Minebea Company, Limited

Shingo Okada

Takao Takehara

This invention solves various problems of an inverter device caused by a winding transformer by using a piezoelectric transformer, and also provides a drive device for a cold cathode tube using a piezoelectric transformer so as to enable lighting and light control of the cold cathode tube. In a cold cathode tube lighting device having a cold cathode tube and piezoelectric circuit to light the cold cathode tube, a series resonance circuit is formed at primary side of the piezoelectric transformer. An operation control device is installed for ON-OFF control of the series resonance circuit, by a switching element, at timing with the phase advanced from the resonance frequency of the resonance circuit, and a chopper circuit for stepping-up the input voltage and supplying a power source to the resonance circuit is installed, and ON-OFF control of the power switching element of the chopper circuit is performed by the operation control device. That is, the power switch of the step-up chopper circuit is driven at the ON-time larger than that of the power switch of the inverter, and the cold cathode tube is connected to the secondary side of the step-up transformer.

Cold cathode tube lighting device using piezoelectric transformer

An object of the present invention is to provide a voltage resonance inverter circuit capable of performing constantly a zero-voltage switching action in response to a change in the input voltage. For achievement of the above object of the present invention, the capacitance of a voltage resonance capacitor is decreased in response to an increase of the input voltage thus increasing the characteristic impedance of a resonance circuit. This will increase the amplitude of a resonance voltage causing a zero-voltage switching action.

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Saijou, Japan

Shingo Okada