Load simulation circuit and rack-mounted load box

Abstract

The utility model provides a load simulation circuit and a rack-mounted load box, and belongs to the field of load boxes, the load simulation circuit comprises a rectification circuit, a diverter, a power module, a fan module and a control and drive circuit, the power module comprises at least one heating tube and at least one transistor, the control and drive circuit comprises a main control circuit, a voltage signal processing circuit, a current signal processing circuit, a power setting and display module and at least one IGBT drive circuit, the base electrode of the transistor is connected to the main control circuit through the IGBT drive circuit, and the power setting and display module is connected to the main control circuit; the transistor is connected to the main control circuit through the IGBT driving circuit, the duty ratio adjusting range of the transistor is from 0 to 1, with the rated power of the heating tubes being 2kW as an example, the output power adjusting range of the heating tubes is from 0 to 2kW, and when the three heating tubes are connected in parallel and the rated power of each heating tube is 2kW, the power of the load simulation circuit can be adjusted within the range of 0-6kW. The problem that an existing load box is large in power span is solved, and high-precision power adjustment of the load box is achieved.

Description

Technical Field

[0001] This utility model relates to the field of load cell technology, and in particular to load simulation circuits and rack-mounted load cells. Background Technology

[0002] A load bank is an electrical load device that typically applies power to a power source and converts or dissipates power. Its function is to simulate a real-world load on a power source, using its energy output to test, support, or protect the power supply. Because real-world loads are distributed, unpredictable, and random, load banks need to provide a wide range of operating characteristics and controllable capacity. Load banks are often used in conjunction with generator sets, battery systems, UPS systems, inverters, etc., as test units to test these devices.

[0003] Currently, rack-mounted resistive load cells all have their output power adjusted manually, such as... Figure 1 As shown, the load box uses resistive heating tubes with different power ratings configured in its internal circuits. Each circuit is equipped with a circuit breaker or contactor or other switching device for switching control, thereby enabling the operation or deactivation of the resistive heating tube and thus adjusting the power of the entire load box.

[0004] Currently, rack-mounted resistive load banks have the following shortcomings: different power combinations can be achieved by switching on and off heating devices (including electric heating tubes and PTC heaters) with different power. Although the initial power can be adjusted and selected, the accuracy is poor. The power adjustment range of most resistive load banks is in the 500W range, which cannot achieve more precise power setting. Utility Model Content

[0005] This invention addresses the problem of designing a load analog circuit with high-precision power regulation.

[0006] This utility model solves the above-mentioned technical problems through the following technical solution: a load simulation circuit, the circuit including a rectifier circuit, a shunt, a power module, a fan module, and a control and drive circuit. The power module includes at least one heating element and at least one transistor. The control and drive circuit includes a main control circuit, a voltage signal processing circuit, a current signal processing circuit, a power setting and display module, and at least one IGBT drive circuit. The input terminal of the rectifier circuit is connected to an external power supply. The negative output terminal of the rectifier circuit is connected in series with the shunt and then connected to the emitter of the transistor. The positive output terminal of the rectifier circuit is connected in series with the heating element and then connected to the collector of the transistor. The base of the transistor is connected to the main control circuit through the IGBT drive circuit. The positive output terminal of the rectifier circuit is connected to the main control circuit through the voltage signal processing circuit. The two ends of the shunt are connected to the main control circuit through the current signal processing circuit. The fan module is connected between the rectifier circuit and the main control circuit. The power setting and display module is connected to the main control circuit.

[0007] In this utility model, the power module of the load simulation circuit has a heating element connected in series with a transistor. The transistor is connected to the main control circuit through an IGBT drive circuit. The duty cycle of the transistor can be adjusted from 0 to 1. Taking the rated power of the heating element as 2kW as an example, the output power of the heating element can be adjusted from 0 to 2kW. According to the load size of the object under test (such as a data center), multiple heating elements are connected in parallel in the power module. When three heating elements are connected in parallel and each heating element has a rated power of 2kW, the load simulation circuit can achieve power adjustment from 0 to 6kW, solving the problem of large power range in existing load boxes and realizing high-precision power adjustment of the load box.

[0008] Preferably, the power module further includes at least one DC contactor and at least one temperature sensing element. The control and drive circuit further includes a relay control circuit. The DC contactor is connected between the positive output of the rectifier circuit and the heating element. The control port of the DC contactor is connected to the main control circuit through the relay control circuit. The temperature sensing element is close to the heating element and connected to the relay control circuit.

[0009] Preferably, the main control circuit includes a main control chip, a crystal oscillator Y1, a capacitor C6, and a capacitor C20. The main control chip is a microcontroller. The first pin of the microcontroller is connected to the output terminal of the voltage signal processing circuit, the second pin of the microcontroller is connected to the output terminal of the current signal processing circuit, the fourteenth pin of the microcontroller is connected to one end of the crystal oscillator Y1 and one end of the capacitor C20, the fifteenth pin of the microcontroller is connected to the other end of the crystal oscillator Y1 and one end of the capacitor C8, the other end of the capacitor C8 is connected to the other end of the capacitor C20 and then grounded, the thirty-first, thirty-second, and thirty-third pins of the microcontroller are connected to the IGBT drive circuit, and the forty-fourth pin of the microcontroller is connected to the output terminal of the power setting and display module.

[0010] Preferably, the voltage signal processing circuit includes a rectifier chip D6, a Zener diode D7, capacitors C16 and C26, resistors R40 and R41. The second and third pins of the rectifier chip D6 are respectively connected to the two output terminals of the rectifier circuit. The first pin of the rectifier chip D6 is respectively connected to the positive plate of capacitor C16 and one end of resistor R40. The other end of resistor R40 is respectively connected to one end of resistor R41, the cathode of Zener diode D7, one end of capacitor C26, and the first pin of the main control chip. The fourth pin of the rectifier chip D6 is respectively connected to the negative plate of capacitor C16, the other end of resistor R41, the anode of Zener diode D7, and the other end of capacitor C26 and grounded.

[0011] Preferably, the number of IGBT drive circuits is the same as the number of heating tubes, and each heating tube corresponds to one heating tube. The IGBT drive circuit includes switching transistors Q3, Q4, Q5, and Q6, a Zener diode D5, resistors R19, R20, R23, and R24. One end of resistor R24 ​​is connected to pin 33 of the main control chip, and the other end of resistor R24 ​​is connected to the base of switching transistor Q5. The collector of switching transistor Q5 is connected to one end of resistor R19, one end of resistor R20, the base of switching transistor Q3, and the Zener diode D5. The base of transistor Q6, the other end of resistor R19, the other end of resistor R20, and the collector of transistor Q3 are connected to the cathode of Zener diode D5 and connected to 18V. The anode of Zener diode D5 is grounded. The emitter of transistor Q3 is connected to the emitter of transistor Q6 and one end of resistor R23. The other end of resistor R23 is connected to the gate of transistor Q4. The source of transistor Q4 is connected to one end of the first heating element. The emitter of transistor Q5, the collector of transistor Q6, and the drain of transistor Q4 are connected to the other end of the first heating element and grounded.

[0012] Preferably, the load simulation circuit further includes a temperature probe, and the control and drive circuit further includes a temperature sampling circuit. The temperature sampling circuit includes a resistor R18 and a capacitor C21. One end of the resistor R18 is connected to one end of the temperature probe, one end of the capacitor C21, and the 42nd pin of the main control chip. The other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and grounded.

[0013] Preferably, the control and drive circuit further includes an air volume setting and display module and a fan speed control circuit. The air volume setting and display module is connected to the main control circuit, and the fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle.

[0014] Preferably, the control and drive circuit further includes a power switching and DC / DC conversion circuit. The power switching and DC / DC conversion circuit includes chip U1, chip U2, MOSFETs M1, M2, M3, and M4, diodes D1 and D2, capacitors C1-C7, C9-C15, and C17, resistors R4-R9, R11-R14, and R16. One end of resistor R8 is connected to the anodes of diodes D1 and D2 and then to the positive terminal of the 24V input power supply. The other end of resistor R8 is connected to one end of resistor R12 and the gate of MOSFET M3. The other end of resistor R12 is connected to M... The source of MOSFET M3, one end of resistor R11, and the source of MOSFET M4 are connected to ground. The drain of MOSFET M3 is connected to one end of resistor R4, the other end of resistor R11, and the gate of MOSFET M4. The drain of MOSFET M4 is connected to one end of resistor R9. The other end of resistor R4 is connected to the source of MOSFET M1 and then to the positive terminal of another 24V input power supply. The other end of resistor R9 is connected to the gate of MOSFET M1, one end of resistor R5, and the gate of MOSFET M2. The other end of resistor R5 is connected to the drain of MOSFET M1 and the drain of MOSFET M2. The source of MOSFET M2 is connected to the cathode of diode D1, the cathode of diode D2, and ground. One end of resistor R6, one end of capacitor C1, one end of capacitor C2, one end of capacitor C3, and the first pin of chip U2 are connected. The other end of resistor R6 is connected in series with resistor R14 and then connected to one end of capacitor C13, one end of capacitor C14, one end of capacitor C15, and the third pin of chip U1. The other ends of capacitors C1, C2, C3, C4, C5, C6, and C7 are connected to one end of resistor R7 and then grounded. The other end of resistor R7 is connected to the third pin of chip U2, one end of resistor R13, the other end of resistor R13, the other end of capacitor C4, the other end of capacitor C5, and capacitor C6. The other end of capacitor C13, the other end of capacitor C14, the other end of capacitor C15, one end of capacitor C17, and the first pin of chip U1 are connected to ground. The second pin of chip U1 is connected to one end of capacitor C9, one end of capacitor C10, one end of capacitor C11, one end of capacitor C12, and the thirty-eighth pin of the main control chip, and connected to 5V. The other end of capacitor C9, the other end of capacitor C10, and the other end of capacitor C11 are connected to one end of resistor R16 and grounded. The other end of resistor R16 is connected to the other end of capacitor C12 and the fourth pin of the main control chip.

[0015] Preferably, the control and drive circuit further includes a 2.5V reference voltage circuit, which includes a linear regulator chip T1, a resistor R22, a capacitor C22, and a capacitor C23. One end of the resistor R22 is connected to a 5V voltage, and the other end of the resistor R22 is connected to one end of the capacitor C22, one end of the capacitor C23, the first pin of the linear regulator chip T1, the second pin of the linear regulator chip T1, and the third pin of the main control chip. The other ends of the capacitors C22 and C23 and the third pin of the linear regulator chip T1 are connected and then grounded.

[0016] Preferably, the control and drive circuit further includes an indicator circuit and an alarm circuit. The input terminals of the indicator circuit and the alarm circuit are respectively connected to the main control circuit. The indicator circuit includes resistor R3, resistor R10, indicator light D3, and switching transistor Q1. One end of resistor R10 is connected to the eighteenth pin of the main control chip, and the other end of resistor R10 is connected to the base of switching transistor Q1. The collector of switching transistor Q1 is connected to the cathode of indicator light D3. The anode of indicator light D3 is connected in series with resistor R3 and then connected to a 5V voltage. The emitter of switching transistor Q1 is grounded. The alarm circuit includes resistor R15, resistor R17, alarm light D4, and switching transistor Q2. One end of resistor R17 is connected to the nineteenth pin of the main control chip, and the other end of resistor R17 is connected to the base of switching transistor Q2. The collector of switching transistor Q2 is connected to the cathode of indicator light D4. The anode of alarm light D4 is connected in series with resistor R15 and then connected to a 5V voltage. The emitter of switching transistor Q2 is grounded.

[0017] This utility model also provides a rack-mounted load cell, including the aforementioned load simulation circuit, and also includes a housing, wherein the load simulation circuit is located inside the housing.

[0018] The advantages provided by this utility model are:

[0019] (1) In the power module of the load simulation circuit of this utility model, the heating tube and the transistor are connected in series. The transistor is connected to the main control circuit through the IGBT drive circuit. The duty cycle adjustment range of the transistor is from 0 to 1. Taking the rated power of the heating tube as 2kW as an example, the output power adjustment range of the heating tube is from 0 to 2kW. According to the load size of the object under test (such as the data center), multiple heating tubes are connected in parallel in the power module. When three heating tubes are connected in parallel and the rated power of each heating tube is 2kW, the load simulation circuit can achieve power adjustment from 0 to 6kW, which solves the problem of large power range in the existing load box and realizes high-precision power adjustment of the load box.

[0020] (2) This utility model arranges a temperature sensing element near the heating tube. When the temperature sensing element measures that the temperature of the heating tube exceeds the set threshold, which may cause the heating tube to burn out, the main control circuit controls the relay control circuit to output a drive signal, controls the DC contactor to disconnect, disconnects the circuit where the heating tube is located, and stops working, thus protecting the heating tube.

[0021] (3) By setting up a temperature sampling circuit, this utility model can collect the temperature inside the load box and perform temperature compensation on the actual working resistance of the heating tube.

[0022] (4) This utility model sets up an air volume setting and display module for inputting the set air volume value. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle to realize air volume adjustment. This can solve the problem in the prior art that the fans are running at full speed, resulting in an unstable temperature difference between the inlet and outlet air of the equipment, and cannot simulate the working conditions of actual computer room servers and other equipment.

[0023] (5) By setting up an indicator circuit and an alarm circuit, this utility model can easily indicate the operating status of the system. When the system power supply is normal and the system is working normally, the indicator circuit will work. When the system has low voltage or excessive power deviation, the alarm circuit will work, thereby improving the safety of the load box operation. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the principle of output power adjustment in a rack-mounted resistive load cell by switching heating elements with different power ratings.

[0025] Figure 2 A schematic diagram of the load simulation circuit provided for an embodiment of this utility model;

[0026] Figure 3 A schematic diagram of the control and drive circuit in the load simulation circuit provided for an embodiment of this utility model;

[0027] Figure 4 A circuit diagram of the main control circuit in the load simulation circuit provided for an embodiment of this utility model;

[0028] Figure 5 A circuit diagram of the voltage signal processing circuit in the load simulation circuit provided for an embodiment of this utility model;

[0029] Figure 6 A circuit diagram of the IGBT drive circuit in the load simulation circuit provided for an embodiment of this utility model;

[0030] Figure 7 A circuit diagram of another IGBT drive circuit in the load simulation circuit provided in this embodiment of the utility model;

[0031] Figure 8A circuit diagram of another IGBT drive circuit in the load simulation circuit provided in this embodiment of the utility model;

[0032] Figure 9 A circuit diagram of the temperature sampling circuit in the load simulation circuit provided for an embodiment of this utility model;

[0033] Figure 10 A circuit diagram of the voltage conversion and display circuit in the load simulation circuit provided in this embodiment of the utility model;

[0034] Figure 11 A circuit diagram of the fan speed control circuit in the load simulation circuit provided for an embodiment of this utility model;

[0035] Figure 12 A circuit diagram of the power switching and DC / DC conversion circuit in the load simulation circuit provided in this embodiment of the utility model;

[0036] Figure 13 A circuit diagram of the signal-to-voltage conversion circuit in the load analog circuit provided for an embodiment of this utility model;

[0037] Figure 14 A circuit diagram of the 2.5V reference voltage circuit in the load simulation circuit provided for an embodiment of this utility model;

[0038] Figure 15 Circuit diagram of the programming and communication circuit in the load simulation circuit provided for embodiments of this utility model;

[0039] Figure 16 A circuit diagram of the indicator circuit in the load simulation circuit provided for an embodiment of this utility model;

[0040] Figure 17 A circuit diagram of the alarm circuit in the load simulation circuit provided in this embodiment of the utility model;

[0041] Figure 18 A schematic diagram showing the arrangement of various modules in a rack-mounted load cell provided for an embodiment of this utility model;

[0042] In the diagram: 10 Rectifier circuit, 20 Shunt circuit, 30 Power module, 40 Fan module, 50 Control and drive circuit, 51 Main control circuit, 52 Voltage signal processing circuit, 53 Current signal processing circuit, 54 Power setting and display module, 55 IGBT drive circuit, 56 Relay control circuit, 57 Temperature sampling circuit. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model are described clearly and completely below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0044] Explanation of relevant terms:

[0045] Rack-mount load cell: A load cell that meets the external dimensions and structural requirements of a standard 19-inch rack mount.

[0046] Constant power: refers to constant output power, that is, the electrical energy consumed by the equipment remains constant despite changes in external conditions.

[0047] Duty cycle: refers to the proportion of the time the circuit is powered on relative to the total time within a pulse cycle.

[0048] like Figure 2 As shown, this embodiment provides a load simulation circuit, including a rectifier circuit 10, a shunt 20, a power module 30, a fan module 40, and a control and drive circuit 50. The power module 30 includes at least one heating element and at least one transistor. (See reference...) Figure 5 The control and drive circuit 50 includes a main control circuit 51, a voltage signal processing circuit 52, a current signal processing circuit 53, a power setting and display module 54, and at least one IGBT drive circuit 55. The input terminal of the rectifier circuit 10 is connected to an external power supply. The negative output terminal of the rectifier circuit 10 is connected in series with the shunt 20 and then connected to the emitter of the transistor. The positive output terminal of the rectifier circuit 10 is connected in series with the heating element and then connected to the collector of the transistor. The base of the transistor is connected to the main control circuit 51 through the IGBT drive circuit 55. The positive output terminal of the rectifier circuit 10 is connected to the main control circuit 51 through the voltage signal processing circuit 52. The two ends of the shunt 20 are connected to the main control circuit 51 through the current signal processing circuit 53. The fan module 40 is connected between the rectifier circuit 10 and the main control circuit 50. The power setting and display module 54 is connected to the main control circuit 51.

[0049] Existing load analog circuits adjust power by switching on a resistor, which limits the accuracy of power adjustment to the minimum power that can be applied to a single resistor. This is constrained by the number of branches in the load, and most resistive load boxes on the market have a power adjustment range of 500W or 1000W, with very few at 100W. However, they still suffer from a large power range and cannot automatically adjust the power according to changes in the input power supply.

[0050] In this utility model, the power module of the load simulation circuit has a heating element connected in series with a transistor. The transistor is connected to the main control circuit through an IGBT drive circuit. The duty cycle of the transistor can be adjusted from 0 to 1. Taking the rated power of the heating element as 2kW as an example, the output power of the heating element can be adjusted from 0 to 2kW. According to the load size of the object under test (such as a data center), multiple heating elements are connected in parallel in the power module. When three heating elements are connected in parallel and each heating element has a rated power of 2kW, the load simulation circuit can achieve power adjustment from 0 to 6kW, solving the problem of large power range in existing load boxes and realizing high-precision power adjustment of the load box.

[0051] The power setting and display module 54 of this invention is used to input the set power value. The main control circuit 51 collects the voltage and current of the external power supply and calculates the rated power value. Based on the set power value and the rated power value, it calculates the signal duty cycle and outputs a PWM wave. This PWM wave is then used by the IGBT drive circuit 55 to control the transistor's on / off state, dynamically adjusting the actual output power of the load simulation circuit to maintain consistency with the set power value. The signal duty cycle is calculated as: Set power value / Rated power value. By adjusting the ratio of the load's on-time to the total on-time, the output power of the load simulation circuit is made equal to the set power. For example, when the required output power of the load simulation circuit is 100% of the rated power, the set power equals the rated power, and the ratio is 1, meaning the load simulation circuit's resistor is always on. In this case, the output power of the load simulation circuit equals the rated power. When the output power of the load simulation circuit is required to be 50% of the rated power, the power is set to 50% of the rated power, and the proportion is 0.5. That is, the resistance of the load simulation circuit is only 50% applied per unit time. At this time, the output power of the load simulation circuit is equal to 50% of the rated power. The other proportions are similar. This utility model adjusts the power by adjusting the proportion, i.e., the time parameter. The main control circuit has high precision in time control compared to... Figure 1 This invention achieves different power combinations by switching heating devices with different power levels, and its power regulation accuracy is very high.

[0052] The main control circuit 51 collects the current from the external power supply to fine-tune the signal duty cycle. When the deviation between the rated power value and the set power value exceeds a set threshold, the main control circuit 51 calculates the current power value based on the collected current and fine-tunes the signal duty cycle according to the magnitude of the current power value and the rated power value. If the current power value is greater than the rated power value, the signal duty cycle is fine-tuned to decrease; if the current power value is less than the rated power value, the signal duty cycle is fine-tuned to increase, until the deviation between the rated power value and the set power value is within the set threshold range. This invention considers that the heating element will slightly change with temperature and usage time, thus affecting power accuracy. By collecting the current signal, calculating the current system power, comparing it with the set power, and then fine-tuning the duty cycle, it achieves closed-loop control of the output power, further improving the accuracy of power regulation in rack-mounted load cells.

[0053] The input terminal of rectifier circuit 10 is connected to an external power supply to rectify the external input voltage and output it. It supports AC220V and DC270V input, with a minimum power of 8kW. A bridge rectifier module with a heat sink is selected, model MDQ100A.

[0054] The input terminal of shunt 20 is connected to the output terminal of rectifier circuit 10, and the output terminal of shunt 20 is connected to the emitter of transistor. The shunt is connected to main control circuit 51 through current signal processing circuit 53 to collect current signals in the line and input them to main control circuit 51. The shunt is a 30A / 75mV high-precision shunt, model FL-2.

[0055] Continue reading Figure 2 and Figure 3 The power module 30 also includes at least one DC contactor and at least one temperature sensing element. The control and drive circuit 50 also includes a relay control circuit 56. The DC contactor is connected between the positive output of the rectifier circuit 10 and the heating element. The control port of the DC contactor is connected to the main control circuit 51 through the relay control circuit 56. The temperature sensing element is close to the heating element to measure the temperature of the heating element and inputs the temperature signal into the main control circuit 51 through the relay control circuit 56. When the temperature of the heating element measured by the temperature sensing element exceeds the set threshold, which may cause the heating element to burn out, the main control circuit 51 controls the relay control circuit 56 to output a drive signal, controls the DC contactor to open, disconnects the circuit where the heating element is located, and stops working, thus protecting the heating element.

[0056] The number of heating elements in the power module is determined based on the load of the object under test (such as a data center). When multiple heating elements are selected, they are connected in parallel, and each branch of the heating element is connected to a DC contactor and a transistor. Each heating element has a temperature sensing element nearby. In this embodiment, three heating elements are connected in parallel: the first heating element, the second heating element, and the third heating element. Each heating element is a dry-burning electric heating element with a rated power of 2kW. One end of the first DC contactor, one end of the second DC contactor, and one end of the third DC contactor are connected together and then connected to the output terminal of the rectifier circuit. The other end of the first DC contactor is connected in series with the first heating element and then connected to the collector of the first transistor. The other end of the second DC contactor is connected in series with the second heating element and then connected to the collector of the second transistor. The other end of the third DC contactor is connected in series with the third heating element and then connected to the collector of the third transistor. The bases of the first, second, and third transistors are respectively connected to the input terminals of the IGBT drive circuit. The output terminal of the IGBT drive circuit is connected to the main control circuit. The control ports of the first, second, and third DC contactors are all connected to the output terminals of the relay control circuit. The input terminal of the control circuit is connected to the main control circuit. By controlling the conduction time of the first, second, and third transistors, the load bank can be adjusted from 0 to 6 kW.

[0057] like Figure 4 As shown, the main control circuit 51 includes a main control chip, crystal oscillator Y1, capacitor C6, and capacitor C20. The main control chip is a microcontroller, model STC90C58AD, and crystal oscillator Y1 is model CRYSTAL-1. The first pin of the microcontroller is connected to the output of the voltage signal processing circuit 52, the second pin is connected to the output of the current signal processing circuit 53, the fourteenth pin is connected to one end of crystal oscillator Y1 and one end of capacitor C20, the fifteenth pin is connected to the other end of crystal oscillator Y1 and one end of capacitor C8, and the other end of capacitor C8 is connected to the other end of capacitor C20 and then grounded. The thirty-first, thirty-second, and thirty-third pins of the microcontroller are connected to the IGBT drive circuit 55, and the forty-fourth pin is connected to the output of the power setting and display module 54. The main control chip has an AD port and multiple IO output ports, has high integration, and can easily acquire analog and digital signals of the system and output PWM signals and control signals.

[0058] See Figure 3 The voltage signal processing circuit 52 includes a voltage sampling circuit and a peak hold circuit. An external voltage signal is input to the voltage sampling circuit for sampling. The sampled signal is input to the peak hold circuit for filtering to obtain the voltage waveform peak value, which is then input to the first pin of the main control chip.

[0059] like Figure 7 As shown, the voltage signal processing circuit 52 includes a rectifier chip D6, a Zener diode D7, capacitors C16 and C26, resistors R40 and R41. The second and third pins of the rectifier chip D6 are connected to the two output terminals of the rectifier circuit, respectively. The first pin of the rectifier chip D6 is connected to the positive plate of capacitor C16 and one end of resistor R40. The other end of resistor R40 is connected to one end of resistor R41, the cathode of Zener diode D7, one end of capacitor C26, and the first pin of the main control chip. The fourth pin of the rectifier chip D6 is connected to the negative plate of capacitor C16, the other end of resistor R41, the anode of Zener diode D7, and the other end of capacitor C26, and is grounded. The rectifier chip D6 is an ABS210. The use of the rectifier chip allows the circuit to adapt to both AC and DC power inputs. The peak power value is obtained through the peak voltage held by capacitors, the voltage divider formed by resistors, and the overvoltage protection of the Zener diode.

[0060] The current signal processing circuit 53 includes an amplifier circuit and a peak hold circuit. The current signal collected by the shunt is input to the amplifier circuit, the amplified signal is input to the peak hold circuit, and the peak value of the output current waveform after filtering is input to the second pin of the main control chip. The amplifier circuit of this invention can be an existing amplifier circuit, and the peak hold circuit can be a peak hold circuit from a voltage signal processing circuit.

[0061] The relay control circuit 56 includes a three-position, two-stage selector switch, which is powered by the 24V power supply of the main board. The operator controls the contactor to engage or disengage by switching the selector switch. At the same time, the drive signal of the contactor is connected in series with the temperature control switch of the heating element controlled by each contactor, so as to realize the operator's control of the heating element to engage / disengagement and the over-temperature protection of the heating element.

[0062] like Figure 6As shown, the IGBT driver circuit 55 includes switching transistors Q3, Q4, Q5, and Q6, a Zener diode D5, resistors R19, R20, R23, and R24. One end of resistor R24 ​​is connected to pin 33 of the main control chip, and the other end of resistor R24 ​​is connected to the base of switching transistor Q5. The collector of switching transistor Q5 is connected to one end of resistor R19, one end of resistor R20, the base of switching transistor Q3, and the base of switching transistor Q6, respectively. The other end of resistor R19... The other end of resistor R20 is connected to the collector of switch Q3 and then connected to the cathode of Zener diode D5 and connected to an 18V power supply. The anode of Zener diode D5 is grounded. The emitter of switch Q3 is connected to the emitter of switch Q6 and one end of resistor R23. The other end of resistor R23 is connected to the gate of switch Q4. The source of switch Q4 is connected to one end of the first heating element. The emitter of switch Q5, the collector of switch Q6, and the drain of switch Q4 are connected and then connected to the other end of the first heating element and grounded.

[0063] The IGBT driver circuit includes transistor amplification, push-pull sections, and overvoltage protection, enabling high-frequency driving of the IGBT. The number of IGBT driver circuits 55 corresponds to the number of heating elements. When multiple heating elements are used, multiple IGBT driver circuits are also used, each corresponding to a heating element. In this embodiment, three heating elements are used, so three IGBT driver circuits are used. Figure 7 As shown, the second IGBT drive circuit includes switching transistors Q7, Q8, Q9, and Q10, resistors R26, R27, R29, and R30. One end of resistor R30 is connected to pin 32 of the main control chip, and the other end of resistor R30 is connected to the base of switching transistor Q9. The collector of switching transistor Q9 is connected to one end of resistor R26, one end of resistor R27, the base of switching transistor Q7, and the base of switching transistor Q10. The other ends of resistor R26, the other ends of resistor R27, and the collector of switching transistor Q7 are connected and then connected to an 18V power supply. The emitter of switching transistor Q7 is connected to the emitter of switching transistor Q10 and one end of resistor R29. The other end of resistor R29 is connected to the gate of switching transistor Q8. The source of switching transistor Q8 is connected to one end of the second heating element. The emitter of switching transistor Q9, the collector of switching transistor Q10, and the drain of switching transistor Q8 are connected and then connected to the other end of the second heating element and grounded.

[0064] like Figure 8As shown, the third IGBT driver circuit includes switching transistors Q11, Q12, Q13, and Q14, resistors R34, R35, R36, and R37. One end of resistor R37 is connected to pin 31 of the main control chip, and the other end of resistor R37 is connected to the base of switching transistor Q13. The collector of switching transistor Q13 is connected to one end of resistor R34, one end of resistor R35, the base of switching transistor Q11, and the base of switching transistor Q14, respectively. The other ends of resistor R34 and R35, and the collector of switching transistor Q11 are connected to an 18V power supply. The emitter of switching transistor Q11 is connected to the emitter of switching transistor Q14 and one end of resistor R36. The other end of resistor R36 is connected to the gate of switching transistor Q12. The source of switching transistor Q12 is connected to one end of the third heating element. The emitter of switching transistor Q13, the collector of switching transistor Q14, and the drain of switching transistor Q12 are connected to the other end of the third heating element and grounded. Switches Q3, Q6, Q7, Q10, Q11, and Q14 are all MMBT8550D, and switches Q4, Q8, and Q12 are all FGA25N120AND.

[0065] Temperature probes are placed at the air inlet of the load cell and inside the cell. (See also...) Figure 3 The control and drive circuit 50 also includes a temperature sampling circuit 57. Each temperature probe is connected to the main control circuit 51 through the temperature sampling circuit 57, and is used to measure the inlet air temperature and the internal temperature of the chamber, respectively. This invention can perform temperature compensation on the actual working resistance of the heating element by collecting the internal temperature of the load chamber. The calibrated resistance of the heating element is R0 at 25℃. Based on the calibrated temperature coefficient α of the alloy heating resistor and the collected internal temperature T, according to the formula R... t =R0(1+α(T-25)) Calculate the actual working resistance R of the heat pipe t This further improves the adjustment accuracy of the load cell power.

[0066] like Figure 9 As shown, the temperature sampling circuit 57 includes a resistor R18 and a capacitor C21. One end of the resistor R18 is connected to one end of the temperature probe, one end of the capacitor C21, and pin 42 of the main control chip. The other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and grounded. This invention places temperature probes at the air inlet of the rack-mounted load box and inside the box, respectively. The outputs of the two temperature sampling circuits are connected to pins 42 and 43 of the main control chip, respectively. The temperature probes use NTC temperature sensors to collect the temperature at the air inlet and inside the box, converting it into a voltage value and sending it to the AD port.

[0067] Continue reading Figure 3 The control and drive circuit also includes an air volume setting and display module and a fan speed control circuit. The air volume setting and display module is connected to the main control circuit 51 for inputting the set air volume value. The fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle to realize air volume adjustment. This can solve the problem in the existing technology where the fan runs at full speed, resulting in an unstable temperature difference between the inlet and outlet air of the equipment, and cannot simulate the working conditions of actual computer room servers and other equipment.

[0068] The power setting and display module and the fan speed setting and display module have identical circuits, both including an adjustable resistor circuit and a voltage conversion and display circuit. The power setting and display module adjusts the input signal voltage via the adjustable resistor knob, and this voltage is input to the A / D port of the microcontroller. This signal is simultaneously converted to a voltage value equal to the set power value, and then connected to a voltmeter to display the set power value. Similarly, the fan speed setting and display module adjusts the input signal voltage via the adjustable resistor knob, and this voltage is input to the A / D port of the microcontroller. This signal is simultaneously converted to a voltage value equal to the set fan speed value, and then connected to a voltmeter to display the set fan speed value. Through the adjustable resistor on the panel and the voltage conversion circuit, the set voltage and the digital display window are displayed synchronously.

[0069] like Figure 10 As shown, the voltage conversion and display circuit includes resistors R28, R32, and R33, and capacitor C25. One end of resistor R28 is connected to 18V. The other end of resistor R28 is connected to one end of an adjustable resistor, one end of resistor R32, and the digital display interface. The other end of the adjustable resistor is grounded. The other end of resistor R32 is connected to one end of resistor R33, one end of capacitor C25, and pin 44 of the main control chip. The other end of resistor R33 is connected to the other end of capacitor C25 and grounded. (Continue reading...) Figure 4 The fan module 40 includes a switching power supply module and at least one DC fan. The switching power supply module is model LM150-20B24. The input terminal of the switching power supply module is connected to the output terminal of the rectifier circuit 10, which is used to convert the output voltage of the rectifier circuit into different voltage levels to power the DC fan, control and drive circuits respectively. The DC fan is connected to the main control circuit through a fan speed control circuit. Figure 11 As shown, the fan speed control circuit includes a resistor R1. One end of the resistor R1 is connected to a 5V voltage, and the other end is connected to a DC fan. The 23rd pin of the microcontroller outputs a speed control signal to the DC fan.

[0070] Continue reading Figure 3The control and drive circuit also includes a power switching and DC / DC conversion circuit, a signal voltage conversion circuit, a 2.5V reference voltage circuit, and a programming and communication circuit.

[0071] like Figure 12As shown, the power switching and DC / DC conversion circuit includes chip U1, chip U2, MOSFETs M1, M2, M3, and M4, diodes D1 and D2, capacitors C1-C7, C9-C15, and C17, resistors R4-R9, R11-R14, and R16. One end of resistor R8 is connected to the anodes of diodes D1 and D2, and then to the positive terminal of the 24V input power supply. The other end of resistor R8 is connected to one end of resistor R12 and the gate of MOSFET M3. The other end of resistor R12 is connected to the source of MOSFET M3, one end of resistor R11, and the gate of MOSFET M3. The source of transistor M4 is grounded. The drain of MOSFET M3 is connected to one end of resistor R4, the other end of resistor R11, and the gate of MOSFET M4. The drain of MOSFET M4 is connected to one end of resistor R9. The other end of resistor R4 is connected to the source of MOSFET M1 and then to the positive terminal of another 24V input power supply. The other end of resistor R9 is connected to the gate of MOSFET M1, one end of resistor R5, and the gate of MOSFET M2. The other end of resistor R5 is connected to the drain of MOSFET M1 and the drain of MOSFET M2. The source of MOSFET M2 is connected to the cathode of diode D1, the cathode of diode D2, one end of resistor R6, and one end of capacitor C1. One end of capacitor C2, one end of capacitor C3, and the first pin of chip U2; the other end of resistor R6, connected in series with resistor R14, are connected to one end of capacitor C13, one end of capacitor C14, one end of capacitor C15, and the third pin of chip U1. The other ends of capacitors C1, C2, C3, C4, C5, C6, and C7 are connected to one end of resistor R7 and then grounded. The other end of resistor R7 is connected to the third pin of chip U2, one end of resistor R13, the other end of resistor R13, the other end of capacitor C4, the other end of capacitor C5, the other end of capacitor C6, and the capacitor... The other end of C7 is connected to the second pin of chip U2 and then connected to 18V. The other ends of capacitors C13, C14, C15, and C17 are connected to the first pin of chip U1 and then grounded. The second pin of chip U1 is connected to one end of capacitors C9, C10, C11, and C12, and then to the thirty-eighth pin of the main control chip and connected to 5V. The other ends of capacitors C9, C10, and C11 are connected to one end of resistor R16 and then grounded. The other end of resistor R16 is connected to the other end of capacitor C12 and then to the fourth pin of the main control chip.The model number of chip U1 is LY-7250M, the model number of chip U2 is ZLDO1117K50TC, the model numbers of MOSFETs M1 and M2 are both PV507BA, the model numbers of MOSFETs M3 and M4 are both L2N7002LTIG, and the model numbers of diodes D1 and D2 are both SS54BF.

[0072] The power switching and DC / DC conversion circuit supports dual 24V power inputs and can automatically select one of the power sources as the system's operating power, improving system reliability. It includes 24 / 18V and 24 / 5V voltage conversion circuits to provide operating power for different modules. The power switching and DC / DC conversion circuit also provides operating power to the fan and relay control circuits. The cathode of diode D1 is connected in series with a fuse and then connected to the power input terminals of the fan and the relay control circuit, respectively. The series fuse protects the fan.

[0073] like Figure 13 As shown, the signal voltage conversion circuit includes an AC / DC mode selection switch and a resistor R21. One end of the resistor R21 is connected to a 5V voltage, and the other end of the resistor R21 is connected to the first pin of the AC / DC mode selection switch. The second pin of the AC / DC mode selection switch is connected to the twentieth pin of the main control chip, and the third pin of the AC / DC mode selection switch is grounded.

[0074] like Figure 14 As shown, the 2.5V reference voltage circuit includes a linear regulator chip T1, resistor R22, capacitor C22, and capacitor C23. One end of resistor R22 is connected to a 5V voltage. The other end of resistor R22 is connected to one end of capacitor C22, one end of capacitor C23, the first pin of linear regulator chip T1, the second pin of linear regulator chip T1, and the third pin of the main control chip. The other ends of capacitors C22 and C23, and the third pin of linear regulator chip T1 are connected to ground. The linear regulator chip T1 is model SMAZ5V1-13-F. The 2.5V reference voltage circuit provides a 2.5V reference voltage for reference when calculating peak voltages internally in the program, avoiding deviations in calculation results caused by power supply voltage fluctuations.

[0075] like Figure 15As shown, the input terminal of the programming and communication circuit is connected to the output terminal of the main control circuit, and the output terminal of the programming and communication circuit is connected to the programming port and the communication port respectively. The programming and communication circuit includes chip J12, chip P2, and chip J. The model of chip J12 is CHUSB-AF900102. The second and third pins of chip J12 are connected to the fortieth and forty-first pins of the main control chip respectively. The second and sixth pins of chip J are connected to the seventh and fifth pins of the main control chip respectively. The second and third pins of chip P2 are connected to the seventh and fifth pins of the main control chip respectively.

[0076] like Figure 16 and Figure 17 As shown, the control and drive circuit 50 also includes an indicator circuit and an alarm circuit. The input terminals of the indicator circuit and the alarm circuit are connected to the main control circuit. The indicator circuit includes resistors R3 and R10, indicator light D3, and switching transistor Q1. One end of resistor R10 is connected to pin 18 of the main control chip, and the other end of resistor R10 is connected to the base of switching transistor Q1. The collector of switching transistor Q1 is connected to the cathode of indicator light D3. The anode of indicator light D3 is connected in series with resistor R3 and then connected to a 5V voltage. The emitter of switching transistor Q1 is grounded. The alarm circuit includes resistors R15 and R17, alarm light D4, and switching transistor Q2. One end of resistor R17 is connected to pin 19 of the main control chip, and the other end of resistor R17 is connected to the base of switching transistor Q2. The collector of switching transistor Q2 is connected to the cathode of indicator light D4. The anode of alarm light D4 is connected in series with resistor R15 and then connected to a 5V voltage. The emitter of switching transistor Q2 is grounded. Switches Q1 and Q2 are both LMBT3904LT1G. By setting up indicator circuits and alarm circuits, the operating status of the system can be easily indicated. When the system power supply is normal and the system is working normally, the indicator circuit will work (green light is on). When the system experiences low voltage, excessive power deviation, or other issues, the alarm circuit will work (red light is on).

[0077] Working principle: such as Figure 18 As shown, the modules and components are rationally arranged within the load cell to form a rack-mount load cell. The overall dimensions of the chassis are 430mm (width) × 177.8mm (height) × 550mm (depth), accommodating 19-inch rack mounting. The chassis is made of sheet metal and finished in black. Multiple load cells can be arranged within the same rack, and the power and airflow of each load cell can be set to improve the overall power consumption of the rack.

[0078] This utility model rack-mount load cell can be used for testing and verification in data centers, aging tests of UPS power supplies, and full-load tests of power distribution cabinets. Here, we take the testing and verification in a data center as an example to introduce the working principle of this utility model rack-mount load cell. Before testing, the load cell is installed in a cabinet in the data center. Then, the power cord of the load cell is inserted into the PDU socket of the cabinet to connect the load cell to the power supply system of the data center.

[0079] During the test, the power and airflow values ​​were set according to the pre-compiled test specifications, and the load cell was started. The set power and airflow values ​​were input to the main control chip of the main control circuit. The main control chip of this invention uses a microcontroller. The microcontroller collects the voltage and current signals of the external power supply based on the set power and airflow values, and calculates the rated power value of the load cell. The set power value is divided by the rated power value to obtain the signal duty cycle. The microcontroller outputs a PWM wave based on the signal duty cycle value, which controls the conduction or cutoff of the transistor through the IGBT drive circuit, adjusting the ratio of the load input time to the total time, so that the output power of the load cell is equal to the set power value. This achieves dynamic adjustment of the actual output power of the load cell and keeps it consistent with the set power value. The load cell of this invention has the characteristic of consuming constant electrical energy and converting it all into heat.

[0080] Depending on the mode switch selection, the microcontroller identifies whether the input signal is DC or AC. When the input signal is DC, the mode switch selects DC, and after the microcontroller recognizes the signal, the system's rated power equals (voltage value * voltage value) / (loop resistance). When the system input is AC, the mode switch selects AC, and after the microcontroller recognizes the signal, the system's rated power equals (voltage value * voltage value) / (loop resistance * 2). The loop resistance is equal to the total resistance of multiple heating elements connected in parallel.

[0081] The rack-mount load cell uses sampling and control technology to automatically adjust the load cell power to a set power based on changes in the external input power, achieving closed-loop power control. Furthermore, by adjusting the fan speed, the air intake of the device is made equal to the set air volume value, thereby achieving automatic adjustment of the load cell power and air volume.

[0082] This utility model is used for testing and verification in data centers. As an electrical device, it is installed in the server rack in the data center and connected to the power supply system via cables. During the testing of the equipment and lines, it can effectively overcome the influence of changes in the voltage at the power source, maintain a constant output power, and ensure the smooth progress of the test. Furthermore, by adjusting the airflow, it can accurately match the airflow data of the server in the later stage, realize the accurate simulation of the test scenario, and ensure the accuracy and validity of the test data.

[0083] The above embodiments are only used to illustrate the technical solutions of this utility model, and are not intended to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A load simulation circuit, characterized in that: The circuit includes a rectifier circuit (10), a shunt (20), a power module (30), a fan module (40), and a control and drive circuit (50). The power module (30) includes at least one heating element and at least one transistor. The control and drive circuit (50) includes a main control circuit (51), a voltage signal processing circuit (52), a current signal processing circuit (53), a power setting and display module (54), and at least one IGBT drive circuit (55). The input terminal of the rectifier circuit (10) is connected to an external power supply, and the negative output terminal of the rectifier circuit (10) is connected in series with the shunt (20). The positive output of the rectifier circuit (10) is connected in series with the heating tube and then connected to the collector of the transistor. The base of the transistor is connected to the main control circuit (51) through the IGBT drive circuit (55). The positive output of the rectifier circuit (10) is connected to the main control circuit (51) through the voltage signal processing circuit (52). The two ends of the shunt (20) are connected to the main control circuit (51) through the current signal processing circuit (53). The fan module (40) is connected between the rectifier circuit (10) and the main control circuit (50). The power setting and display module (54) is connected to the main control circuit (51).

2. The load simulation circuit according to claim 1, characterized in that: The power module (30) also includes at least one DC contactor and at least one temperature sensing element. The control and drive circuit (50) also includes a relay control circuit (56). The DC contactor is connected between the positive output of the rectifier circuit (10) and the heating tube. The control port of the DC contactor is connected to the main control circuit (51) through the relay control circuit (56). The temperature sensing element is close to the heating tube and connected to the relay control circuit (56).

3. The load simulation circuit according to claim 1, characterized in that: The main control circuit (51) includes a main control chip, crystal oscillator Y1, capacitor C6, and capacitor C20. The main control chip is a microcontroller. The first pin of the microcontroller is connected to the output terminal of the voltage signal processing circuit (52). The second pin of the microcontroller is connected to the output terminal of the current signal processing circuit (53). The fourteenth pin of the microcontroller is connected to one end of crystal oscillator Y1 and one end of capacitor C20. The fifteenth pin of the microcontroller is connected to the other end of crystal oscillator Y1 and one end of capacitor C8. The other end of capacitor C8 is connected to the other end of capacitor C20 and then grounded. The thirty-first, thirty-second, and thirty-third pins of the microcontroller are connected to the IGBT drive circuit (55). The forty-fourth pin of the microcontroller is connected to the output terminal of the power setting and display module (54).

4. The load simulation circuit according to claim 1, characterized in that: The voltage signal processing circuit (52) includes a rectifier chip D6, a Zener diode D7, a capacitor C16, a capacitor C26, a resistor R40, and a resistor R41. The second and third pins of the rectifier chip D6 are respectively connected to the two output terminals of the rectifier circuit. The first pin of the rectifier chip D6 is respectively connected to the positive plate of the capacitor C16 and one end of the resistor R40. The other end of the resistor R40 is respectively connected to one end of the resistor R41, the cathode of the Zener diode D7, one end of the capacitor C26, and the first pin of the main control chip. The fourth pin of the rectifier chip D6 is respectively connected to the negative plate of the capacitor C16, the other end of the resistor R41, the anode of the Zener diode D7, and the other end of the capacitor C26 and grounded.

5. The load simulation circuit according to claim 1, characterized in that: The number of IGBT drive circuits (55) is the same as the number of heating tubes and corresponds one-to-one with each heating tube. The IGBT drive circuit (55) includes switching transistors Q3, Q4, Q5, and Q6, a Zener diode D5, resistors R19, R20, R23, and R24. One end of resistor R24 ​​is connected to pin 33 of the main control chip, and the other end of resistor R24 ​​is connected to the base of switching transistor Q5. The collector of switching transistor Q5 is connected to one end of resistor R19, one end of resistor R20, and the base of switching transistor Q3, respectively. The base of switch Q6, the other end of resistor R19, the other end of resistor R20, and the collector of switch Q3 are connected to the cathode of Zener diode D5 and connected to 18V. The anode of Zener diode D5 is grounded. The emitter of switch Q3 is connected to the emitter of switch Q6 and one end of resistor R23. The other end of resistor R23 is connected to the gate of switch Q4. The source of switch Q4 is connected to one end of the first heating element. The emitter of switch Q5, the collector of switch Q6, and the drain of switch Q4 are connected to the other end of the first heating element and grounded.

6. The load simulation circuit according to claim 1, characterized in that: The load simulation circuit also includes a temperature probe, and the control and drive circuit (50) also includes a temperature sampling circuit (57). The temperature sampling circuit (57) includes a resistor R18 and a capacitor C21. One end of the resistor R18 is connected to one end of the temperature probe, one end of the capacitor C21, and the 42nd pin of the main control chip. The other end of the resistor R18 is connected to a 5V voltage, and the other end of the capacitor C21 is connected to the other end of the temperature probe and grounded.

7. The load simulation circuit according to claim 1, characterized in that: The control and drive circuit also includes an air volume setting and display module and a fan speed control circuit. The air volume setting and display module is connected to the main control circuit (51), and the fan speed control circuit is connected between the main control circuit and the fan module. The main control circuit inputs a control signal to the fan speed control circuit according to the signal duty cycle.

8. The load simulation circuit according to claim 1, characterized in that: The control and drive circuit also includes a power switching and DC / DC conversion circuit. This circuit includes chip U1, chip U2, MOSFETs M1, M2, M3, and M4, diodes D1 and D2, capacitors C1-C7, C9-C15, capacitor C17, resistors R4-R9, R11-R14, and resistor R16. One end of resistor R8 is connected to the anodes of diodes D1 and D2, and then to the positive terminal of the 24V input power supply. The other end of resistor R8 is connected to one end of resistor R12 and the gate of MOSFET M3. The other end of resistor R12 is connected to the gate of MOSFET M3. The source of transistor M3, one end of resistor R11, and the source of MOSFET M4 are connected to ground. The drain of MOSFET M3 is connected to one end of resistor R4, the other end of resistor R11, and the gate of MOSFET M4. The drain of MOSFET M4 is connected to one end of resistor R9. The other end of resistor R4 is connected to the source of MOSFET M1 and then to the positive terminal of another 24V input power supply. The other end of resistor R9 is connected to the gate of MOSFET M1, one end of resistor R5, and the gate of MOSFET M2. The other end of resistor R5 is connected to the drain of MOSFET M1 and the drain of MOSFET M2. The source of MOSFET M2 is connected to the cathode of diode D1, the cathode of diode D2, and resistor R... One end of resistor R6, one end of capacitor C1, one end of capacitor C2, one end of capacitor C3, and the first pin of chip U2; the other end of resistor R6 is connected in series with resistor R14 and then connected to one end of capacitor C13, one end of capacitor C14, one end of capacitor C15, and the third pin of chip U1. The other ends of capacitors C1, C2, C3, C4, C5, C6, and C7 are connected to one end of resistor R7 and then grounded. The other end of resistor R7 is connected to the third pin of chip U2, one end of resistor R13, the other end of resistor R13, the other end of capacitor C4, the other end of capacitor C5, and the other end of capacitor C6. The other end of capacitor C7 is connected to the second pin of chip U2 and then connected to 18V. The other ends of capacitor C13, C14, C15, and C17 are connected to the first pin of chip U1 and then grounded. The second pin of chip U1 is connected to one end of capacitor C9, one end of capacitor C10, one end of capacitor C11, one end of capacitor C12, and the thirty-eighth pin of the main control chip and then connected to 5V. The other ends of capacitor C9, C10, and C11 are connected to one end of resistor R16 and then grounded. The other end of resistor R16 is connected to the other end of capacitor C12 and the fourth pin of the main control chip.

9. The load simulation circuit according to claim 1, characterized in that: The control and drive circuit (50) also includes an indicator circuit and an alarm circuit. The input terminals of the indicator circuit and the alarm circuit are respectively connected to the main control circuit (51). The indicator circuit includes resistor R3, resistor R10, indicator light D3, and switch Q1. One end of resistor R10 is connected to the eighteenth pin of the main control chip, and the other end of resistor R10 is connected to the base of switch Q1. The collector of switch Q1 is connected to the cathode of indicator light D3. The anode of indicator light D3 is connected in series with resistor R3 and then connected to a 5V voltage. The emitter of switch Q1 is grounded. The alarm circuit includes resistor R15, resistor R17, alarm light D4, and switch Q2. One end of resistor R17 is connected to the nineteenth pin of the main control chip, and the other end of resistor R17 is connected to the base of switch Q2. The collector of switch Q2 is connected to the cathode of indicator light D4. The anode of alarm light D4 is connected in series with resistor R15 and then connected to a 5V voltage. The emitter of switch Q2 is grounded.

10. A rack-mounted load cell, comprising the load simulation circuit according to any one of claims 1-9, characterized in that: It also includes a housing, inside which the load simulation circuit is located.

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