| 摘要 |
PURPOSE:To vary an output voltage from 0 volt stably over a wide range, by using a transformer with L-shaped inductance characteristics and a low-voltage dummy current circuit in combination for a switching power source. CONSTITUTION:A transformer 1 consists of a core having L-shaped inductance characteristics and the low-voltage dummy current controlling circuit consists of the TR2 and TR3. Zenor diode D5 constant-current diode D6, diode D7, and resistances R7-R10 of a broken-line part LDC. A desired voltage is set through a resistance RV1 and the turn-on width of the TR1 is set by a pulse width controlling circuit Ic1; and the transformer T1 is driven to generate an output voltage. An operational amplifier IC2 makes a comparison between a reference voltage applied to its plus terminal and the output voltage applied to its minus terminal to drive a photocoupler P11/2 by its output, and feedback to a photocoupler P12/2 is provided to control the pulse width controlling circuit IC1. Thus, the output voltage is varied from 0 volt stably over a wide range. |
