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

A new ac-ac converter using switched-capacitor (SC) transformers is pr esented. The proposed converter is shown to be useful for electrolumin escent 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 swi tches. The basic operation is described that an ac input voltage is sa mpled into n charge-transfer capacitors by the input-side switches, an d each sampled voltage is selected to the output port by the output-si de switches with an arbitrary frequency. Since the ac input voltage ne ed not convert once to a de form, the power stage is simple and the ef ficiency is high. A prototype circuit using five charge-transfer capac itors (the total capacitance: 149 mu F) shows experimentally that it c an convert a commercial line voltage (100 V/60 Hz) to a quasi-sinusoid al wave (400 Hz) with a high efficiency (more than 85 percent) and lig hten an EL (size: 1 m(2)) effectively. The proposed converter can norm ally supply a power even to an inductive load without a spike noise. T he inductance of the smoothing coil can be reduced 1/484 in comparison with the case of a conventional converter with a rectangular output.