| 摘要 |
PURPOSE:To prevent the malfunction of an image forming part by providing a control means which detects a power output to a control part and brings a power supply to the image forming part to a stop when the power output is below a predetermined level. CONSTITUTION:A control IC 19 of a primary-side power supply control part of a high-tension power source for an electro static charger controls a switching control part 191 according to a control signal inputted from an error amplifier 193 via a detection circuit to make a secondary-side output current or voltage stable. Then, a conducting duty ratio, frequency. etc., of a switching transistor 702 is controlled, and a voltage or current to be outputted to the secondary side of a switching transformer 701 is controlled to be constant or to be a predetermined value. If a 5V output from a 5V generation circuit 4 is lower than a predetermined voltage VH, a transistor Tr is interrupted, the switching control part 191 of the control IC 19 stops the switching of the switching transistor 702, and a high-tension output is inhibited. Therefore, the malfunction of an image forming part can be prevented even if control signals 15-18 are in unstable condition. |
