| 摘要 |
PURPOSE:To accurately detect an overcurrent generated when a picture forming device becomes abnormal by switching the target value of the overcurrent to a value conforming with each state in accordance with the state of the image forming device. CONSTITUTION:When the device is initialized, a target overcurrent value switching signal 111 is sent from a control unit and a selector 206 is set to a target value I2 side, namely, to a storage circuit 205 side. The then current value is about 1-2A. On the other hand, since the target value I2 is set at 3A, no overcurrent can be detected when the overcurrent has a normal standby-type waveform. However, when an abnormal waveform is generated due to a slight short, etc., an overcurrent detecting unit 203 can detect the abnormal waveform, sine the abnormal current exceeds the target value I2. As a result, a power unit 102 disconnects a power source 103. When copying operations are started, the selector 206 is switched to another target value I1 side and the target value is set at 10A. During the copying operations, any electric current can be detected, because the current fluctuates between about 3A and 8A. When the copying operations are completed, the selector 206 is again switched to the target value I2 side. |
