| 摘要 |
PURPOSE:To secure the safety of an equipment through simple constitution by utilizing the protecting circuit of a switching power source, and then stopping the supply of electric power to a load when an abnormal high voltage is generated or when a load short-circuits. CONSTITUTION:According to the oscillation of an oscillator 3, a switching transistor (TR) 2 connected in series to the primary side of a transformer 1 supplies electric power to a load 4 connected to the secondary side of the transformer 1. To permit the oscillator 3 to oscillate stably at an oscillation frequency, the signal obtained by dividing the voltage of a horizontal component outputted from the secondary side of the flyback transformer in the load 4 is supplied to a synchronizing input terminal B. Diodes 5 and 6, and a capacitor 7 constitute a peak detecting circuit which detects the maximum value of the voltage at the upper end of a resistor 8 and a signal inputted to the input terminal B, and its output is supplied to the control terminal A of the oscillator 3. Then, the oscillator 3 stops oscillating when the voltage at the control terminal has a predetermined value. |
