| 摘要 |
PURPOSE:To keep the output power constant by connecting a Zener diode in series to a resistance of the discharge circuit of a condenser and by varying the change rate of the time of discharge of the condenser against an input voltage. CONSTITUTION:A self-oscillating switching power unit is composed of rectification circuits 1 and 3, a bias circuit 2, a control circuit 4, a switching transformer S, a switching transistor Q1, a photocoupler P1, etc. A condenser C1 is charged and discharged with the voltage induced between a control winding S3 of the transformer S, varying the pulse width by this discharge time constant. On this occasion, a resistance R3, a Zener diode ZD1 inserted in series and a negative resistance element D2 provided side by side with it. Thus, when the input voltage varies, the change rate of the time of discharge of the condenser C1 agrees with this change and the pulse width varies, so that the maximum output power can be kept constant.
|
