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Development of Capacitive Energy Storage High-speed Solenoid Driver (1)
Abstract: This paper introduces a capacitor storage type high-speed solenoid valve drive circuit. Through the use of high-end current feedback control feedback PWM output to achieve the precise control of the solenoid valve current. Compared with the traditional solenoid valve drive circuit, the control logic is simple, more in line with the current response characteristics of the solenoid valve, and help to reduce power consumption and prevent solenoid valve overload. Keywords: high-speed solenoid valve; drive circuit; capacitive energy storage; high-end current detection Introduction High-pressure common rail fuel injection system is one of the development directions of diesel engines. The system guarantees the engine's requirements on fuel injection timing, precise fuel injection quantity and ideal fuel injection rate by controlling the common rail pressure of fuel and quick opening and closing of the fuel injector. One of the key implementation of the device is a high-speed solenoid valve, the current response characteristics of its drive circuit should meet the following basic requirements. 1. Electromagnetic control valve before the opening of the strong power drive module should be as high as possible for the solenoid valve injection of energy to ensure that electromagnetic control valve in the opening process to produce sufficient electromagnetic force to shorten the turn on response time. 2. Electromagnetic control valve is opened, due to the smaller working air gap, the magnetic circuit is very low magnetic resistance, the electromagnetic coil into the smaller holding current can produce enough electromagnetic force to ensure the reliable solenoid valve open. Small holding current can reduce energy consumption, reduce the coil heat, while the electromagnetic control valve is conducive to the rapid closure. In summary, the solenoid valve drive circuit design requirements in different stages of the solenoid valve should maintain the appropriate ideal drive current. The current common solenoid valve drive circuit can be divided into adjustable resistance, dual voltage, pulse width modulation and dual voltage pulse width modulation 4 kinds. Which adjustable resistance drive circuit structure is simple but larger power consumption, dual-voltage power consumption has been reduced but still not ideal. Pulse width modulation and dual voltage pulse width modulation are used to control the solenoid valve to maintain current, greatly reducing power consumption. Compared with the pulse width modulation, dual voltage pulse width modulation of the benefits is that the solenoid valve to maintain the current provided by the battery, reducing the DC / DC boost circuit load. However, several common problems of the above driving circuits are that it is difficult to ensure the normal opening of the electromagnetic valve under the overlapping timing of the injection pulse width. This is because when two fuel injection signals overlap in phase, the conduction of one of the solenoid valves will cause the instantaneous voltage drop of the DC / DC boost circuit. At this time, the voltage will not be able to ensure the normal opening of the other solenoid valve. In the background of this paper, the dual-injector front and back cylinders of diesel high-pressure common rail rotator are equipped with dual injectors respectively, that is, the pilot injectors and the main injectors are independently controlled, and the injection timing of two injectors in some jobs overlapping. Therefore, it is necessary to design and develop a new type of driving circuit to ensure that the injector can work normally under these circumstances, that is, to ensure the injection timing and the precise injection quantity. Capacitance energy-saving high-speed solenoid valve drive circuit main circuit capacitor energy-saving high-speed solenoid valve drive circuit shown in Figure 1. The ignition pulse width signal INJ1 of the front cylinder of the rotor and the pilot injection pulse width signal INJ3 of the rear cylinder are input to the high-side driver chip for driving the high-side power MOS transistor Q1 after the DC / DC boost The 100V power supply charges capacitor C1 through Q1 and turns off Q1 during the injection pulse width period. The PWM generator controls the duty cycle of the 12V power input through the power MOSFET Q2. The sources of Q1 and Q2 are connected to the upper ends of the solenoid valves L1 and L3 through diodes D11 and D12 respectively. The roles of D11 and D12 are to isolate two different voltages of 100V and 12V. INJ1 and INJ3 through the low-end power MOS tubes Q4 and Q5 to achieve the election cylinder. D13, D14 for freewheeling diode. Current sense amplifier and PWM generator connected to achieve feedback control. Figure 1 Capacitive energy-saving high-speed solenoid valve drive circuit schematic diagram 2 solenoid valve current waveform diagram 3 high-side current detection circuit diagram