A light guide switch driving device of a large-current constant current source

Abstract

The application belongs to the technical field of power electronic drive, and relates to a light guide switch driving device of a large-current constant current source, which comprises: an output end of a single-chip microcomputer control circuit is connected with an input end of a constant current control circuit; an output end of the constant current control circuit is connected with an input end of a front-stage MOS tube current expansion circuit; an output end of the front-stage MOS tube current expansion circuit is connected with an input end of a totem pole gate drive circuit; an output end of the totem pole gate drive circuit is connected with a control end of a rear-stage MOS tube output circuit; an output end of the rear-stage MOS tube output circuit is connected with an input end of a light guide switch load circuit, and the output end is connected with a feedback input end of the constant current control circuit; the large-current precise constant current drive of the light guide switch is realized, the circuit is simple, the current sharing effect is good, the constant current precision is high, and the working stability and reliability under the large-current working condition are improved.

Description

Technical Field

[0001] This invention relates to the field of power electronic drive technology, and specifically discloses a photoconductive switch drive device with a high current constant current source. Background Technology

[0002] As a type of light-controlled switching element, photoconductive switches require stable operation under high current conditions in some industrial scenarios. Therefore, a matching high-current constant current source driving circuit is needed to provide the operating current. In existing technologies, the conventional approach to achieve high-current constant current drive is to use multiple MOSFETs connected in parallel for current amplification, and then combine them with an operational amplifier to form a constant current feedback loop. However, this design has obvious technical drawbacks: First, simply connecting MOSFETs in parallel is prone to uneven current distribution, and a single MOSFET may burn out due to overheating from overcurrent, reducing circuit reliability; second, when the operational amplifier directly drives multiple parallel MOSFETs, the total gate drive capability is insufficient, and the switching speed of the MOSFETs is slow and the losses are high. These circuit problems can easily lead to unstable operation or even damage to the photoconductive switch due to current fluctuations.

[0003] In view of this, the present invention proposes a photoconductive switch driving device with a high current constant current source. By designing a two-stage hierarchical current amplification architecture including multi-tube parallel current sharing in the front stage, totem pole boosting drive, and single-tube high-power output in the rear stage, the three major problems of current sharing, driving capability, and reliability in high current constant current driving are solved. This provides a high-precision, high-stability, and high-reliability driving solution for loads such as photoconductive switches that have stringent power requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a photoconductive switch driving device with a high-current constant current source, solving the problems of uneven current distribution, insufficient driving capability, and poor reliability in traditional driving schemes; the specific solution is as follows: A photoconductive switch driving device with a high current constant current source includes a microcontroller front-end control circuit, a constant current control circuit, a sampling feedback circuit, and a photoconductive switch load circuit. It also includes a microcontroller control circuit, a front-end MOSFET current amplification circuit, a totem pole gate driving circuit, and a rear-end MOSFET output circuit. The output terminal of the microcontroller control circuit is connected to the input terminal of the constant current control circuit, and is used to output DAC voltage signal to set the target constant current value; its main body is selected as STM32F103C8T6 microcontroller, which, together with power supply regulation circuit, key input circuit, reset circuit, clock circuit and digital-to-analog conversion circuit, completes the parameter setting, state control and digital signal output of constant current drive system. The output terminal of the constant current control circuit is connected to the input terminal of the front-stage MOS transistor current amplification circuit, which is used to output an adjustable constant current control voltage and receive feedback signals to realize closed-loop regulation. The output terminal of the pre-stage MOS transistor current amplification circuit is connected to the input terminal of the totem pole gate drive circuit to achieve initial current sharing and amplification, and to transmit control signals to the totem pole gate drive circuit; the initial current value is less than 5A. The output terminal of the totem pole gate drive circuit is connected to the control terminal of the subsequent MOS transistor output circuit to enhance the gate drive capability and drive the subsequent MOS transistor to turn on and off quickly. The output terminal of the subsequent MOSFET output circuit is connected to the input terminal of the photoconductive switch load circuit to provide a constant current operating power supply for the photoconductive switch; the power of the subsequent MOSFET is greater than 190W. The input terminal of the sampling feedback circuit is connected to the output terminal of the photoconductive switch load circuit, and the output terminal is connected to the feedback input terminal of the constant current control circuit. The ground terminal is grounded. It is used to collect the current signal of the load circuit and convert it into a voltage signal to be fed back to the constant current control circuit.

[0005] Furthermore, the constant current control circuit uses an LM358 operational amplifier; The non-inverting input of the LM358 operational amplifier is connected to the DAC voltage signal output by the microcontroller control circuit, the inverting input is connected to the output of the sampling feedback circuit, and the output is connected to the input of the pre-stage MOS transistor current amplification circuit as the output of the constant current control circuit.

[0006] Furthermore, the front-end MOS transistor current amplification circuit includes multiple N-channel MOS transistors connected in parallel, as well as gate resistors and current sharing resistors corresponding to each MOS transistor. The gate of each MOSFET is connected in series with a gate resistor and then connected to the output of the constant current control circuit. The drain is connected to a DC power supply, and the source is connected in series with a current sharing resistor and then connected to the same power supply, forming the output of the current amplification circuit of the front-stage MOSFET.

[0007] Furthermore, the N-channel MOSFET is an IRF540 type, the gate resistor is a 1kΩ carbon film resistor, and the current sharing resistor is a 0.1Ω, 1W metal film resistor.

[0008] Furthermore, the totem pole gate drive circuit includes an NPN transistor, a PNP transistor, a base current limiting resistor, and multiple emitter resistors; One end of the base limiting current resistor is connected to the output terminal of the front-stage MOS transistor current amplification circuit, and the other end is connected to the base of both the NPN transistor and the PNP transistor. The collector of the NPN transistor is connected to a DC power supply, and the emitter is connected in series with an emitter resistor. The collector of the PNP transistor is grounded, and the emitter is connected in series with another emitter resistor and then connected to the emitter output terminal of the NPN transistor to form the output terminal of the totem pole gate drive circuit.

[0009] Furthermore, the NPN transistor is selected as type S9013, the PNP transistor is selected as type S9012, the base current limiting resistor is selected as 10kΩ, and the emitter resistor is selected as 100Ω.

[0010] Furthermore, the output circuit of the subsequent MOSFET includes an N-channel MOSFET; The gate of the MOS transistor is connected to the output of the totem pole gate drive circuit as the control terminal, the drain is connected to the DC power supply, and the source is connected to the photoconductive switch load circuit as the output terminal.

[0011] Furthermore, the N-channel MOSFET is selected as the IRFP250 type with a rated current of 200A and a withstand voltage of 600V.

[0012] Furthermore, the sampling feedback circuit includes a sampling resistor; One end of the sampling resistor is connected to the output terminal of the photoconductive switch load circuit, and the other end is grounded. The connection node between the sampling resistor and the photoconductive switch load circuit serves as the output terminal of the sampling feedback circuit, which is electrically connected to the feedback input terminal of the constant current control circuit.

[0013] Furthermore, the sampling resistor is selected as a 0.1Ω, 100W metal film resistor.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention replaces the traditional parallel MOSFET approach with a two-stage, graded current amplification architecture. The first stage employs multiple MOSFETs connected in parallel with a current-sharing resistor in series at the source, completely resolving the overheating and burnout problem of single MOSFETs caused by uneven current distribution in traditional parallel schemes, achieving uniform current distribution and initial amplification. The second stage introduces a totem-pole driver circuit, significantly enhancing the gate's charging and discharging driving capability, solving the problem of insufficient driving capability in the preceding stage, and enabling rapid driving of a single high-power MOSFET in the subsequent stage. The final current amplification is achieved using a single high-power MOSFET, fundamentally avoiding the current sharing and reliability risks associated with multiple parallel MOSFETs. This results in high-current (up to 100A), high-precision, and high-stability constant current driving, significantly improving the operational stability of the photoconductive switch and the reliability of the entire driving device. Attached Figure Description

[0015] Figure 1 An exemplary structural diagram of a photoconductive switch driving device for a high-current constant current source provided by the present invention; Figure 2 The peripheral circuit diagram of the microcontroller control circuit provided for this invention; Figure 3 The microcontroller circuit diagram provided by the present invention is a microcontroller control circuit. Figure 4 This is a closed-loop connection circuit diagram of the constant current control circuit and the photoconductive switch of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0017] This invention employs a dual MOS transistor current amplification circuit, such as... Figure 1 As shown, the present invention provides a high-current constant current source photoconductive switch driving device, including a microcontroller front-end control circuit, a constant current control circuit, a sampling feedback circuit and a photoconductive switch load circuit, a microcontroller control circuit, a front-stage MOSFET current amplification circuit, a totem pole gate driving circuit and a rear-stage high-power MOSFET output circuit.

[0018] The output of the microcontroller control circuit is connected to the input of the constant current control circuit to output a DAC voltage signal to set the target constant current value. For example... Figure 2 and Figure 3 As shown, the power supply regulation circuit uses an AMS1117-3V3 linear regulator to convert the input external DC power supply into a stable 3.3V voltage to power the microcontroller and its peripheral circuits, ensuring the stability of the system's operating voltage. The key input circuit consists of tactile buttons S1 and S2 with pin headers, converting external button actions into digital control signals that are connected to the microcontroller's I / O ports for manual control functions such as system start, stop, or mode switching. The reset circuit consists of button S2, a 1kΩ pull-down resistor R1, and a 10µF reset capacitor CE1. During power-up, the capacitor charges the RST pin to briefly maintain a low level, achieving automatic reset; pressing button S2 pulls the RST pin low for manual reset, ensuring reliable system startup and fault recovery. The clock circuit consists of a 12MHz passive crystal oscillator X1 and two 0.1µF load capacitors C1 and C2, providing a stable external oscillation signal to the microcontroller through ports XTAL1 and XTAL2, ensuring the normal timing of the program. The microcontroller connects to a DAC8532IDGK digital-to-analog converter chip via an SPI bus. Digital control signals output by the microcontroller are transmitted through the SPI interface (including the receiver of CS-SPI NSS signals). The signal (including the DIN port for receiving SPI MOSI signals and the SCLK port for receiving SPI SCK signals) is transmitted to the DAC chip, converted into an analog voltage signal DAC_VOUT, and output to the op-amp input of the back-end constant current drive circuit as the target current setpoint. Together with the current sampling feedback signal, a closed-loop control is formed to achieve high-precision adjustment of the output current.

[0019] The output of the constant current control circuit is electrically connected to the input of the preceding MOSFET current amplification circuit. It outputs a precise constant current control voltage and receives a sampling feedback signal to achieve closed-loop regulation. The constant current control circuit is responsible for outputting a high-precision, closed-loop adjustable constant current control voltage, with a voltage control accuracy of 10mV or better. This circuit receives a setpoint signal representing the target current and a feedback signal from the sampling feedback circuit. By amplifying the difference between the two signals, it generates a closed-loop regulated constant current control voltage to make the actual output current approach the target setpoint.

[0020] Specifically, such as Figure 4 The constant current control circuit shown uses an LM358 operational amplifier as its core component. The non-inverting input of the operational amplifier is used to receive the target voltage signal VDAC from the digital-to-analog converter (DAC), which corresponds to the required set constant current value. The inverting input of the operational amplifier serves as the feedback input and is electrically connected to the output of the sampling feedback circuit. The power supply terminal of the operational amplifier is connected to a +12V DC power supply VCC, and its ground terminal is connected to system ground GND. Its output serves as the output of the constant current control circuit and is connected to the preceding MOSFET current amplification circuit. During operation, the constant current control circuit compares the target voltage VDAC with the feedback voltage VFB in real time. When the load current increases, causing VFB to exceed VDAC, the constant current control circuit decreases the output voltage; conversely, it increases it, thus achieving constant current closed-loop regulation.

[0021] The output of the pre-amplifier MOSFET current amplification circuit is electrically connected to the input of the totem-pole gate driver circuit. This connection is used to achieve initial small current amplification and transmit control signals to the driver circuit. The core function of the pre-amplifier MOSFET current amplification circuit is to perform the first stage of current amplification, achieving initial small current amplification and current sharing. It converts the weak voltage signal output from the constant current control circuit into a driver signal with initially amplified current capability (e.g., 5A for a single channel, reaching a total output capability of 20A), preparing it for driving the heavy load in the subsequent stages.

[0022] Specifically, as the first-stage current amplification circuit, the pre-amplifier MOSFET current amplification circuit includes four parallel N-channel MOSFETs. These MOSFETs are IRF540 type. Each MOSFET's gate is connected in series with a gate resistor. The input terminals of these gate resistors are common, serving as the input terminal of the entire pre-amplifier MOSFET current amplification circuit, receiving the output voltage from the constant current control circuit. The gate resistors are used to suppress parasitic oscillations that may occur in the MOSFETs, protecting the pre-amplifier. The drains of all MOSFETs are directly connected to the +12V DC power supply VCC. Each MOSFET's source is connected in series with a current-sharing resistor. The output terminals of these four current-sharing resistors are connected together, serving as the output terminal of the pre-amplifier MOSFET current amplification circuit. Due to the presence of the current-sharing resistors, even if there are slight differences in the conduction parameters of the four MOSFETs, the negative feedback effect on the current-sharing resistors can force the four currents to tend towards balance, effectively preventing single-tube overheating and runaway problems caused by current imbalance. Preferably, the gate resistor is a 1kΩ carbon film resistor, and the current-sharing resistor is a 0.1Ω, 1W metal film resistor.

[0023] The output of the totem-pole gate driver circuit is electrically connected to the control terminal of the subsequent high-power MOSFET output circuit. This connection enhances the gate drive capability, enabling the high-power MOSFET to turn on and off. The core function of the totem-pole gate driver circuit is to improve drive capability. It receives the output signal from the preceding current-amplifying circuit and, through its internal push-pull structure, provides extremely large instantaneous source and sink currents. This allows for rapid charging and discharging of the gate capacitor of the subsequent high-power MOSFET, ensuring high-speed turn-on and turn-off and reducing switching losses.

[0024] Specifically, the totem-pole gate driver circuit, as a key intermediate stage connecting the preceding and following current-amplifying stages, includes an NPN transistor (preferably S9013), a PNP transistor (preferably S9012), a base-limiting current resistor (preferably 10kΩ), and two 100Ω emitter resistors. One end of the base-limiting current resistor serves as the input terminal, connected to the output node of the preceding current-amplifying circuit; the other end is connected to the base of both the NPN and PNP transistors, used to limit the base current of the transistors and protect them. The collector of the NPN transistor is connected to the +12V power supply VCC, and the collector of the PNP transistor is grounded to GND. Each emitter of the transistor is connected in series with a 100Ω emitter resistor, and these resistors are connected together to form the total output terminal of the totem-pole gate driver circuit, which is directly connected to the gate of the subsequent high-power MOSFET. This totem pole structure effectively improves the gate drive current capability, solves the problem of insufficient drive capability of the front-stage current amplification circuit to drive the high-power MOSFET in the back-stage, realizes the rapid turn-on and turn-off of the MOSFET, and reduces switching losses.

[0025] The output terminal of the high-power MOSFET output circuit is connected to the input terminal of the photoconductive switch load circuit, providing a constant high-current operating power supply for the photoconductive switch. As the final output stage, the high-power MOSFET output circuit preferably uses a single high-power MOSFET to directly supply the required constant high current of 100A to the photoconductive switch load circuit from the power supply (VCC).

[0026] Specifically, the high-power MOSFET output circuit, as the second and final power amplification stage, is centered around a single N-channel high-power MOSFET, preferably the IRFP250 type, with a rated current of up to 200A and a withstand voltage of 600V. The gate of the N-channel high-power MOSFET serves as the control terminal, connected to the output of the totem-pole driver circuit. Its drain is connected to the +12V DC mains power supply VCC, while its source serves as the final output of the entire driver device, connected to the photoconductive switch load circuit. Replacing the traditional multi-MOSFET parallel connection with a single high-power MOSFET fundamentally avoids the risk of uneven current distribution in parallel connections, significantly simplifying the circuit structure. Combined with the powerful driving capability of the totem-pole circuit, a single N-channel high-power MOSFET can stably output a large current of 100A.

[0027] The output of the photoconductive switch load circuit is connected to the input of the sampling feedback circuit, and the output of the sampling feedback circuit is electrically connected to the feedback input of the constant current control circuit. The sampling feedback circuit is used to collect the current signal of the load circuit and convert it into a voltage signal to feed back to the constant current control circuit. The ground terminal of the sampling feedback circuit is electrically connected to the system ground. The sampling feedback circuit is connected in series in the main power circuit and is responsible for collecting the current signal flowing through the photoconductive switch load in real time and linearly converting it into a voltage signal, providing accurate feedback for the constant current control circuit, thus forming a complete closed-loop control system.

[0028] The sampling feedback circuit is used to implement closed-loop control, and its core is a high-power, low-resistance sampling resistor. The sampling resistor is connected in series in the main current loop, with one end connected to the output of the photoconductive switch load circuit and the other end directly grounded (GND). In other words, the current flowing from the load must pass through the sampling resistor to ground. According to Ohm's law, the voltage drop VFB across the sampling resistor is proportional to the current ILOAD flowing through it. Therefore, the sampling resistor converts the current signal into a voltage signal. The connection point between the sampling resistor and the photoconductive switch load circuit serves as the output of the sampling feedback circuit, directly connected back to the inverting input of the operational amplifier's constant current control circuit, providing the feedback voltage VFB. To ensure accurate sampling and controllable power consumption, the sampling resistor is preferably a 0.1Ω, 100W metal film resistor.

[0029] The entire device uses a DAC to set a voltage value VDAC corresponding to the target current of 100A for the constant current control circuit. When the circuit starts, the load current is 0, the feedback voltage VFB is 0, and the constant current control circuit outputs a high voltage, driving the entire current amplification link and turning on Q7. Current begins to flow through the photoconductive switch load and the sampling resistor R6. The feedback voltage VFB on R6 begins to rise. The constant current control circuit compares VDAC and VFB in real time, dynamically adjusting its output to control the conduction level of Q7, ultimately ensuring that VFB is precisely equal to VDAC. At this point, the load current ILOAD is precisely kept constant at the target value of 100A set by VDAC. When external factors cause current fluctuations, this closed-loop feedback system responds and adjusts immediately to ensure a highly constant output current. Example

[0030] This embodiment details the working principle and implementation process of a two-stage current-amplifying high-current constant-current photoconductive switch driver circuit. Each module works collaboratively to complete constant current setting, current amplification output, and closed-loop feedback, as detailed below: Implementation of constant current control Target current setting: The external DAC inputs a voltage signal to the non-inverting input (pin 3) of the operational amplifier U1A LM358 in the operational amplifier constant current control circuit through the DAC_VOUT pin. This voltage value corresponds to the target constant current value required by the photoconductive switch. If the target current is set to 100A, the DAC_VOUT outputs the corresponding voltage to set the constant current reference.

[0031] Closed-loop comparison adjustment: The inverting input terminal (pin 2) of the constant current control circuit acquires the voltage signal at the upper end of the sampling resistor R6 (0.1Ω). This voltage is proportional to the load current (Vfeedback = Iload × R6). The constant current control circuit compares the target voltage at the non-inverting input with the feedback voltage at the inverting input in real time. Through the internal amplification circuit, it adjusts the drive voltage at the output terminal (pin 1) to keep the feedback voltage close to the target voltage, thereby locking the load current.

[0032] Implementation of two-stage current amplification The first-stage current amplification is clearly defined as a parallel current-sharing and amplification structure of four IRF540 MOSFETs in the front stage. The drive voltage output from the U1A LM358 drives the gates of the four MOSFETs through four 1kΩ gate resistors (R2, R3, R4, R5), turning on the MOSFETs. The drains of the four MOSFETs are connected to VCC, and the sources are connected in series with 0.1Ω current-sharing resistors (R10, R11, R12, R13) to form a single front-stage output node. The current-sharing resistors ensure that the current of the four MOSFETs is evenly distributed. The rated output of a single MOSFET is about 5A, and the total output capacity of the first-stage current amplification is about 20A, completing the initial current sharing and amplification on the low-voltage side.

[0033] The second-stage current amplification is clearly defined as a totem-pole push-pull drive amplification and a final current amplification structure using a single high-power MOSFET in the subsequent stage; the output node of the first-stage current amplification is connected to the base of NPN transistor Q6 (S9013) and PNP transistor Q5 (S9012) via a 10kΩ current-limiting resistor (R9) to form a push-pull totem-pole drive structure.

[0034] When the drive signal is high, Q6 conducts, providing pull-up current from VCC to the gate of the subsequent MOSFET; when the drive signal is low, Q5 conducts, providing sink current to GND, rapidly charging and discharging the gate capacitance of the subsequent MOSFET, thus solving the defect of insufficient drive capability at the first-stage current amplification output. The output of the totem pole drive circuit is directly connected to the gate of the subsequent high-power MOSFET Q7 (IRFP250); the drain of Q7 is connected to VCC, and the source is connected to the photoconductive switch load. This MOSFET has a rated current of 200A, which further amplifies the 20A level control signal of the first-stage current amplification output to a 100A level high-current output, completing the final current amplification of the second stage; the single-tube high-power output structure avoids the problems of uneven current distribution and thermal runaway burnout caused by the traditional parallel connection of multiple MOSFETs from the root.

[0035] This invention pioneers a two-stage, hierarchical current amplification architecture that combines parallel current sharing and amplification of multiple MOSFETs in the front stage with a totem-pole gate drive. Unlike existing technologies that simply use parallel MOSFETs for current amplification or a single totem-pole drive, this invention achieves a substantial breakthrough in driving capability, current sharing effect, circuit reliability, and high-current output stability. The first stage of current amplification employs a four-MOSFET parallel configuration, with gate current-limiting resistors and source current-sharing resistors to achieve uniform current distribution across all stages. This initially amplifies the control signal into a stable, low-current drive signal, completely resolving the current unevenness and single-transistor overheating / burnout problems that easily occur with traditional parallel multi-MOSFET configurations. The second stage of current amplification, centered on a totem-pole push-pull drive circuit, receives the output signal from the first stage and utilizes the complementary conduction characteristics of NPN and PNP transistors to significantly enhance gate charging and discharging capabilities. This rapidly drives a single high-power MOSFET in the subsequent stage to achieve final current amplification, amplifying the low-current drive signal to a high-current output at the hundred-ampere level. This approach avoids the current-sharing defects of traditional multi-tube parallel connections by relying on the high-power output of a single MOSFET, and also compensates for the insufficient current-amplifying capability of the preceding stage through totem-pole driving. Ultimately, it provides a high-current, high-precision, and high-reliability constant current drive for the photoconductive switch. This two-stage current-amplifying scheme, combining parallel current sharing of MOSFETs with totem-pole driving, is a novel technical solution that cannot be achieved by a single current-amplifying structure or a single driving structure in existing technologies.

[0036] This invention does not employ a totem-pole circuit alone to achieve the driving function. Instead, it uses it as the core intermediate coupling unit in a two-stage hierarchical current amplification architecture. This unit, along with the front-stage multi-channel MOSFETs connected in parallel for current sharing and amplification, and the rear-stage single high-power MOSFET for power output, forms an organically coordinated and inseparable overall technical solution. This invention pioneers an integrated and coordinated current amplification architecture that combines the first-stage current amplification with the front-stage multi-channel MOSFETs connected in parallel for current sharing, the intermediate stage with the totem-pole gate drive, and the second-stage current amplification with the rear-stage single high-power MOSFET, achieving the final current amplification at the hundred-ampere level. This solves the problems of uneven current distribution and thermal runaway risks inherent in traditional parallel MOSFET current amplification, and also compensates for the lack of power amplification capability in conventional totem-pole drives. The three components work together in circuit structure and support each other functionally, forming a novel high-current constant-current driving solution specifically for photoconductive switches.

[0037] Implementation of closed-loop feedback Current sampling: The photoconductor load is connected in series between the source of Q7 and the sampling resistor R6 (0.1Ω). All the photoconductor load current flows through R6. According to Ohm's law, a voltage drop proportional to the load current is generated across R6: Vsample = Iload × 0.1Ω Signal feedback: The sampling voltage at the top of R6 is directly connected to the inverting input terminal (pin 2) of the constant current control circuit, forming a closed-loop feedback circuit. The constant current control circuit adjusts the conduction level of the front-stage MOSFET and the back-stage MOSFET in real time according to the difference between the sampling voltage and the target voltage, ensuring that the load current is stable at the set value and achieving high-precision constant current control.

[0038] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A photoconductive switch driving device for a high-current constant current source, comprising a constant current control circuit, a sampling feedback circuit, and a photoconductive switch load circuit, characterized in that, It also includes a microcontroller control circuit, a front-stage MOSFET current amplification circuit, a totem-pole gate drive circuit, and a rear-stage MOSFET output circuit; The output terminal of the microcontroller control circuit is connected to the input terminal of the constant current control circuit, and is used to output a DAC voltage signal to set the target constant current value. The output terminal of the constant current control circuit is connected to the input terminal of the front-stage MOS transistor current amplification circuit, which is used to output an adjustable constant current control voltage and receive feedback signals to realize closed-loop regulation. The pre-stage MOSFET current amplification circuit includes multiple N-channel MOSFETs connected in parallel, as well as gate resistors and current-sharing resistors corresponding to each MOSFET. The gates of each MOSFET are connected in series with gate resistors and then connected to the output terminal of the constant current control circuit. The drains are connected to a DC power supply, and the sources are connected in series with current-sharing resistors and then connected to each other, forming the output terminal of the pre-stage MOSFET current amplification circuit. The output terminal of the pre-stage MOSFET current amplification circuit is connected to the input terminal of the totem pole gate drive circuit to achieve initial current sharing and amplification, and to transmit control signals to the totem pole gate drive circuit. The initial current value is less than 5A. The output terminal of the totem pole gate drive circuit is connected to the control terminal of the subsequent MOS transistor output circuit to enhance the gate drive capability and drive the subsequent MOS transistor to turn on and off quickly. The output circuit of the subsequent MOSFET includes an N-channel MOSFET. The gate of the MOSFET is connected to the output of the totem pole gate drive circuit as the control terminal, the drain is connected to a DC power supply, and the source is connected to the input of the photoconductive switch load circuit as the output terminal, which is used to provide a constant current operating power supply for the photoconductive switch; the power of the subsequent MOSFET is greater than 190W. The input terminal of the sampling feedback circuit is connected to the output terminal of the photoconductive switch load circuit, and the output terminal is connected to the feedback input terminal of the constant current control circuit. The ground terminal is grounded. It is used to collect the current signal of the load circuit and convert it into a voltage signal to be fed back to the constant current control circuit.

2. The photoconductive switch driving device for a high-current constant current source according to claim 1, characterized in that, The constant current control circuit uses an LM358 operational amplifier. The non-inverting input of the LM358 operational amplifier is connected to the DAC voltage signal output by the microcontroller control circuit, the inverting input is connected to the output of the sampling feedback circuit, and the output is connected to the input of the pre-stage MOS transistor current amplification circuit as the output of the constant current control circuit.

3. The photoconductive switch driving device for a high-current constant current source according to claim 1, characterized in that, The N-channel MOSFET is an IRF540 type, the gate resistor is a 1kΩ carbon film resistor, and the current sharing resistor is a 0.1Ω, 1W metal film resistor.

4. The photoconductive switch driving device for a high-current constant current source according to claim 1, characterized in that, The totem pole gate drive circuit includes an NPN transistor, a PNP transistor, a base current limiting resistor, and multiple emitter resistors; One end of the base limiting current resistor is connected to the output terminal of the front-stage MOS transistor current amplification circuit, and the other end is connected to the base of both the NPN transistor and the PNP transistor. The collector of the NPN transistor is connected to a DC power supply, and the emitter is connected in series with an emitter resistor. The collector of the PNP transistor is grounded, and the emitter is connected in series with another emitter resistor and then connected to the emitter output terminal of the NPN transistor to form the output terminal of the totem pole gate drive circuit.

5. The photoconductive switch driving device for a high-current constant current source according to claim 4, characterized in that, The NPN transistor is an S9013 type, the PNP transistor is an S9012 type, the base current limiting resistor is a 10kΩ resistor, and the emitter resistor is a 100Ω resistor.

6. The photoconductive switch driving device for a high-current constant current source according to claim 1, characterized in that, The N-channel MOSFET is an IRFP250 type with a rated current of 200A and a withstand voltage of 600V.

7. The photoconductive switch driving device for a high-current constant current source according to claim 1, characterized in that, The sampling feedback circuit includes a sampling resistor; One end of the sampling resistor is connected to the output terminal of the photoconductive switch load circuit, and the other end is grounded. The connection node between the sampling resistor and the photoconductive switch load circuit serves as the output terminal of the sampling feedback circuit, which is electrically connected to the feedback input terminal of the constant current control circuit.

8. The photoconductive switch driving device for a high-current constant current source according to claim 7, characterized in that, The sampling resistor is a 0.1Ω, 100W metal film resistor.

Images