CN105978397B - Driving Structure of Piezoelectric Injector - Google Patents

Abstract

The invention relates to a driving structure of a piezoelectric fuel injector, which is characterized in that it comprises an actuator driving circuit module, a processor MCU, a voltage difference slope monitoring circuit and a short circuit protection circuit. By charging and discharging the high and low ends of the actuator at the same time, the voltage of the capacitor cannot be changed to form a driving voltage difference, that is, the high-end voltage of the actuator is used as the reference voltage to control the low-end discharge to form a voltage difference; The compensation method establishes the slope of the voltage difference between the high and low ends of the capacitor to control the current accuracy. The drive structure of the present invention is beneficial to the stability of the drive current, and has no inductance energy storage requirement for the filter inductance of the drive loop; in addition, the current has no multi-peak oscillation, which is beneficial to improve the EMC capability of the system.

Description

Driving Structure of Piezoelectric Injector

technical field

The invention relates to a driving structure of a piezoelectric fuel injector, which belongs to the technical field of electronic control of fuel injectors of a common rail system.

Background technique

The piezoelectric drive in foreign patents is based on the charging and discharging structure of the linear regulator mode, such as US20090038590AI or US7819337B2 of DESN Company, that is, the high-voltage source is charged to the high-end of the actuator, and then the high-end of the actuator is discharged to the ground. The whole process is controlled by The voltage and current feedback control the PWM switch of the high-end switching tube to control the high-end voltage of the actuator, and the low-end forms a gating loop to the ground through the gating circuit. This structure has great energy storage requirements for the energy storage inductance, and due to the discrete nature of the parameters in the driving structure, the slope and accuracy of the current cannot be fully guaranteed.

There are two types of injectors for the common rail system: high-speed solenoid valve type and piezoelectric crystal type. Due to its special piezoelectric effect and capacitance characteristics, the piezoelectric ceramic actuator can maintain a certain amount of elongation under certain high-voltage driving conditions, so that the fuel injector can be opened to realize the fuel injection function. Therefore, the driving process of the piezoelectric actuator includes three stages of charge-hold-discharge; that is, the actuator is first charged to open the fuel injector, and the discharge makes the elongation of the actuator smaller, and then closes the fuel injector to realize a fuel injection process.

The current piezoelectric actuator is driven by a BUCK structure that charges the actuator through high voltage, then discharges to the ground, and the low-side strobes to the ground. Through the voltage and current feedback PWM switching MOS tube, the average value of the driving voltage and driving current is kept at a relatively reasonable threshold.

Since the charging voltage of the capacitor rises exponentially, the topological structure of the circuit presents a highly discrete nature. In addition, under complex working conditions, the dielectric parameters of the piezoelectric actuator change, making the charging current difficult to control with high precision; generally through The PWM-type switch realizes the charging and discharging structure of the actuator. On the one hand, it has high requirements on the inductive energy storage of the charging and discharging inductance. On the other hand, it cannot guarantee the consistency of the slope of the driving voltage, that is, the opening time of the injector cannot be guaranteed. Accuracy; In addition, the impact of peak current on the actuator may reduce the performance and life of the actuator.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, to provide a driving structure of the piezoelectric fuel injector, through the driving current control, to ensure the accuracy of the current and the linearity of the rising slope of the driving voltage, and to improve the fuel injector The stability of the actuator reduces the impact of the peak current on the actuator and improves the reliability of the actuator.

According to the technical solution provided by the present invention, the driving structure of the piezoelectric fuel injector is characterized in that it includes an actuator driving circuit module, a processor MCU and a voltage difference slope monitoring circuit;

The actuator drive circuit module includes an actuator PT1, the high-voltage end of the actuator PT1 is connected to one end of the inductor L1 and one end of the resistor R1, and the other end of the inductor L1 is connected to the cathode end of the diode D1, the anode end of the diode D4, and the switching tube The drain terminal of Q3 is connected to one end of the resistor R21, the anode terminal of the diode D1 is connected to the source terminal of the switch tube Q1 and the drain terminal of the switch tube Q5, and the drain terminal of the switch tube Q1 is connected to the high voltage source HIV and the cathode terminal of the diode D4, The source end of the switch tube Q5 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded; the low-voltage end of the actuator PT1 is connected to one end of the inductor L2 and one end of the resistor R3, and the other end of the inductor L2 is connected to the cathode of the diode D2. terminal, the anode terminal of the diode D3, the drain terminal of the switch tube Q4 and the other end of the resistor R21, the anode terminal of the diode D2 is connected to the source terminal of the switch tube Q2 and the drain terminal of the switch tube Q6, and the drain terminal of the switch tube Q2 is connected to the drain terminal of the switch tube Q2 The high voltage source HIV is connected to the cathode end of the diode D3, the source end of the switch tube Q6 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded; the source end of the switch tube Q3 is connected to one end of the resistor R6, and the other end of the resistor R6 One end is grounded; the other end of the resistor R1 is connected to the voltage difference slope monitoring circuit and one end of the resistor R2, and the other end of the resistor R2 is grounded; the other end of the resistor R3 is connected to the voltage difference slope monitoring circuit and one end of the resistor R4 connected, the other end of the resistor R4 is grounded; the source terminal of the switch tube Q4 is connected to one end of the resistor R5, and the other end of the resistor R5 is grounded.

Further, the output terminal of the voltage difference slope monitoring circuit is connected to the processor MCU.

Further, the gates of the switching tube Q1, switching tube Q2, switching tube Q3, switching tube Q4, switching tube Q5 and switching tube Q6 are all connected to the processor MCU, and all adopt MOS tubes, which are controlled by the processor MCU to open and closure.

Further, the voltage difference slope monitoring circuit includes an amplifier U1, an amplifier U2, an amplifier U3, and an amplifier U4. The non-directional end of the amplifier U1 is connected to one end of the resistor R15 and one end of the resistor R18, the other end of the resistor R15 is grounded, and the resistor The other end of R18 is connected with the other end of resistor R1 and one end of resistor R2; the reverse end of the amplifier U1 is connected with one end of resistor R17 and one end of resistor R16, the output end of amplifier U1 is connected with the other end of resistor R16, the capacitor One terminal of C3, the non-inverting terminal of amplifier U4 is connected to the non-inverting terminal of amplifier U2, the inverting terminal of amplifier U2 is connected to reference voltage VREF1, the inverting terminal of amplifier U4 is connected to reference voltage VREF2, the other terminal of capacitor C3 is connected to one terminal of resistor R20 and The inverting end of the amplifier U3 is connected, the non-inverting end of the amplifier U3 is connected to one end of the resistor R19, the other end of the resistor R19 is grounded, and the output end of the amplifier U3 is connected to the other end of the resistor R20.

Further, the output terminals of the amplifier U1, the amplifier U2, the amplifier U3 and the amplifier U4 are connected to the processor MCU.

Further, it also includes a short-circuit protection circuit, the first input end of the short-circuit protection circuit is connected to the source end of the switch tube Q3 and one end of the resistor R6, and the second input end of the short-circuit protection circuit is connected to the source end of the switch tube Q4 and the end of the resistor R5 One end is connected, and the output end of the short-circuit protection circuit is connected with the processor MCU.

Further, the short-circuit protection circuit includes an amplifier U5 and an amplifier U6, the non-inverting end of the amplifier U5 is connected to one end of the capacitor C4, the reverse end of the amplifier U5 is connected to the other end of the capacitor C4, one end of the resistor R203, and one end of the resistor R206 , the other end of the resistor R203 is grounded, the output end of the amplifier U5 is connected to the other end of the resistor R206 and one end of the resistor R202, the other end of the resistor R202 is connected to one end of the capacitor C5 and the reverse end of the amplifier U6, and the non-inverting end of the amplifier U6 The other end of the capacitor C5 is connected to the reference voltage VREF, the output end of the amplifier U6 is connected to one end of the resistor R204 and one end of the resistor R205, the other end of the resistor R204 is connected to the VCC voltage, and the other end of the resistor R205 is connected to the processor MCU.

Further, the positive power supply terminal of the amplifier U5 is connected to the VCC voltage, and the positive power supply terminal of the amplifier U5 is grounded through the capacitor C6; the positive power supply terminal of the amplifier U6 is connected to the VCC voltage, and the negative power supply terminal of the amplifier U6 is grounded.

The driving structure of the piezoelectric fuel injector described in the present invention, by charging and discharging the high and low ends of the actuator at the same time, utilizes the voltage non-variable characteristics of the capacitor to form a driving pressure difference, that is, the high-end voltage of the actuator is used as a reference voltage to control the low voltage. Discharge at the end to form a voltage difference; in the establishment of the drive process, the slope of the voltage difference between the high and low ends of the capacitor is established by means of external capacitance compensation to control the current accuracy. The drive structure of the present invention is beneficial to the stability of the drive current, and has no inductance energy storage requirement for the filter inductance of the drive loop; in addition, the current has no multi-peak oscillation, which is beneficial to improve the EMC capability of the system.

Description of drawings

Fig. 1 is a frame diagram of the driving structure of the present invention.

FIG. 2 is a schematic diagram of a voltage difference slope monitoring circuit.

FIG. 3 is a schematic diagram of a short circuit protection circuit.

Figure 4 is a schematic diagram of the current flow of the high-voltage source charging the high and low terminals and capacitors of the actuator.

Figure 5 is a schematic diagram of the current flow of the low-end discharge of the actuator.

Figure 6 is a schematic diagram of the current flow of the high-end discharge of the actuator.

detailed description

The present invention will be further described below in conjunction with specific drawings.

As shown in Figure 1, the present invention includes an actuator drive circuit module, a processor MCU, a voltage difference slope monitoring circuit and a short circuit protection circuit;

The actuator drive circuit module includes an actuator PT1, the high-voltage end of the actuator PT1 is connected to one end of the inductor L1 and one end of the resistor R1, and the other end of the inductor L1 is connected to the cathode end of the diode D1, the anode end of the diode D4, and the switching tube The drain terminal of Q3 is connected to one end of the resistor R21, the anode terminal of the diode D1 is connected to the source terminal of the switch tube Q1 and the drain terminal of the switch tube Q5, and the drain terminal of the switch tube Q1 is connected to the high voltage source HIV and the cathode terminal of the diode D4, The source end of the switch tube Q5 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded; the low-voltage end of the actuator PT1 is connected to one end of the inductor L2 and one end of the resistor R3, and the other end of the inductor L2 is connected to the cathode of the diode D2. terminal, the anode terminal of the diode D3, the drain terminal of the switch tube Q4 and the other end of the resistor R21, the anode terminal of the diode D2 is connected to the source terminal of the switch tube Q2 and the drain terminal of the switch tube Q6, and the drain terminal of the switch tube Q2 is connected to the drain terminal of the switch tube Q2 The high voltage source HIV is connected to the cathode terminal of the diode D3, the source terminal of the switch tube Q6 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded.

The source end of the switch tube Q3 is connected to the short-circuit protection circuit and one end of the resistor R6, and the other end of the resistor R6 is grounded;

The other end of the resistor R1 is connected to the voltage difference slope monitoring circuit and one end of the resistor R2, and the other end of the resistor R2 is grounded;

The other end of the resistor R3 is connected to the voltage difference slope monitoring circuit and one end of the resistor R4, and the other end of the resistor R4 is grounded;

The source end of the switch tube Q4 is connected to the short circuit protection circuit and one end of the resistor R5, and the other end of the resistor R5 is grounded;

The output terminals of the voltage difference slope monitoring circuit and the short circuit protection circuit are connected with the processor MCU.

The gates of the switching tubes Q1, Q2, Q3, Q4, Q5 and Q6 are all connected to the processor MCU, and are all MOS tubes, which are turned on and off by the processor MCU.

The current piezoelectric actuator drive is a single-ended charging method in which the low-end of the actuator is gated to the ground, and the ground plane is used as a reference to form a loop, and the high-voltage is controlled to charge the high-end of the actuator. Current control uses the storage capacity of the inductor to achieve continuous charge and discharge or discontinuous charge and discharge modes to control the drive current.

The solution of the present invention takes the voltage difference between the two ends of the actuator as the control object, and ensures sufficient driving voltage by controlling the voltage difference between the high and low ends in real time.

From u=∫itdt/c, get It can be deduced that the slope of the driving current and the driving voltage difference presents a linear relationship. For the three modes of piezoelectric drive, the corresponding current slope relationship is as follows:

(1) Trapezoidal wave mode:

(2) Triangular wave single peak mode:

(3) Multi-peak mode:

In different working modes, the driving coefficient of the driving current can be kept at the calculated value, so that the driving of the output current in different modes has high control accuracy characteristics, and the energy storage requirement of the inductor is low. Among them, A is the preset current threshold, k is the slope of the driving differential pressure, and C is the capacitance value of the piezoelectric actuator. The calculated value is fed back through the MCU.

Piezoelectric fuel injectors mainly use the inverse piezoelectric effect of piezoelectric materials to drive the fuel injector switch, thereby controlling the accuracy of fuel volume and fuel injection characteristics. The drive structure of the present invention controls the fixed pressure difference between the high and low ends of the piezoelectric actuator and real-time control of the discharge slope as the minimum drive unit parameter to drive the actuator, ensuring current accuracy and stable charging efficiency.

As shown in Figure 2, the voltage difference slope monitoring circuit includes an amplifier U1, an amplifier U2, an amplifier U3, and an amplifier U4, the same direction end of the amplifier U1 is connected with one end of the resistor R15 and one end of the resistor R18, and the other end of the resistor R15 The other end of the resistor R18 is connected to the other end of the resistor R1 and one end of the resistor R2; the reverse end of the amplifier U1 is connected to one end of the resistor R17 and one end of the resistor R16, and the output end of the amplifier U1 is connected to the other end of the resistor R16 One terminal, one terminal of capacitor C3, the non-inverting terminal of amplifier U4 and the non-inverting terminal of amplifier U2 are connected, the reverse terminal of amplifier U2 is connected to reference voltage VREF1, the negative terminal of amplifier U4 is connected to reference voltage VREF2, the other terminal of capacitor C3 is connected to resistor R20 One end of the amplifier U3 is connected to the reverse end of the amplifier U3, the same phase end of the amplifier U3 is connected to one end of the resistor R19, the other end of the resistor R19 is grounded, and the output end of the amplifier U3 is connected to the other end of the resistor R20; the amplifier U1, the amplifier U2 , the output terminals of the amplifier U3 and the amplifier U4 are connected with the processor MCU; the output terminal of the amplifier U1 outputs a differential pressure signal 10, the output terminal of the amplifier U2 differential pressure high-end threshold signal 7, and the output terminal of the amplifier U3 outputs a differential circuit signal 8 , the amplifier U4 outputs a low-end threshold signal 11.

The working principle of the present invention is to realize the driving requirements of the actuator by controlling the pressure difference between the high and low ends. Compared with the triangular wave, trapezoidal wave and multi-peak triangular wave, there are three calculations of the slope coefficient of the pressure difference; after monitoring and adjusting the k coefficient Get the expected pressure drop slope threshold, and adjust the driving duty cycle after the actual sampling process. First turn on the switch tubes Q1 and Q2 to make the high voltage source HIV form a loop to the high and low ends of the actuator PT1, so that its pressure difference is 0 and maintain a high voltage to the ground. At the same time, the PWM mode turns on the switch tubes Q5 and Q6 to make the capacitors C1 and C2 Charging to the equipotential voltage of the actuator PT1 provides current compensation for the subsequent driving process; the current flow in this state is shown in Figure 4. Then turn off the switch tubes Q1 and Q2, turn on the switch tubes Q5, Q4, and Q6 to form a loop from C1-L1-PT1-L2-Q4 to the ground (the current flow direction is shown in Figure 5), through the voltage difference between the high and low terminals of the actuator The calculation, until the reference voltage VREF1 of the voltage difference slope monitoring circuit is triggered, in the designed driving mode, the high and low end discharge duty cycle is calculated. Due to the clamping effect of the inductor L2 and the diode D2, the low-end voltage of the actuator will not be discharged to the ground immediately, which is enough for the processing of the feedback time of the voltage difference sampling. During this period, the slope of the differential pressure is sampled through the differential circuit, and compared with the expected algorithm value, the duty cycle of the switching tubes Q4 and Q6 is adjusted by feedback. Due to the current compensation function of capacitors C1 and C2, according to the KCL law (Kirchhoff's law), it can buffer the discharge voltage of the high and low ends of the actuator. When the pressure difference between the high and low ends of the AB actuator reaches a predetermined value, in order to maintain a constant pressure difference, while the low end discharges, the high end also needs to discharge at the same slope. The process is like a mirror image of the low end, forming C2-L2-PT1- The loop of L1-Q3 (the current flow direction is shown in Figure 6) forms the result of the high-end discharge of the actuator. When the low-end voltage reaches 0, the reference voltage VREF2 of the voltage difference slope monitoring circuit is triggered, and the high-end discharge effect is turned off, that is, the switching tubes Q3 and Q4 are turned off.

When the actuator drive ends, it is necessary to reduce the pressure difference between the high and low ends of the actuator. Since the low end voltage is 0 at this time, it is necessary to continue to open the C2-L2-PT1-L1-Q3 circuit to discharge, that is, to open the switch tube Q3. Same as starting the driving process, it is also necessary to correct the duty cycle of the switching tubes Q5 and Q3 through the k coefficient; compare the differential pressure signal 10 with the low-end threshold signal 11 to obtain the logic signal to turn off the switching tube Q3 and reopen the switching tube Q1, Q2, when the voltage difference between the high and low ends of the actuator is 0, the actuator is turned off, thereby realizing a driving cycle.

The working process of the present invention is described in detail as follows:

(1) After the power-on initialization is completed, the current working mode is detected, and the pressure difference threshold and the pressure difference slope k are established. During the T1 time period, the charging of the high and low end voltage of the actuator is completed. Since there is no return to the ground, the pressure difference is zero. That is, turn on the switch tubes Q1 and Q2, and turn on the switch tubes Q5 and Q6 in PWM mode, and charge the capacitors C1 and C2 while charging the actuator, so as to reach the current compensation potential.

(2) The actuator starts to be driven during the T2 period, the low end of the actuator is discharged, and the switch tube Q4 is turned on to start discharging, forming a pressure difference between the high and low ends of the actuator, and Q5 and Q6 provide current compensation, and the switch is controlled by the MCU;

At this time, the voltage difference slope monitoring circuit feeds back the differential pressure signal 10 to the processor MCU and the differential voltage high-end threshold signal 7 to determine the switching logic, and the differential circuit signal 8 is calculated by an algorithm and compared with the target value to adjust the Q4 switch duty cycle; when the actual voltage If the differential slope is higher than the expected calculated value k coefficient, the duty cycle of Q4 is increased and the duty cycle of Q6 is decreased; when the actual differential pressure slope is lower than the expected value, the duty cycle of Q4 is decreased and the duty cycle of Q6 is increased.

(3) The T3 time period means that when the driving pressure difference threshold is reached, Q3 is turned on, and the high and low ends are discharged with the same slope through MCU control until the low end voltage is 0; in this period of injection maintenance stage, when the low end voltage is 0, it is turned off All the switching tubes are not controlled, and a loop is formed by large resistors R1, R2, R3 and R4 to maintain the driving state of the voltage difference.

(4) T4 time period is the actuator closed drive state, its working process and T2 section and T3 section present a mirror image action, that is, open Q6 to form a discharge circuit, PWM controls Q3 and Q5; the pressure difference signal 10 is fed back to the MCU and the pressure difference The low-side threshold signal 11 determines the switching logic;

The differential circuit signal 8 is compared with the target coefficient k to adjust the duty cycle of Q3 and Q5. When the pressure difference is 0, close Q3 and Q5, open Q1 and Q2 to continue charging and prepare for the next cycle.

The short-circuit protection circuit always monitors the charging and discharging current at the high and low ends of the piezoelectric actuator, and feeds back a protection signal to the MCU to decide whether to turn off the drive. As shown in Figure 3, the short circuit protection circuit includes an amplifier U5 and an amplifier U6, the non-inverting end of the amplifier U5 is connected to one end of the capacitor C4, the reverse end of the amplifier U5 is connected to the other end of the capacitor C4, one end of the resistor R203 and the resistor R206 One end of the resistor R203 is connected to the ground, the output end of the amplifier U5 is connected to the other end of the resistor R206 and one end of the resistor R202, the other end of the resistor R202 is connected to one end of the capacitor C5 and the reverse end of the amplifier U6, and the amplifier U6 The non-inverting end of the capacitor C5 is connected to the other end of the capacitor C5 and the reference voltage VREF, the output end of the amplifier U6 is connected to one end of the resistor R204 and one end of the resistor R205, the other end of the resistor R204 is connected to the VCC voltage, and the other end of the resistor R205 is connected to the processor MCU connected to output the current signal I_PROTECT; the positive power supply end of the amplifier U5 is connected to the VCC voltage, and the positive power supply end of the amplifier U5 is grounded through the capacitor C6; the positive power supply end of the amplifier U6 is connected to the VCC voltage, and the negative power supply of the amplifier U6 end grounded.

The present invention realizes reducing the switching loss of power devices and improving The accuracy of the injector current control improves the working accuracy of the injector.

Claims (8)

1. A drive structure of a piezoelectric fuel injector, characterized in that: comprising an actuator drive circuit module, a processor MCU and a voltage difference slope monitoring circuit; The actuator drive circuit module includes an actuator PT1, the high-voltage end of the actuator PT1 is connected to one end of the inductor L1 and one end of the resistor R1, and the other end of the inductor L1 is connected to the cathode end of the diode D1, the anode end of the diode D4, and the switching tube The drain terminal of Q3 is connected to one end of the resistor R21, the anode terminal of the diode D1 is connected to the source terminal of the switch tube Q1 and the drain terminal of the switch tube Q5, and the drain terminal of the switch tube Q1 is connected to the high voltage source HIV and the cathode terminal of the diode D4, The source end of the switch tube Q5 is connected to one end of the capacitor C1, and the other end of the capacitor C1 is grounded; the low-voltage end of the actuator PT1 is connected to one end of the inductor L2 and one end of the resistor R3, and the other end of the inductor L2 is connected to the cathode of the diode D2. terminal, the anode terminal of the diode D3, the drain terminal of the switch tube Q4 and the other end of the resistor R21, the anode terminal of the diode D2 is connected to the source terminal of the switch tube Q2 and the drain terminal of the switch tube Q6, and the drain terminal of the switch tube Q2 is connected to the drain terminal of the switch tube Q2 The high voltage source HIV is connected to the cathode end of the diode D3, the source end of the switch tube Q6 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded; the source end of the switch tube Q3 is connected to one end of the resistor R6, and the other end of the resistor R6 One end is grounded; the other end of the resistor R1 is connected to the voltage difference slope monitoring circuit and one end of the resistor R2, and the other end of the resistor R2 is grounded; the other end of the resistor R3 is connected to the voltage difference slope monitoring circuit and one end of the resistor R4 connected, the other end of the resistor R4 is grounded; the source terminal of the switch tube Q4 is connected to one end of the resistor R5, and the other end of the resistor R5 is grounded. 2. The driving structure of the piezoelectric fuel injector according to claim 1, characterized in that: the output terminal of the voltage difference slope monitoring circuit is connected to the processor MCU. 3. The driving structure of the piezoelectric fuel injector according to claim 1, characterized in that: the gates of the switching tube Q1, switching tube Q2, switching tube Q3, switching tube Q4, switching tube Q5 and switching tube Q6 are Both are connected to the processor MCU, and all use MOS tubes, which are turned on and off by the processor MCU. 4. The driving structure of the piezoelectric injector according to claim 1, characterized in that: said voltage difference slope monitoring circuit comprises amplifier U1, amplifier U2, amplifier U3 and amplifier U4, the same direction terminal of amplifier U1 is connected to One end of the resistor R15 is connected to one end of the resistor R18, the other end of the resistor R15 is grounded, the other end of the resistor R18 is connected to the other end of the resistor R1 and one end of the resistor R2; the reverse end of the amplifier U1 is connected to one end of the resistor R17 and One end of the resistor R16 is connected, the output end of the amplifier U1 is connected to the other end of the resistor R16, one end of the capacitor C3, the non-inverting end of the amplifier U4 and the non-inverting end of the amplifier U2, the reverse end of the amplifier U2 is connected to the reference voltage VREF1, and the output of the amplifier U4 The reverse end is connected to the reference voltage VREF2, the other end of the capacitor C3 is connected to one end of the resistor R20 and the reverse end of the amplifier U3, the non-inverting end of the amplifier U3 is connected to one end of the resistor R19, the other end of the resistor R19 is grounded, and the output of the amplifier U3 The end is connected with the other end of the resistor R20. 5. The driving structure of the piezoelectric fuel injector according to claim 4, characterized in that: the output terminals of the amplifier U1, the amplifier U2, the amplifier U3 and the amplifier U4 are connected to the processor MCU. 6. The driving structure of the piezoelectric fuel injector according to claim 1, further comprising a short circuit protection circuit, the first input terminal of the short circuit protection circuit is connected to the source terminal of the switch tube Q3 and one end of the resistor R6, The second input terminal of the short-circuit protection circuit is connected with the source terminal of the switch tube Q4 and one end of the resistor R5, and the output terminal of the short-circuit protection circuit is connected with the processor MCU. 7. The driving structure of the piezoelectric fuel injector according to claim 6, characterized in that: the short-circuit protection circuit includes an amplifier U5 and an amplifier U6, the non-inverting end of the amplifier U5 is connected to one end of the capacitor C4, and the inverting end of the amplifier U5 The opposite end is connected to the other end of the capacitor C4, one end of the resistor R203 and one end of the resistor R206, the other end of the resistor R203 is grounded, the output end of the amplifier U5 is connected to the other end of the resistor R206 and one end of the resistor R202, and the other end of the resistor R202 One end of the capacitor C5 is connected to the reverse end of the amplifier U6, the non-inverting end of the amplifier U6 is connected to the other end of the capacitor C5 and the reference voltage VREF, the output end of the amplifier U6 is connected to one end of the resistor R204 and one end of the resistor R205, and the resistor R204 The other end of the resistor R205 is connected to the VCC voltage, and the other end of the resistor R205 is connected to the processor MCU. 8. The driving structure of the piezoelectric fuel injector according to claim 7, characterized in that: the positive power supply terminal of the amplifier U5 is connected to the VCC voltage, and the positive power supply terminal of the amplifier U5 is grounded through a capacitor C6; The positive power supply terminal of U6 is connected to the VCC voltage, and the negative power supply terminal of the amplifier U6 is grounded.