PULSE MOTOR DRIVE CIRCUIT

PURPOSE:To detect electric failure quickly and protect a motor or peripheral circuit element against burning by suspending the driving of a pulse motor forcibly when the chopping duty ratio deviates from predetermined upper or lower limits. CONSTITUTION:When the collector-emitter of a CHOPTR 6, i.e., the lines VP1 and COM1, shorticircuit, output of an HDTY 20 goes High to turn a PCUTTR 22 OFF. Consequently, the second control input C2 of motor exciting circuits 8-11 goes Low thus sustaining INDTRs 8a-11a forcibly in OFF state irrespective of the level of a first control input C1. According to the constitution, a pulse motor 4 can be protected against burning due to excessive current flow through the exciting phases 42, 44 and the INDTRs 8a, 9a upon short circuit of the lines VP1-COM1. The motor can be protected similarly in case of short circuit of lines VP2-COM2.