| 摘要 |
PURPOSE:To reduce the power loss of a transistor for current control, by providing a constant voltage necessary for actuating a current control means. CONSTITUTION:The winding current is maintained to the current corresponding to the current reference signal a1 by a transistor 21 for current control, a current detecting resistance 31 and a differential amplification circuit 41. Into a differential amplification circuit 71 the collector voltage of the transistor 21 for current control and the voltage setting signal bb are inputted. A switching transistor 51 is ON/OFF controlled through the voltage control unit 81 based on the output of the circuit 71. At this moment, as the necessary minimum of the voltage is supplied to a current control means, the power lose in the current control means is minimized. |
