HANDOTAISHUSEKIKAIROSOCHITORANPUTENTOHOHO

摘要

PURPOSE:To reduce a current upon current limiting operation, by a method wherein a pulse width modulating signal in inverse proportion to the value of the current is formed to control a power output element when the current flowing through the power output element has a larger value than a given value of current. CONSTITUTION:A power switch circuit is employed for a lamp driving circuit for vehicles and a power output element MOS is operated as a switch for forming the driving current of a lamp LP for vehicles. A sense current Is, corresponding to the driving current of the element MOS, is detected by a current sense circuit IS and is outputted after converting it into a voltage signal Vs. A comparing circuit CMP compares the voltage signal Vs with a lamp voltage Vr formed by a triangular wave generating circuit RPG while the result of the comparison is inputted into a PWM width modulating circuit PWM to form a pulse width driving signal VC in inverse proportion to the value of the current Is upon overcurrent. According to this method, the driving signal VC is used as the control signal of a gate circuit G to drive the element MOS intermittently.