| 摘要 |
PURPOSE: A driving circuit of a solenoid valve is provided to secure stable driving of a solenoid valve by making uniform the peak currents flowing in a solenoid valve regardless of voltage change of a battery. CONSTITUTION: A solenoid valve driving circuit comprises: a capacitor(C1) charging the voltage supplied from a battery(VBB) with a uniform high voltage by a first transistor driven by a PWM(Pulse Width Modulation) signal; a second transistor(TR2) driven by the control of a control signal generating unit at an early stage of solenoid valve(SV) driving, and discharging the charge voltage of the capacitor to the solenoid valve; a third transistor(TR3) driven reverse to the second transistor, and providing the output voltage of the battery as a driving voltage of the solenoid valve; and a fourth transistor(TR4) driven by the solenoid driving signal of the control signal generating unit, and controlling the opening of the solenoid valve opened for the injection of fuel. The fourth transistor is driven by the PWM waveform outputted from the control signal generating unit to keep the open state of the solenoid valve. As the voltage outputted from the battery flows through the solenoid valve and the fourth transistor, the minimum current flows in the solenoid valve. Therefore, opening and shutoff time of the solenoid valve is kept uniform and fuel injection time is controlled accurately.
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