Vehicle-mounted TBOX low-voltage starting prevention switch circuit

Abstract

The utility model discloses a vehicle-mounted TBOX low-voltage starting prevention switching circuit which is composed of a power input circuit, a protection circuit, a decoupling circuit, a fuse, a slow starting circuit, an MOS switching tube circuit, a filter circuit, a decoupling circuit, a low-voltage starting prevention circuit and a system main power supply DC / DC circuit. The protection circuit comprises an electrostatic, filtering and anti-surge circuit; the low-voltage starting prevention circuit is controlled to start by elements such as a Zener diode. When the vehicle-mounted battery supplies power, the circuit is subjected to multiple processing, and when the voltage is lower than a safety threshold value, the TBOX communication terminal is prevented from being started, battery discharging is slowed down, premature over-discharging is avoided, meanwhile, the problems that the input voltage is too low, and a power supply is frequently started for power failure are solved, and stable operation of the vehicle-mounted battery and a TBOX system is effectively guaranteed.

Description

Technical Field

[0001] This utility model relates to a TBOX communication device, specifically to a vehicle-mounted TBOX low-voltage start-up switch circuit. Background Technology

[0002] Current in-vehicle TBOX data communication devices are powered by the vehicle's backup battery (12V). Even when the vehicle is stationary, the TBOX continues to communicate with the backend, further consuming the 12V battery power. Currently, the power circuits of TBOX communication terminals on the market are directly powered by 12V. The normal operating voltage of these power circuits is 5-24V. This means that when the backup battery voltage is too low, it will continue to drain the backup battery, ultimately leading to over-discharge of the vehicle's battery. Furthermore, the T-BOM terminal is generally not turned off when the vehicle is off, continuing to consume the backup battery power and potentially damaging it.

[0003] Therefore, it is necessary to improve traditional switching circuits. Utility Model Content

[0004] The purpose of this utility model is to provide a vehicle-mounted TBOX low-voltage start switch circuit. The purpose of designing this vehicle-mounted TBOX low-voltage start switch circuit is to prevent the vehicle battery from being over-discharged prematurely.

[0005] To solve the above technical problems, this utility model provides the following solution: A vehicle-mounted TBOX low-voltage start switch circuit includes a power input circuit powered by a vehicle battery. The switch circuit further includes:

[0006] The protection circuit is connected as a branch to the power input circuit;

[0007] The decoupling circuit is connected as a branch to the power input circuit.

[0008] Fuse R300 is connected to the power input circuit and is located in the subsequent stage of the protection circuit and decoupling circuit;

[0009] A soft-start circuit is connected to the subsequent circuit of the fuse R300;

[0010] The MOS switching transistor circuit is connected to the subsequent circuit of the fuse R300;

[0011] The first filter circuit is connected to the drain D of the MOS switching transistor circuit;

[0012] The decoupling circuit is connected as a branch to the subsequent circuit of the first filter circuit;

[0013] A low-voltage start-up protection circuit is connected to the output terminal of the first filter circuit;

[0014] The system's main power supply DC / DC circuit has its power supply terminal connected to the output terminal of the first filter circuit. The system's main power supply DC / DC circuit is also connected to the low-voltage start-up protection circuit.

[0015] Furthermore, the protection circuit includes:

[0016] An electrostatic protection circuit is connected as a branch to the power input circuit.

[0017] The second filter circuit is connected as a branch to the power input circuit;

[0018] A surge protection circuit is connected as a branch to the power input circuit.

[0019] Furthermore, the power input circuit is connected to the power supply via a three-pin J300 plug, with pin 1 outputting voltage and pins 2 and 3 interconnected and grounded;

[0020] The electrostatic discharge protection circuit includes an ESD protection transistor D300, the second end of which is connected to pin 1 of the J300 connector, and the first end of which is grounded.

[0021] The second filter circuit includes capacitor C300 and capacitor C301. The first end of capacitor C300 is connected to pin 1 of the J300 connector, and its second end is grounded. The first end of capacitor C301 is connected to pin 1 of the J300 connector, and its second end is grounded.

[0022] The surge protection circuit includes a surge protection tube T303, the first end of which is connected to pin 1 of the J300 plug, and the second end is grounded.

[0023] Furthermore, the soft-start circuit includes a capacitor C302, which is a soft-start capacitor. Its first end is connected to the subsequent circuit of the fuse R300, and its second end is connected to the gate G of the MOS switch circuit.

[0024] The MOS switching circuit includes a MOS transistor Q300. The source S of the MOS transistor Q300 is connected to the subsequent circuit of the fuse R300. A resistor R301 is connected between its source S and its gate G. The gate G of the MOS transistor Q300 is also connected to a resistor R302. The other end of the resistor R302 is connected to the positive terminal of the diode D301, and the negative terminal of the diode D301 is grounded.

[0025] Furthermore, the first filter circuit is configured such that the drain D of the MOS switch circuit is connected to the first terminal of the inductor L301, and the second terminal of the inductor L301 outputs the VBUS_IN circuit.

[0026] The decoupling circuit includes decoupling capacitor C304 and decoupling capacitor C305. The first terminals of decoupling capacitor C304 and decoupling capacitor C305 are both connected to the second terminal of inductor L301, and the second terminals of decoupling capacitor C304 and decoupling capacitor C305 are respectively grounded.

[0027] Furthermore, the low-voltage start-up protection circuit includes:

[0028] A current-limiting filter circuit, with its input terminal connected to the output terminal of the filter circuit;

[0029] Zener diode D310, the negative terminal of which is connected to the output of the current limiting filter circuit;

[0030] Resistor R344 is a pull-down resistor. Its first terminal is connected to the positive terminal of Zener diode D310, and its second terminal is grounded.

[0031] Diode T304 has its negative terminal connected to the positive terminal of Zener diode D310, and its positive terminal is grounded.

[0032] The base of transistor Q302 is connected to the positive terminal of Zener diode D310 after being connected to the first resistor. Its emitter is grounded. A second resistor is connected between the base and emitter of transistor Q302. The collector of transistor Q302 is connected to the system power button.

[0033] Resistor R343, the first end of which is connected to the positive terminal of Zener diode D310, and the second end of which is connected to the main power supply DC / DC circuit of the system.

[0034] Furthermore, the current limiting filter circuit includes a series circuit consisting of resistors R340, R341, and R342 connected in sequence, as well as capacitors C350 and C351.

[0035] The first terminal of the series circuit is connected to the output terminal of the first filter circuit, and the second terminal is connected to the negative terminal of the Zener diode D310.

[0036] The first end of the capacitor C350 is connected to the circuit node between the resistors R340 and R341, and its second end is grounded.

[0037] The first end of the capacitor C351 is connected to the circuit node between the resistors R341 and R342, and its second end is grounded.

[0038] Furthermore, the system's main power supply DC / DC circuit includes:

[0039] The voltage regulator chip U300 has its EN pin 11 connected to the second end of resistor R343 and resistor R346. The other end of resistor R346 is grounded. Multiple IN pins of the voltage regulator chip U300 are interconnected and connected to the subsequent circuit of the first filter circuit. The voltage regulator chip U300 has multiple grounding pins GND.

[0040] The third filtering circuit includes four filtering capacitors. The first terminals of the four filtering capacitors are all connected to multiple IN pins of the voltage regulator chip U300, and the second terminals of the four filtering capacitors are grounded respectively.

[0041] Resistor R306, the first end of which is connected to pin 9 MODE of the voltage regulator chip U300, and the second end is grounded;

[0042] Resistor R307, the first end of which is connected to pin 13 FS of the voltage regulator chip U300, and the second end is grounded.

[0043] A capacitor C310 is connected to pin 1 (BS) of the voltage regulator chip U300, and the second end of the capacitor C310 is connected to multiple LX pins of the voltage regulator chip U300.

[0044] An inductor L300 is connected to multiple LX pins of the voltage regulator chip U300. The other end of the inductor L300 is connected to the first end of the resistor R304, the first end of the capacitor C311, five parallel capacitors, and the TVS transient voltage suppressor T302. The other ends of the five parallel capacitors are grounded. The second end of the TVS transient voltage suppressor T302 has two pins, which are interconnected and grounded.

[0045] Pin 14 FB of the voltage regulator chip U300 is connected to the first end of resistor R305, the second end of resistor R304, and the first end of resistor R309. The second end of resistor R305 is connected to the second end of capacitor C311, and the second end of resistor R309 is grounded.

[0046] A resistor R308 is connected to pin 15 (ILMT) of the voltage regulator chip U300, and the other end of the resistor R308 is grounded.

[0047] The capacitor C318 is connected to pin 10 (SS) of the voltage regulator chip U300, and the other end of the capacitor C318 is grounded.

[0048] A capacitor C317 is connected to pin 16 (VCC) of the voltage regulator chip U300, and the other end of the capacitor C317 is grounded.

[0049] Compared with the prior art, the beneficial effects of this utility model are: this utility model effectively prevents the TBOX communication terminal from being activated when the voltage of the vehicle backup battery is too low or below the safety threshold, effectively slowing down the battery discharge rate, preventing the battery voltage from being not drawn when the battery is low, and avoiding premature over-discharge of the vehicle battery.

[0050] This utility model of vehicle-mounted TBOX low-voltage start switch circuit effectively solves the problems of excessively low input voltage and frequent power-on failures. Attached Figure Description

[0051] Figure 1-2 The connection forms the overall diagram of the front-end circuit and the back-end circuit of the MOS switching transistor circuit of this utility model.

[0052] Figure 3 This is the circuit diagram for preventing low-voltage startup of this utility model.

[0053] Figure 4-5 After connection, it forms the main power supply DC / DC circuit diagram of this utility model system.

[0054] Figure 6 This is a pin diagram of the MODE system of this utility model.

[0055] Figure 7 To improve the waveform diagram of the previous system power signal and power-on signal.

[0056] Figure 8 This is a waveform diagram of the improved low-pressure state of this utility model.

[0057] Figure 9 This is a waveform diagram of the present invention during normal startup.

[0058] The attached diagram is labeled as follows: 1. Low-voltage start-up protection circuit; 2. Main power supply DC / DC circuit for the system. Detailed Implementation

[0059] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments, so that the advantages and features of the present utility model can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present utility model. Obviously, the embodiments described in this utility model are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0060] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0061] Example 1: The specific structure of this utility model is as follows:

[0062] Please refer to the appendix. Figure 1-6 This utility model discloses a vehicle-mounted TBOX low-voltage start switch circuit, including a power input circuit powered by a vehicle battery. The switch circuit further includes:

[0063] The protection circuit is connected as a branch to the power input circuit;

[0064] The decoupling circuit is connected as a branch to the power input circuit.

[0065] Fuse R300 is connected to the power input circuit and is located in the subsequent stage of the protection circuit and decoupling circuit;

[0066] A soft-start circuit is connected to the subsequent circuit of the fuse R300;

[0067] The MOS switching transistor circuit is connected to the subsequent circuit of the fuse R300;

[0068] The first filter circuit is connected to the drain D of the MOS switching transistor circuit;

[0069] The decoupling circuit is connected as a branch to the subsequent circuit of the first filter circuit;

[0070] The low-voltage start-up protection circuit 1 is connected to the output terminal of the first filter circuit;

[0071] The system's main power supply DC / DC circuit 2 has its power supply terminal connected to the output terminal of the first filter circuit. The system's main power supply DC / DC circuit is also connected to the low-voltage start-up protection circuit.

[0072] Example 2:

[0073] like Figure 1-2 As shown, Figure 1-2 Connect via AA. Figure 1-2 After connection, the front-end circuit and rear-end circuit of the MOS switching transistor circuit of this utility model are formed. Specifically, the protection circuit includes:

[0074] An electrostatic protection circuit is connected as a branch to the power input circuit.

[0075] The second filter circuit is connected as a branch to the power input circuit;

[0076] A surge protection circuit is connected as a branch to the power input circuit.

[0077] The power input circuit is connected to the power supply via a three-pin J300 plug. Pin 1 outputs voltage, and pins 2 and 3 are interconnected and grounded.

[0078] The electrostatic discharge protection circuit includes an ESD protection transistor D300, the second end of which is connected to pin 1 of the J300 connector, and the first end of which is grounded.

[0079] The second filter circuit includes capacitor C300 and capacitor C301. The first end of capacitor C300 is connected to pin 1 of the J300 connector, and its second end is grounded. The first end of capacitor C301 is connected to pin 1 of the J300 connector, and its second end is grounded.

[0080] The surge protection circuit includes a surge protection tube T303, the first end of which is connected to pin 1 of the J300 plug, and the second end is grounded.

[0081] The soft-start circuit includes a capacitor C302, which is a soft-start capacitor. Its first end is connected to the subsequent circuit of the fuse R300, and its second end is connected to the gate G of the MOS switch circuit.

[0082] The MOS switching circuit includes a MOS transistor Q300. The source S of the MOS transistor Q300 is connected to the subsequent circuit of the fuse R300. A resistor R301 is connected between its source S and its gate G. The gate G of the MOS transistor Q300 is also connected to a resistor R302. The other end of the resistor R302 is connected to the positive terminal of the diode D301, and the negative terminal of the diode D301 is grounded.

[0083] The first filter circuit connects the drain D of the MOS switch circuit to the first terminal of the inductor L301, and the second terminal of the inductor L301 outputs the VBUS_IN circuit.

[0084] The decoupling circuit includes decoupling capacitor C304 and decoupling capacitor C305. The first terminals of decoupling capacitor C304 and decoupling capacitor C305 are both connected to the second terminal of inductor L301, and the second terminals of decoupling capacitor C304 and decoupling capacitor C305 are respectively grounded.

[0085] Figure 1-2 The working principle of the circuit:

[0086] Power input circuit: Power is supplied by a 12V car battery, with the 12V input via connector J300. The voltage passes through ESD protection diode D300, then capacitors C300 and C301 to remove power supply noise, followed by surge protection diode T303. Capacitor C303 acts as a pre-amplifier decoupling capacitor. Fuse R300 is a pre-amplifier resettable fuse. Capacitor C302 and resistor R301 act as pull-up and pull-down resistors for the gate (G) of MOS transistor Q300. Diode D301 (a Schottky diode) turns on MOS transistor Q300. MOS transistor Q300 is a P-MOS transistor. The input is a 12V power supply. The 12V power supply passes through the MOS transistor Q300, is filtered by the inductor L301, and is then decoupled by the decoupling capacitors C304 and C305 before reaching the next stage of the power system's main power supply DC / DC circuit 2.

[0087] Working principle of MOS transistor Q300: The MOS transistor Q300 is a P-MOS transistor. It is turned on when VGS<=0V and turned off when VGS>0V. Capacitor C302 is used to slow down the start-up time of MOS transistor Q300. Diode D301 is pulled down to ground by default, so that VGS<0V, thus turning on MOS transistor Q300.

[0088] Example 3:

[0089] like Figure 3 As shown, Figure 3 This is a circuit diagram for the low-voltage start protection of this utility model. The low-voltage start protection circuit includes:

[0090] A current-limiting filter circuit, with its input terminal connected to the output terminal of the filter circuit;

[0091] Zener diode D310, the negative terminal of which is connected to the output of the current limiting filter circuit;

[0092] Resistor R344 is a pull-down resistor. Its first terminal is connected to the positive terminal of Zener diode D310, and its second terminal is grounded.

[0093] Diode T304 has its negative terminal connected to the positive terminal of Zener diode D310, and its positive terminal is grounded.

[0094] The base of transistor Q302 is connected to the positive terminal of Zener diode D310 after being connected to the first resistor. Its emitter is grounded. A second resistor is connected between the base and emitter of transistor Q302. The collector of transistor Q302 is connected to the system power button.

[0095] Resistor R343, the first end of which is connected to the positive terminal of Zener diode D310, and the second end of which is connected to the main power supply DC / DC circuit of the system.

[0096] The current limiting filter circuit includes a series circuit consisting of resistors R340, R341, and R342 connected in sequence, as well as capacitors C350 and C351.

[0097] The first terminal of the series circuit is connected to the output terminal of the first filter circuit, and the second terminal is connected to the negative terminal of the Zener diode D310.

[0098] The first end of the capacitor C350 is connected to the circuit node between the resistors R340 and R341, and its second end is grounded.

[0099] The first end of the capacitor C351 is connected to the circuit node between the resistors R341 and R342, and its second end is grounded.

[0100] Based on the circuit connections above, the working principle of the low-voltage start-up protection circuit diagram is as follows:

[0101] The power supply is output from MOS transistor Q300, passing through resistor R340, capacitor C350, resistor R341, capacitor C351, and resistor R342 for progressive current limiting and filtering before reaching Zener diode D310. Zener diode D310 is a 6.2V Zener diode with a maximum avalanche voltage of 6.5V. With the current-limiting resistor in the preceding stage, the input current is <5mA to prevent burnout. Zener diode D310 conducts when the input voltage is >6.5V and cuts off when it is <6.5V. Resistor R344 acts as a pull-down resistor, ensuring the base of transistor Q302 is at a default low level. When Zener diode D310 is conducting, VSYS_EN is also high (greater than 6.5V), outputting to the next-level system's main power supply DC / DC circuit for step-down. Transistor Q302 is an NPN transistor; when the base voltage of Q302 is >0.6V, Q302 conducts. When Zener diode D310 is turned on, the output is greater than 6.5V. Transistor Q302 is turned on, and PM8550_CBL_PWM_N is at a default high level of 1.8V. When transistor Q302 is turned on, it pulls the system power button of PM8550_CBL_PWM_N low, and the system is powered on. At the same time, when the battery input voltage is lower than 6.5V, the back-end step-down power supply and the system main controller will not be turned on.

[0102] Example 4:

[0103] The system's main power supply DC / DC circuit includes:

[0104] The voltage regulator chip U300 has its EN pin 11 connected to the second end of resistor R343 and resistor R346. The other end of resistor R346 is grounded. Multiple IN pins of the voltage regulator chip U300 are interconnected and connected to the subsequent circuit of the first filter circuit. The voltage regulator chip U300 has multiple grounding pins GND.

[0105] The third filtering circuit includes four filtering capacitors. The first terminals of the four filtering capacitors are all connected to multiple IN pins of the voltage regulator chip U300, and the second terminals of the four filtering capacitors are grounded respectively.

[0106] Resistor R306, the first end of which is connected to pin 9 MODE of the voltage regulator chip U300, and the second end is grounded;

[0107] Resistor R307, the first end of which is connected to pin 13 FS of the voltage regulator chip U300, and the second end is grounded.

[0108] A capacitor C310 is connected to pin 1 (BS) of the voltage regulator chip U300, and the second end of the capacitor C310 is connected to multiple LX pins of the voltage regulator chip U300.

[0109] An inductor L300 is connected to multiple LX pins of the voltage regulator chip U300. The other end of the inductor L300 is connected to the first end of the resistor R304, the first end of the capacitor C311, five parallel capacitors, and the TVS transient voltage suppressor T302. The other ends of the five parallel capacitors are grounded. The second end of the TVS transient voltage suppressor T302 has two pins, which are interconnected and grounded.

[0110] Pin 14 FB of the voltage regulator chip U300 is connected to the first end of resistor R305, the second end of resistor R304, and the first end of resistor R309. The second end of resistor R305 is connected to the second end of capacitor C311, and the second end of resistor R309 is grounded.

[0111] A resistor R308 is connected to pin 15 (ILMT) of the voltage regulator chip U300, and the other end of the resistor R308 is grounded.

[0112] The capacitor C318 is connected to pin 10 (SS) of the voltage regulator chip U300, and the other end of the capacitor C318 is grounded.

[0113] A capacitor C317 is connected to pin 16 (VCC) of the voltage regulator chip U300, and the other end of the capacitor C317 is grounded.

[0114] Based on the circuit connections above, the main power supply DC / DC circuit of the system is fed from MOS transistor Q300 to pre-amplifier capacitors C306, C307, C308, and C309 for filtering, and then to regulator chip U300IN. Pin 11 EN of regulator chip U300 is the DC / DC switch EN, which is current-limited by pre-amplifier resistor R343. When the voltage level is high, regulator chip U300 is turned on, and the DC / DC step-down output is 4V.

[0115] Figure 7 To improve the waveform diagram of the previous system power signal and power-on signal.

[0116] Figure 8 The waveform diagram shows the improved low-voltage state of this invention. When the voltage is <6.5V, the system voltage does not frequently start abnormally.

[0117] Figure 9 This is a waveform diagram of the normal startup of this utility model. When >6.5V, Figure 9 This is the waveform during normal startup.

[0118] In summary, this invention effectively prevents the TBOX communication terminal from activating when the vehicle's backup battery voltage is too low, specifically below the safety threshold. This effectively slows down the battery's discharge rate, prevents the battery voltage from being depleted during low-voltage periods, and avoids premature over-discharge of the vehicle battery. The vehicle TBOX low-voltage start-up switch circuit of this invention effectively solves the problems of low input voltage and frequent power-on / off cycles.

[0119] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. Any equivalent structural or procedural transformations made based on the contents of the present utility model specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present utility model.

Claims

1. A vehicle-mounted TBOX low-voltage start switch circuit, comprising a power input circuit powered by a vehicle battery, characterized in that, The switching circuit also includes: The protection circuit is connected as a branch to the power input circuit; The decoupling circuit is connected as a branch to the power input circuit. Fuse R300 is connected to the power input circuit and is located in the subsequent stage of the protection circuit and decoupling circuit; A soft-start circuit is connected to the subsequent circuit of the fuse R300; The MOS switching transistor circuit is connected to the subsequent circuit of the fuse R300; The first filter circuit is connected to the drain D of the MOS switching transistor circuit; The decoupling circuit is connected as a branch to the subsequent circuit of the first filter circuit; A low-voltage start-up protection circuit is connected to the output terminal of the first filter circuit; The system's main power supply DC / DC circuit has its power supply terminal connected to the output terminal of the first filter circuit. The system's main power supply DC / DC circuit is also connected to the low-voltage start-up protection circuit.

2. The vehicle-mounted TBOX low-voltage start-up protection switch circuit according to claim 1, characterized in that, The protection circuit includes: An electrostatic protection circuit is connected as a branch to the power input circuit. The second filter circuit is connected as a branch to the power input circuit; A surge protection circuit is connected as a branch to the power input circuit.

3. The vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 2, characterized in that, The power input circuit is connected to the power supply via a three-pin J300 plug. Pin 1 outputs voltage, and pins 2 and 3 are interconnected and grounded. The electrostatic discharge protection circuit includes an ESD protection transistor D300, the second end of which is connected to pin 1 of the J300 connector, and the first end of which is grounded. The second filter circuit includes capacitor C300 and capacitor C301. The first end of capacitor C300 is connected to pin 1 of the J300 connector, and its second end is grounded. The first end of capacitor C301 is connected to pin 1 of the J300 connector, and its second end is grounded. The surge protection circuit includes a surge protection tube T303, the first end of which is connected to pin 1 of the J300 plug, and the second end is grounded.

4. The vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 1, characterized in that, The soft-start circuit includes a capacitor C302, which is a soft-start capacitor. Its first end is connected to the subsequent circuit of the fuse R300, and its second end is connected to the gate G of the MOS switch circuit. The MOS switching circuit includes a MOS transistor Q300. The source S of the MOS transistor Q300 is connected to the subsequent circuit of the fuse R300. A resistor R301 is connected between its source S and its gate G. The gate G of the MOS transistor Q300 is also connected to a resistor R302. The other end of the resistor R302 is connected to the positive terminal of the diode D301, and the negative terminal of the diode D301 is grounded.

5. The vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 1, characterized in that, The first filter circuit connects the drain D of the MOS switch circuit to the first terminal of the inductor L301, and the second terminal of the inductor L301 outputs the VBUS_IN circuit. The decoupling circuit includes decoupling capacitor C304 and decoupling capacitor C305. The first terminals of decoupling capacitor C304 and decoupling capacitor C305 are both connected to the second terminal of inductor L301, and the second terminals of decoupling capacitor C304 and decoupling capacitor C305 are respectively grounded.

6. The vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 1, characterized in that, The low-voltage start-up protection circuit includes: A current-limiting filter circuit, with its input terminal connected to the output terminal of the filter circuit; Zener diode D310, the negative terminal of which is connected to the output terminal of the current limiting filter circuit; Resistor R344 is a pull-down resistor. Its first terminal is connected to the positive terminal of Zener diode D310, and its second terminal is grounded. Diode T304 has its negative terminal connected to the positive terminal of Zener diode D310, and its positive terminal is grounded. The base of transistor Q302 is connected to the positive terminal of Zener diode D310 after being connected to the first resistor. Its emitter is grounded. A second resistor is connected between the base and emitter of transistor Q302. The collector of transistor Q302 is connected to the system power button. Resistor R343, the first end of which is connected to the positive terminal of Zener diode D310, and the second end of which is connected to the main power supply DC / DC circuit of the system.

7. A vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 6, characterized in that, The current limiting filter circuit includes a series circuit consisting of resistors R340, R341, and R342 connected in sequence, as well as capacitors C350 and C351. The first terminal of the series circuit is connected to the output terminal of the first filter circuit, and the second terminal is connected to the negative terminal of the Zener diode D310. The first end of the capacitor C350 is connected to the circuit node between the resistors R340 and R341, and its second end is grounded. The first end of the capacitor C351 is connected to the circuit node between the resistors R341 and R342, and its second end is grounded.

8. A vehicle-mounted TBOX low-voltage start-up switch circuit according to claim 6, characterized in that, The system's main power supply DC / DC circuit includes: The voltage regulator chip U300 has its EN pin 11 connected to the second end of resistor R343 and resistor R346. The other end of resistor R346 is grounded. Multiple IN pins of the voltage regulator chip U300 are interconnected and connected to the subsequent circuit of the first filter circuit. The voltage regulator chip U300 has multiple grounding pins GND. The third filtering circuit includes four filtering capacitors. The first terminals of the four filtering capacitors are all connected to multiple IN pins of the voltage regulator chip U300, and the second terminals of the four filtering capacitors are grounded respectively. Resistor R306, the first end of which is connected to pin 9 MODE of the voltage regulator chip U300, and the second end is grounded; Resistor R307, the first end of which is connected to pin 13 FS of the voltage regulator chip U300, and the second end is grounded; A capacitor C310 is connected to pin 1 (BS) of the voltage regulator chip U300, and the second end of the capacitor C310 is connected to multiple LX pins of the voltage regulator chip U300. An inductor L300 is connected to multiple LX pins of the voltage regulator chip U300. The other end of the inductor L300 is connected to the first end of the resistor R304, the first end of the capacitor C311, five parallel capacitors, and the TVS transient voltage suppressor T302. The other ends of the five parallel capacitors are grounded. The second end of the TVS transient voltage suppressor T302 has two pins, which are interconnected and grounded. Pin 14 FB of the voltage regulator chip U300 is connected to the first end of resistor R305, the second end of resistor R304, and the first end of resistor R309. The second end of resistor R305 is connected to the second end of capacitor C311, and the second end of resistor R309 is grounded. A resistor R308 is connected to pin 15 (ILMT) of the voltage regulator chip U300, and the other end of the resistor R308 is grounded. The capacitor C318 is connected to pin 10 (SS) of the voltage regulator chip U300, and the other end of the capacitor C318 is grounded. A capacitor C317 is connected to pin 16 (VCC) of the voltage regulator chip U300, and the other end of the capacitor C317 is grounded.

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