PURPOSE:To arbitrarily set a voltage and a frequency with smaller ROM capacity by providing a plurality of waveform generating data tables on a RAM as a sinusoidal wave PWM signal generator. CONSTITUTION:In a sinusoidal wave PWM signal generator of an inverter using a 1-chip microcomputer, the microcomputer has a CPU 101, a timer 102, a RAM 103 for storing waveform generating data, a ROM 104 for storing waveform data tables, an address pointer 105, and a PWM signal output port 106. In this case, a plurality of waveform generating data tables are provided on the RAM 103, the waveform generating data written in the ROM by forming it by a personal computer is formed in the microcomputer, and written in the RAM 103. The PWM signal is generated on the basis of the data to eliminate the necessity of having a lot of data in the ROM 104, and the voltage and the frequency can be arbitrarily set.
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