Atmospheric environment detection load starting current suppression system

Abstract

The invention provides an atmospheric environment detection load starting current suppression system, which comprises a primary starting current suppression circuit, a filter circuit, a primary power supply conversion circuit, a secondary starting current suppression circuit and a secondary power supply conversion circuit which are connected with one another, and is characterized in that the primary starting current suppression circuit is connected with a whole satellite platform through a short-circuit protection circuit; the secondary power conversion circuit is connected with the load single machine; the secondary starting current suppression circuit comprises a suppression circuit composed of a relay, an NTC loop and a short-circuit resistor loop, and is configured to suppress a secondary starting current generated when the internal power supply of the atmospheric exploration load is started; a processor in the load single machine is connected with the primary power conversion circuit and the relay, and the processor monitors telemetering data of secondary power voltage and sends opening and closing signals to the relay so as to control on-off of the NTC loop and the short-circuit resistor loop. According to the invention, two starting currents can be effectively suppressed, and the power supply safety and reliability of the load and the whole satellite platform are ensured.

Description

Technical Field

[0001] The present application belongs to the field of atmospheric detection technology, and in particular, relates to an atmospheric environment detection load starting current suppression system. Background Art

[0002] Atmospheric sounding technology is an effective detection technology that uses the global satellite navigation system (GNSS) to detect environmental parameters of the atmosphere and ionosphere. With the rapid development of commercial aerospace in recent years, this detection technology has been continuously improved, and the detection accuracy and detection speed have been greatly improved. The atmospheric sounding payload is a commercial satellite detection payload. The purpose of the design is to complete the specified atmospheric data detection mission through this payload, obtain atmospheric data, and then solve the data and transmit it down to complete the accurate acquisition of atmospheric temperature, humidity, pressure and other parameters. This detection technology is of great significance to improving the accuracy of weather forecasts and the accuracy of the Beidou navigation and positioning system.

[0003] The atmospheric detection payload is one of the multiple satellite payloads of the entire satellite platform. The power supply is unified by the entire satellite platform. The platform power supply belongs to the primary power supply. At the moment the primary power supply is powered on, due to the existence of the front-end capacitive load inside the atmospheric single machine, it will cause a large starting current. This current belongs to the primary starting current. Conventional design schemes all have suppression solutions for this problem.

[0004] However, with the rapid development of commercial aerospace, the output power requirements of power modules are getting higher and higher, and miniaturization design is required. In response to this actual demand, more polymer tantalum capacitors need to be configured at the back end of the internal switching power output of the payload to meet the needs of stable output of the secondary power supply. Polymer tantalum capacitors are a type of chip-type multilayer capacitor that uses a high-conductivity polymer material as the cathode. It has an ultra-low ESR and does not require a derating design in actual use. It has a lower failure rate and excellent performance in filtering high-frequency harmonics.

[0005] Since the polymer tantalum capacitor itself has a large capacitance, the conventional design requires a capacitor capacity of at least 1000uF at the back end of the switching power supply. This results in the first starting current after the primary power supply is powered on. After a short time, when the secondary power supply starts to output, the larger capacitor capacity configured at the back end of the switching power supply will cause the secondary starting current to be generated. Generally, the secondary power supply starting current will be greater than the primary starting current. If this current is not limited, the excessive starting current will cause the internal fuse of the single machine to blow. In severe cases, it will cause abnormal power supply to the entire satellite, resulting in failure of other loads of the entire satellite to work normally, resulting in catastrophic accidents. Summary of the invention

[0006] In view of this, the present application aims to propose an atmospheric environment detection load starting current suppression system, which ensures the safe operation of the atmospheric load and the entire satellite and improves reliability by suppressing the first starting current and the second starting current respectively.

[0007] To achieve the above purpose, the technical solution of this application is implemented as follows: The present application provides an atmospheric environment detection load starting current suppression system, comprising a primary starting current suppression circuit, a filter circuit, a primary power conversion circuit, a secondary starting current suppression circuit and a secondary power conversion circuit connected to each other, wherein the primary starting current suppression circuit is connected to the entire satellite platform through a short-circuit protection circuit, and is configured to suppress the first starting current generated when the entire satellite platform starts the atmospheric load power supply, and the secondary power conversion circuit is connected to a single load unit, and is used to provide a working voltage to each load inside the single load unit; The secondary starting current suppression circuit includes a suppression circuit composed of a relay, an NTC circuit and a short-circuit resistor circuit, and is configured to suppress a second starting current generated when the internal power supply of the atmospheric detection payload is started; The internal processor of the load unit is connected to the primary power conversion circuit and the relay respectively. The processor monitors the telemetry data of the secondary power supply voltage and sends an opening and closing signal to the relay to control the on and off of the NTC circuit and the short-circuit resistor circuit.

[0008] Furthermore, the primary startup current suppression circuit includes a first switch tube, a first electrode of the first switch tube is grounded through a voltage control loop, and a second electrode of the first switch tube is connected to the filter circuit; The short-circuit protection circuit is composed of two branch fuses connected in unbalanced parallel connection, one end of the two branch fuses is connected to the first pole of the first switch tube, and the other end is connected to the soft start module of the whole satellite platform. The fuse of one branch is connected to a series resistance loop, and the series resistance loop is used to protect the operation of the fuse in the branch.

[0009] Furthermore, the first switch tube is a MOS switch tube, and the MOS switch tube adopts a PMOS tube, the source of the PMOS tube is connected to the fuse, the gate of the PMOS tube is connected to the voltage control loop, and the drain of the PMOS tube is connected to the filter circuit.

[0010] Furthermore, the filter circuit includes a filter chip, the eighth pin and the ninth pin of the filter chip are connected to the drain of the first switch tube, the first pin and the tenth pin of the filter chip are connected to the negative pole of the primary power supply, and the fourth pin, the fifth pin, the sixth pin and the seventh pin of the filter chip are connected to the primary power conversion circuit through a voltage stabilizing filter loop.

[0011] Further, the primary power conversion circuit is configured to convert the 28V voltage supplied by the entire satellite platform into a 12V voltage, and includes a power conversion chip, the voltage input positive electrode and input negative electrode of the power conversion chip are connected to the CASE pin of the filter chip through two series capacitors to reduce the power module noise; The output end of the primary power conversion circuit is connected to the secondary starting current suppression circuit through a voltage stabilizing loop.

[0012] Furthermore, a telemetry circuit is provided at the rear end of the voltage stabilizing loop. The telemetry circuit is composed of four resistors and a voltage stabilizing capacitor, wherein two resistors are connected in series and then in parallel with the other two resistors, and the voltage stabilizing capacitor is connected to two of the parallel resistors.

[0013] Further, the relay has a dual-path control loop, the third pin and the eighth pin of the relay are connected to the output end of the primary power conversion circuit, the fifth pin and the ninth pin of the relay are connected to the NTC loop, the fourth pin and the tenth pin of the relay are connected to the short-circuit resistor loop, and the other end of the NTC loop and the short-circuit resistor loop is connected to the secondary power conversion circuit; The NTC circuit is composed of two thermistors connected in parallel, and the short-circuit resistor circuit is composed of two resistors connected in parallel.

[0014] Furthermore, the internal processor of the load unit is connected to the first pin and the sixth pin of the relay, and the on and off of the NTC circuit and the short-circuit resistor circuit are controlled by controlling the first pin and the sixth pin of the relay.

[0015] Furthermore, the relay adopts a 2JB1-910 / V12-1 model relay, and uses an external voltage VCC as an independent power supply.

[0016] Furthermore, the filter chip adopts the Vicor series EMI filter chip, model MQPI-18LP.

[0017] Compared with the prior art, the atmospheric environment detection load starting current suppression system described in this application has the following beneficial effects: The atmospheric environment detection payload starting current suppression system described in the present application can effectively suppress the starting current twice, thereby ensuring the safe and reliable power supply of the payload and the entire satellite platform, and effectively ensuring the normal operation of the entire satellite payload. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a block diagram of a starting current suppression system for an atmospheric environment detection load described in an embodiment of the present application; Figure 2 This is a schematic diagram of the connection of the short-circuit protection circuit, the primary startup current suppression circuit and the filter circuit described in the embodiment of the present application; Figure 3 A connection diagram of a primary power conversion circuit according to an embodiment of the present application; Figure 4 This is a connection diagram of the secondary starting current suppression circuit described in an embodiment of the present application. DETAILED DESCRIPTION

[0019] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0020] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the embodiments of the present application should have the usual meanings understood by people with ordinary skills in the field to which the present application belongs. The words "first", "second" and similar words used in the embodiments of the present application do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprises" and other similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and other similar words are not limited to physical or mechanical connections, but can be Including electrical connections, whether direct or indirect. "Up", "down", "left", "right", etc. are only used to indicate relative position relationships. When the absolute position of the object being described changes, the relative position relationship may also change accordingly.

[0021] The purpose of the atmospheric detection payload design is to complete the specified atmospheric data detection task through the payload, obtain the atmospheric data, and then solve the data and transmit it down to complete the accurate acquisition of parameters such as atmospheric temperature, humidity and pressure. The atmospheric detection payload is one of the multiple loads of the entire satellite platform. When the atmospheric detection payload begins to prepare for the mission, the entire satellite platform will turn on the atmospheric payload power supply. The platform power supply belongs to the primary power supply. Due to the instantaneous power-on of the power supply, the first power-on spike current will appear inside the atmospheric detection payload; when the primary power supply reaches the startup requirements of the atmospheric payload internal power module, the internal power supply of the atmospheric detection payload starts to start, and the primary power supply is converted to the secondary power supply output. At this time, the second power-on spike current will appear. For the two power-on spike currents, there are strict threshold requirements in the entire satellite design. When the power-on current is too large, it will not only cause abnormal circuit behaviors such as overcurrent protection inside the atmospheric detection payload, but also cause the power supply of the entire satellite platform to be unstable in severe cases, resulting in catastrophic accidents.

[0022] In response to the above-mentioned problems, the present application proposes a starting current suppression system for an atmospheric environment detection payload, which specifically includes a slow start design for the entire satellite power supply module, a first starting current suppression circuit inside the atmospheric detection payload, and a second starting current suppression circuit inside the atmospheric detection payload. Through this system design, the two starting currents can be effectively suppressed, ensuring the safe and reliable power supply of the payload and the entire satellite platform, and effectively ensuring the normal operation of the entire satellite payload.

[0023] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0024] See also Figure 1 As shown, this embodiment provides an atmospheric environment detection load starting current suppression system, including a primary starting current suppression circuit, a filter circuit, a primary power conversion circuit, a secondary starting current suppression circuit and a secondary power conversion circuit connected to each other. The primary starting current suppression circuit is connected to the entire satellite platform through a short-circuit protection circuit, and is configured to suppress the first starting current generated when the entire satellite platform starts the atmospheric load power supply. The secondary power conversion circuit is connected to the load unit to provide a working voltage to each load inside the load unit; The secondary starting current suppression circuit includes a suppression circuit composed of a relay, an NTC circuit and a short-circuit resistor circuit, and is configured to suppress a second starting current generated when the internal power supply of the atmospheric detection payload is started; The internal processor of the load unit is connected to the primary power conversion circuit and the relay respectively. The processor monitors the telemetry data of the secondary power supply voltage and sends opening and closing signals to the relay to control the on and off of the NTC circuit and the short-circuit resistor circuit.

[0025] like Figure 1As shown, it is the overall scheme block diagram of this embodiment. The atmospheric detection payload is uniformly powered by the whole satellite platform, and the power supply voltage is 28V. When the atmospheric payload begins to prepare to perform the detection mission, the platform starts to power the single-machine payload. After the whole satellite platform starts to power the back-end load, the power first passes through the MOS tube slow start module inside the whole satellite platform. The basic principle is to use the slow start function of the MOS tube, and control the voltage difference between the gate and source of the MOS tube to control the conductive channel between the source and drain of the MOS tube to gradually open, so as to avoid instantaneous power-on of the power supply and generate a large surge current.

[0026] like Figure 2 As shown, after passing through the short-circuit protection circuit, in order to improve reliability, the module circuit adopts a fuse unbalanced parallel design scheme, the fuse rated current is 1.5A, the resistance is about 12mΩ, and the resistance of the series resistance loop uses two 0.5Ω resistors with a package of 2512 connected in series with the fuse. Through analysis, the current passing through the fuse F1 is about 95% of the entire path, and the current passing through the fuse F2 with a series resistor is about 5% of the entire path. In this way, even if an abnormal situation occurs, such as a short-term latch of the back-end device, a large current occurs, even if the fuse path passing the large current is burned out, it will not affect the fuse of the series resistance loop. When the latch is released, the fuse path of the series resistor can still be used normally, ensuring that the load unit can still work normally.

[0027] After the fuse path, a startup current suppression circuit is added. This suppression circuit also uses the slow-start characteristic of the MOS tube to effectively suppress the first startup current. The MOS tube model is IRF5210S, and the type is PMOS. When a single machine is powered on, due to the presence of capacitors C1 and C5, the G pole voltage of the MOS is equal to the S pole voltage, that is, the VGS voltage difference is 0, and the MOS is turned off. As the capacitor charges, the G pole voltage increases, and the VGS voltage difference increases. When the voltage difference exceeds the threshold, the PMOS gradually opens to meet the actual needs of a slow start of the power supply. The MOS slow start module is also used in the power supply startup module of the entire satellite platform, which can ensure that the power supply mode of the power provider is also a slow start mode, so that the startup surge current can be minimized to ensure the safety of the entire satellite and equipment.

[0028] After the MOS tube, an EMI filter circuit is added to filter the primary power supply to ensure that EMI does not exceed the standard and reduce the adverse effects of the primary power supply on the EMI sensitive devices inside the single machine. The EMI filter device uses the Vicor series EMI filter chip, model MQPI-18LP. This chip is specifically designed for the common mode noise and differential mode noise of the 28V input power supply, and has a good filtering effect. It can support a maximum current of 7A. Considering the primary power input, in order to ensure the safety of the load, all voltage stabilization and filtering capacitors need to be connected in series to increase reliability. In this way, even if a capacitor is short-circuited due to an abnormality, it will not affect the normal operation of the power module.

[0029] Among them, the eighth and ninth pins of the filter chip are connected to the positive pole of the primary power supply, the first and tenth pins are connected to the negative pole of the primary power supply, the sixth and seventh pins are the output positive poles, connected to the positive pole of the power input of the back-end DCDC conversion module, the fourth and fifth pins are the output negative poles, connected to the negative pole of the back-end DCDC input, the second and third pins are the SHILD pins of the EMI chip, which contain more power supply noise. In actual design, it is necessary to connect the pin and the negative pole of the EMI filter chip, as well as the input and output of the first-stage DCDC conversion module at the back end to the CASE through two series capacitors. The CASE is equivalent to the chassis ground, so that the power supply noise can be filtered out and the best filtering effect can be achieved.

[0030] After the EMI filter circuit, it is a power conversion circuit, such as Figure 3 As shown, the function is to convert the 28V voltage provided by the entire satellite platform into a secondary voltage of 12V. The core of this module is the DCM2322T50T1360M60 of the Vicor series, with an output power of 60W. Among them, A1 and E1 are the positive and negative voltage inputs of the chip. An appropriate amount of voltage-stabilizing capacitors need to be added between the two pins to ensure stable voltage input. The C1 pin is the enable pin of the chip, which is internally pulled up. Externally, only a capacitor to ground needs to be added to achieve default enable.

[0031] The A2, C2 and B2, D2 pins are the positive and negative output voltage of the chip respectively. As mentioned above, the positive and negative poles of the input and output ends of the DCDC conversion module need to be connected to the CASE module through two series capacitors respectively to minimize the power module noise.

[0032] The output end of the DCDC conversion module is a 12V voltage output. In order to ensure the stability of the power supply and provide sufficient power for the back-end load, a capacitor with a capacity of at least 1000uF must be added to the output end. Therefore, this embodiment uses 7 polymer tantalum capacitors in parallel, with a single capacity of 220uF and a total capacity of 1440uF to ensure that the 12V output voltage is stable and reliable.

[0033] At the rear end of the output capacitor, a 12V telemetry circuit is added. Four resistors and a voltage-stabilizing capacitor are used to form the telemetry circuit to ensure that the telemetry is stable and reliable. Specifically, two 10K resistors R19 and R20 are connected in series and then connected in parallel with two 10K resistors. The voltage value of the telemetry point is 2.4V. The voltage is sent to the internal processor of the load unit for monitoring. When the voltage reaches the normal state, the processor can be triggered to send a switching signal to control the relay action. The function of this relay module is to suppress the second starting current.

[0034] like Figure 4 As shown in the figure, it is a secondary starting current suppression circuit, which is implemented by a relay with an NTC (thermistor) circuit and a short-circuit resistor circuit. The module is based on a military-grade relay, the specific model is 2JB1-910 / V12-1, the action time is ≤2ms, the operating temperature range is -65℃~125℃, and it has extremely high reliability and stability. The relay uses an external voltage VCC as an independent power supply, which can ensure that a certain path can be turned on or off in the initial power-on state of a single machine. The relay has a dual-path control function. The initial default state turns on the NTC circuit and closes the short-circuit resistor path. NTC is a thermistor with a negative temperature coefficient, that is, the higher the temperature, the lower the resistance.

[0035] Before the secondary voltage starts to output, the filter capacitor is in an unpowered state, and the voltage across the capacitor is 0V. Since the voltage across the capacitor cannot change suddenly, the voltage is still 0V for a short time after the load is powered on, which is equivalent to a short circuit. Therefore, the voltage drop mainly falls on the NTC. If there is no NTC in the loop, or the resistance of the NTC is very small, then due to the large capacity of the back-end capacitor of the DCDC conversion module, the starting current in the circuit will be very large, which will have an adverse effect on the load and the operation of the entire satellite.

[0036] In this embodiment, the specific model of the NTC resistor is B57236S0509M0. The typical resistance of the NTC resistor at room temperature is 5Ω. When the temperature rises to 50°C, the typical value decreases to about 2Ω. A parallel design scheme is adopted to enhance circuit reliability.

[0037] After the stand-alone machine is powered on, the relay opens the NTC path by default, VCC12V is used as the input signal of the relay, and the first pin of the relay is grounded by default. Therefore, the relay switch will be connected to the NTCR circuit in the initial state, and the sixth pin of the relay is pulled up by the R14 pull-up resistor by default. This path connects the short-circuit resistor circuit, which is not conductive by default. Among them, D1, D2, D3, and D4 are freewheeling diodes, which are used to avoid the large switching voltage generated during the switching process of the relay switch, because the inductor itself is an energy storage element and the current cannot change suddenly. After adding the freewheeling diode, the influence of this voltage can be eliminated.

[0038] The parallel resistance of the NTC resistor in the NTC circuit is 2.5Ω, that is, this resistance will reduce the second starting current to 40% of that without the NTC module, which can greatly reduce the impact of the second starting current. As the system voltage stabilizes and starts to work normally, the NTC resistor gradually heats up and the resistance gradually decreases. When it rises to about 50℃, the NTC circuit resistance becomes 1Ω, which basically has no effect on the circuit voltage and power consumption.

[0039] Since the NTC resistor has a higher resistance value when it is initially powered on, it can effectively suppress the second startup current. After the system power supply stabilizes, the thermal effect of the resistor causes the resistance value of the NTC resistor to decrease, which will not cause a large voltage drop in the circuit, affect the back-end voltage, or generate additional losses.

[0040] However, in the case where the load unit is powered on quickly after a power outage, the temperature of the thermistor cannot be reduced immediately and the resistance value of the NTC resistor will not change suddenly, so the suppression effect will be worse. For this use case, the telemetry parameters of the secondary power supply voltage are transmitted to the internal processor of the back-end load unit. Based on the internal preset normal state range of the secondary voltage, when the secondary power supply is stable, the back-end processor sends start and shutdown signals to shut down the NTC circuit and open the short-circuit resistor circuit. In this way, when the power is off and then on under normal conditions, the default state is that the NTC circuit is turned on, which will also have a better suppression effect on the secondary starting current.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

[0042] The embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present application should be included in the scope of protection of the present application.

Claims

1. An atmospheric environment detection load starting current suppression system, characterized in that: It includes a primary starting current suppression circuit, a filter circuit, a primary power conversion circuit, a secondary starting current suppression circuit and a secondary power conversion circuit connected to each other. The primary starting current suppression circuit is connected to the entire satellite platform through a short-circuit protection circuit and is configured to suppress the first starting current generated when the entire satellite platform starts the atmospheric load power supply. The secondary power conversion circuit is connected to the load unit and is used to provide a working voltage to each load inside the load unit; The secondary starting current suppression circuit includes a suppression circuit composed of a relay, an NTC circuit and a short-circuit resistor circuit, and is configured to suppress a second starting current generated when the internal power supply of the atmospheric detection payload is started; The internal processor of the load unit is connected to the primary power conversion circuit and the relay respectively. The processor monitors the telemetry data of the secondary power supply voltage and sends an opening and closing signal to the relay to control the on and off of the NTC circuit and the short-circuit resistor circuit.

2. The system according to claim 1, characterized in that: The primary startup current suppression circuit comprises a first switch tube, a first electrode of the first switch tube is grounded through a voltage control loop, and a second electrode of the first switch tube is connected to the filter circuit; The short-circuit protection circuit is composed of two branch fuses connected in unbalanced parallel connection, one end of the two branch fuses is connected to the first pole of the first switch tube, and the other end is connected to the soft start module of the whole satellite platform. The fuse of one branch is connected to a series resistance loop, and the series resistance loop is used to protect the operation of the fuse in the branch.

3. The system according to claim 2, characterized in that: The first switch tube is a MOS switch tube, and the MOS switch tube adopts a PMOS tube. The source of the PMOS tube is connected to the fuse, the gate of the PMOS tube is connected to the voltage control loop, and the drain of the PMOS tube is connected to the filter circuit.

4. The system according to claim 3, characterized in that: The filter circuit includes a filter chip, the eighth pin and the ninth pin of the filter chip are connected to the drain of the first switch tube, the first pin and the tenth pin of the filter chip are connected to the negative electrode of the primary power supply, and the fourth pin, the fifth pin, the sixth pin and the seventh pin of the filter chip are connected to the primary power conversion circuit through a voltage stabilizing filter loop.

5. The system according to claim 4, characterized in that: The primary power conversion circuit is configured to convert the 28V voltage supplied by the entire satellite platform into a 12V voltage, and includes a power conversion chip, wherein the voltage input positive electrode and input negative electrode of the power conversion chip are connected to the CASE pin of the filter chip through two series capacitors to reduce the power module noise; The output end of the primary power conversion circuit is connected to the secondary starting current suppression circuit through a voltage stabilizing loop.

6. The system according to claim 5, characterized in that: A telemetry circuit is provided at the rear end of the voltage stabilizing loop. The telemetry circuit is composed of four resistors and a voltage stabilizing capacitor, wherein two resistors are connected in series and then connected in parallel with the other two resistors, and the voltage stabilizing capacitor is connected to the two resistors in parallel.

7. The system according to claim 4, characterized in that: The relay has a dual-path control loop, the third pin and the eighth pin of the relay are connected to the output end of the primary power conversion circuit, the fifth pin and the ninth pin of the relay are connected to the NTC loop, the fourth pin and the tenth pin of the relay are connected to the short-circuit resistor loop, and the other end of the NTC loop and the short-circuit resistor loop is connected to the secondary power conversion circuit; The NTC circuit is composed of two thermistors connected in parallel, and the short-circuit resistor circuit is composed of two resistors connected in parallel.

8. The system according to claim 7, characterized in that: The internal processor of the load unit is connected to the first pin and the sixth pin of the relay, and controls the on and off of the NTC circuit and the short-circuit resistor circuit by controlling the first pin and the sixth pin of the relay.

9. The system according to claim 7, characterized in that: The relay adopts a 2JB1-910 / V12-1 relay model, and uses an external voltage VCC as an independent power supply.

10. The system according to claim 4, characterized in that: The filter chip adopts the Vicor series EMI filter chip, model MQPI-18LP.

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