| 摘要 |
PURPOSE:To surely protect a device, by detecting the lowering of the output voltage of a detecting winding generated by the increment of load current according to the relation of being larger or small of the output voltage in a plurality of charging or discharging means generated due to the difference of a time constant. CONSTITUTION:The power supply device of an electronic photographic apparatus or the like is composed of a step-up transformer 1 for putting AC component together with input high-tension direct-current and generating the output of high-tension alternating-current, diodes 4, 8, a power source controlling IC 14, driving transistors 17, 18, and the like. The input of the output of a secondary coil 1c, to the capacitor 6 of a charge element via the diode 4 is provided, and the input to the capacitor 10 of a second charge element from the diode 8 is provided, and the output of charge and discharge voltage amounts (Va, Vb) with respectively different time constants is generated. Said IC 14 is provided with comparators 15, 16, and by both the output amounts, the driving of transistors 18, 19 is controlled via a PWM circuit and the like. Besides, by the comparator 15, the voltage Va and the voltage Vb are compared with each other, and the abnormal state of a load is prevented from being generated or working like that is performed. |
