Protective circuit for a switched-mode power supply circuit

摘要

The invention relates to a protective circuit for a switched-mode power supply circuit (or link power supply circuit) in which, whenever a constant voltage is not output, the through-connection/blocking operation of a switching transistor is ended if an overvoltage appears at the output of the power supply circuit. This protective circuit essentially contains a switching transistor, a diode, a phototransistor, a thyristor, a capacitor etc. connected to a photodiode, a Zener diode, a thyristor etc. as well as other conventional components. Whenever, for example because of a short-circuit of the load circuit, an overvoltage is emitted, or a current surge flows, the protective circuit is capable of protecting the power supply circuit while, at the same time, unnecesssary waste of the current supplied via the current-input terminal can be avoided. <IMAGE>