capacitance, the secondary side capacitance and the predetermined leakage inductance value which occurs from said secondary winding included in the step-up transformer constituting a serial resonance circuit having a predetermined Q value, and
wherein said discharge lamp is connected in parallel with the said secondary side capacitance, whereby a predetermined step-up ratio is obtained to light said discharge lamp, and a phase of the primary winding current of said step-up transformer is approximately the same as a phase of a real value of the primary winding voltage of said step-up transformer.

11 more elements

A current resonance inverter circuit for a discharge lamp comprising:

a step-up transformer including a predetermined leakage inductance value which occurs from a secondary winding of the step-up transformer and a secondary side capacitance and the discharge lamp;
a power source;
a power controlling circuit;
a self-oscillation circuit;
and
a switching transistor for controlling said power controlling circuit, the switching transistor being connected between said power source of said self-oscillation circuit and said power controlling circuit,
wherein switching timing of said switching transistor which controls said power controlling circuit is made (A) irrespective of an oscillation frequency of said current resonance inverter circuit, or (B) such that a phase of a waveform of an effective value of a voltage applied to said primary winding of said step-up transformer becomes substantially equal to that of a waveform of a current which is caused to flow through said primary winding, if and when an oscillation frequency of said power controlling circuit is synchronized with an oscillation frequency of a current resonance circuit,
wherein when said switching transistor of said current resonance inverter circuit is turned OFF, an oscillating current which is caused to flow through said primary winding of said step-up transformer due to a parasitic oscillation is caused to flow in a direction opposite to that of a resonance current of said current resonance inverter circuit, whereby an energy of the resonance current due to the parasitic oscillation is regenerated in said power source, thereby damping the oscillating current.

5 more elements

Dependencies are inferred from the claim text.