| 摘要 |
PROBLEM TO BE SOLVED: To reduce peak inverse voltage of a semiconductor and to provide the stable AC voltage by controlling the voltage on a primary side of a transformer. SOLUTION: A controller 3 for outputting the lower limit voltage of voltage fluctuation estimated from a nominal value in respect to a change range of the power supply voltage is installed on the primary side of a transformer 4. When the voltage of a power source 1 is fluctuated, the voltage in 70% of the nominal voltage value is constantly outputted between a common terminal C and a control output terminal D by controlling non-conduction rate of the voltage between input terminals A and B by a transistor unit 2. Namely, even when the voltage between A and B is changed in -30% and +30% in respect to the nominal voltage value, the controller 3 feeds back the voltage between the common terminal C and the control output terminal D, controls a gate of the transistor unit 2 and controls it into the voltage in 70% of the nominal voltage value. On the assumption a control velocity at such a time is 6 kilocycles, when frequency of the nominal voltage is 60 kilocycles, the ratio control of non-conduction/conduction is performed in 100 cycles per cycle and waveform distortion is improved.
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