POWER-SUPPLY FOR ELECTROLUMINESCENT LAMP EMPLOYING A SWITCHED-CAPACITOR AC-AC CONVERTER

A new ac-ac converter using switched-capacitor (SC) transformers is presented. The proposed converter is shown to be useful for electroluminescent lamps (EL). The proposed converter has a novel configuration of ac-ac conversion characterized by the parallel power stage of several SC transformers with 1 : 1 ratio and the unique driving method of switches. The basic operation is described that an ac input voltage is sampled into n charge-transfer capacitors by the input-side switches, and each sampled voltage is selected to the output port by the output-side switches with an arbitrary frequency. Since the ac input voltage need not convert once to a de form, the power stage is simple and the efficiency is high. A prototype circuit using five charge-transfer capacitors (the total capacitance: 149 mu F) shows experimentally that it can convert a commercial line voltage (100 V/60 Hz) to a quasi-sinusoidal wave (400 Hz) with a high efficiency (more than 85 percent) and lighten an EL (size: 1 m(2)) effectively. The proposed converter can normally supply a power even to an inductive load without a spike noise. The inductance of the smoothing coil can be reduced 1/484 in comparison with the case of a conventional converter with a rectangular output.