| 摘要 |
PURPOSE:To reduce the number of circuit parts so as to decrease the cost by controlling a unidirectional semiconductor switch of an auxiliary voltage- lowering part using counter electromotive force generated in the speed regulation terminal of a motor. CONSTITUTION:An output signal is transmitted to one of bidirectional semiconductor switches 6a-6c by one of output terminals 3a-3c of a controller 3. Counter electromotive force generated on the output side of the semiconductor switch 6a is transmitted to a control terminal 7d of a thyristor 7b. Accordingly, even if any of the bidirectional semiconductor switches 6a-6c is turned on, the thyristor 7b is switched on and an auxiliary voltage-lowering part 7 is connected in parallel with the main voltage-down part 1, so a DC stabilizing part 2 can supply more power. Accordingly, supply voltage to the controller 3 increases and stable power supply is performed against the load current increase of the controller 3. |
