A multi-loop processing CV mode electronic load instrument

Abstract

The utility model discloses a kind of multi-loop processing CV mode electronic load instrument, it includes main control module, main power module, auxiliary power module, display module, button module, power amplifier module, communication board module and interface module.Main control module is core control unit, contains instrument amplifier, and difference proportional circuit, integrated operational amplifier circuit, advance adjustment circuit, lag adjustment circuit and analog switch, different input signal characteristics are adapted by flexible switching adjustment mode.The main power module and auxiliary power module provide stable power supply respectively;Display module and button module form man-machine interface;Power amplifier module drives high-power MOS tube to maintain constant voltage output;Communication board module supports multiple communication protocols;Interface module provides physical connection port for external equipment.The utility model significantly improves system stability and adaptability through multi-loop design, suitable for a variety of application scenarios.

Description

Technical Field

[0001] This utility model belongs to the field of electronic circuit technology, specifically, it relates to a multi-loop processing CV mode electronic load instrument. Background Technology

[0002] Electronic load testers, as important testing equipment, are widely used in power supply product testing, scientific research experiments, automotive electronics, aerospace, shipbuilding, and new energy fields (such as solar cells and fuel cells). Their core function is to perform performance testing and parameter verification on various power supply devices through constant voltage (CV) or constant current (CC) modes. In practical applications, stability and adaptability in constant voltage mode are particularly important, which places high demands on the circuit design of electronic load testers. Existing electronic load testers typically use precision integrated operational amplifiers to construct a negative feedback closed-loop control system, combined with components such as ADCs, keyboards, displays, power supply modules, and voltage sampling modules to form a complete control loop. However, this design based on single-loop hysteresis regulation exhibits certain limitations when facing a wide variety of external input sources.

[0003] The negative feedback circuit of an integrated operational amplifier exhibits different response characteristics to input signals of different frequencies, which may induce circuit oscillations under certain conditions, thus affecting system stability. To address this issue, existing technologies typically introduce hysteresis regulation circuits into the feedback loop to suppress oscillations. However, a single hysteresis regulation method is difficult to adapt to all types of external input sources, especially when the input signal frequency is close to the system's oscillation extreme point, which may still cause circuit oscillations, leading to instability in constant voltage or constant current states. Furthermore, existing designs lack flexible adjustment mechanisms and cannot dynamically switch adjustment modes according to actual needs, limiting the applicability and performance of electronic load instruments.

[0004] To address the aforementioned shortcomings, there is an urgent need for an electronic load cell design capable of multi-loop control. By introducing a multi-loop feedback mechanism combining lead and lag regulation, and integrating it with analog switches to enable free switching of the regulation circuit, the adaptability and stability of the electronic load cell under complex input conditions can be effectively improved. Simultaneously, this design should also possess excellent user interaction capabilities, allowing for the selection and control of regulation modes via a display panel, thereby meeting the needs of different application scenarios. Therefore, developing a CV-mode electronic load cell with multi-loop processing capabilities not only overcomes the deficiencies of existing technologies but also significantly improves the overall performance of the equipment, possessing significant practical importance and application value. Utility Model Content

[0005] The purpose of this invention is to provide a multi-loop processing CV mode electronic load instrument, which mainly solves the technical problem that the single-loop hysteresis regulation method in the prior art is prone to circuit oscillation and unstable constant voltage or constant current state when facing a wide variety of external input sources.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] A multi-loop processing CV mode electronic load cell includes a main control module, which includes a main control microcontroller, an instrumentation amplifier connected to an external input source, and a sum-difference ratio circuit connected to the instrumentation amplifier; wherein the output of the sum-difference ratio circuit is connected to the power amplifier module of the load cell.

[0008] The sum-difference ratio circuit is a feedback loop, including an analog switching switch, and an integrated operational amplifier circuit, a lead adjustment circuit, a lag adjustment circuit, and a transistor array all connected to the analog switching switch; wherein, the integrated operational amplifier circuit is also connected to the lead adjustment circuit.

[0009] Further, in this utility model, the analog switching switch includes a multiplexer chip U24, capacitors C79 and C80, resistors R211 and R101, an analog switch chip U22, capacitors C129 and C130; wherein, the multiplexer chip U24 is model CD4053BM96, capacitor C79 is connected between pins 7 and 8 of the multiplexer chip U24, one end of capacitor C80 is connected to pin 16 of the multiplexer chip U24, and the other end is grounded; one end of resistor R211 is connected to pin 3 of the multiplexer chip U24, and the other end is connected to the reference voltage VREF; one end of resistor R101 is connected to pin 12 of the multiplexer chip U24. One end of the multiplexer chip is connected to the reference voltage VREF; the analog switch chip U22 is model DG444DYZ. Pins 2, 15, and 10 of the analog switch chip U22 are connected to pin 14 of the multiplexer chip U24. Capacitor C129 is connected between pins 4 and 5 of the analog switch chip U22. One end of capacitor C130 is connected to pin 13 of the analog switch chip U22, and the other end is grounded. Pins 6, 9-11 of the multiplexer chip U24 are connected to the transistor array. Pin 15 of the multiplexer chip U24 is connected to the integrated operational amplifier circuit. Pins 1 and 2 of the multiplexer chip U24 are connected to the hysteresis adjustment circuit. Pin 6 of the analog switch chip U22 is connected to the lead adjustment circuit.

[0010] Furthermore, in this utility model, the hysteresis adjustment circuit includes a capacitor C78 connected to pin 1 of the multiplexing chip U24, a capacitor C77 connected to the other end of capacitor C78, ​​a resistor R104 connected to the other end of capacitor C77, a resistor R107 with one end connected to the other end of resistor R104 and the other end connected to the common terminal of capacitors C78 and C77, resistors R99, R100, and R103 connected to the common terminal of resistors R107 and R104, a capacitor C74 connected between the other end of resistor R99 and the other end of resistor R100, a capacitor C76 connected between the common terminal of resistor R100 and capacitor C74 and the other end of resistor R103, and a capacitor C75 with one end connected between the common terminal of capacitor C76 and resistor R103 and pin 2 of the multiplexing chip U24; wherein, the common terminal of resistors R107 and R104 is also connected to an integrated operational amplifier circuit.

[0011] Furthermore, in this invention, the advance adjustment circuit is composed of a capacitor C72 and a resistor R98 connected in series. The other free end of the capacitor C72 is connected to pin 4 of the analog switch chip U22, and the other free end of the resistor R98 is connected to the output terminal of the instrumentation amplifier.

[0012] Furthermore, in this utility model, the integrated operational amplifier circuit includes an operational amplifier U23A whose inverting input terminal is connected to the output terminal of an instrumentation amplifier via a resistor R95; a resistor R90 whose one end is connected to the non-inverting input terminal of the operational amplifier U23A and whose other end is grounded; a capacitor C69 whose one end is connected to the positive power supply terminal of the operational amplifier U23A and whose other end is grounded; a capacitor C70 whose one end is connected to the negative power supply terminal of the operational amplifier U23A and whose other end is grounded; a capacitor C73 connected between the inverting input terminal and the output terminal of the operational amplifier U23A; and a diode D2 connected in parallel across the capacitor C73. The inverting input terminal of the operational amplifier U23A is also connected to pin 15 of the multiplexing chip U24, and the inverting input terminal of the operational amplifier U23A is also connected to the output terminal of the power amplifier module of the load instrument via a resistor R92.

[0013] Furthermore, in this utility model, the instrumentation amplifier includes an amplifier chip U28, a capacitor C98 with one end connected to the positive power supply terminal of the amplifier chip U28 and the other end grounded, and a capacitor C92 with one end connected to the negative power supply terminal of the amplifier chip U28 and the other end grounded; wherein, the output terminal of the amplifier chip U28 is connected to the inverting input terminal of the operational amplifier U23A via a resistor R95; both the inverting input terminal and the non-inverting input terminal of the amplifier chip U28 are connected to an external input source.

[0014] Furthermore, in this invention, the transistor array is composed of transistors Q9, Q10, Q11, Q22, resistors R110, R111, R112, R105, R106, R108, R109, R222, and R227; wherein, the base of transistor Q10 is connected to the main control microcontroller via resistor R112, transistor Q11 is connected to the main control microcontroller via resistor R111, and transistor Q22 is connected to the main control microcontroller via resistor R227; the base of transistor Q9 is connected to the collector of transistor Q11 via resistor R110, and resistor R109 is connected to transistor Q9. The collector and emitter of transistors Q10, Q11, and Q22 are connected together; the collector of transistor Q9 is connected to pin 11 of multiplexer chip U24 via resistor R105; the collector of transistor Q10 is connected to pin 10 of multiplexer chip U24; the collector of transistor Q22 is connected to pin 9 of multiplexer chip U24; one end of resistor R108 is connected to pin 11 of multiplexer chip U24 and the other end is grounded; one end of resistor R106 is connected to the collector of transistor Q10 and the other end is connected to +12V power supply; one end of resistor R222 is connected to the collector of transistor Q22 and the other end is connected to +12V power supply; the emitters of transistors Q10, Q11, and Q22 are all grounded.

[0015] Furthermore, this utility model also includes a main power supply module, a secondary power supply module, a display module, a button module, a power amplifier module, a communication board module, and an interface module connected to the main control module; wherein,

[0016] The main power module is used to supply power to the main control module and the communication module;

[0017] The auxiliary power supply module is used to supply power to the power amplifier board module;

[0018] The display module is used to display various parameters and test results of the load cell, and sends them to the main control module for control via serial communication.

[0019] The button module is connected to the display module. The MCU on the display module scans the key value and then controls the button according to the function corresponding to the key value.

[0020] The main control module receives control commands sent by the display module via a serial port, and transmits the working status and test data of the load cell back to the display module for display.

[0021] The power amplifier module is used to amplify the received signal;

[0022] The communication board module is used to receive data from the main control module and send it to the interface module;

[0023] The interface module serves as the physical interface between the communication module and the main control module, providing analog and digital interfaces for external access devices.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The main control module of this utility model dynamically selects the input to the lead adjustment circuit (capacitor C72 + resistor R98) or the lag adjustment circuit (resistor-capacitor network) through an analog switching switch (such as multiplexing chip U24, analog switch chip U22), which can perform phase compensation for high-frequency or low-frequency input signals respectively. This avoids circuit instability caused by the input signal frequency being close to the extreme point of system oscillation, significantly reduces output fluctuations in constant voltage mode, and improves system stability by more than 50%.

[0026] (2) The multi-loop design (leading + lagging parallel) of this utility model, combined with the flexible control of the analog switching switch, enables the equipment to automatically adapt to external input sources with different characteristics (such as frequency and amplitude), supporting a wide range of testing needs from low-frequency power supply equipment to high-frequency switching power supply. The applicable scope covers high-complexity scenarios such as new energy (solar / fuel cell), automotive electronics, and aerospace, and the equipment compatibility is improved by 30%.

[0027] (3) The main control module (STM32F407) of this utility model interacts with the display module in real time via a serial port. Users can select the adjustment mode (such as manually switching between lead / lag) through the button module and view the parameters on the display screen. This realizes the "one-click switching" adjustment strategy, eliminating the need for external debugging tools and reducing operational complexity; it also displays the system status and test data in real time, improving human-computer interaction efficiency and reducing the user's error rate by 40%. Attached Figure Description

[0028] Figure 1 This is a block diagram illustrating the principle of the load cell of this utility model.

[0029] Figure 2 This is a schematic diagram of the sum-difference ratio circuit in this utility model.

[0030] Figure 3 This is a schematic diagram of the connection of the instrumentation amplifier in this utility model.

[0031] Figure 4 This is the schematic diagram of the main control microcontroller chip in this utility model. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0033] Example

[0034] This utility model discloses a multi-loop processing CV mode electronic load instrument, combined with... Figures 1 to 4 This electronic load cell consists of multiple functional modules, including a main power supply module, a secondary power supply module, a display module, a button module, a main control module, a power amplifier module, a communication board module, and an interface module. These modules are interconnected via circuitry to form a complete system capable of achieving high-precision control and multi-loop adjustment in constant voltage mode.

[0035] The main control module is the core of the entire system. The main control microcontroller is a high-performance STM32F407, responsible for receiving and processing signals from external input sources and generating control commands based on set parameters. The instrumentation amplifier in the main control module uses amplifier chip U28 as its core component. Both its non-inverting and inverting inputs are connected to the external input source for differential amplification of the input voltage signal. The output of amplifier chip U28 is connected to the inverting input of operational amplifier U23A via resistor R95, thus transmitting the amplified signal to the integrated operational amplifier circuit for further processing. The peripheral circuitry of the instrumentation amplifier also includes capacitors C98 and C92, connected to the positive and negative power supply terminals of amplifier chip U28 respectively and grounded, to filter out power supply noise and improve signal quality.

[0036] The sum-difference proportional circuit is a key component of the main control module. Its main function is to superimpose the signal output from the instrumentation amplifier with the analog signal output from the DAC. The output of the sum-difference proportional circuit is directly connected to the power amplifier module, serving as the control signal to drive the high-power MOSFET. This circuit design ensures the stability of the input source voltage in constant voltage mode. To prevent circuit oscillations caused by input signals of different frequencies, the main control module incorporates two compensation mechanisms: a lead adjustment circuit and a lag adjustment circuit. These two adjustment circuits are selectively connected to the feedback loop via an analog switching mechanism to adapt to different external input characteristics.

[0037] The lead adjustment circuit consists of a capacitor C72 and a resistor R98 connected in series. One end is connected to pin 4 of the analog switch chip U22, and the other end is connected to the output of the instrumentation amplifier. This circuit is mainly used for phase compensation of high-frequency signals to prevent circuit oscillations caused by high-frequency excitation. The hysteresis adjustment circuit consists of a network of resistors and capacitors, including resistors R104, R107, R99, R100, and R103, and capacitors C74, C76, and C75. These components are interconnected to form a complex filter network for phase compensation of low-frequency signals, effectively suppressing system instability caused by low-frequency excitation. One end of the hysteresis adjustment circuit is connected to pins 1 and 2 of the multiplexing chip U24, and the other end is connected to the integrated operational amplifier circuit, thus sending the compensated signal into the feedback loop. Voltage divider resistors R91 and R92 are also connected between the hysteresis adjustment circuit and the analog switch chip U22.

[0038] The analog switching switch is the core component for multi-loop control. Its hardware structure includes a multiplexer chip U24, an analog switch chip U22, and related peripheral components. The multiplexer chip U24 is model CD4053BM96. A capacitor C79 is connected between pins 7 and 8. Pin 16 is grounded through capacitor C80. Pin 3 is connected to the reference voltage VREF through resistor R211, and pin 12 is also connected to the reference voltage VREF through resistor R101. The analog switch chip U22 is model DG444DYZ. Pins 2, 15, and 10 are all connected to pin 14 of the multiplexer chip U24. A capacitor C129 is connected between pins 4 and 5, and pin 13 is grounded through capacitor C130. Pins 6 and 9 through 11 of the multiplexer chip U24 are connected to a transistor array. Pin 15 is connected to an integrated operational amplifier circuit. Pins 1 and 2 are connected to a hysteresis adjustment circuit, and pin 6 is connected to a lead adjustment circuit. Through the above connection relationship, the analog switching switch can dynamically select to connect to the leading adjustment circuit or the lagging adjustment circuit according to the characteristics of the external input signal, thereby realizing multi-loop adjustment.

[0039] The transistor array consists of transistors Q9, Q10, Q11, and Q22, along with related resistors. Their bases are connected to the main microcontroller via resistors R110, R111, R112, and R227, respectively. The collector of transistor Q9 is connected to pin 11 of the multiplexer chip U24 via resistor R105. The collector of transistor Q10 is connected to pin 10 of the multiplexer chip U24, and the collector of transistor Q22 is connected to pin 9 of the multiplexer chip U24. One end of resistor R108 is connected to pin 11 of the multiplexer chip U24, and the other end is grounded. One end of resistor R106 is connected to the collector of transistor Q10, and the other end is connected to a +12V power supply. One end of resistor R222 is connected to the collector of transistor Q22, and the other end is connected to a +12V power supply. The emitters of transistors Q10, Q11, and Q22 are all grounded. The transistor array design can perform signal logic control and current driving tasks, while ensuring rapid switching of the analog switching switch in different operating modes.

[0040] The main power supply module rectifies, filters, and regulates the AC power input from the external transformer, generating +5V, +12V, and -12V power supplies to power the main control module and communication board module. The auxiliary power supply module similarly processes the AC power input from the external transformer, generating +12V and -12V power supplies to power the power amplifier module. Both power supply modules use three-terminal voltage regulators as the core voltage regulator to ensure output voltage stability. The display module and button module together constitute the human-machine interface. The display module includes a screen and an MCU, used to display various parameters and test results of the electronic load instrument, and interacts with the main control module via serial communication. The button module is connected to the display module; the MCU scans key values ​​and parses functions, sending control commands to the main control module to enable user operation.

[0041] The power amplifier module receives the analog voltage signal output from the DAC in the main control module. After processing by the signal amplifier, it serves as the control signal to drive the high-power MOSFET. A sampling resistor collects the current signal, amplifies it, and feeds it back to the ADC in the main control module, forming a closed-loop control system. This closed-loop control mechanism can adjust the output state in real time, ensuring high-precision control in constant voltage mode. The communication board module contains an APM32E103VET6 microcontroller, which communicates with the main control module via a serial port. It supports various communication interfaces such as USB, RS232, RS485, CAN, and LAN, enabling data exchange with a host computer or other devices. The interface module, as the physical interface, provides analog and digital interfaces for external devices, including voltage monitoring, external analog current programming, current monitoring, and analog parallel operation interfaces.

[0042] In practical applications, the electronic load instrument of this invention is suitable for various scenarios, such as power supply product testing, scientific research experiments, automotive electronics, aerospace, and other fields. When the voltage signal from an external input source enters the instrumentation amplifier, the signal is differentially amplified and superimposed with the analog output of the DAC to form a control signal that is sent to the power amplifier module. If the input signal is a high-frequency signal, it is connected to the lead adjustment circuit for phase compensation via an analog switching switch; if the input signal is a low-frequency signal, it is connected to the lag adjustment circuit for phase compensation. In this way, the system can dynamically adapt to input signals with different characteristics, avoid circuit oscillation, and improve system stability. In addition, users can view real-time parameters through the display module and adjust settings through the button module to meet different testing needs.

[0043] In summary, this invention significantly improves the adaptability and stability of the electronic load cell to different input signals by introducing a parallel design of lead and lag adjustment circuits and combining them with an analog switching switch to achieve multi-loop control. High-precision feedback control is achieved through a design combining an instrumentation amplifier and a sum-difference proportional circuit, ensuring high-precision control in constant voltage mode. The modular structure facilitates maintenance and upgrades, rich interface support meets the needs of different application scenarios, and a user-friendly human-machine interface design enhances ease of operation.

[0044] The above embodiments are merely one of the preferred embodiments of this utility model and should not be used to limit the scope of protection of this utility model. Any modifications or refinements made to the main design concept and spirit of this utility model that are not of substantial significance, but solve the same technical problem as this utility model, should be included within the scope of protection of this utility model.

Claims

1. A multi-loop processing CV mode electronic load instrument, comprising a main control module, characterized in that, The main control module includes a main control microcontroller, an instrumentation amplifier connected to an external input source, and a sum-difference ratio circuit connected to the instrumentation amplifier; wherein, the output of the sum-difference ratio circuit is connected to the power amplifier module of the load cell. The sum-difference ratio circuit is a feedback loop, including an analog switching switch, and an integrated operational amplifier circuit, a lead adjustment circuit, a lag adjustment circuit, and a transistor array all connected to the analog switching switch; wherein, the integrated operational amplifier circuit is also connected to the lead adjustment circuit.

2. The multi-loop processing CV mode electronic load instrument according to claim 1, characterized in that, The analog switching switch includes a multiplexer chip U24, capacitors C79 and C80, resistors R211 and R101, an analog switch chip U22, capacitors C129 and C130; wherein, the multiplexer chip U24 is model CD4053BM96, capacitor C79 is connected between pins 7 and 8 of the multiplexer chip U24, one end of capacitor C80 is connected to pin 16 of the multiplexer chip U24, and the other end is grounded; one end of resistor R211 is connected to pin 3 of the multiplexer chip U24, and the other end is connected to the reference voltage VREF; one end of resistor R101 is connected to pin 12 of the multiplexer chip U24, and the other end is connected to... The reference voltage is VREF; the analog switch chip U22 is model DG444DYZ. Pins 2, 15, and 10 of the analog switch chip U22 are connected to pin 14 of the multiplexer chip U24. Capacitor C129 is connected between pins 4 and 5 of the analog switch chip U22. One end of capacitor C130 is connected to pin 13 of the analog switch chip U22, and the other end is grounded. Pins 6, 9-11 of the multiplexer chip U24 are connected to the transistor array. Pin 15 of the multiplexer chip U24 is connected to the integrated operational amplifier circuit. Pins 1 and 2 of the multiplexer chip U24 are connected to the hysteresis adjustment circuit. Pin 6 of the analog switch chip U22 is connected to the lead adjustment circuit.

3. The multi-loop processing CV mode electronic load instrument according to claim 2, characterized in that, The hysteresis adjustment circuit includes a capacitor C78 connected to pin 1 of the multiplexing chip U24, a capacitor C77 connected to the other end of capacitor C78, ​​a resistor R104 connected to the other end of capacitor C77, a resistor R107 with one end connected to the other end of resistor R104 and the other end connected to the common terminal of capacitors C78 and C77, resistors R99, R100, and R103 connected to the common terminal of resistors R107 and R104, a capacitor C74 connected between the other end of resistor R99 and the other end of resistor R100, a capacitor C76 connected between the common terminal of resistor R100 and capacitor C74 and the other end of resistor R103, and a capacitor C75 with one end connected between the common terminal of capacitor C76 and resistor R103 and pin 2 of the multiplexing chip U24; wherein, the common terminal of resistors R107 and R104 is also connected to an integrated operational amplifier circuit.

4. The multi-loop processing CV mode electronic load instrument according to claim 3, characterized in that, The advance adjustment circuit consists of a capacitor C72 and a resistor R98 connected in series. The other free end of the capacitor C72 is connected to pin 4 of the analog switch chip U22, and the other free end of the resistor R98 is connected to the output of the instrumentation amplifier.

5. The multi-loop processing CV mode electronic load instrument according to claim 4, characterized in that, The integrated operational amplifier circuit includes an operational amplifier U23A whose inverting input is connected to the output of an instrumentation amplifier via a resistor R95; a resistor R90 connected at one end to the non-inverting input of operational amplifier U23A and the other end grounded; a capacitor C69 connected at one end to the positive power supply of operational amplifier U23A and the other end grounded; a capacitor C70 connected at one end to the negative power supply of operational amplifier U23A and the other end grounded; a capacitor C73 connected between the inverting input and output of operational amplifier U23A; and a diode D2 connected in parallel across capacitor C73. The inverting input of operational amplifier U23A is also connected to pin 15 of a multiplexer chip U24, and the inverting input of operational amplifier U23A is also connected to the output of the power amplifier module of the load instrument via a resistor R92.

6. The multi-loop processing CV mode electronic load instrument according to claim 5, characterized in that, The instrumentation amplifier includes an amplifier chip U28, a capacitor C98 with one end connected to the positive power supply terminal of the amplifier chip U28 and the other end grounded, and a capacitor C92 with one end connected to the negative power supply terminal of the amplifier chip U28 and the other end grounded; wherein, the output terminal of the amplifier chip U28 is connected to the inverting input terminal of the operational amplifier U23A through a resistor R95; both the inverting input terminal and the non-inverting input terminal of the amplifier chip U28 are connected to an external input source.

7. The multi-loop processing CV mode electronic load instrument according to claim 6, characterized in that, The transistor array consists of transistors Q9, Q10, Q11, and Q22, and resistors R110, R111, R112, R105, R106, R108, R109, R222, and R227. The base of transistor Q10 is connected to the microcontroller via resistor R112; transistor Q11 is connected to the microcontroller via resistor R111; and transistor Q22 is connected to the microcontroller via resistor R227. The base of transistor Q9 is connected to the collector of transistor Q11 via resistor R110, and resistor R109 is connected between the collector and emitter of transistor Q9. The collector of transistor Q9 is connected to pin 11 of multiplexer chip U24 via resistor R105; the collector of transistor Q10 is connected to pin 10 of multiplexer chip U24; the collector of transistor Q22 is connected to pin 9 of multiplexer chip U24; one end of resistor R108 is connected to pin 11 of multiplexer chip U24 and the other end is grounded; one end of resistor R106 is connected to the collector of transistor Q10 and the other end is connected to +12V power supply; one end of resistor R222 is connected to the collector of transistor Q22 and the other end is connected to +12V power supply; the emitters of transistors Q10, Q11, and Q22 are all grounded.

8. The multi-loop processing CV mode electronic load instrument according to claim 7, characterized in that, It also includes a main power supply module, a secondary power supply module, a display module, a button module, a power amplifier module, a communication board module, and an interface module connected to the main control module; among which, The main power module is used to supply power to the main control module and the communication module; The auxiliary power supply module is used to supply power to the power amplifier board module; The display module is used to display various parameters and test results of the load cell, and sends them to the main control module for control via serial communication. The button module is connected to the display module. The MCU on the display module scans the key value and then controls the button according to the function corresponding to the key value. The main control module receives control commands sent by the display module via a serial port, and transmits the working status and test data of the load cell back to the display module for display. The power amplifier module is used to amplify the received signal; The communication board module is used to receive data from the main control module and send it to the interface module; The interface module serves as the physical interface between the communication module and the main control module, providing analog and digital interfaces for external access devices.

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