Patent ID: 6377428
Filing Date: 2002-04-23
Classification: H03K

Abstract:
A switching device, comprising:a driving device which outputs a drive signal in response to a drive command signal; a first switching device inserted in a power supply circuit connecting a power supply and a load, the first switching device being adapted to conduct in response to the drive signal and close the power supply circuit; a reference resistor which generates a reference voltage by receiving a current from the power supply; a second switching device inserted in a shunt circuit connecting the power supply and the reference resistor, the second switching device being adapted to conduct in response to the drive signal and close the shunt circuit; an abnormality determining device which determines an abnormality by comparing an output voltage from the first switching device and the reference voltage so as to stop the driving device from outputting the drive signal; an on/off counter circuit which outputs a latch command signal when the first switching device has repeated conduction and nonconduction a set number of times in accordance with a state of the load by monitoring a state of the first switching device; and a cutoff latch circuit which renders the first switching device in a nonconducting state in response to the latch command signal and latches the nonconducting state.