| 摘要 |
A boosting circuit and an electronic power steering system are provided to prevent a motor from stopping by continuously supplying low voltage to the motor in wrong operation of a switching element of a chopper circuit and by assembling the boosting circuit with the electric power steering system. A battery(E) of a vehicle is connected to a chopper circuit(13) through an ignition switch(11) and a fault detection circuit(12), and the chopper circuit is composed of a first switching element(TR1) comprising an inductor(L1) and a power MOSFET, a second switching element(TR2) and a smooth condenser(C1) connected to an output side. A gate terminal of the first switching element is connected to a control unit(10), and the fault detection circuit is composed of a current detection resistor(R1) connected between the inductor and the ignition switch and an amplifier(OP1) detecting voltage at both ends of the resistor. A cutoff relay switch(14) is connected between the inductor and the first switching element, and turned on and off by the control unit. The control unit controls pulse width modulation of the first switching element in turning on the ignition switch, monitors signals from the fault detection circuit, and turns off the relay switch by deciding disconnection of the first switching element in case of voltage detected from the resistor to be over the predetermined value to cut off the switching element from the inductor.
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