| 摘要 |
PURPOSE:To suppress stress on a switching element and protect the circuit concerned by furnishing a protector circuit in a power supply, and actuating it when the sensed voltage is over the specified value while the sensed current of a current transformer remains below the specified level. CONSTITUTION:The output voltage of the secondary winding of an insulative transformer Tf is sensed by an output voltage sensing circuit 11, and if the sensed voltage exceeds the specified value, a protector circuit 12 is actuated. The protector circuit 12 is also actuated when the sensed current in an output current sensing circuit is below the specified value. At this time, a zenor diode ZD1 is turned on, and a trigger signal is fed to the gate of a thyristor Q4 which is thus turned on. With it a light emitting element of a photo-coupler PC1 generates a photo-signal, and a light receiving element is turned on so as to shortcircuit between the gate and source of a MOS transistor Q2 of an inverter circuit 4, and thereby oscillating is stopped. This actuates the protector circuit 12, and the stress on a switching element is suppressed to cause protecting of the circuit. |
