| 摘要 |
PURPOSE:To detect an abnormal state of a load without breaking down a switching element, by closing the switching element for a fixed time, converting a load current to a voltage signal, sample-holding this signal, and comparing it with a reference value. CONSTITUTION:A switching element is closed for a fixed time, a current flowing to a load connected in series is converted to a voltage signal, this signal is sample-held and is compared with a reference value, and as a result, an abnormal state of the load is detected. For instance, from an output port 3 of an I/O interface 2 connected to a central processor CPU1, a signal for turning on a switching element 4 is outputted for a fixed time, and a current flowing to a load 5 is detected by a potential drop across a low resistance 6 inserted in series to a load circuit. Subsequently, the potential drop across the low resistance 6 is amplified by an amplifier 7, is held by a sample-holding circuit 8, and this held value is digitally converted by an A/D converter 9, is read in the CPU1, and is compared with a reference value stored in advance in a memory 10. |
