Current detecting circuit

摘要

In a current detecting circuit, a virtual earth generating circuit 7 generates a low voltage VSS lower by a predetermined potential difference than a battery voltage VBT outputted from anon-vehicle battery 1. A CPU 5 operates while the low voltage VSS is used as an earth potential and the voltage VBT higher by the predetermined voltage value than the low voltage VSS is used as a power-supply voltage. A/D conversion input terminals 53 and 54 of the CPU 5 are connected to the battery 1 side of a current detecting resistor 3 and the load 4 side of the resistor 3. The voltages on the battery 1 side and the load 4 side of the resistor 3 to be inputted to the terminals 53 and 54 are detected by an A/D converter 60. A load current ILD is calculated based on the detected results and the resistor 3 resistance.