| 摘要 |
PURPOSE:To prevent the further increase of a load current by utilizing the fact that the alternating voltage generated at the secondary coil of a transformer become zero when a load voltage is lowered to an input voltage by the operation of an overcurrent protecting circuit. CONSTITUTION:When a current higher than a rated value flows through a load, an overcurrent detecting circuit operates to shorten the conducting time of a transistor TR1 in an oscillator circuit, with the result that the voltage generated at the secondary coil NS2 of the transformer T1 decreases. When the load current I0 increases, the transistor TR1 becomes completely nonconductive. Thus, no voltage is produced at the secondary coil NS2, and the transistor TR2 becomes nonconductive. Since the maximum of the load current I0 is I0, the power consumption of the overcurrent detecting resistor R3 will not increase. When the load becomes normal, it can be automatically reset. |
