A floating semiconductor laser digital-analog hybrid low-noise constant current source

Abstract

This invention discloses a floating-ground semiconductor laser mixed-signal low-noise constant current source, comprising a low-noise power supply, a voltage reference module, a voltage follower, a current setting module, a voltage-controlled constant current source module, an acquisition and display module, an IIC isolation module, and a main control DSP module. The entire circuit adopts a floating-ground connection, with the laser negative terminal grounded, ensuring high safety and reducing interference signals, thus improving electromagnetic compatibility. The current setting module is compatible with both analog and digital settings of the output current, and a negative feedback loop composed of a precision operational amplifier and MOSFET transistors achieves constant current output. The use of an IIC isolation module solves the IIC level conflict problem between the setting and display sections caused by the floating connection, allowing the entire circuit system to communicate via the same IIC bus in a floating-ground state. This invention provides a stable current for semiconductor lasers, exhibiting low noise, high reliability, and good stability.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor laser constant current source technology, and specifically relates to a floating semiconductor laser mixed-signal low-noise constant current source. Background Technology

[0002] Semiconductor lasers rely on current injection to operate, and the magnitude and performance of this current significantly affect the laser's frequency, power stability, and overall performance. Therefore, the current magnitude must be controlled to ensure a continuously adjustable and stable output current. Current constant current source technology for lasers often employs a closed-loop negative feedback scheme with the laser negative electrode floating and the sampling resistor grounded. However, this approach presents certain safety risks, makes laser modulation signal injection difficult, and is incompatible with both analog and digital current settings, resulting in low reliability. Furthermore, the floating connection of the digital-to-analog converter circuit can cause level conflicts with other digital circuits in the system, complicating communication and posing challenges to the design of digital settings. Summary of the Invention

[0003] The purpose of this invention is to provide a floating semiconductor laser mixed-signal low-noise constant current source, which solves the above-mentioned problems of the prior art, provides high-performance current for semiconductor lasers, and improves the stability of laser light source and system reliability.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A floating-ground semiconductor laser mixed-signal low-noise constant current source includes a low-noise power supply, a voltage reference module, a first voltage follower, a current setting module, a voltage-controlled constant current source module, an acquisition and display module, and an IIC isolation module, wherein:

[0006] The low-noise power supply is used to provide the circuit with a positive voltage Vreg+, and it includes a delayed start circuit for adjusting the power-on sequence and has a soft start function.

[0007] The voltage reference module provides a parallel reference voltage as a floating ground reference level Vreg-;

[0008] The first voltage follower isolates the circuits before and after it;

[0009] The current setting module sets the output current magnitude and is compatible with both digital and analog modes. The main control DSP module achieves digital setting by writing the current setting value through the IIC bus, or achieves analog setting through the knob potentiometer.

[0010] The voltage-controlled constant current source module achieves closed-loop control through a precision operational amplifier negative feedback loop, outputting a constant current of 0-200mA, which is connected to a semiconductor laser through an SMA interface to drive the laser to work at a set value.

[0011] The acquisition and display module is used to display the actual current, the set current, the switch status, and to provide abnormal alarms. It communicates with the main control DSP module via the IIC bus.

[0012] The IIC isolation module isolates the IIC bus of the digital current setting module and the acquisition and display module, enabling the entire circuit system to communicate through the same set of IIC buses in a floating ground state.

[0013] The main control DSP module is used for system communication and control, parameter adjustment, and driving the OLED screen in the acquisition and display module to achieve display function.

[0014] Furthermore, the low-noise power supply (1) consists of a delayed start circuit, an LM317T three-terminal voltage regulator chip, a soft start circuit, and an RC filter circuit.

[0015] Furthermore, the voltage reference module adopts a parallel voltage reference chip LM399. The voltage reference chip LM399 maintains a voltage of 6.95V between its positive and negative terminals. The positive output is connected to the output Vreg+ of the low-noise power supply (1), and the negative output is connected to -9V through the first resistor R1 and to the first voltage follower (3) through the second resistor R2. The third resistor is connected in parallel between the output Vreg+ of the low-noise power supply and the input of the first voltage follower to divide the reference output.

[0016] Furthermore, the current setting module is connected in a floating-ground configuration and consists of potentiometer J3, DAC8571 digital-to-analog converter chip U6, and setting selection switch J4. The upper node of potentiometer J3 is connected to the output Vreg+ of the low-noise power supply, and the lower node of potentiometer J3 is connected to the output of the first voltage follower via the fourth resistor R4. The sliding terminal of potentiometer J3 is connected to the first input terminal of setting selection switch J4, forming the analog setting section. The power supply pin and reference pin of DAC8571 digital-to-analog converter chip U6 are connected to the output Vreg+ of the low-noise power supply, and the ground pin is connected to the output of the first voltage follower, i.e., the floating ground reference level Vreg-, to achieve a floating-ground connection. The SCL and SDA pins of DAC8571 digital-to-analog converter chip U6 are connected to the main control DSP module via the IIC isolation module, communicate with the main control via the IIC bus, write digital setting values, and the output pin is connected to the second input terminal of setting selection switch J4, forming the digital setting section. The setting selection switch J4 selects the setting mode by shorting either input terminal or output terminal.

[0017] Furthermore, the voltage-controlled constant current source module consists of a second-order RC filter, a first operational amplifier U1, a first MOSFET transistor M1, a sampling resistor RS1, and an RC attenuation network. The input terminal of the second-order RC filter is connected to the output terminal of the current setting module, and the output terminal is connected to the non-inverting input terminal of the first operational amplifier U1. The output terminal of the first operational amplifier U1 is connected to the gate of the first MOSFET transistor M1 via a fifth resistor R5. The RC attenuation network is connected in series between the output Vreg+ of the low-noise power supply and the output terminal of the first operational amplifier U1. The RC attenuation network consists of a sixth resistor R6 and a first capacitor C1 connected in series. One end of the sampling resistor RS1 is connected to the source of the first MOSFET transistor M1, and the other end is connected to the inverting input terminal of the first operational amplifier U1 and the output Vreg+ of the low-noise power supply, forming a negative feedback loop. The drain of the first MOSFET transistor M1 is connected to the positive terminal of the SMA interface via a first diode D1. The semiconductor laser is connected through the SMA interface to provide output current, and the negative terminal of the SMA interface is grounded.

[0018] Furthermore, the acquisition and display module includes an instrumentation amplifier, a second voltage follower, and an analog-to-digital converter (ADC). The input terminals of the instrumentation amplifier are connected to both ends of the sampling resistor. The second voltage follower is connected between the instrumentation amplifier and the ADC to provide isolation. The ADC includes an ADS1119 ADC chip. The power supply pin of the ADC chip is connected to 3.3V, the reference pin is connected to 2.5V, and the ground pin is grounded. The SCL and SDA pins are connected to the main control DSP module via an IIC isolation module and communicate through the IIC bus.

[0019] Furthermore, the IIC bus of the DAC8571 digital-to-analog converter chip U6 and the analog-to-digital converter chip is isolated by an IIC isolation module; the IIC isolation module is a bidirectional IIC isolator of model CA-IS3020, with the A group power supply pin connected to 3.3V voltage, the ground pin grounded, and the SCL and SDA pins connected to the analog-to-digital converter chip and the main control DSP module respectively; the B group power supply pin is connected to the output Vreg+ of the low-noise power supply, the ground pin is connected to the output of the first voltage follower (3), i.e., the floating ground reference level Vreg-, and the SCL and SDA pins are connected to the DAC8571 digital-to-analog converter chip U6.

[0020] Beneficial effects:

[0021] This invention discloses a floating-ground semiconductor laser mixed-signal low-noise constant current source. It uses a negative feedback loop closed-loop control composed of an ultra-low noise, low-distortion precision operational amplifier AD797ARZ and a field-effect transistor. Current sampling is performed through a low-temperature drift resistor. The entire circuit adopts a floating-ground connection, with the laser negative terminal grounded and the sampling resistor floating. The closed-loop negative feedback scheme, in which the closed-loop control unit and the main laser power supply system share a common ground, has higher safety and introduces less noise.

[0022] The present invention has an output current range of 0 to 200mA, with noise of less than 1μA and current fluctuation of less than 10μA. It can achieve compatibility between digital and analog settings. The use of IIC isolation module solves the problem of IIC level conflict between the setting part and the display part caused by floating ground connection. It enables the entire circuit system to communicate through the same set of IIC buses in floating ground state. It has the advantages of high stability, good reliability and low noise. Attached Figure Description

[0023] Figure 1 This is a block diagram of a floating semiconductor laser mixed-signal low-noise constant current source control according to the present invention;

[0024] Figure 2 for Figure 1 Control block diagram of a low-to-medium noise power supply;

[0025] Figure 3 for Figure 1 Circuit schematic diagram of the medium voltage reference module, the first voltage follower, and the current setting module;

[0026] Figure 4 for Figure 1 Circuit schematic diagram of medium-voltage controlled constant current source module;

[0027] Figure 5 for Figure 1 Control block diagram of the data acquisition and display module;

[0028] Figure 6 for Figure 1 Circuit schematic diagram of the IIC isolation module;

[0029] The meanings of the labels in the figure are as follows: 1 is a low-noise power supply, 2 is a voltage reference module, 3 is a voltage follower, 4 is a current setting module, 5 is a voltage-controlled constant current source module, 6 is a data acquisition and display module, 7 is an IIC isolation module, 8 is a main control DSP module, 1-1 is a delayed start circuit, 1-2 is an LM317T three-terminal voltage regulator chip, 1-3 is a soft start circuit, 1-4 is an RC filter circuit, 5-1 is a second-order RC filter, 5-2 is an RC attenuation network, 6-1 is an instrumentation amplifier, 6-2 is a voltage follower, and 6-3 is an analog-to-digital converter circuit. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] like Figure 1 As shown, a floating semiconductor laser mixed-signal low-noise constant current source of the present invention includes a low-noise power supply 1, a voltage reference module 2, a voltage follower 3, a current setting module 4, a voltage-controlled constant current source module 5, an acquisition and display module 6, an IIC isolation module 7, and a main control DSP module 8.

[0032] The low-noise power supply 1 is connected to the current setting module 4 and the voltage-controlled constant current source module 5, and is used to provide the circuit with the positive voltage Vreg+. It includes a delayed start circuit for adjusting the power-on sequence and has a soft start function.

[0033] The voltage reference module 2 is connected to the voltage follower 3, providing a parallel reference voltage as a floating ground reference level Vreg-;

[0034] The voltage follower 3 isolates the front and rear circuits and outputs to the current setting module 4;

[0035] The output of the current setting module 4 is connected to the voltage-controlled constant current source module 5 to set the output current magnitude, which is compatible with both digital and analog modes. The main control DSP module 8 is connected to the current setting module 4 through the IIC bus to write the current setting value into the DAC chip to achieve digital setting, or to achieve analog setting through the knob potentiometer.

[0036] The voltage-controlled constant current source module 5 achieves closed-loop control through a precision operational amplifier negative feedback loop, outputs a constant current of 0-200mA, and connects to a semiconductor laser through an SMA interface to drive the semiconductor laser to work at a set value.

[0037] The acquisition and display module 6 is connected to the voltage-controlled constant current source module 5 for voltage acquisition, and is connected to the main control DSP module 8 via the IIC bus to achieve communication with the main control DSP module 8; the IIC isolation module 7 is connected to the current setting module 4 and the acquisition and display module 6 respectively, and isolates the IIC bus of the digital current setting module 4 and the acquisition and display module 6, so that the entire circuit system can communicate through the same set of IIC buses in floating ground mode; the main control DSP module 8 performs system communication and control, realizes parameter adjustment, drives the OLED screen in the acquisition and display module 6 to display the actual current, set current, switch status, and perform abnormal alarms.

[0038] Figure 2 for Figure 1 The control block diagram of the low-noise power supply 1 is as follows: Figure 2 As shown, the low-noise power supply 1 consists of a delayed start circuit 1-1, an LM317T three-terminal voltage regulator chip 1-2, a soft start circuit 1-3, and an RC filter circuit 1-4. The input terminal of the delayed start circuit 1-1 is connected to the positive voltage terminal +12V, and the output terminal is connected to the input terminal of the LM317T voltage regulator chip 1-2. The input voltage is delayed for a period of time (approximately 5ms) before being input to the LM317T voltage regulator chip 1-2, used to coordinate with other circuits to adjust the power-on sequence. The ADJ pin of the LM317T voltage regulator chip 1-2 is connected to the soft start circuit 1-3, and the output voltage and start-up time can be adjusted by adjusting the resistance and capacitance parameters between the pins. The output Vreg+ of the LM317T voltage regulator chip 1-2 is used to power the constant current source main circuit through the RC filter circuit 1-4.

[0039] Figure 3 The part within the dashed box on the left is Figure 1 The circuit schematic of the medium voltage reference module 2 is as follows: Figure 3 As shown, the voltage reference module 2 uses a parallel voltage reference chip LM399. The H+ and H- pins of the LM399 are connected to +9V and -9V respectively, maintaining a voltage of 6.95V between its positive and negative outputs. The positive output VZ+ is connected to the output Vreg+ of the low-noise power supply 1, and the negative output VZ- is connected to -9V through a first resistor R1 and to a voltage follower 3 through a second resistor R2. A third resistor R3 is connected in parallel between the output Vreg+ of the low-noise power supply 1 and the input of the voltage follower 3 to divide the reference output. The voltage follower 3 follows the divided reference output and isolates the preceding and following circuits, outputting a floating ground reference level Vreg-.

[0040] Figure 3 The right side is Figure 1 The circuit schematic of the medium current setting module 4 is as follows: Figure 3As shown, the current setting module 4 is connected to floating ground and consists of potentiometer J3, DAC8571 digital-to-analog converter chip U6, and setting selection switch J4. The upper node of potentiometer J3 is connected to the output Vreg+ of low-noise power supply 1, and the lower node of potentiometer J3 is connected to the output terminal of voltage follower 3 via the fourth resistor R4. The sliding terminal of potentiometer J3 is connected to the first input terminal of setting selection switch J4, forming the analog setting section, which outputs the analog setting voltage value CURRENT_SETA. The power supply pin and reference pin of digital-to-analog converter chip U6 are connected to the output Vreg+ of low-noise power supply 1, and the ground pin is connected to the output of voltage follower 3, i.e., the floating ground reference level Vreg-, to achieve a floating ground connection. The SCL and SDA pins of the digital-to-analog converter chip U6 are connected to the main control DSP module 8 via the IIC isolation module 7. It communicates with the main control DSP module 8 through the IIC bus, writes digital setting values, and connects the output pin to the second input terminal of the setting selection switch J4 to form the digital setting part, which outputs the digital setting voltage value CURRENT_SETD. The setting selection switch J4 selects the setting mode by shorting any one of the input and output terminals, and provides the setting voltage CURRENT_SET to the voltage-controlled constant current source module 5.

[0041] Figure 4 for Figure 1 The circuit schematic of the medium-voltage controlled constant current source module 5 is as follows: Figure 4 As shown, the voltage-controlled constant current source module 5 adopts a closed-loop control scheme with a precision operational amplifier negative feedback loop. The laser negative terminal is grounded, the sampling resistor is floating, and the closed-loop control unit shares a common ground with the main laser power supply system. The voltage-controlled constant current source module 5 consists of a second-order RC filter 5-1, a first operational amplifier U1 (AD797ARZ), a first MOSFET transistor M1, a sampling resistor RS1, and an RC attenuation network 5-2. The input terminal of the second-order RC filter 5-1 is connected to the output terminal of the current setting module 4, and the output terminal is connected to the non-inverting input terminal of the first operational amplifier U1. The output of operational amplifier U1 is connected to the gate of the first MOSFET transistor M1 via the fifth resistor R5. The RC attenuation network 5-2 is connected in series between the output Vreg+ of the constant current source low-noise power supply 1 and the output of the first operational amplifier U1. The RC attenuation network 5-2 consists of the sixth resistor R6 and the first capacitor C1 connected in series. One end of the sampling resistor RS1 is connected to the source of the first MOSFET transistor M1, and the other end is connected to the inverting input terminal FB- of the first operational amplifier U1 and the output Vreg+ of the low-noise power supply 1, forming a negative feedback loop. The drain of the first MOSFET transistor M1 is connected to the positive terminal LD+ of the SMA interface via the first diode D1. The SMA interface is connected to a semiconductor laser to provide output current, and the negative terminal of the SMA interface is grounded.

[0042] Figure 5 for Figure 1 The control block diagram of the acquisition and display module 6 is as follows: Figure 5 As shown, the acquisition and display module 6 includes an instrumentation amplifier 6-1, a second voltage follower 6-2, and an analog-to-digital converter circuit 6-3. The input terminals of the instrumentation amplifier 6-1 are connected to the two ends of the sampling resistor RS1. The second voltage follower 6-2 is connected between the instrumentation amplifier 6-1 and the analog-to-digital converter circuit 6-3 for isolation. The analog-to-digital converter circuit 6-3 is mainly composed of an ADS1119 analog-to-digital converter chip. The power supply pin of the analog-to-digital converter chip is connected to a 3.3V voltage, the reference pin is connected to a 2.5V voltage, and the ground pin is grounded. It converts the sampling voltage from an analog quantity to a digital quantity. The SCL and SDA pins are connected to the main control DSP module 8 through the IIC isolation module 7 and communicate through the IIC bus.

[0043] Figure 6 for Figure 1 The circuit schematic of the IIC isolation module 7 is as follows: Figure 6 As shown, the IIC bus of the digital-to-analog converter chip U6 and the analog-to-digital converter chip is isolated by the IIC isolation module 7. The IIC isolation module 7 is a bidirectional IIC isolator U2 of model CA-IS3020. The power supply pin VDDA of group A is connected to 3.3V voltage, and the ground pin GNDA is grounded. The SCLA and SDAA pins are respectively connected to the SDA and SCL pins of the analog-to-digital converter chip ADS1119 and the main control DSP module 8 for IIC communication. The power supply pin VDDB of group B is connected to the output Vreg+ and DA_GND pins of the low-noise power supply 1, and the ground pin GNDB is connected to the output of the first voltage follower 3, i.e., the floating ground reference level Vreg-. The SCLB and SDAB pins are connected to the DA_SCL and DA_SDA pins of the digital-to-analog converter chip U6. This solves the problem of IIC level conflict under floating ground connection, so that the IIC communication of AD and DA circuits can be carried out in a state of mutual non-interference.

[0044] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A floating semiconductor laser mixed-signal low-noise constant current source, characterized in that: It includes a low-noise power supply (1), a voltage reference module (2), a first voltage follower (3), a current setting module (4), a voltage-controlled constant current source module (5), a data acquisition and display module (6), an IIC isolation module (7), and a main control DSP module (8), wherein: The low-noise power supply (1) is used to provide the circuit with a positive voltage Vreg+, and it includes a delayed start circuit for adjusting the power-on sequence and has a soft start function. The voltage reference module (2) provides a parallel reference voltage as a floating ground reference level Vreg-; The first voltage follower (3) isolates the circuits before and after it; The current setting module (4) sets the output current magnitude and is compatible with both digital and analog modes. The main control DSP module writes the current setting value through the IIC bus to achieve digital setting, or achieves analog setting through the knob potentiometer. The voltage-controlled constant current source module (5) achieves closed-loop control through a precision operational amplifier negative feedback loop, outputs a constant current of 0~200mA, and connects to a semiconductor laser through an SMA interface to drive the laser to work at a set value; The acquisition and display module (6) is used to display the actual current, the set current, the switch status, and to perform abnormal alarms. It communicates with the main control DSP module through the IIC bus. The IIC isolation module (7) isolates the IIC bus of the digital current setting module (4) and the acquisition and display module (6), so that the entire circuit system can communicate through the same set of IIC buses in a floating state; The main control DSP module (8) is used for system communication and control, parameter adjustment and driving the OLED screen in the acquisition and display module (6) to realize the display function; The current setting module (4) is connected in a floating configuration and consists of potentiometer J3, DAC8571 digital-to-analog converter chip U6, and setting selection switch J4. The upper node of potentiometer J3 is connected to the output Vreg+ of the low-noise power supply (1), and the lower node of potentiometer J3 is connected to the output terminal of the first voltage follower (3) via the fourth resistor R4. The sliding terminal of potentiometer J3 is connected to the first input terminal of setting selection switch J4, forming the analog setting section. The power supply pin and reference pin of DAC8571 digital-to-analog converter chip U6 are connected to the low-noise power supply. The output Vreg+ of the power supply (1) is connected to the ground pin of the first voltage follower (3), which is the floating ground reference level Vreg-, to achieve a floating ground connection; the SCL and SDA pins of the DAC8571 digital-to-analog converter chip U6 are connected to the main control DSP module (8) through the IIC isolation module (7), and communicate with the main control through the IIC bus to write digital setting values. The output pin is connected to the second input terminal of the setting selection switch J4 to form the digital setting part; the setting selection switch J4 can select the setting mode by shorting any one of the input terminals and the output terminal; The IIC bus of the DAC8571 digital-to-analog converter chip U6 and the analog-to-digital converter chip is isolated by the IIC isolation module (7). The IIC isolation module (7) is a bidirectional IIC isolator of model CA-IS3020. The A group power supply pin is connected to 3.3V voltage, the ground pin is grounded, and the SCL and SDA pins are respectively connected to the analog-to-digital converter chip and the main control DSP module (8). The B group power supply pin is connected to the output Vreg+ of the low noise power supply (1), the ground pin is connected to the output of the first voltage follower (3), i.e., the floating ground reference level Vreg-, and the SCL and SDA pins are connected to the DAC8571 digital-to-analog converter chip U6.

2. The floating semiconductor laser mixed-signal low-noise constant current source according to claim 1, characterized in that, The low-noise power supply (1) consists of a delayed start circuit (1-1), an LM317T three-terminal voltage regulator chip (1-2), a soft start circuit (1-3), and an RC filter circuit (1-4).

3. The floating semiconductor laser mixed-signal low-noise constant current source according to claim 1, characterized in that, The voltage reference module (2) uses a parallel voltage reference chip LM399. The voltage reference chip LM399 maintains a voltage of 6.95V between its positive and negative terminals. The positive output is connected to the output Vreg+ of the low-noise power supply (1), and the negative output is connected to -9V through the first resistor R1 and to the first voltage follower (3) through the second resistor R2. The third resistor is connected in parallel between the output Vreg+ of the low-noise power supply (1) and the input of the first voltage follower (3) to divide the reference output.

4. A floating semiconductor laser mixed-signal low-noise constant current source according to claim 1, characterized in that, The voltage-controlled constant current source module (5) consists of a second-order RC filter (5-1), a first operational amplifier U1, a first MOSFET transistor M1, a sampling resistor RS1, and an RC attenuation network (5-2). The input terminal of the second-order RC filter is connected to the output terminal of the current setting module (4), and the output terminal is connected to the non-inverting input terminal of the first operational amplifier U1. The output terminal of the first operational amplifier U1 is connected to the gate of the first MOSFET transistor M1 via a fifth resistor R5. The RC attenuation network is connected in series between the output Vreg+ of the low-noise power supply (1) and the output terminal of the first operational amplifier U1. The RC attenuation network consists of a sixth resistor R6 and a first capacitor C1 connected in series. One end of the sampling resistor RS1 is connected to the source of the first MOSFET transistor M1, and the other end is connected to the inverting input terminal of the first operational amplifier U1 and the output Vreg+ of the low-noise power supply (1) respectively, forming a negative feedback loop. The drain of the first MOSFET transistor M1 is connected to the positive terminal of the SMA interface via a first diode D1, and the semiconductor laser is connected through the SMA interface to provide output current. The negative terminal of the SMA interface is grounded.

5. A floating semiconductor laser mixed-signal low-noise constant current source according to claim 1, characterized in that, The acquisition and display module (6) includes an instrumentation amplifier (6-1), a second voltage follower (6-2), and an analog-to-digital conversion circuit (6-3). The input terminals of the instrumentation amplifier (6-1) are respectively connected to the two ends of the sampling resistor. The second voltage follower (6-2) is connected between the instrumentation amplifier and the analog-to-digital conversion circuit to provide isolation. The analog-to-digital conversion circuit includes an analog-to-digital conversion chip of model ADS1119. The power supply pin of the analog-to-digital conversion chip is connected to a 3.3V voltage, the reference pin is connected to a 2.5V voltage, and the ground pin is grounded. The SCL and SDA pins are connected to the main control DSP module (8) through the IIC isolation module (7) and communicate through the IIC bus.

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