Bipolar high-voltage pulse driving circuit and driving method of air-coupled ultrasonic transducer

Abstract

The invention discloses a bipolar high-voltage pulse driving circuit and driving method of an air coupling ultrasonic transducer, the driving circuit comprises a control circuit, an auxiliary power supply circuit, a pulse transmitting unit and a high-voltage output unit, and the high-voltage output unit comprises a high-frequency inverter circuit, a high-frequency transformer T1 and a voltage doubling rectifying circuit. According to the bipolar high-voltage pulse driving circuit and the driving method, a bipolar high-voltage controllable excitation signal can be generated while the high-voltage driving requirement of the ultrasonic transducer is met by only one low-voltage power supply, and the received ultrasonic energy is remarkably improved.

Description

Technical Field

[0001] The present invention relates to a high-voltage pulse driving circuit and a driving method, in particular to a bipolar high-voltage pulse driving circuit and a driving method for an air-coupled ultrasonic transducer. Background Art

[0002] There are two types of pulse generators developed so far. One is a unipolar spike pulse generator, which is most commonly used to detect samples with low attenuation, uniformity and fine grains, such as metals, forgings, etc. The spike pulse generator has the advantage of a wide spectrum, providing a voltage of up to 800V for low-frequency sensors. However, the single pulse excitation signal is not as energetic as the bipolar pulse excitation signal, resulting in the emission of ultrasonic waves that are insufficient to penetrate lithium battery defects, making it difficult to achieve air-coupled ultrasonic lithium battery defect detection.

[0003] Another method is to use a pulse transformer to generate a bipolar pulse voltage to excite the piezoelectric ceramic inside the ultrasonic transducer. However, in order to achieve ultrasonic energy that can penetrate the defects of lithium batteries, only a single transformer is used for voltage boosting. Using a lower input voltage will result in a too large transformer turns ratio, which will increase the size of the transformer and require high insulation. Its distributed capacitance and leakage inductance will also have a significant impact on the system. In addition, the voltage has high requirements on the withstand voltage of the components of the transformer secondary rectifier circuit.

[0004] Air-coupled ultrasonic testing technology has broken through the limitations of traditional methods. Its non-contact, non-destructive and real-time characteristics have great potential in the detection of internal defects in lithium batteries. However, air-coupled ultrasonic testing technology still has bottlenecks that need to be broken through in the application of lithium batteries. The acoustic impedance differences between air, ultrasonic matching layer, and lithium battery materials are significant. Especially when there are bubbles or stratification defects inside the battery, multiple gas-solid alternating interfaces will be formed between the transducer and the sensor, which have a large attenuation of ultrasonic waves. Due to the limitation of insufficient energy, ultrasonic waves may have difficulty penetrating the bubble-containing area of ​​the lithium battery, making air-coupled ultrasonic detection not ideal for the detection of defects such as bubbles, pole piece perforations, wrinkles and stratification.

[0005] The deficiencies in the prior art are: (1) the driving method only uses a single pulse transformer to generate high-voltage pulses. Due to the working principle of the pulse transformer, any transformer has leakage inductance. A too high turns ratio will cause the magnetic core to deviate from the optimal magnetic flux density during operation, resulting in core saturation or increased hysteresis loss, thereby reducing the efficiency of the transformer; (2) In order to support a higher turns ratio, more coil turns may be required, which increases the complexity of design and manufacturing, increases the size and cost of the transformer, and when the turns ratio is too large, the voltage on the secondary coil may be too high, which may exceed the withstand voltage limit of the insulating material, increasing the risk of insulation breakdown; (3) For the traditional unipolar pulse driving method, although there is no design impact caused by transformer-related problems, because the single pulse excitation signal is not as energetic as the bipolar pulse excitation signal, the emitted ultrasonic wave is insufficient to penetrate the lithium battery defects, making it difficult to achieve air-coupled ultrasonic lithium battery defect detection. Summary of the invention

[0006] The purpose of the invention is to provide a bipolar high-voltage pulse driving circuit and driving method for an air-coupled ultrasonic transducer, which can generate a bipolar high-voltage pulse signal that meets the high-voltage driving requirements of the ultrasonic transducer.

[0007] Technical solution: The bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer described in the present invention includes a control circuit, an auxiliary power supply circuit, a pulse transmitting unit and a high-voltage output unit, and the high-voltage output unit includes a high-frequency inverter circuit, a high-frequency transformer T1 and a voltage doubler rectifier circuit; the input end of the high-frequency inverter circuit is used to connect to a 12V DC input, and the output end of the high-frequency inverter circuit is electrically connected to the input side of the high-frequency transformer T1; the output side of the high-frequency transformer T1 is electrically connected to the input end of the voltage doubler rectifier circuit, and the output end of the voltage doubler rectifier circuit is electrically connected to the high-voltage input end of the pulse transmitting unit; the control circuit is electrically connected to the control end of the high-frequency inverter circuit and the control end of the pulse transmitting unit respectively; the output end of the pulse transmitting unit is used to electrically connect to the input end of the air-coupled ultrasonic high-voltage transducer to output an ultrasonic driving signal to the air-coupled ultrasonic high-voltage transducer; the auxiliary power supply circuit supplies power to the control circuit and the pulse transmitting unit respectively.

[0008] Furthermore, the pulse emission unit includes an optocoupler isolation circuit, a MOSFET drive circuit and a power amplifier circuit; the control end of the optocoupler isolation circuit is electrically connected to the control circuit, and the output end of the optocoupler isolation circuit is electrically connected to the input end of the MOSFET drive circuit; the output end of the MOSFET drive circuit is electrically connected to the control end of the power amplifier circuit, and is used to drive and control the power amplifier circuit; the output end of the power amplifier circuit is used to be electrically connected to the input end of the air-coupled ultrasonic high-voltage transducer, and output an ultrasonic drive signal to the air-coupled ultrasonic high-voltage transducer.

[0009] Further, the high-frequency inverter circuit includes a MOS transistor Q1 and a MOS transistor Q2; the voltage doubler rectifier circuit includes a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a diode D1, a diode D2, a diode D3 and a diode D4; the G poles of the MOS transistor Q1 and the MOS transistor Q2 are electrically connected to the control circuit; the D pole of the MOS transistor Q1 is electrically connected to one end of the primary coil of the high-frequency transformer T1, and the D pole of the MOS transistor Q2 is electrically connected to the other end of the primary coil of the high-frequency transformer T1; the S poles of the MOS transistor Q1 and the MOS transistor Q2 are both used to be electrically connected to the negative pole of the 12V DC input; the midpoint of the primary coil of the high-frequency transformer T1 is used to be electrically connected to the positive pole of the 12V DC input; One end of the secondary coil of the high-frequency transformer T1 is electrically connected to one end of the capacitor C1 and one end of the capacitor C3, respectively; the other end of the secondary coil of the high-frequency transformer T1 is electrically connected to one end of the capacitor C2, the positive electrode of the diode D1, one end of the capacitor C4 and the negative electrode of the diode D3, respectively; the other end of the capacitor C1 is electrically connected to the negative electrode of the diode D1 and the positive electrode of the diode D2, respectively; the negative electrode of the diode D2 and the other end of the capacitor C2 are electrically connected to serve as the positive output end of the voltage doubler rectifier circuit; the other end of the capacitor C4 is electrically connected to the positive electrode of the diode D4; the other end of the capacitor C3, the positive electrode of the diode D3 and the negative electrode of the diode D4 are electrically connected to serve as the negative output end of the voltage doubler rectifier circuit.

[0010] Further, the optocoupler isolation circuit includes an optocoupler isolator M1 and an optocoupler isolator M2; the MOSFET driving circuit includes a MOS driver Q5 and a MOS driver Q6; the power amplifier circuit includes a MOS tube Q3, a MOS tube Q4, a resistor R1, a resistor R2, a resistor R3, a diode D5, a diode D6, a capacitor C5 and a resistor R4; the input ends of the optocoupler isolator M1 and the optocoupler isolator M2 are both electrically connected to the control circuit, the output end of the optocoupler isolator M1 is electrically connected to the input end of the MOS driver Q5, and the output end of the optocoupler isolator M2 is electrically connected to the input end of the MOS driver Q6; the output end of the MOS driver Q5 is electrically connected to the G pole of the MOS tube Q3; the output end of the MOS driver Q6 is electrically connected to the G pole of the MOS tube Q3; the output end of the MOS driver Q6 is electrically connected to the G pole of the MOS tube Q3. The output end is electrically connected to the G pole of the MOS tube Q4; the D pole of the MOS tube Q3, one end of the resistor R1 and the cathode of the diode D5 are all electrically connected to the positive output end of the voltage doubler rectifier circuit; the S pole of the MOS tube Q3 is respectively electrically connected to the other end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and the D pole of the MOS tube Q4; the S pole of the MOS tube Q4 is respectively electrically connected to the other end of the resistor R2 and the anode of the diode D6 and then grounded; the cathode of the diode D6 is respectively electrically connected to the other end of the resistor R3, the a end of the capacitor C5 and the anode of the diode D5; the b end of the capacitor C5 is electrically connected to one end of the resistor R4 and serves as the output end of the power amplifier circuit; the other end of the resistor R4 is grounded.

[0011] The present invention also provides a driving method for a bipolar high-voltage pulse driving circuit of an air-coupled ultrasonic transducer, comprising a high-voltage output step and an excitation output step;

[0012] The steps for high voltage output are:

[0013] The control circuit sends pulse drive signals K1 and K2 alternately to the S poles of the MOS tube Q1 and the MOS tube Q2. When the pulse drive signal K1 is received, the MOS tube Q1 is turned on, and the current flows into a part of the primary coil of the high-frequency transformer T1 through the 12V DC input. When the pulse drive signal K2 is received, the MOS tube Q2 is turned on, and the current flows into another part of the primary coil of the high-frequency transformer T1 through the 12V DC input, thereby generating a high-frequency AC voltage waveform in the primary coil of the high-frequency transformer T1.

[0014] The high-frequency transformer T1 outputs a boosted AC voltage on the secondary coil, and then the diode D1, the diode D2, the capacitor C1 and the capacitor C2 convert the positive half cycle of the AC voltage waveform into DC power, and the diode D3, the diode D4, the capacitor C3 and the capacitor C4 convert the negative half cycle of the AC voltage waveform into DC power;

[0015] The DC power converted in the positive half cycle and the DC power converted in the negative half cycle form a complete DC output voltage, which is recorded as HVDD.

[0016] The steps of stimulus output are:

[0017] When charging, the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, MOS tubes Q3 and Q4 are turned off, and the DC output voltage is divided by resistors R1 and R2 of the same resistance value to charge the a-end of the capacitor C5 and reach a potential half of HVDD. The b-end of C5 maintains the same potential as GND through the resistor R4.

[0018] When emitting a pulse, the control circuit sends a pulse drive signal K3 to the optocoupler isolator M1, MOS driver Q5 is turned on, MOS driver Q5 pulls up the control pulse of MOS tube Q3, and the control pulse of MOS tube Q4 is pulled down and remains unchanged, MOS tube Q3 is turned on, MOS tube Q4 is turned off, and the voltage at the a end of capacitor C5 is connected to the DC output voltage through MOS tube Q3 and suddenly changes to HVDD, while the potential difference across capacitor C5 does not change instantaneously, so the voltage at the b end of capacitor C5 becomes half of HVDD; then the control circuit sends a pulse drive signal K4 to the optocoupler isolator M2, MOS driver Q6 is turned on, MOS driver Q6 pulls up the control pulse of MOS tube Q4, and the control pulse of MOS tube Q3 At the same time, the MOS tube Q4 is turned on, the MOS tube Q3 is turned off, and the voltage at the a end of the capacitor C5 suddenly changes to GND, while the potential difference at both ends of the capacitor C5 does not change instantaneously, so the voltage at the b end of the capacitor C5 becomes half of -HVDD; then the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, and the control pulses of the MOS tubes Q3 and Q4 are pulled down at the same time, the MOS tubes Q4 and Q3 are turned off, and the a end of the capacitor C5 is restored to the voltage after being divided by two resistors R1 and R2 with the same resistance value, reaching a potential of half of HVDD, and the b end of the capacitor C5 is kept at the same potential as GND through the resistor R4, thereby forming a bipolar pulse;

[0019] By repeating the above charging and transmitting pulses, a bipolar high-voltage pulse train is formed to excite the air-coupled ultrasonic transducer.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the present invention can generate the required 1100V bipolar high-voltage pulse to drive the ultrasonic transducer with a 12V low-voltage power supply, thereby reducing the design difficulty brought by the positive and negative dual power supplies, and effectively isolates the low-voltage drive control signal and the high-voltage pulse emission through the optical coupling isolation device, thereby improving the safety of the circuit and making the output waveform easier to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall circuit structure of the present invention;

[0022] Figure 2 This is a basic principle diagram of the air-coupled ultrasonic penetration method of the present invention;

[0023] Figure 3 It is a schematic diagram of the circuit structure of the high-voltage output unit of the present invention;

[0024] Figure 4 It is a timing diagram of input control signal and output pulse of the high voltage unit of the present invention;

[0025] Figure 5 The ultrasonic transducer bipolar high voltage driving circuit of the present invention;

[0026] Figure 6 It is a timing diagram of the control signal and output pulse of the driving circuit of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the embodiments.

[0028] The air-coupled ultrasonic testing method analyzes whether the material has defects by studying the corresponding characteristic values ​​of the ultrasonic receiving signal after the ultrasonic wave passes through the material to be tested, such as reflection, transmission and other energy changes. Figure 2 As shown in the figure, the detection system uses bipolar high-voltage pulses to excite the transmitting transducer, causing it to generate ultrasonic waves and transmit them to the lithium battery. After passing through the lithium battery, the ultrasonic waves carry the internal structure information of the lithium battery and are captured by the receiving transducer. The receiving transducer converts the received ultrasonic waves into receiving signals for analysis. The signal quality of the received signal becomes one of the key factors for accurate analysis of lithium batteries, so improving the quality of the received signal is of great significance to the ultrasonic detection system.

[0029] like Figure 1 As shown, the bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer disclosed in the present invention includes: a control circuit, an auxiliary power supply circuit, a pulse transmitting unit and a high-voltage output unit, and the high-voltage output unit includes a high-frequency inverter circuit, a high-frequency transformer T1 and a voltage doubling rectifier circuit; the input end of the high-frequency inverter circuit is used to connect to a 12V DC input, and the output end of the high-frequency inverter circuit is electrically connected to the input side of the high-frequency transformer T1; the output side of the high-frequency transformer T1 is electrically connected to the input end of the voltage doubling rectifier circuit, and the output end of the voltage doubling rectifier circuit is electrically connected to the high-voltage input end of the pulse transmitting unit; the control circuit is electrically connected to the control end of the high-frequency inverter circuit and the control end of the pulse transmitting unit respectively; the output end of the pulse transmitting unit is used to be electrically connected to the input end of the air-coupled ultrasonic high-voltage transducer to output an ultrasonic driving signal to the air-coupled ultrasonic high-voltage transducer; the auxiliary power supply circuit supplies power to the control circuit and the pulse transmitting unit respectively.

[0030] The control circuit, optocoupler isolation circuit and MOSFET drive circuit are powered by inputting 12V DC combined with +5V and +3.3V generated by the auxiliary power supply circuit. The high-voltage output unit uses SG3525 as the control core to provide the required high-voltage DC power for the pulse emission unit based on push-pull inversion combined with bipolar voltage doubler rectification, and its output amplitude can be externally controlled. The ARM controller STM32F407 embedded chip is used as the core of the control circuit. It sends out ultrasonic low-voltage pulse control signals with dead zones to control the subsequent pulse emission units. The pulse waveform is a square wave, and the frequency is consistent with the base frequency required for the normal operation of the transducer. The pulse emission unit uses the optocoupler isolator FODM8071 to isolate the low-voltage control signal from the high-voltage excitation signal to prevent the main control chip from being burned by circuit failure, and uses the MOSFET driver chip IR2213 to drive two power MOS tubes CIM3N150D3, thereby converting the 1100V high-voltage DC provided by the high-voltage unit into a bipolar signal with the same frequency as the ARM control to drive the transducer to work.

[0031] Furthermore, the pulse emission unit includes an optocoupler isolation circuit, a MOSFET drive circuit and a power amplifier circuit; the control end of the optocoupler isolation circuit is electrically connected to the control circuit, and the output end of the optocoupler isolation circuit is electrically connected to the input end of the MOSFET drive circuit; the output end of the MOSFET drive circuit is electrically connected to the control end of the power amplifier circuit, and is used to drive and control the power amplifier circuit; the output end of the power amplifier circuit is used to be electrically connected to the input end of the air-coupled ultrasonic high-voltage transducer, and output an ultrasonic drive signal to the air-coupled ultrasonic high-voltage transducer.

[0032] Further, such as Figure 3As shown, the high-frequency inverter circuit includes a MOS tube Q1 and a MOS tube Q2; the voltage doubler rectifier circuit includes a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a diode D1, a diode D2, a diode D3 and a diode D4; the G poles of the MOS tube Q1 and the MOS tube Q2 are electrically connected to the control circuit; the D pole of the MOS tube Q1 is electrically connected to one end of the primary coil of the high-frequency transformer T1, and the D pole of the MOS tube Q2 is electrically connected to the other end of the primary coil of the high-frequency transformer T1; the S poles of the MOS tube Q1 and the MOS tube Q2 are both used to be electrically connected to the negative pole of the 12V DC input; the midpoint of the primary coil of the high-frequency transformer T1 is used to be electrically connected to the positive pole of the 12V DC input; the high One end of the secondary coil of the high-frequency transformer T1 is electrically connected to one end of the capacitor C1 and one end of the capacitor C3, respectively; the other end of the secondary coil of the high-frequency transformer T1 is electrically connected to one end of the capacitor C2, the positive electrode of the diode D1, one end of the capacitor C4 and the negative electrode of the diode D3, respectively; the other end of the capacitor C1 is electrically connected to the negative electrode of the diode D1 and the positive electrode of the diode D2, respectively; the negative electrode of the diode D2 and the other end of the capacitor C2 are electrically connected to serve as the positive output end of the voltage doubler rectifier circuit; the other end of the capacitor C4 is electrically connected to the positive electrode of the diode D4; the other end of the capacitor C3, the positive electrode of the diode D3 and the negative electrode of the diode D4 are electrically connected to serve as the negative output end of the voltage doubler rectifier circuit.

[0033] The 12V DC input is boosted by 46 times high-frequency inverter through high-frequency transformer T1, and then amplified to DC voltage in a 2x full-wave voltage-doubling rectifier circuit with dual functions of voltage doubling and rectification, ultimately completing a 92x boost. This can reduce the turns ratio and design difficulty of the transformer, and alleviate the voltage stress of the rectifier device, thus achieving a high-gain isolated boost conversion of the circuit.

[0034] In the circuit, when the pulse drive signals K1 and K2 of MOS tube Q1 and MOS tube Q2 are pulled low, MOS tube Q1 and MOS tube Q2 are turned off and the circuit does not work; when a DC high voltage is required, the pulse drive signal controls MOS tube Q1 and MOS tube Q2 to conduct alternately in each clock cycle; when MOS tube Q1 is turned on, the current flows into a part of the primary coil of the high-frequency transformer T1 through the 12V power supply; when MOS tube Q2 is turned on, the current flows into another part of the primary coil of the high-frequency transformer T1. This alternating conduction will generate a high-frequency AC voltage waveform on the primary coil of the high-frequency transformer T1. By boosting the high-frequency transformer T1 with a turns ratio of 1:46, the AC voltage output on the secondary coil is about 560V peak. The positive half-cycle AC is converted into DC through diode D1, diode D2, capacitor C1, and capacitor C2. Similarly, the negative half-cycle AC is converted into DC through diode D3, diode D4, capacitor C3, and capacitor C4, and the final output DC voltage can reach 1100V.

[0035] According to the above analysis, the timing diagram of the circuit's input signal and output voltage is as follows: Figure 4 When the pulse drive signal K1 of MOS tube Q1 and the pulse drive signal K2 of MOS tube Q2 output trigger pulses in turn, the circuit will stimulate a maximum DC voltage of 1100V, which is twice the AC voltage of 560V. This circuit can be used to achieve a 92-fold boost from 12V to a high-voltage DC of 1100V.

[0036] Further, such as Figure 5 As shown, the optocoupler isolation circuit includes an optocoupler isolator M1 and an optocoupler isolator M2; the MOSFET driving circuit includes a MOS driver Q5 and a MOS driver Q6; the power amplifier circuit includes a MOS tube Q3, a MOS tube Q4, a resistor R1, a resistor R2, a resistor R3, a diode D5, a diode D6, a capacitor C5 and a resistor R4; the input ends of the optocoupler isolator M1 and the optocoupler isolator M2 are both electrically connected to the control circuit, the output end of the optocoupler isolator M1 is electrically connected to the input end of the MOS driver Q5, and the output end of the optocoupler isolator M2 is electrically connected to the input end of the MOS driver Q6; the output end of the MOS driver Q5 is electrically connected to the G pole of the MOS tube Q3; the input end of the MOS driver Q6 is electrically connected to the G pole of the MOS tube Q3; The output end is electrically connected to the G pole of the MOS tube Q4; the D pole of the MOS tube Q3, one end of the resistor R1 and the cathode of the diode D5 are all electrically connected to the positive output end of the voltage doubler rectifier circuit; the S pole of the MOS tube Q3 is electrically connected to the other end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and the D pole of the MOS tube Q4 respectively; the S pole of the MOS tube Q4 is electrically connected to the other end of the resistor R2 and the anode of the diode D6 and then grounded; the cathode of the diode D6 is electrically connected to the other end of the resistor R3, the a end of the capacitor C5 and the anode of the diode D5 respectively; the b end of the capacitor C5 is electrically connected to one end of the resistor R4 and serves as the output end of the power amplifier circuit; the other end of the resistor R4 is grounded.

[0037] In order to generate a high-voltage pulse excitation signal with controllable pulse number, the present invention is based on the high voltage output of the above-mentioned high-voltage output voltage, and designs the following by using the RC charging and discharging principle and the switch tube cooperative working method: Figure 5 The bipolar high voltage ultrasonic excitation signal generating circuit shown in the figure uses the high voltage generated above to control the input voltage potential by connecting an equal voltage-dividing resistor R1 and a resistor R2 in parallel at both ends of the MOS tube Q3 and the MOS tube Q4, and then controls the voltage at both ends of the clamping capacitor C5 through the switch tube to generate a bipolar square wave pulse train. The number of pulses of the excitation signal is determined by the control signal of the MOS tube Q3 and the MOS tube Q4. The circuit can effectively reduce the design pressure, improve the pulse drive efficiency, and isolate the high voltage part from the low voltage part through the optical coupling isolation to prevent the high voltage interference signal from damaging the ARM chip. It has good potential in high-precision ultrasonic measurement applications.

[0038] According to the above analysis, the timing diagram of the circuit's input signal and output voltage is as follows: Figure 6 As shown. When the pulse drive signal K3 of the MOS tube Q3 outputs a trigger pulse, the circuit will excite a high-voltage pulse with an equal width of HVDD / 2. When the pulse drive signal K4 of the MOS tube Q4 outputs a trigger pulse, the circuit will excite a high-voltage pulse with an equal width of -HVDD / 2. Therefore, the pulse drive signal K3 and the pulse drive signal K4 output trigger pulses in turn, and the circuit will excite a bipolar high-voltage pulse. The circuit can realize controllable voltage amplitude and pulse width of the high-voltage pulse excitation signal.

[0039] The present invention also provides a driving method for a bipolar high-voltage pulse driving circuit of an air-coupled ultrasonic transducer, comprising a high-voltage output step and an excitation output step;

[0040] The steps for high voltage output are:

[0041] The control circuit sends pulse drive signals K1 and K2 alternately to the S poles of the MOS tube Q1 and the MOS tube Q2. When the pulse drive signal K1 is received, the MOS tube Q1 is turned on, and the current flows into a part of the primary coil of the high-frequency transformer T1 through the 12V DC input. When the pulse drive signal K2 is received, the MOS tube Q2 is turned on, and the current flows into another part of the primary coil of the high-frequency transformer T1 through the 12V DC input, thereby generating a high-frequency AC voltage waveform in the primary coil of the high-frequency transformer T1.

[0042] The high-frequency transformer T1 outputs a boosted AC voltage on the secondary coil, and then the diode D1, the diode D2, the capacitor C1 and the capacitor C2 convert the positive half cycle of the AC voltage waveform into DC power, and the diode D3, the diode D4, the capacitor C3 and the capacitor C4 convert the negative half cycle of the AC voltage waveform into DC power;

[0043] The DC power converted in the positive half cycle and the DC power converted in the negative half cycle form a complete DC output voltage, which is recorded as HVDD.

[0044] The steps of stimulus output are:

[0045] When charging, the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, MOS tubes Q3 and Q4 are turned off, and the DC output voltage is divided by resistors R1 and R2 of the same resistance value to charge the a-end of the capacitor C5 and reach a potential half of HVDD. The b-end of C5 maintains the same potential as GND through the resistor R4.

[0046] When emitting a pulse, the control circuit sends a pulse drive signal K3 to the optocoupler isolator M1, MOS driver Q5 is turned on, MOS driver Q5 pulls up the control pulse of MOS tube Q3, and the control pulse of MOS tube Q4 is pulled down and remains unchanged, MOS tube Q3 is turned on, MOS tube Q4 is turned off, and the voltage at the a end of capacitor C5 is connected to the DC output voltage through MOS tube Q3 and suddenly changes to HVDD, while the potential difference across capacitor C5 does not change instantaneously, so the voltage at the b end of capacitor C5 becomes half of HVDD; then the control circuit sends a pulse drive signal K4 to the optocoupler isolator M2, MOS driver Q6 is turned on, MOS driver Q6 pulls up the control pulse of MOS tube Q4, and the control pulse of MOS tube Q3 At the same time, the MOS tube Q4 is turned on, the MOS tube Q3 is turned off, and the voltage at the a end of the capacitor C5 suddenly changes to GND, while the potential difference at both ends of the capacitor C5 does not change instantaneously, so the voltage at the b end of the capacitor C5 becomes half of -HVDD; then the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, and the control pulses of the MOS tubes Q3 and Q4 are pulled down at the same time, the MOS tubes Q4 and Q3 are turned off, and the a end of the capacitor C5 is restored to the voltage after being divided by two resistors R1 and R2 with the same resistance value, reaching a potential of half of HVDD, and the b end of the capacitor C5 is kept at the same potential as GND through the resistor R4, thereby forming a bipolar pulse;

[0047] By repeating the above charging and transmitting pulses, a bipolar high-voltage pulse train is formed to excite the air-coupled ultrasonic transducer.

[0048] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A bipolar high-voltage pulse driving circuit for an air-coupled ultrasonic transducer, characterized in that: It includes a control circuit, an auxiliary power supply circuit, a pulse transmitting unit and a high-voltage output unit. The high-voltage output unit includes a high-frequency inverter circuit, a high-frequency transformer T1 and a voltage doubler rectifier circuit. The input end of the high-frequency inverter circuit is used to connect to a 12V DC input, and the output end of the high-frequency inverter circuit is electrically connected to the input side of the high-frequency transformer T1. The output side of the high-frequency transformer T1 is electrically connected to the input end of the voltage doubler rectifier circuit, and the output end of the voltage doubler rectifier circuit is electrically connected to the high-voltage input end of the pulse transmitting unit. The control circuit is electrically connected to the control end of the high-frequency inverter circuit and the control end of the pulse transmitting unit respectively. The output end of the pulse transmitting unit is used to electrically connect to the input end of an air-coupled ultrasonic high-voltage transducer to output an ultrasonic driving signal to the air-coupled ultrasonic high-voltage transducer. The auxiliary power supply circuit supplies power to the control circuit and the pulse transmitting unit respectively.

2. The bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer according to claim 1, characterized in that: The pulse transmitting unit includes an optocoupler isolation circuit, a MOSFET driving circuit and a power amplifier circuit; the control end of the optocoupler isolation circuit is electrically connected to the control circuit, and the output end of the optocoupler isolation circuit is electrically connected to the input end of the MOSFET driving circuit; the output end of the MOSFET driving circuit is electrically connected to the control end of the power amplifier circuit, and is used to drive and control the power amplifier circuit; the output end of the power amplifier circuit is used to be electrically connected to the input end of the air-coupled ultrasonic high-voltage transducer, and output an ultrasonic driving signal to the air-coupled ultrasonic high-voltage transducer.

3. The bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer according to claim 1 or 2, characterized in that: The high-frequency inverter circuit includes a MOS tube Q1 and a MOS tube Q2; the voltage doubler rectifier circuit includes a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a diode D1, a diode D2, a diode D3 and a diode D4; the G poles of the MOS tube Q1 and the MOS tube Q2 are electrically connected to the control circuit; the D pole of the MOS tube Q1 is electrically connected to one end of the primary coil of the high-frequency transformer T1, and the D pole of the MOS tube Q2 is electrically connected to the other end of the primary coil of the high-frequency transformer T1; the S poles of the MOS tube Q1 and the MOS tube Q2 are both used to be electrically connected to the negative pole of the 12V DC input; the midpoint of the primary coil of the high-frequency transformer T1 is used to be electrically connected to the positive pole of the 12V DC input; the high-frequency One end of the secondary coil of the transformer T1 is electrically connected to one end of the capacitor C1 and one end of the capacitor C3, respectively; the other end of the secondary coil of the high-frequency transformer T1 is electrically connected to one end of the capacitor C2, the positive electrode of the diode D1, one end of the capacitor C4 and the negative electrode of the diode D3, respectively; the other end of the capacitor C1 is electrically connected to the negative electrode of the diode D1 and the positive electrode of the diode D2, respectively; the negative electrode of the diode D2 and the other end of the capacitor C2 are electrically connected to serve as the positive output end of the voltage doubler rectifier circuit; the other end of the capacitor C4 is electrically connected to the positive electrode of the diode D4; the other end of the capacitor C3, the positive electrode of the diode D3 and the negative electrode of the diode D4 are electrically connected to serve as the negative output end of the voltage doubler rectifier circuit.

4. The bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer according to claim 3 is characterized in that: The optocoupler isolation circuit includes an optocoupler isolator M1 and an optocoupler isolator M2; the MOSFET driving circuit includes a MOS driver Q5 and a MOS driver Q6; the power amplifier circuit includes a MOS tube Q3, a MOS tube Q4, a resistor R1, a resistor R2, a resistor R3, a diode D5, a diode D6, a capacitor C5 and a resistor R4; the input ends of the optocoupler isolator M1 and the optocoupler isolator M2 are both electrically connected to the control circuit, the output end of the optocoupler isolator M1 is electrically connected to the input end of the MOS driver Q5, and the output end of the optocoupler isolator M2 is electrically connected to the input end of the MOS driver Q6; the output end of the MOS driver Q5 is electrically connected to the G pole of the MOS tube Q3; the output end of the MOS driver Q6 The MOS tube Q4 is electrically connected to the G electrode of the MOS tube Q4; the D electrode of the MOS tube Q3, one end of the resistor R1 and the cathode of the diode D5 are all electrically connected to the positive output end of the voltage doubler rectifier circuit; the S electrode of the MOS tube Q3 is respectively electrically connected to the other end of the resistor R1, one end of the resistor R2, one end of the resistor R3 and the D electrode of the MOS tube Q4; the S electrode of the MOS tube Q4 is respectively electrically connected to the other end of the resistor R2 and the anode of the diode D6 and then grounded; the cathode of the diode D6 is respectively electrically connected to the other end of the resistor R3, the a end of the capacitor C5 and the anode of the diode D5; the b end of the capacitor C5 is electrically connected to one end of the resistor R4 and serves as the output end of the power amplifier circuit; the other end of the resistor R4 is grounded.

5. A driving method of the bipolar high-voltage pulse driving circuit of the air-coupled ultrasonic transducer according to claim 4, characterized in that: including a high voltage output step and an excitation output step; The steps for high voltage output are: The control circuit sends pulse drive signals K1 and K2 alternately to the S poles of the MOS tube Q1 and the MOS tube Q2. When the pulse drive signal K1 is received, the MOS tube Q1 is turned on, and the current flows into a part of the primary coil of the high-frequency transformer T1 through the 12V DC input. When the pulse drive signal K2 is received, the MOS tube Q2 is turned on, and the current flows into another part of the primary coil of the high-frequency transformer T1 through the 12V DC input, thereby generating a high-frequency AC voltage waveform in the primary coil of the high-frequency transformer T1. The high-frequency transformer T1 outputs a boosted AC voltage on the secondary coil, and then the diode D1, the diode D2, the capacitor C1 and the capacitor C2 convert the positive half cycle of the AC voltage waveform into DC power, and the diode D3, the diode D4, the capacitor C3 and the capacitor C4 convert the negative half cycle of the AC voltage waveform into DC power; The DC power converted in the positive half cycle and the DC power converted in the negative half cycle form a complete DC output voltage, which is recorded as HVDD. The steps of stimulus output are: When charging, the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, MOS tubes Q3 and Q4 are turned off, and the DC output voltage is divided by resistors R1 and R2 of the same resistance value to charge the a-end of the capacitor C5 and reach a potential half of HVDD. The b-end of C5 maintains the same potential as GND through the resistor R4. When emitting a pulse, the control circuit sends a pulse drive signal K3 to the optocoupler isolator M1, MOS driver Q5 is turned on, MOS driver Q5 pulls up the control pulse of MOS tube Q3, and the control pulse of MOS tube Q4 is pulled down and remains unchanged, MOS tube Q3 is turned on, MOS tube Q4 is turned off, and the voltage at the a end of capacitor C5 is connected to the DC output voltage through MOS tube Q3 and suddenly changes to HVDD, while the potential difference across capacitor C5 does not change instantaneously, so the voltage at the b end of capacitor C5 becomes half of HVDD; then the control circuit sends a pulse drive signal K4 to the optocoupler isolator M2, MOS driver Q6 is turned on, MOS driver Q6 pulls up the control pulse of MOS tube Q4, and the control pulse of MOS tube Q3 At the same time, the MOS tube Q4 is turned on, the MOS tube Q3 is turned off, and the voltage at the a end of the capacitor C5 suddenly changes to GND, while the potential difference at both ends of the capacitor C5 does not change instantaneously, so the voltage at the b end of the capacitor C5 becomes half of -HVDD; then the control circuit stops sending pulse drive signals K3 and K4 to the optocoupler isolator M1 and the optocoupler isolator M2, and the control pulses of the MOS tubes Q3 and Q4 are pulled down at the same time, the MOS tubes Q4 and Q3 are turned off, and the a end of the capacitor C5 is restored to the voltage after being divided by two resistors R1 and R2 with the same resistance value, reaching a potential of half of HVDD, and the b end of the capacitor C5 is kept at the same potential as GND through the resistor R4, thereby forming a bipolar pulse; By repeating the above charging and transmitting pulses, a bipolar high-voltage pulse train is formed to excite the air-coupled ultrasonic transducer.

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