Honda Giken Kogyo K.k.

Yetsuya Oono

Shinichi Inagawa

Yukihisa Ishii

A driving circuit for driving a stepping motor has a plurality of excitation coils, a plurality of excitation transistors for driving the excitation coils of the stepping motor, respectively, and at least one chopping transistor for effecting chopping control of current flowing to the excitation coils. A fault diagnosis transistor is connected in parallel with the chopping transistor. A current limiting resistance is serially connected to the fault diagnosis transistor. A CPU selectively turns on and off the fault diagnosis transistor. The CPU detects output states of the chopping transistor assumed respectively when the fault diagnosis transistor is turned on and turned off. The CPU compares the detected output levels of the chopping transistor with respective predetermined logic levels and detects faults in the driving circuit from results of the comparisons.

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Wako, Japan

Yetsuya Oono