PURPOSE: To avoid such a case where the pulse current higher than a rated level flows to a function gate owing to the trouble of a function driver, etc., by providing a means which calculates the time integration of the pulse current and delivers it as the corresponding voltage and another means which cuts off the pulse current in case said output voltage exceeds a prescribed level.
CONSTITUTION: A current integration arithmetic means 1 is provided together with a current cut-off means 2. In case the pulse current produced by a function driver 3 flows for a prescribed period of time or longer owing to a trouble or noises, etc. or an excessive pulse current flows, the current integration value obtained by the means 1 is increased and the output voltage Vb exceeds the prescribed voltage Vref. As a result, the output of a comparator 21 is turned into the negative voltage and switch circuits 23W25 are turned off to cut off the pulse current flowing to a function gate 4 from the driver 3. Thus it is possible to avoid a case where the current higher than a rated level flows to the gate 4.
NOGAI KENGO
ONODERA TOSHIYA
SHIBATA HIROYUKI
