Patent ID: 6844760

Claim:
A drive circuit comprised of the following: a switching power supply, a switch that interrupts the power supplied from the switching power supply to a driven object, a detecting means that detects the current flowing in the driven object and outputs a detection signal corresponding to the detection result, an error signal generating means that generates an error signal corresponding to the error between the detection signal output from the detecting means and the setpoint signal, a signal holding means that averages the error signal generated by the error signal generating means when the switch is on, holds the averaged error signal when the switch is turned off from the on state, and starts the averaging of the error signal with the level of the held error signal as the initial level when the switch is turned on from the off state, and a switching power supply control means that controls the switching power supply to stop the supply of power to the driven object when the switch is off and controls the power supplied by the switching power supply to the driven object corresponding to the error signal averaged by the signal holding means when the switch is on.