| 摘要 |
PURPOSE:To improve efficiency, by a method wherein feedback control is effected so that a first secondly coil output is kept at a predetermined value while feedback control is effected so that a second secondary coil output is kept at a predetermined value under no load condition of the output. CONSTITUTION:A multi-output switching power source device is constituted of a switching transformer 1, a MOSFET 12, a rectifying and smoothing circuit 3, a voltage detecting amplifier 4, a PWM control circuit 5, a voltage detecting amplifier 6 and a series control regulator 7. A control signal terminal 21, an inverter 22, transistors Tra, Trb, resistors R5, R6 and an output voltage detecting amplifier 24 are added to the control unit of the multi-output switching power source device. The output voltage Va of the rectifying and smoothing circuit 6 is detected and when the output voltage has exceeded a predetermined value, a photocoupler outputs. According to this constitution, feedback control is effected so that when said first rectifying output voltage V1 is under no load condition, a second rectifying output voltage V2 is kept at a predetermined value whereby a power consumption in the series control regulator 7 may be minimized.
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