A vehicle-mounted equipment power low-voltage protection and standby battery switching control circuit

Abstract

The utility model discloses a kind of vehicle-mounted equipment power supply low-voltage protection and spare battery switching control circuit, including first power conversion circuit, second power conversion circuit, hysteresis comparator circuit and spare battery switch circuit.First power conversion circuit is filtered to vehicle-mounted power supply, DC-DC conversion is carried out, and multiple protection circuits are set;Second power conversion circuit reduces voltage output stable voltage to vehicle-mounted power supply;Hysteresis comparator circuit real-time monitoring vehicle-mounted power supply voltage;Spare battery switch circuit switches to spare battery power supply when low voltage.It can real-time monitoring vehicle-mounted power supply voltage, when voltage is lower than set threshold, cut off vehicle-mounted power supply and rear-end equipment connection, prevent automobile battery overdischarge, while automatically switched to spare battery power supply, guarantee vehicle-mounted equipment continuous operation.In addition, through hysteresis voltage comparator design, avoid circuit frequently switching, improve system stability and reliability, ensure the continuity of automobile intelligent function.

Description

Technical Field

[0001] This utility model relates to vehicle power supply, specifically to a low-voltage protection and backup battery switching control circuit for vehicle equipment power supply. Background Technology

[0002] With the continuous development of automotive intelligence, the number of intelligent in-vehicle devices is also increasing. Some traditional mechanically controlled devices in cars (such as doors and seats) have been transformed into intelligent controls, including devices that collect vehicle information in real time and upload it to cloud servers (such as T-boxes and intelligent sensors). The power supply is drawn from the car's 12V or 24V battery.

[0003] If a car is not started for a period of time or if high-power devices inside the car are used for an extended period of time, the battery may be over-discharged or even suffer permanent damage. Utility Model Content

[0004] The purpose of this utility model is to provide a low-voltage protection and backup battery switching control circuit for vehicle equipment power supply, so as to solve the problem of over-discharge of automobile batteries, and at the same time switch to the backup battery of the vehicle equipment in a timely manner when the automobile battery is low-voltage.

[0005] To solve the above technical problems, this utility model provides the following solution: A vehicle-mounted equipment power low-voltage protection and backup battery switching control circuit, comprising:

[0006] The first power conversion circuit has an input terminal connected to the vehicle power supply. Its circuit is connected to a first filter circuit that filters the incoming vehicle power supply and a DC-DC conversion circuit after the input power supply is filtered. The DC-DC conversion circuit outputs a VBAT circuit and a second filter circuit, an overvoltage protection circuit, a voltage detection circuit and a reverse connection protection circuit are set during the process of the DC-DC conversion circuit outputting the VBAT circuit.

[0007] The second power conversion circuit has an input terminal connected to the vehicle power supply. Its input section is equipped with a current-limiting resistor R115 and filtered by a capacitor C122 before being fed into a voltage regulator U103. The voltage regulator U103 steps down to output the first voltage and sets up a feedback circuit and a third filter circuit on the output circuit branch.

[0008] The hysteresis comparator circuit has a voltage divider circuit at its input. The input of the voltage divider circuit is connected to the vehicle power supply. The input power supply is divided and then connected to the operational amplifier U102. The input power supply of the operational amplifier U102 is the power output from the voltage regulator U103. The output of the operational amplifier U102 is connected to the first switching transistor circuit.

[0009] The backup battery switching circuit has a power switching circuit with two MOS switching transistors. The first MOS switching transistor is connected to the backup battery, and the second MOS switching transistor is connected to the first MOS switching transistor in a DS connection structure. The gate circuit of the second MOS switching transistor is connected to the output circuit of the operational amplifier U102.

[0010] Furthermore, the DC-DC conversion circuit is equipped with a DC-DC conversion chip U101, and pin 2 VIN of the DC-DC conversion chip U101 is connected to the vehicle power supply.

[0011] Furthermore, the first filter circuit includes a first parallel circuit composed of polarized capacitors C105, C106, C107 and C108 connected in parallel. The first terminal of the first parallel circuit is connected to pin 2 VIN of the DC-DC converter chip U101, and its second terminal is grounded. The negative terminal of the polarized capacitor C105 is grounded.

[0012] The EN pin of the DC-DC converter chip U101 is the enable control pin, which is connected to resistor R101, resistor R102, and the DCDC_EN circuit. The other end of resistor R102 is connected to the vehicle power supply, and the other end of resistor R101 is grounded.

[0013] The RT / CLK pin of the DC-DC converter chip U101 is the frequency setting pin, which is connected to resistor R103. The other end of resistor R103 is grounded.

[0014] The 6-pin COMP of the DC-DC converter chip U101 is a compensation pin, which is used for circuit compensation. It is connected to resistor R104 and capacitor C110. The other end of resistor R104 is connected to capacitor C109, the other end of capacitor C109 is grounded, and the other end of capacitor C110 is connected to the ground terminal of capacitor C109.

[0015] Pin 9, T_GND, of the DC-DC converter chip U101 is grounded;

[0016] Pin 7 (GND) of the DC-DC converter chip U101 is grounded;

[0017] Pin 5 (FB) of the DC-DC converter chip U101 is used for output voltage feedback to ensure stable output voltage. Pin 5 (FB) of the DC-DC converter chip U101 is connected to the VSYS_5V_FB circuit.

[0018] Furthermore, the second filter circuit is an LC filter circuit, which includes an inductor L102, a capacitor C112, a capacitor C113, a capacitor C114, a capacitor C115, and a capacitor C116.

[0019] The first end of the inductor L102 is connected to pin 8 (SW) of the DC-DC converter chip U101 and capacitor C111, and the other end of the capacitor C111 is connected to pin 1 (BOOT) of the DC-DC converter chip U101.

[0020] One end of each of the capacitors C112, C113, C114, C115 and C116 is grounded, and the other end of each is connected to the second end of the inductor L102.

[0021] Furthermore, the overvoltage protection circuit includes a TVS transient voltage suppression diode T103, the first terminal of which is connected to the second terminal of the inductor L102, and the second terminal is grounded.

[0022] Furthermore, the voltage detection circuit includes a first series circuit consisting of resistors R105, R106, and R107 connected in sequence. The first end of the first series circuit is connected to the second end of the inductor L102, and the second end of the first series circuit is grounded.

[0023] The circuit node between resistors R106 and R107 is connected to pin 5 (FB) of the DC-DC converter chip U101.

[0024] The reverse connection protection circuit includes a Zener diode D102, the positive terminal of which is grounded and the negative terminal is connected to the first end of the inductor L102. The Zener diode D102 prevents the circuit from being damaged when the power supply is reversed.

[0025] Furthermore, pin 2 (VIN) of the voltage regulator U103 is connected to capacitor C122, current-limiting resistor R115, and resistor R116 respectively. The other end of the current-limiting resistor R115 is connected to the vehicle power supply, and the other end of the capacitor C122 is grounded.

[0026] The fourth pin (SHDN) of the voltage regulator U103 is the enable pin, which is connected to the other end of the resistor R116.

[0027] The voltage regulator U103's pin 3 (GND) is grounded;

[0028] The power output from pin 7 (OUT) of the voltage regulator U103 is fed into the hysteresis comparator circuit.

[0029] The feedback circuit includes resistors R117 and R118. The first end of the series connection of resistors R117 and R118 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the series connection is grounded.

[0030] Pin 6 FB of the voltage regulator U103 is connected to the circuit node between resistors R117 and R118;

[0031] The third filter circuit includes capacitors C123 and C124. The first end of the parallel connection of capacitors C123 and C124 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the parallel connection of capacitors C123 and C124 is grounded.

[0032] Furthermore, the voltage divider circuit includes a second series circuit consisting of resistors R108, R109, and R110. The first end of the second series circuit is connected to the vehicle power supply, and the second end is grounded.

[0033] The circuit node between resistors R108 and R109 is also connected to capacitor C119, and the other end of capacitor C119 is grounded.

[0034] The inverting input terminal of the operational amplifier U102 is connected to the circuit node between resistors R108 and R109;

[0035] The non-inverting input terminal of the operational amplifier U102 is connected to capacitor C120, resistor R119 and resistor R111 respectively. The other end of capacitor C120 is grounded, the other end of resistor R119 is connected to the output terminal of the operational amplifier U102, and the other end of resistor R111 is connected to the VREF pin of the operational amplifier U102.

[0036] The V+ pin of the operational amplifier U102 is connected to capacitor C118 and the first voltage of the step-down output of the voltage regulator U103.

[0037] The operational amplifier U102's V- pin is grounded;

[0038] The output terminal of the operational amplifier U102 is connected to resistor R112, and the other end of resistor R112 is connected to resistor R113, capacitor C121 and BACKUP_EN circuit respectively.

[0039] The other end of the capacitor C121 is grounded;

[0040] The first switching transistor circuit includes an N-MOS transistor Q101. The gate of the N-MOS transistor Q101 is connected to the other end of the resistor R113 and the resistor R114. The other end of the resistor R114 is grounded. The source of the N-MOS transistor Q101 is grounded, and its drain is connected to pin 3 EN of the DC-DC converter chip U101.

[0041] Furthermore, the first MOS switch is an N-MOS transistor Q102, and the second MOS switch is an N-MOS transistor Q103;

[0042] An RC circuit is connected between the gate (G) and the drain (D) of the N-MOS transistor Q102. The RC circuit includes a resistor R121 and a capacitor C126 connected in parallel.

[0043] The drain of the N-MOS transistor Q102 is also connected to a capacitor C125 and a TVS transient suppression diode T104. The other end of the capacitor C125 is grounded, the other end of the TVS transient suppression diode T104 is grounded, and the drain of the N-MOS transistor Q102 is also connected to the positive output of the backup battery.

[0044] The negative terminal of the backup battery is connected to resistor R120, and the other end of resistor R120 is connected to the battery detection signal pin BAT_ID.

[0045] The backup battery's pin 3 is grounded;

[0046] The gate of the N-MOS transistor Q102 is also connected to a resistor R122, and the other end of the resistor R122 is connected to the drain of the N-MOS transistor Q103.

[0047] The S pin of the N-MOS transistor Q102 is connected to the BAT circuit and capacitor C127, and the other end of capacitor C127 is grounded.

[0048] The S pin of the N-MOS transistor Q103 is grounded;

[0049] The gate of the N-MOS transistor Q103 is connected to resistors R123 and R124 and capacitor C128, respectively. The other end of resistor R123 is connected to the BACKUP_EN circuit, the other end of resistor R124 is grounded, and the other end of capacitor C128 is grounded.

[0050] Compared with the prior art, the beneficial effects of this utility model are:

[0051] 1. The vehicle-mounted equipment power supply low-voltage protection and backup battery switching control circuit of this utility model has a low-voltage protection function: it can monitor the vehicle power supply voltage in real time, and when the voltage is lower than the set threshold, it will cut off the connection between the vehicle power supply and the back-end vehicle equipment in time to prevent the car battery from being over-discharged and extend the service life of the car battery.

[0052] 2. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit of this utility model has a backup battery switching function: when the vehicle power supply is low, it automatically switches to backup battery power supply to ensure that the vehicle-mounted equipment can continue to operate, and promptly reports and backs up vehicle information to the cloud server to ensure the continuity of vehicle intelligent functions.

[0053] 3. The vehicle-mounted equipment power supply low-voltage protection and backup battery switching control circuit system of this utility model is stable: through the design of the hysteresis voltage comparator, the frequent switching of the circuit caused by the fluctuation of the vehicle power supply voltage near the critical value is avoided, thereby improving the stability and reliability of the system. Attached Figure Description

[0054] Figure 1-2 The connection forms the power supply circuit diagram of this utility model.

[0055] Figure 3 This invention provides a voltage regulator circuit diagram for supplying power to a hysteresis voltage comparator.

[0056] Figure 4-5 The circuit diagram of the hysteresis voltage comparator of this utility model is formed after connection.

[0057] Figure 6 This is the circuit diagram of the backup battery switch of this utility model. Detailed Implementation

[0058] 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.

[0059] 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.

[0060] Example 1: The specific structure of this utility model is as follows:

[0061] Please refer to the appendix. Figure 1-6 This utility model discloses a low-voltage protection and backup battery switching control circuit for vehicle-mounted equipment, comprising:

[0062] The first power conversion circuit has an input terminal connected to the vehicle power supply. Its circuit is connected to a first filter circuit that filters the incoming vehicle power supply and a DC-DC conversion circuit after the input power supply is filtered. The DC-DC conversion circuit outputs a VBAT circuit and a second filter circuit, an overvoltage protection circuit, a voltage detection circuit and a reverse connection protection circuit are set during the process of the DC-DC conversion circuit outputting the VBAT circuit.

[0063] The second power conversion circuit connects to the vehicle's power supply at its input. Its input section includes a current-limiting resistor R115 and is filtered by a capacitor C122 before being fed into a voltage regulator U103. This regulator U103 steps down the output voltage to provide a first voltage and includes a feedback circuit and a third filter circuit on the output circuit branch. The current-limiting resistor R115 limits the current, preventing excessive current from flowing into subsequent circuits and protecting circuit components.

[0064] The hysteresis comparator circuit has a voltage divider circuit at its input. The input of the voltage divider circuit is connected to the vehicle power supply. The input power supply is divided and then connected to the operational amplifier U102. The input power supply of the operational amplifier U102 is the power output from the voltage regulator U103. The output of the operational amplifier U102 is connected to the first switching transistor circuit.

[0065] The backup battery switching circuit has a power switching circuit with two MOS switching transistors. The first MOS switching transistor is connected to the backup battery, and the second MOS switching transistor is connected to the first MOS switching transistor in a DS connection structure. The gate circuit of the second MOS switching transistor is connected to the output circuit of the operational amplifier U102.

[0066] Example 2:

[0067] like Figure 1-2 As shown, Figure 1 and Figure 2 Connecting points A forms the power supply circuit diagram of this utility model.

[0068] The DC-DC conversion circuit includes a DC-DC conversion chip U101, whose pin 2 (VIN) is connected to the vehicle power supply. The model number of the DC-DC conversion chip U101 is DSQ2965-QA. The vehicle power supply VCC_12V is filtered by a capacitor and then connected to pin 2 (VIN) of the DC-DC conversion chip U101 to provide operating power.

[0069] The first filter circuit includes a first parallel circuit composed of polarized capacitors C105, C106, C107 and C108 connected in parallel. The first terminal of the first parallel circuit is connected to pin 2 VIN of the DC-DC converter chip U101, and its second terminal is grounded. The negative terminal of the polarized capacitor C105 is grounded.

[0070] Pin 3 (EN) of the DC-DC converter chip U101 is the enable control pin, which is connected to resistors R101 and R102 and the DC-DC_EN circuit. The other end of resistor R102 is connected to the vehicle power supply, and the other end of resistor R101 is grounded. The signal of the DC-DC_EN circuit is divided by resistors R101 and R102 and then connected to the EN pin (pin 3) of the DC-DC converter chip U101 to control whether the DC-DC converter chip U101 is working. It is active high.

[0071] The RT / CLK pin 4 of the DC-DC converter chip U101 is the frequency setting pin. This frequency setting pin is connected to resistor R103, and the other end of resistor R103 is grounded. The RT / CLK pin 4 sets the operating frequency of the DC-DC converter chip U101 through resistor R103, resistor R104 and capacitor C109.

[0072] Pin 6 COMP of the DC-DC converter chip U101 is a compensation pin used for circuit compensation. It is connected to resistor R104 and capacitor C110. The other end of resistor R104 is connected to capacitor C109, and the other end of capacitor C109 is grounded. The other end of capacitor C110 is connected to the ground terminal of capacitor C109. Pin 6 COMP, connected to capacitor C110, is used for circuit compensation and to optimize stability.

[0073] The 9th pin (T_GND) of the DC-DC converter chip U101 is grounded.

[0074] Pin 7 of the DC-DC converter chip U101 is grounded (GND).

[0075] Pin 5 (FB) of the DC-DC converter chip U101 is used for output voltage feedback to ensure stable output voltage. Pin 5 (FB) of the DC-DC converter chip U101 is connected to the VSYS_5V_FB circuit to ensure stable output voltage.

[0076] The second filter circuit is an LC filter circuit, which includes inductor L102, capacitor C112, capacitor C113, capacitor C114, capacitor C115, and capacitor C116. The second filter circuit filters out high-frequency noise in the power supply, making the output VBAT power supply cleaner.

[0077] The first end of the inductor L102 is connected to pin 8 (SW) of the DC-DC converter chip U101 and capacitor C111. The other end of capacitor C111 is connected to pin 1 (BOOT) of the DC-DC converter chip U101. Pin 8 (SW) is the switch output pin, and pin 1 (BOOT) is connected to output terminal A through capacitor C111 to increase the drive voltage of the high-side power transistor.

[0078] One end of each of the capacitors C112, C113, C114, C115 and C116 is grounded, and the other end of each is connected to the second end of the inductor L102.

[0079] The overvoltage protection circuit includes a TVS transient voltage suppressor diode T103. The first terminal of the TVS transient voltage suppressor diode T103 is connected to the second terminal of the inductor L102, and the second terminal is grounded. The TVS transient voltage suppressor diode T103 is used to suppress transient overvoltages that may occur on VBAT, protecting the downstream circuitry.

[0080] The voltage detection circuit includes a first series circuit consisting of resistors R105, R106, and R107 connected in sequence. The first end of the first series circuit is connected to the second end of the inductor L102, and the second end of the first series circuit is grounded.

[0081] The circuit node between resistors R106 and R107 is connected to pin 5 (FB) of the DC-DC converter chip U101; resistors R105, R106, and R107 form a voltage divider circuit, which divides the VBAT voltage and connects it to the VSYS_5V_FB circuit to detect the VBAT voltage and feed it back to the control circuit.

[0082] The reverse connection protection circuit includes a Zener diode D102, the positive terminal of which is grounded and the negative terminal is connected to the first end of the inductor L102. The Zener diode D102 prevents the circuit from being damaged when the power supply is reversed.

[0083] Example 3:

[0084] like Figure 3 As shown, Figure 3 This invention provides a voltage regulator circuit diagram for supplying power to a hysteresis voltage comparator.

[0085] The voltage regulator U103 has its pin 2 (VIN) connected to capacitor C122, current-limiting resistor R115, and resistor R116, respectively. The other end of the current-limiting resistor R115 is connected to the vehicle power supply, and the other end of capacitor C122 is grounded. The voltage regulator U103 is model IC-LDO-MPQ2016DD-AEC1. The voltage regulation circuit steps down the 12V voltage from the vehicle power supply to 5V and outputs it to the hysteresis comparator circuit.

[0086] The fourth pin (SHDN) of the voltage regulator U103 is the enable pin, which is connected to the other end of the resistor R116.

[0087] The voltage regulator U103's pin 3 (GND) is grounded;

[0088] The power output from pin 7 (OUT) of the voltage regulator U103 is fed into the hysteresis comparator circuit.

[0089] The feedback circuit includes resistors R117 and R118. The first end of the series connection of resistors R117 and R118 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the series connection is grounded.

[0090] Pin 6 FB of the voltage regulator U103 is connected to the circuit node between resistors R117 and R118;

[0091] The third filter circuit includes capacitors C123 and C124. The first end of the parallel connection of capacitors C123 and C124 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the parallel connection of capacitors C123 and C124 is grounded.

[0092] Example 4:

[0093] like Figure 4-6 As shown, Figure 4-5 The circuit diagram of the hysteresis voltage comparator of this utility model is formed after the connection at point B. Figure 6 This is the circuit diagram of the backup battery switch of this utility model.

[0094] The voltage divider circuit includes a second series circuit consisting of resistors R108, R109 and R110. The first end of the second series circuit is connected to the vehicle power supply, and the second end is grounded.

[0095] The circuit node between resistors R108 and R109 is also connected to capacitor C119, the other end of which is grounded. The vehicle power supply VCC_12V adjusts the voltage through a resistor divider network composed of resistors R108, R109, and R110. Capacitor C119 is a filter capacitor used to filter out power supply noise. VDD_5V supplies power to operational amplifier U102, and capacitor C118 serves as a power supply decoupling capacitor.

[0096] The inverting input terminal of the operational amplifier U102 is connected to the circuit node between resistors R108 and R109;

[0097] The non-inverting input of operational amplifier U102 is connected to capacitor C120, resistor R119, and resistor R111. The other end of capacitor C120 is grounded, the other end of resistor R119 is connected to the output of operational amplifier U102, and the other end of resistor R111 is connected to the VREF pin of operational amplifier U102. Resistor R111 is the input signal feedback resistor, and resistor R119 is the negative feedback resistor. The negative feedback mechanism stabilizes the amplifier gain and processes the input signal. The output signal is output from the OUT pin. The VREF pin may be used to set a reference voltage, affecting the operating state of operational amplifier U102.

[0098] The V+ pin of the operational amplifier U102 is connected to capacitor C118 and the first voltage of the step-down output of the voltage regulator U103.

[0099] The V-pin of the operational amplifier U102 is grounded.

[0100] The output terminal of the operational amplifier U102 is connected to resistor R112, and the other end of resistor R112 is connected to resistor R113, capacitor C121 and BACKUP_EN circuit respectively.

[0101] The other end of the capacitor C121 is grounded.

[0102] The first switching transistor circuit includes an N-MOS transistor Q101. The gate of the N-MOS transistor Q101 is connected to the other end of the resistor R113 and the resistor R114. The other end of the resistor R114 is grounded. The source of the N-MOS transistor Q101 is grounded, and its drain is connected to pin 3 EN of the DC-DC converter chip U101.

[0103] The first MOS switch is an N-MOS transistor Q102, and the second MOS switch is an N-MOS transistor Q103;

[0104] An RC circuit is connected between the gate (G) and the drain (D) of the N-MOS transistor Q102. The RC circuit includes a resistor R121 and a capacitor C126 connected in parallel.

[0105] The drain of the N-MOS transistor Q102 is also connected to a capacitor C125 and a TVS transient suppression diode T104. The other end of the capacitor C125 is grounded, the other end of the TVS transient suppression diode T104 is grounded, and the drain of the N-MOS transistor Q102 is also connected to the positive output of the backup battery.

[0106] The negative terminal of the backup battery is connected to resistor R120, and the other end of resistor R120 is connected to the battery detection signal pin BAT_ID.

[0107] The backup battery's pin 3 is grounded;

[0108] The gate of the N-MOS transistor Q102 is also connected to a resistor R122, and the other end of the resistor R122 is connected to the drain of the N-MOS transistor Q103.

[0109] The S pin of the N-MOS transistor Q102 is connected to the BAT circuit and capacitor C127, and the other end of capacitor C127 is grounded.

[0110] The S pin of the N-MOS transistor Q103 is grounded;

[0111] The gate of the N-MOS transistor Q103 is connected to resistors R123 and R124 and capacitor C128, respectively. The other end of resistor R123 is connected to the BACKUP_EN circuit, the other end of resistor R124 is grounded, and the other end of capacitor C128 is grounded.

[0112] The hysteresis voltage comparator uses an SGM8706YN6G / TR operational amplifier. The 12V from the car battery is divided and connected to the hysteresis voltage comparator's IN-, while Vref (1.2V) is connected to IN+, forming an inverting comparator circuit. Resistors R108, R109, and R110 set the 12V low-voltage protection threshold VL_TH for the car battery. When the divided battery voltage exceeds VL_TH, the hysteresis voltage comparator outputs a low level. The BACKUP_EN backup battery enable switch outputs a low voltage, while DCDC_EN remains at its original high level. At this time, the backup battery switch MOS is in the off state, and the DCDC_BUCK circuit is in the working state, providing system power.

[0113] When the car battery voltage, after voltage division, is less than VL_TH, the hysteresis voltage comparator outputs a high level. The BACKUP_EN backup battery enable switch outputs a high voltage, and the DCDC_EN level is pulled low to 0V by the N-MOS transistor Q101. At this time, the backup battery enable switch is open, the DCDC_BUCK enable switch is closed, and the system is powered by the backup battery, thus providing low-voltage protection for the car battery and preventing over-discharge. Due to the electrical characteristics of the hysteresis voltage comparator, when the car battery is in a recognized low-voltage state, the comparator output is high. Only when the car battery voltage is charged and rises to VH_TH will the comparator output switch from high voltage to low voltage and reopen.

[0114] In summary, the vehicle-mounted equipment power supply low-voltage protection and backup battery switching control circuit of this utility model has a low-voltage protection function: it can monitor the vehicle power supply voltage in real time, and when the voltage is lower than the set threshold, it will disconnect the vehicle power supply from the back-end vehicle equipment in time to prevent the car battery from being over-discharged and extend the service life of the car battery.

[0115] This utility model's vehicle-mounted equipment low-voltage protection and backup battery switching control circuit has a backup battery switching function: when the vehicle power supply is low-voltage, it automatically switches to backup battery power supply to ensure that the vehicle-mounted equipment can continue to operate, and promptly reports and backs up vehicle information to the cloud server to ensure the continuity of the vehicle's intelligent functions.

[0116] The present invention relates to a vehicle-mounted equipment power supply low-voltage protection and backup battery switching control circuit system with stable performance: through the design of a hysteresis voltage comparator, frequent circuit switching caused by fluctuations in the vehicle power supply voltage near the critical value is avoided, thereby improving the stability and reliability of the system.

[0117] This patented circuit can detect low battery voltage and promptly disconnect the car battery from the on-board equipment. While protecting the car battery, it can also activate the backup battery of the on-board equipment to extend its operating time, allowing for timely reporting and backup of vehicle information to the cloud server. Through a hysteresis voltage comparator and a MOSFET power control circuit, this patented circuit can disconnect the car battery from the on-board equipment when the battery voltage falls below a certain threshold, while simultaneously activating the power supply to the on-board backup battery.

[0118] 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 low-voltage protection and backup battery switching control circuit for vehicle-mounted equipment, characterized in that, include: The first power conversion circuit has an input terminal connected to the vehicle power supply. Its circuit is connected to a first filter circuit that filters the incoming vehicle power supply and a DC-DC conversion circuit after the input power supply is filtered. The DC-DC conversion circuit outputs a VBAT circuit and a second filter circuit, an overvoltage protection circuit, a voltage detection circuit and a reverse connection protection circuit are set during the process of the DC-DC conversion circuit outputting the VBAT circuit. The second power conversion circuit has an input terminal connected to the vehicle power supply. Its input section is equipped with a current-limiting resistor R115 and filtered by a capacitor C122 before being fed into a voltage regulator U103. The voltage regulator U103 steps down to output the first voltage and sets up a feedback circuit and a third filter circuit on the output circuit branch. The hysteresis comparator circuit has a voltage divider circuit at its input. The input of the voltage divider circuit is connected to the vehicle power supply. The input power supply is divided and then connected to the operational amplifier U102. The input power supply of the operational amplifier U102 is the power output from the voltage regulator U103. The output of the operational amplifier U102 is connected to the first switching transistor circuit. The backup battery switching circuit has a power switching circuit with two MOS switching transistors. The first MOS switching transistor is connected to the backup battery, and the second MOS switching transistor is connected to the first MOS switching transistor in a DS connection structure. The gate circuit of the second MOS switching transistor is connected to the output circuit of the operational amplifier U102.

2. The low-voltage protection and standby battery switching control circuit for a vehicle-mounted device according to claim 1, characterized by The DC-DC conversion circuit is equipped with a DC-DC conversion chip U101, and pin 2 (VIN) of the DC-DC conversion chip U101 is connected to the vehicle power supply.

3. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 2, characterized in that, The first filter circuit includes a first parallel circuit composed of polarized capacitors C105, C106, C107 and C108 connected in parallel. The first terminal of the first parallel circuit is connected to pin 2 VIN of the DC-DC converter chip U101, and its second terminal is grounded. The negative terminal of the polarized capacitor C105 is grounded. The EN pin of the DC-DC converter chip U101 is the enable control pin, which is connected to resistor R101, resistor R102, and the DCDC_EN circuit. The other end of resistor R102 is connected to the vehicle power supply, and the other end of resistor R101 is grounded. The 4th pin RT / CLK of the DC-DC converter chip U101 is the frequency setting pin, which is connected to resistor R103. The other end of resistor R103 is grounded. The 6-pin COMP of the DC-DC converter chip U101 is a compensation pin, which is used for circuit compensation. It is connected to resistor R104 and capacitor C110. The other end of resistor R104 is connected to capacitor C109, the other end of capacitor C109 is grounded, and the other end of capacitor C110 is connected to the ground terminal of capacitor C109. Pin 9, T_GND, of the DC-DC converter chip U101 is grounded; Pin 7 (GND) of the DC-DC converter chip U101 is grounded; Pin 5 (FB) of the DC-DC converter chip U101 is used for output voltage feedback to ensure stable output voltage. Pin 5 (FB) of the DC-DC converter chip U101 is connected to the VSYS_5V_FB circuit.

4. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 2, characterized in that, The second filter circuit is an LC filter circuit, which includes an inductor L102, a capacitor C112, a capacitor C113, a capacitor C114, a capacitor C115, and a capacitor C116. The first end of the inductor L102 is connected to pin 8 (SW) of the DC-DC converter chip U101 and capacitor C111, and the other end of the capacitor C111 is connected to pin 1 (BOOT) of the DC-DC converter chip U101. One end of each of the capacitors C112, C113, C114, C115 and C116 is grounded, and the other end of each is connected to the second end of the inductor L102.

5. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 4, characterized in that, The overvoltage protection circuit includes a TVS transient voltage suppression diode T103. The first terminal of the TVS transient voltage suppression diode T103 is connected to the second terminal of the inductor L102, and its second terminal is grounded.

6. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 4, characterized in that, The voltage detection circuit includes a first series circuit consisting of resistors R105, R106, and R107 connected in sequence. The first end of the first series circuit is connected to the second end of the inductor L102, and the second end of the first series circuit is grounded. The circuit node between resistors R106 and R107 is connected to pin 5 (FB) of the DC-DC converter chip U101. The reverse connection protection circuit includes a Zener diode D102, the positive terminal of which is grounded and the negative terminal is connected to the first end of the inductor L102. The Zener diode D102 prevents the circuit from being damaged when the power supply is reversed.

7. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 2, characterized in that, The voltage regulator U103 has two pins, VIN, connected to capacitor C122, current-limiting resistor R115, and resistor R116 respectively. The other end of the current-limiting resistor R115 is connected to the vehicle power supply, and the other end of capacitor C122 is grounded. The fourth pin (SHDN) of the voltage regulator U103 is the enable pin, which is connected to the other end of the resistor R116. The voltage regulator U103's pin 3 (GND) is grounded; The power output from pin 7 (OUT) of the voltage regulator U103 is fed into the hysteresis comparator circuit. The feedback circuit includes resistors R117 and R118. The first end of the series connection of resistors R117 and R118 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the series connection is grounded. Pin 6 FB of the voltage regulator U103 is connected to the circuit node between resistors R117 and R118; The third filter circuit includes capacitors C123 and C124. The first end of the parallel connection of capacitors C123 and C124 is connected to pin 7 OUT of the voltage regulator U103, and the second end of the parallel connection of capacitors C123 and C124 is grounded.

8. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 2, characterized in that, The voltage divider circuit includes a second series circuit composed of resistors R108, R109 and R110. The first end of the second series circuit is connected to the vehicle power supply and the second end is grounded. The circuit node between resistors R108 and R109 is also connected to capacitor C119, and the other end of capacitor C119 is grounded. The inverting input terminal of the operational amplifier U102 is connected to the circuit node between resistors R108 and R109; The non-inverting input terminal of the operational amplifier U102 is connected to capacitor C120, resistor R119 and resistor R111 respectively. The other end of capacitor C120 is grounded, the other end of resistor R119 is connected to the output terminal of the operational amplifier U102, and the other end of resistor R111 is connected to the VREF pin of the operational amplifier U102. The V+ pin of the operational amplifier U102 is connected to capacitor C118 and the first voltage of the step-down output of the voltage regulator U103. The operational amplifier U102's V- pin is grounded; The output terminal of the operational amplifier U102 is connected to resistor R112, and the other end of resistor R112 is connected to resistor R113, capacitor C121 and BACKUP_EN circuit respectively. The other end of the capacitor C121 is grounded; The first switching transistor circuit includes an N-MOS transistor Q101. The gate of the N-MOS transistor Q101 is connected to the other end of the resistor R113 and the resistor R114. The other end of the resistor R114 is grounded. The source of the N-MOS transistor Q101 is grounded, and its drain is connected to pin 3 EN of the DC-DC converter chip U101.

9. The vehicle-mounted equipment low-voltage protection and backup battery switching control circuit according to claim 8, characterized in that, The first MOS switch is an N-MOS transistor Q102, and the second MOS switch is an N-MOS transistor Q103; An RC circuit is connected between the gate (G) and the drain (D) of the N-MOS transistor Q102. The RC circuit includes a resistor R121 and a capacitor C126 connected in parallel. The drain of the N-MOS transistor Q102 is also connected to a capacitor C125 and a TVS transient suppression diode T104. The other end of the capacitor C125 is grounded, the other end of the TVS transient suppression diode T104 is grounded, and the drain of the N-MOS transistor Q102 is also connected to the positive output of the backup battery. The negative terminal of the backup battery is connected to resistor R120, and the other end of resistor R120 is connected to the battery detection signal pin BAT_ID. The backup battery's pin 3 is grounded; The gate of the N-MOS transistor Q102 is also connected to a resistor R122, and the other end of the resistor R122 is connected to the drain pin of the N-MOS transistor Q103. The S pin of the N-MOS transistor Q102 is connected to the BAT circuit and capacitor C127, and the other end of capacitor C127 is grounded. The S pin of the N-MOS transistor Q103 is grounded; The gate of the N-MOS transistor Q103 is connected to resistors R123 and R124 and capacitor C128, respectively. The other end of resistor R123 is connected to the BACKUP_EN circuit, the other end of resistor R124 is grounded, and the other end of capacitor C128 is grounded.

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