A circuit and method for preventing the internal temperature of a vehicle terminal from being too high

Abstract

The present invention discloses a circuit for preventing the internal temperature of a vehicle terminal from being too high, comprising: a bridge circuit composed of four resistors, an operational amplifier, a voltage comparator, an MPU and a heat dissipation module; one of the four resistors is a platinum thermal resistor, and the two input ends of the operational amplifier are respectively connected to the two output ends of the bridge circuit; the output end of the operational amplifier is connected to an input end of the voltage comparator; an input end of the MPU is connected to the output end of the voltage comparator to detect the change in the resistance value of the platinum thermal resistor, and the MPU is connected to the heat dissipation module to control the on or off of the heat dissipation module according to the change in the resistance value of the platinum thermal resistor. The present invention can realize the timed over-temperature detection of the vehicle-mounted multimedia terminal equipment and the accelerated timed heat dissipation in the state of over-temperature, thereby ensuring the performance stability of the vehicle-mounted multimedia terminal equipment and avoiding the restart or crash of the equipment caused by the instability of the equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle-mounted multimedia terminals, and in particular to a circuit and method for preventing the internal temperature of a vehicle-mounted terminal from being too high. Background Art

[0002] With the rapid development of the automobile market, in-vehicle multimedia terminals are being used more and more widely in automobiles. At the same time, customers are demanding more and more entertainment functions from in-vehicle multimedia terminal devices, which has led to an increasing performance requirement for CPUs and faster CPU speeds. Although almost all CPUs support the dynamic voltage and frequency adjustment (DVFS) function, which can automatically adjust its voltage and frequency according to the currently running application to reduce power consumption, multimedia terminal devices generally have many functions (such as audio and video playback, video display, etc.), so it is difficult to reduce power consumption. If the CPU is running at a relatively high speed, various functions are running simultaneously in the foreground or background, and the power amplifier is outputting at high power, it may cause the internal temperature of the device to be too high. Although in product design, independent heat sinks are added to some major heating components (generally mainly power amplifier ICs and CPUs) to improve the heat dissipation effect of the device. However, the in-car environment is often complex, and adding a heat sink may not necessarily achieve the desired effect. In addition, the terminal equipment has many functions, and the internal heating components are not only the CPU and power amplifier, but also LDO, PMIC, video decoding chips, etc. These will bring a certain amount of heat to the equipment. When designing, it is impossible to add a heat sink to each heating chip. When the multimedia terminal equipment is working normally, if the heat is not dissipated from the inside of the equipment in time, it will often cause the overall temperature of the equipment to increase, and ultimately affect the performance stability of the multimedia terminal equipment. In severe cases, it may directly cause a crash; working for a long time under a state of excessively high temperature will also affect the service life of the entire vehicle-mounted multimedia terminal equipment. To address this problem, an optimization method and circuit to prevent the internal temperature of the vehicle terminal from being too high is needed to ensure that the equipment works at a relatively suitable internal ambient temperature, ensure the performance stability of the equipment, and extend the service life of the equipment. Summary of the invention

[0003] The main purpose of the present invention is to provide a circuit and method for preventing the internal temperature of a vehicle terminal from being too high, so as to enable the vehicle multimedia terminal device to operate at a relatively suitable internal ambient temperature, ensure the performance stability of the device, and extend the service life of the device.

[0004] The present invention adopts the following technical solution:

[0005] On the one hand, the present invention provides a circuit for preventing the internal temperature of a vehicle-mounted terminal from being too high, comprising: a bridge circuit composed of four resistors, an operational amplifier, a voltage comparator, an MPU and a heat dissipation module; one of the four resistors is a platinum thermal resistor, and the two input ends of the operational amplifier are respectively connected to the two output ends of the bridge circuit; the output end of the operational amplifier is connected to an input end of the voltage comparator; an input end of the MPU is connected to the output end of the voltage comparator to detect changes in the resistance value of the platinum thermal resistor, and the MPU is connected to the heat dissipation module to control the on or off of the heat dissipation module according to the changes in the resistance value of the platinum thermal resistor.

[0006] Preferably, the circuit further includes: a second diode; an anode of the diode connected to an output end of the operational amplifier; and a cathode of the diode connected to an input end of the voltage comparator.

[0007] Preferably, the circuit also includes: the MPU is connected to the single-pole double-throw switch to control the switching of the moving end of the single-pole double-throw switch according to the change of the resistance value of the platinum thermal resistor, and the heat dissipation module is turned on or off according to the switching of the moving end of the single-pole double-throw switch.

[0008] Preferably, the heat dissipation module includes a blowing fan and an air suction fan.

[0009] Preferably, the MPU is connected to the PMIC via a second I2C interface to adjust the MPU core voltage according to the change in the resistance value of the platinum thermal resistor.

[0010] Preferably, the MPU is connected to the sound processing module via the first I2C interface to adjust the volume of the vehicle-mounted multimedia terminal according to the change in the resistance value of the platinum thermal resistor.

[0011] Preferably, the bridge circuit includes a first resistor, a second resistor, a third resistor and a PT resistor; the first resistor and the PT resistor are connected in series; the second resistor and the third resistor are connected in series; one end of the operational amplifier is connected to the connection point of the first resistor and the PT resistor; the other end of the operational amplifier is connected to the connection point of the second resistor and the third resistor; the resistance value of the first resistor is equal to the resistance value of the second resistor; the resistance value of the third resistor is equal to the resistance value of the PT resistor at a preset temperature.

[0012] Preferably, one end of the operational amplifier is connected to the connection point of the first resistor and the PT resistor through a fifth resistor and a sixth resistor; one end of the fifth resistor is connected to the connection point of the first resistor and the PT resistor, and the other end of the fifth resistor and one end of the sixth resistor are connected to one end of the operational amplifier; the other end of the sixth resistor is grounded.

[0013] Preferably, the circuit also includes: a third voltage regulator tube and a fourth voltage regulator tube; the cathode of the third voltage regulator tube is connected to the output end of the operational amplifier; the anode of the third voltage regulator tube is grounded; the cathode of the fourth voltage regulator tube is connected to one end of the voltage comparator, and the anode of the fourth voltage regulator tube is grounded.

[0014] On the other hand, a method for preventing the internal temperature of a vehicle terminal from being too high, based on the circuit for preventing the internal temperature of a vehicle terminal from being too high, comprises:

[0015] S101, the MPU periodically detects whether the value of the input port connected to the voltage comparator is a first preset level, if it is the first preset level, go to S102; otherwise, go to S105;

[0016] S102, the MPU sets the preset output port value to a second preset level and controls the heat dissipation module to turn on;

[0017] S103, the MPU performs frequency reduction processing, and controls the PMIC through the second I2C interface to control the core voltage of the MPU to be lower than the preset core voltage;

[0018] S104, the MPU is connected to the sound effect adjustment processing module through the first I2C interface to control the volume of the vehicle multimedia terminal to be less than or equal to a preset volume;

[0019] S105, the MPU reads the current core voltage from the PMIC through the second I2C interface. If the core voltage is not equal to the preset core voltage, the preset output port value is set to a third preset level, and the heat dissipation module is controlled to be turned off; at the same time, the preset clock frequency and the preset core voltage are restored.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention discloses a circuit and method for preventing the internal temperature of a vehicle-mounted terminal from being too high. The circuit and method utilize the temperature characteristics of a bridge circuit and a platinum thermal resistor (the resistance of which increases at a uniform rate as the temperature rises), adopt a voltage comparator and an I / O port detection and control technology and an I2C communication technology, thereby realizing the timed over-temperature detection of a multimedia terminal device and the accelerated timed heat dissipation of the multimedia terminal device when the temperature is too high, as well as the power consumption optimization of the device itself. The internal heat of the multimedia terminal device can be dissipated to the external environment in time, while also reducing the heat generation of the device itself. Thus, the performance stability of the multimedia terminal device is ensured, and device restart or crash caused by the instability of the device is avoided.

[0022] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention so that it can be implemented in accordance with the contents of the specification, and in order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below.

[0023] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A circuit diagram of the vehicle-mounted multimedia terminal device of the present invention;

[0025] Figure 2 A partial circuit diagram of the vehicle-mounted multimedia terminal device of the present invention;

[0026] Figure 3 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] See also Figure 1 and 2 As shown, on the one hand, the present invention provides a circuit for preventing the internal temperature of a vehicle-mounted terminal from being too high, comprising: a bridge circuit composed of four resistors, an operational amplifier U7, a voltage comparator U6, an MPU (U3) and a heat dissipation module; one of the four resistors is a platinum thermal resistor PT, and the two input ends of the operational amplifier U7 are respectively connected to the two output ends of the bridge circuit; the output end of the operational amplifier U7 is connected to an input end of the voltage comparator U6; an input end of the MPU (U3) is connected to the output end of the voltage comparator U6 to detect changes in the resistance value of the platinum thermal resistor PT, and the MPU (U3) is connected to the heat dissipation module to control the on or off of the heat dissipation module according to changes in the resistance value of the platinum thermal resistor PT.

[0029] Further, the bridge circuit includes a first resistor R1, a second resistor R2, a third resistor R3 and a PT resistor; the first resistor R1 and the PT resistor are connected in series; the second resistor R2 and the third resistor R3 are connected in series; one end of the operational amplifier U7 is connected to the connection point OUT1 of the first resistor R1 and the PT resistor; the other end of the operational amplifier U7 is connected to the connection point OUT2 of the second resistor R2 and the third resistor R3; the resistance value of the first resistor R1 is equal to the resistance value of the second resistor R2; the resistance value of the third resistor R3 is equal to the resistance value of the PT resistor at a preset temperature. Wherein, the connection point of the first resistor R1 and the second resistor R2 is A, and the voltage at point A is VA.

[0030] In this embodiment, the resistance value of the third resistor R3 is equal to the resistance value of the platinum thermal resistor PT when the temperature is -40°C (only needs to be lower than -30°C in actual use); the purpose of this is to ensure that when the multimedia terminal device is working normally, the voltage at OUT1 is greater than the voltage at OUT2; because vehicle regulations generally require that the operating temperature range of the equipment is required to be between -30°C and 85°C.

[0031] One end of the first resistor R1 and one end of the second resistor R2 are both connected to the output end of the power module U1, and the power module U1 includes a DC-DC and LDO power supply part. The input end of the power module U1 is connected to the external power supply B+; the control end S1 of the power module U1 is connected to the ACC detection module U2. In actual use, the ACC detection module U2 can use an optocoupler combination circuit or a triode combination control circuit. When the ACC detection module U2 detects the ACC signal, it controls the voltage of the power module U1 to turn on.

[0032] Furthermore, a primary filtering circuit including a first inductor L1 (magnetic bead), a first capacitor C1 and a second capacitor C2, and a secondary filtering circuit including a first diode D1 and a third capacitor C3 are arranged between the bridge circuit and the power module.

[0033] In this embodiment, the operational amplifier U7 is an inverting amplifier, one end of the operational amplifier U7 is connected to the connection point OUT1 of the first resistor R1 and the PT resistor through the fifth resistor R5 and the sixth resistor R6; one end of the fifth resistor R5 is connected to the connection point of the first resistor R1 and the PT resistor, the other end of the fifth resistor R5 and one end of the sixth resistor R6 are connected to one end (positive input end) of the operational amplifier U7; the other end of the sixth resistor R6 is grounded. The reverse input end of the operational amplifier U7 is connected to OUT2 through the fourth resistor R4, and the reverse input end of the operational amplifier U7 is connected to the output end through the seventh resistor R7. The power supply voltage of the operational amplifier U7 is VCC1.

[0034] The fourth resistor R4, the fifth resistor R5, the sixth resistor R6 and the seventh resistor R7 are current limiting resistors, the resistance of the fourth resistor R4 is equal to the resistance of the fifth resistor R5, the resistance of the sixth resistor R6 is equal to the resistance of the seventh resistor R7, and the amplification factor of the operational amplifier U7 can be changed by changing the ratio of the sixth resistor R6 to the fifth resistor R5.

[0035] The output end of the operational amplifier U7 is connected to the voltage comparator U6 through the eighth resistor R8 and the second diode D2. One end of the eighth resistor R8 is connected to the output end of the operational amplifier U7, and the other end of the eighth resistor R8 is connected to the anode of the second diode D2; the cathode of the second diode D2 is connected to an input end of the voltage comparator U6. The connection point between the eighth resistor R8 and the second diode D2 is connected to the cathode of the third voltage regulator D3, and the anode of the third voltage regulator D3 is grounded. The circuit also includes a fifth capacitor C5 and a sixth capacitor C6 for filtering.

[0036] The eighth resistor R8 is a current limiting resistor, and the third voltage regulator D3 can ensure that the voltage is not too high. The fifth capacitor C5 and the sixth capacitor C6 are filter capacitors, the voltage drop of the second diode D2 is VD, and the second diode D2 can isolate the voltage of the operational amplifier U7 and the voltage comparator U6.

[0037] In this embodiment, the voltage comparator U6 is a non-inverting voltage comparator U6. The positive input terminal of the voltage comparator U6 is connected to the cathode of the second diode D2, and the reverse input terminal of the voltage comparator U6 is connected to the second DC power supply VCC2 through the eleventh resistor R11. The reverse output terminal of the voltage comparator U6 is also grounded through the fourth voltage regulator D4, and the voltage of the voltage regulator is VN. The power supply terminal of the voltage comparator U6 is connected to the second DC power supply VCC2 through the fourth inductor L4 (magnetic bead). The digital end of the voltage comparator U6 is connected to the input terminal I / O1 of the MPU (U3) through the twelfth resistor, and the ground terminal of the voltage comparator U6 is connected to the input terminal I / O1 of the MPU (U3) through the thirteenth resistor R13. The twelfth resistor and the thirteenth resistor R13 are voltage-dividing and current-limiting resistors, which ensure that the detection level of the input terminal I / O1 of the MPU (U3) will not be higher than the I / O power supply voltage of the MPU (U3) itself.

[0038] Specifically, the voltage comparator U6 is a high-precision voltage comparator U6, the voltage at the same-direction input terminal P is VP, the voltage at the reverse input terminal N is VN, when VP is greater than VN, it indicates an over-temperature state, and when VP is less than or equal to VN, it indicates a normal temperature operation state. The MPU (U3) is a core system module, which contains CPU, DDR3, EMMC, etc., has audio and video encoding and decoding functions, and includes a dual-channel LVDS interface, an HDMI interface, a MIPI_CSI interface, and functions of combined circuits such as WIFI, Bluetooth, and GPS. It actually runs on the Android platform. I / O1 and I / O2 are internal GPIO ports of the MPU (U3), I / O1 is configured as an input port, which is low by default; I / O2 is an output port, which is low by default.

[0039] The output port I / O2 of the MPU (U3) is connected to the control terminal S1 of the single-pole double-throw switch K1, and the control terminal S1 is grounded through the fourteenth resistor R14. The fourteenth resistor R14 is a pull-down resistor, which can ensure that the output port I / O2 is at a low level when the MPU (U3) is powered on. The active terminal A1 of the single-pole double-throw switch K1 is connected to the third DC power supply VCC3; the first fixed terminal B1 of the single-pole double-throw switch K1 is grounded through the tenth capacitor; the second fixed terminal C1 of the single-pole double-throw switch K1 is connected to the heat dissipation module through the eleventh capacitor and the twelfth capacitor connected in parallel.

[0040] The heat dissipation module includes a blowing fan S1 and an air suction fan S2. The power supply voltage of the blowing fan S1 and the air suction fan S2 is VCC3.

[0041] When I / O1 is high, the dual fan mode is turned on regularly to speed up the air convection between the inside and outside of the device to achieve rapid heat dissipation.

[0042] Furthermore, in this embodiment, the MPU (U3) is connected to the PMIC (U8) via the second I2C interface I2C2 to adjust the MPU (U3) core voltage according to the change in the resistance value of the platinum thermal resistor PT. The PMIC (U8) is used to power the MPU (U3) core, DDR3, etc. The MPU (U3) can configure the PMIC (U8) with relevant voltages via I2C2.

[0043] Before configuring the core voltage, the MPU (U3) first actively performs frequency reduction processing, and then reconfigures the internal PMIC (U8) to perform voltage reduction processing to reduce the heat generated by the CPU itself.

[0044] Furthermore, in this embodiment, the MPU (U3) is connected to the sound processing module U4 via the first I2C interface to adjust the volume of the vehicle multimedia terminal according to the change in the resistance value of the platinum thermal resistor PT.

[0045] Specifically, the sound effect processing module U4 is a processing chip with an internal sound effect processing function, such as TEF6638 in actual use. The MPU (U3) communicates with the sound effect processing module U4 through I2C, and the MPU (U3) can configure the relevant registers of the sound effect processing module U4 through I2C1. The sound effect processing module U4 is connected to the audio power amplifier module U5. The audio power amplifier module U5 is a 4*20W car audio power amplifier, such as TDA7576B in actual use, which amplifies the power of the analog signal output by the sound effect processing module U4.

[0046] The present invention provides a circuit for preventing the internal temperature of a vehicle terminal from being too high. The circuit utilizes the temperature characteristics of a bridge circuit and a platinum thermal resistor (whose resistance value will increase at a uniform rate as the temperature rises), uses a voltage comparator to perform voltage comparison, and the MPU performs timed detection of the level after the voltage comparator compares. When I / O1 is high, the dual fan mode is turned on timedly to accelerate the air convection between the inside and outside of the device to achieve the purpose of rapid heat dissipation. Furthermore, the MPU actively performs frequency reduction processing, and reconfigures the internal PMIC to perform voltage reduction processing to reduce the heat generated by the CPU itself. At the same time, the current volume value of the sound effect processing module is read to see if it exceeds the default volume (the volume value set when the device is powered on and initialized, generally half of the total volume is set). If the volume exceeds the default value, the CPU will automatically reduce the volume to the default value. If the volume is less than or equal to the default value, the current volume is maintained. Because the volume is too loud, it will also cause an increase in the heat of the power amplifier, and when the power amplifier volume is played using the default value, it will not affect the normal listening of the customer. When the MPU detects that I / O1 is low, the MPU will determine whether the core voltage is the default value V0. If it is, it means that the device is still running at the frequency and core voltage of the initialization state, and no other configuration is required; if the core voltage is not the default value V0, it means that the MPU has been actively down-clocked and down-voltaged, and the fan has been turned on. At this time, the S1 and S2 fans need to be turned off; at the same time, the MPU needs to automatically restore the operating frequency and core voltage at the time of initialization; at this time, U4 is not reconfigured and the current volume is maintained. Through this optimization method, the multimedia terminal equipment can be guaranteed to work in a relatively stable temperature environment for a long time, ensuring the stability and life of the equipment system.

[0047] See also Figure 3 As shown, on the other hand, a method for preventing the internal temperature of a vehicle terminal from being too high includes:

[0048] 1. When the device is powered on and initialized, I / O1 is configured as an input port and is low by default, and I / O2 is configured as an output port and is low by default; and the MPU (U3) initializes the volume of the sound processing module U4 to VOL through I2C1 and initializes the core voltage to V0 through I2C2.

[0049] 2. When the device is operating normally, the MPU (U3) checks whether the I / O1 port is high every time t (set as needed, such as 1 second); if I / O1 is high, it indicates that the temperature inside the multimedia terminal device is too high, and the MPU (U3) will pull up I / O2 and control K1, so that A1 inside K1 is connected to C1, thereby turning on the power of the SI and S2 fans, so that the two fans are in normal high-speed operation, accelerating the air circulation inside and outside the terminal device and accelerating heat dissipation; at the same time, the MPU (U3) will actively perform frequency reduction processing, and reconfigure the relevant registers of the PMIC (U8) through I2C2 to reduce the core voltage of the MPU (U3), so that when the MPU frequency is reduced, the MPU core voltage is also reduced accordingly to achieve the purpose of reducing the power consumption of the MPU itself, that is, the heat generation; at this time, the MPU (U3) also reads the register value corresponding to the current volume of the sound processing module U4 through I2C1, and converts it into the corresponding current volume value VOL1, and compares it with the default value VOL. If VOL1 is greater than VOL, MPU (U3) will reconfigure the relevant registers of the sound processing module U4 through I2C1, so that VOL1 is adjusted to VOL to reduce the heat generated by the power amplifier; if VOL1 is less than or equal to VOL, the current volume VOL1 is maintained, and MPU (U3) does not reconfigure. After these operations, the device not only reduces its own heat generation, but also accelerates the heat dissipation operation, which can keep the internal temperature of the device running at a certain temperature, prevent the internal temperature of the device from rising continuously, and ensure the system stability of the multimedia terminal device.

[0050] 3. If I / O1 is low, it means that the multimedia terminal device is working at normal temperature. At this time, MPU (U3) actively reads the relevant core voltage register value through I2C2 and converts it into voltage value V1. MPU (U3) determines whether V1 is equal to the default value V0 of the core voltage at the time of initialization; if V1 is equal to V0, it means that the device is still running in the initialization state, and MPU (U3) maintains the current state without other configuration operations. If V1 is not equal to V0, it means that MPU (U3) has been actively down-clocked and down-voltage processed, and the fan has been turned on. At this time, MPU (U3) will pull down I / O2, turn off S1 and S2 fans, and MPU (U3) will automatically resume operation at the clock frequency and core voltage at the time of initialization; at this time, MPU (U3) does not reconfigure U4 and maintains the current volume.

[0051] 4. It should be noted that although the same-direction voltage comparator is taken as an example in this embodiment, in actual applications, the reverse voltage comparator is also equally applicable. It is only necessary to make corresponding changes to the initial value and judgment conditions of the MPU. The present invention does not provide a specific description.

[0052] The above is only a specific implementation of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial changes to the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A circuit for preventing the internal temperature of a vehicle terminal from being too high, characterized in that: include: A bridge circuit consisting of four resistors, an operational amplifier, a voltage comparator, an MPU and a heat dissipation module; one of the four resistors is a platinum thermal resistor, two input ends of the operational amplifier are respectively connected to two output ends of the bridge circuit; the output end of the operational amplifier is connected to an input end of the voltage comparator; an input end of the MPU is connected to the output end of the voltage comparator to detect changes in the resistance value of the platinum thermal resistor, and the MPU is connected to the heat dissipation module to control the on or off of the heat dissipation module according to the changes in the resistance value of the platinum thermal resistor; The circuit further includes: the MPU is connected to a single-pole double-throw switch to control the switching of the moving end of the single-pole double-throw switch according to the change of the resistance value of the platinum thermal resistor, and the heat dissipation module is turned on or off according to the switching of the moving end of the single-pole double-throw switch; The bridge circuit includes a first resistor, a second resistor, a third resistor and a PT resistor; the first resistor and the PT resistor are connected in series; the second resistor and the third resistor are connected in series; one end of the operational amplifier is connected to the connection point of the first resistor and the PT resistor; the other end of the operational amplifier is connected to the connection point of the second resistor and the third resistor; the resistance value of the first resistor is equal to the resistance value of the second resistor; the resistance value of the third resistor is equal to the resistance value of the PT resistor at a preset temperature; One end of the operational amplifier is connected to the connection point of the first resistor and the PT resistor through the fifth resistor and the sixth resistor; one end of the fifth resistor is connected to the connection point of the first resistor and the PT resistor, and the other end of the fifth resistor and one end of the sixth resistor are connected to one end of the operational amplifier; the other end of the sixth resistor is grounded.

2. The circuit for preventing the internal temperature of the vehicle terminal from being too high according to claim 1, characterized in that: The circuit further includes: a second diode; an anode of the diode connected to the output end of the operational amplifier; and a cathode of the diode connected to an input end of the voltage comparator.

3. The circuit for preventing the internal temperature of the vehicle terminal from being too high according to claim 1, characterized in that: The heat dissipation module includes a blowing fan and an air suction fan.

4. The circuit for preventing the internal temperature of the vehicle terminal from being too high according to claim 1, characterized in that: The MPU is connected to the PMIC via a second I2C interface to adjust the MPU core voltage according to the change in the resistance value of the platinum thermal resistor.

5. The circuit for preventing the internal temperature of the vehicle terminal from being too high according to claim 1, characterized in that: The MPU is connected to the sound processing module via the first I2C interface to adjust the volume of the vehicle-mounted multimedia terminal according to the change in the resistance value of the platinum thermal resistor.

6. The circuit for preventing the internal temperature of the vehicle terminal from being too high according to claim 1, characterized in that: The circuit also includes: a third voltage regulator tube and a fourth voltage regulator tube; the cathode of the third voltage regulator tube is connected to the output end of the operational amplifier; the anode of the third voltage regulator tube is grounded; the cathode of the fourth voltage regulator tube is connected to one end of the voltage comparator, and the anode of the fourth voltage regulator tube is grounded.

7. A method for preventing the internal temperature of a vehicle terminal from being too high, characterized in that: Based on the circuit according to any one of claims 1 to 6, comprising: S101, the MPU periodically detects whether the value of the input port connected to the voltage comparator is a first preset level, if it is the first preset level, go to S102; otherwise, go to S105; S102, the MPU sets the preset output port value to a second preset level and controls the heat dissipation module to turn on; S103, the MPU performs frequency reduction processing, and controls the PMIC through the second I2C interface to control the core voltage of the MPU to be lower than the preset core voltage; S104, the MPU is connected to the sound effect adjustment processing module through the first I2C interface to control the volume of the vehicle multimedia terminal to be less than or equal to a preset volume; S105, the MPU reads the current core voltage from the PMIC through the second I2C interface. If the core voltage is not equal to the preset core voltage, the preset output port value is set to a third preset level, and the heat dissipation module is controlled to be turned off; at the same time, the preset clock frequency and the preset core voltage are restored.

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