To provide a digital converter for eliminating a shunt resistor.
The digital converter has: a voltage boosting chopper 4; a rectification circuit 2 for supplying an input current I to a coil L in the voltage boosting chopper 4; and a computer circuit 3 for repetitively implementing a PWM control of an IGBT in the voltage chopper 4 in a predetermined control cycle, and is operated by different algorithms based on a determination result while it determines a continuous mode in which the input current to the coil is not interrupted or a discontinuous mode in which the input current to the coil is interrupted in the middle of the control cycle. The continuous mode and the discontinuous mode are determined based on measurement values of a coil charge start current in each control cycle, an AC input voltage to the voltage boosting chopper and a DC output voltage from the voltage boosting chopper, a control time of a PWM waveform in each control cycle and an inductance value of the coil. The coil charge start current is determined based on a voltage measurement value between a collector terminal and an emitter terminal of the IGBT.
YOSHIOKA HARUYUKI
TABUCHI TOSHIYUKI
Isabe Tsuyoshi
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