| 摘要 |
PURPOSE: To provide a motor drive circuit in which the effect of high frequency noise generated from a PWM drive circuit can be suppressed. CONSTITUTION: An insulating film 2a is formed on the surface of the metallic base substrate 2 of a brushless motor and a PWM drive circuit 7 is formed on the surface of the film 2a. Filter capacitors Cu, Cv, Cw are formed between the base substrate 2 and wiring patterns 15u, 15v, 15w through which the driving current of a drive coil flows by grounding the baseboard 2. Capacitance of these capacitors is optimized by regulating the profile of the wiring patterns or the thickness of the insulating film 2a. Since the effect of high frequency noise generated from the PWM drive circuit is suppressed, the circuit 7 requires no special shield and fluctuation of a current being supplied to a drive transistor is not required to be gentled. Furthermore, no extra snubber circuit for absorbing noise is required.
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