CONTROL CIRCUIT FOR BLOWER MOTOR IN ONBOARD AIR-CONDITIONER

摘要

PURPOSE:To enhance the performance of an air-conditioner without increasing noise from a blower motor or stopping rotation thereof, by providing a blower motor control circuit for the air-conditioner in which a control signal that varies in part along a function corresponding to a source power voltage of an automobile, is subtracted from the source power voltage, and thus subtracted value is applied to the blower motor. CONSTITUTION:A control circuit 1 is mainly composed of a first signal generating circuit 2, a second signal generating circuit 3, a limiter signal generating circuit 4 and a subtracting circuit 5. The output terminals 21, 31, 41 of the first, second and limiter signal generating circuits 2, 3, 4 are commonly connected so as to synthesize their outputs in order to obtain a control signal. Thereafter, a voltage amplifier 51 in the subtraction circuit 5 to which the control signal is applied, amplifies the control signal up to a suitable voltage, and then delivers the same to a drive transistor 52 connected in series to a blower motor 6 applied with a source power voltage IG. With this arrangement, the voltage between the collector and emitter of the drive transistor 52 is controlled so as to subtract the control signal SG from the power source voltage IG.