JPS553625A - Magnet driving circuit - Google Patents

Abstract

PURPOSE:To reduce the power consumption of a circuit by comparing the output of a circuit generating a saw-tooth reference wave form and the sensed voltage of a current flowing in a magnet by a comparator, with regard to a circuit employed in line printers and the like, and by switching a transistor which receives the comparator output and flows the current through the magnet. CONSTITUTION:A circuit is constituted by a terminal 1 to which a magnet driving signal is input, a transistor 2 which operates in response to the above signal, a comparator 3 which compares a reference voltage V1 and a sensed voltage VO, a transistor 4 for current amplification, a power transistor 5, a magnet coil 6, a resistor RT and a capacitor C which form a reference wave form together with a constant voltage Es, and a flywheel diodes D. Based on such a constitution, the reference voltage Vi and the sensed voltage VO are compared by the comparator 3, and the transistors 4 and 5 are made conductive or non-conductive depending on the resultant amount. Therefore, the operations of the transistors 4 and 5 which excite the coil 6 are intermittent and heating is reduced.