Emergency call system and power supply charging circuit

Abstract

The utility model relates to the technical field of vehicles, in particular to an emergency call system and a power supply charging circuit, and the power supply charging circuit comprises a main control unit, a service life monitoring circuit, a charging unit and an overvoltage monitoring circuit. The charging unit is used for controlling and connecting a main power supply of the vehicle and a standby power supply of the emergency call system; the overvoltage monitoring circuit is used for detecting the open-circuit voltage and the discharge voltage of the standby power supply; the service life monitoring circuit is used for detecting instantaneous discharge current of the standby power supply according to a battery service life test signal; and the main control unit is used for sending the battery life test signal, obtaining the internal resistance of the standby power supply according to the obtained open-circuit voltage, the discharge voltage and the instantaneous discharge current in accordance with a pre-stored formula, and further determining the life of the standby power supply according to the internal resistance of the battery. The power supply charging circuit has a protection function and a service life monitoring function and is low in cost.

Description

Technical Field

[0001] The present application relates to the field of vehicle technology, and in particular to an emergency call system and a power charging circuit. Background Art

[0002] With the increase in the number of cars and the increasing prominence of road traffic safety issues, the automobile emergency call system eCall has been widely used as an important safety technology. When a traffic accident occurs, the rescue center is called manually or automatically, and the location information and timestamp of the accident point are uploaded to facilitate emergency rescue. The backup battery replaces the car battery at critical times and becomes a standard component in the eCall system.

[0003] The backup battery of the eCall system requires environmental protection, safety, reliability and long life, and is suitable for a wide temperature range of automotive environments. After the battery is fully charged once installed in the vehicle, it will basically not be discharged unless the vehicle battery is abnormally disconnected. Therefore, the charging current of the eCall system is small and does not require fast charging, but the charging and discharging process requires common necessary protection measures such as overcharging, overcurrent, overdischarge, and overtemperature. In order to achieve the above functions, the eCall system may require several chips to be used simultaneously. Therefore, the existing eCall system will encounter the following problems:

[0004] 1) There are many types of charge and discharge management chips, but few are automotive grade, and most are consumer grade with high cost;

[0005] 2) Overvoltage and overtemperature monitoring needs to be reported to the main control unit, and the charge and discharge management chip cannot be integrated;

[0006] 3) Existing products only have charging management capabilities and lack life monitoring capabilities. Utility Model Content

[0007] In view of this, the embodiments of the present application provide a low-cost emergency call system and a power charging circuit that have protection functions and life monitoring functions and are low in cost.

[0008] In a first aspect, an embodiment of the present application provides a power charging circuit of an emergency call system, comprising: a main control unit, a life monitoring circuit, a charging unit and an overvoltage monitoring circuit;

[0009] The charging unit is used to control the connection between the main power supply of the vehicle and the backup power supply of the emergency call system;

[0010] The overvoltage monitoring circuit is used to detect the open circuit voltage and discharge voltage of the backup power supply;

[0011] The life monitoring circuit is used to detect the instantaneous discharge current of the backup power supply according to the battery life test signal;

[0012] The main control unit is used to send the battery life test signal, and obtain the internal resistance of the backup power supply according to the acquired open circuit voltage, the discharge voltage and the instantaneous discharge current according to a pre-stored formula, and then determine the life of the backup power supply according to the battery internal resistance.

[0013] In some embodiments, the life monitoring circuit includes a first field effect transistor and a discharge resistor;

[0014] One end of the discharge resistor is used to connect to the backup power supply, and the other end is used to connect to the drain of the first field effect transistor, and the source of the first field effect transistor is used to be grounded; the gate of the first field effect transistor is connected to a test pin of the main control unit; the main control unit is used to send the battery life test signal through the test pin.

[0015] In some embodiments, the charging unit includes a charging circuit and a charging switch circuit; the charging circuit is connected between the main power supply and the backup power supply; the charging switch circuit is used to control the on and off of the charging circuit.

[0016] In some embodiments, the charging switch circuit includes a second field effect transistor and a third field effect transistor; an anti-backflow unit is serially connected to the charging line;

[0017] The source of the second field effect transistor is connected to the main power supply, and the drain is connected to the backup power supply; the gate of the second field effect transistor is connected to the drain of the third field effect transistor;

[0018] The source of the third field effect tube is used for grounding, and the gate of the third field effect tube is used for connecting to the charging control pin of the main control unit; the main control unit is used for sending a charging control signal through the charging control pin to control the conduction of the charging circuit;

[0019] The backflow prevention unit is arranged between the second field effect transistor and the backup power supply, and is used to prohibit the current of the backup power supply from flowing to the main power supply.

[0020] In some embodiments, a current limiting resistor is further connected in series between the second field effect transistor and the backup power supply on the charging line.

[0021] In some embodiments, the overvoltage monitoring circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor;

[0022] One end of the first voltage-dividing resistor is used to connect to the backup power supply, and the other end is connected to one end of the second voltage-dividing resistor; the other end of the second voltage-dividing resistor is used to ground;

[0023] The main control unit is connected to the series node between the first voltage-dividing resistor and the second voltage-dividing resistor via a voltage sampling pin, so as to collect and obtain the open-circuit voltage or the discharge voltage.

[0024] In some embodiments, the overvoltage monitoring circuit further includes a low-pass filter; the low-pass filter is connected in parallel with the second voltage-dividing resistor.

[0025] In some embodiments, an over-temperature protection circuit is also included; the backup power supply includes a built-in temperature sensor;

[0026] The over-temperature protection circuit comprises a pull-up resistor; one end of the pull-up resistor is used to connect to the working power supply; the other end of the pull-up resistor is connected to the temperature sensor;

[0027] The main control unit is connected to the series node between the pull-up resistor and the temperature sensor through a voltage division collection pin, so as to collect the voltage division of the temperature sensor.

[0028] In some embodiments, the over-temperature protection circuit includes a transient voltage suppression diode and a capacitor;

[0029] One end of the transient voltage suppression diode and the capacitor are both connected to the series node between the pull-up resistor and the temperature sensor, and the other ends are both grounded.

[0030] In a second aspect, an embodiment of the present application provides an emergency call system, which includes a backup power supply and also includes: a power charging circuit for the emergency call system provided in the first aspect of the present application.

[0031] The embodiments of the present application have the following beneficial effects:

[0032] The power charging circuit in the present application is used to control the backup power supply connected to the main power supply of the vehicle and the emergency call system; the overvoltage monitoring circuit is used to detect the open circuit voltage and discharge voltage of the backup power supply; the life monitoring circuit is used to detect the instantaneous discharge current of the backup power supply according to the battery life test signal; the main control unit is used to send the battery life test signal, and obtain the internal resistance of the backup power supply according to the acquired open circuit voltage, the discharge voltage and the instantaneous discharge current according to the pre-stored formula, and then determine the life of the backup power supply according to the battery internal resistance. The present application not only realizes overvoltage protection through the overvoltage monitoring circuit, but also can monitor the life of the backup power supply in combination with the life monitoring circuit. The circuits complement each other, are simple to construct and low in cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram showing a structure of a power supply charging circuit of an emergency call system according to an embodiment of the present application is shown;

[0035] Figure 2 A circuit diagram showing a power charging circuit of an emergency call system according to an embodiment of the present application;

[0036] Figure 3 Another structural schematic diagram of the power charging circuit of the emergency call system according to an embodiment of the present application is shown.

[0037] Description of main component symbols:

[0038] 100-main control unit; 200-charging unit; 210-charging switch circuit; 300-life monitoring circuit; 400-overvoltage monitoring circuit; 500-backup power supply; 600-main power supply; 700-overtemperature protection circuit. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0040] The components of the embodiments of the present application generally described and shown in the drawings herein may be arranged and designed in various configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

[0041] Hereinafter, the terms "including", "having" and their cognates that can be used in various embodiments of the present application are intended only to indicate specific features, numbers, steps, operations, elements, components or a combination of the foregoing items, and should not be understood as first excluding the existence of one or more other features, numbers, steps, operations, elements, components or a combination of the foregoing items or increasing the possibility of one or more features, numbers, steps, operations, elements, components or a combination of the foregoing items. In addition, the terms "first", "second", "third" and the like are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance.

[0042] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meanings as those generally understood by those skilled in the art to which the various embodiments of the present application belong. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meanings as the contextual meanings in the relevant technical field and will not be interpreted as having idealized meanings or overly formal meanings unless clearly defined in the various embodiments of the present application.

[0043] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0044] The present application proposes a low-cost emergency call system and a power charging circuit with protection function and life monitoring function.

[0045] The power charging circuit of the emergency call system is described below in conjunction with some specific embodiments.

[0046] Figure 1 A schematic diagram of a power charging circuit of an emergency call system according to an embodiment of the present application is shown. Exemplarily, the power charging circuit of the emergency call system includes: a main control unit 100 , a charging unit 200 , a life monitoring circuit 300 and an overvoltage monitoring circuit 400 .

[0047] The charging unit 200 is used to control the connection between the main power supply 600 of the vehicle and the backup power supply 500 of the emergency call system.

[0048] The overvoltage monitoring circuit 400 is used to detect the open circuit voltage and the discharge voltage of the backup power supply 500 .

[0049] The life monitoring circuit 300 is used to detect the instantaneous discharge current of the backup power supply 500 according to the battery life test signal.

[0050] The main control unit 100 is used to send the battery life test signal, and obtain the internal resistance of the backup power supply 500 according to the obtained open circuit voltage, the discharge voltage and the instantaneous discharge current according to a pre-stored formula, and then determine the life of the backup power supply 500 according to the battery internal resistance. The main control unit 100 can be an MCU.

[0051] Wherein, the pre-stored formula is: R 电池represents the internal resistance of the backup power supply (also called the internal resistance of the backup battery); V1 represents the open circuit voltage, that is, the voltage value of the backup power supply 500 when it is not discharged; V2 represents the instantaneous discharge voltage of the backup power supply; Itest represents the test current of the instantaneous discharge. The open circuit voltage V1 and the instantaneous discharge voltage V2 of the backup power supply are respectively measured by the overvoltage monitoring circuit 400 of the backup battery (backup power supply).

[0052] In one embodiment, the charging unit 200 includes a charging circuit and a charging switch circuit 210; the charging circuit is connected between the main power supply 600 and the backup power supply 500; the charging switch circuit 210 is used to control the on and off of the charging circuit.

[0053] Furthermore, if Figure 2 As shown, the charging line is provided with an anti-backflow unit D1 in series; the charging switch circuit 210 includes a second field effect transistor Q2 and a third field effect transistor Q3.

[0054] The source of the second field effect transistor Q2 is connected to the main power supply 600, and the drain is connected to the backup power supply 500; the gate of the second field effect transistor Q2 is connected to the drain of the third field effect transistor Q3;

[0055] The source of the third field effect transistor Q3 is used for grounding, and the gate of the third field effect transistor Q3 is used for connecting the charging control pin of the main control unit 100; the main control unit 100 is used to send a charging control signal BAT_CHRG_EN through the charging control pin to control the conduction of the charging circuit. Exemplarily, the charging switch circuit 210 is implemented using a common PMOS+NMOS field effect transistor. The second field effect transistor Q2 is a PMOS tube, and the third field effect transistor Q3 is an NMOS tube. The anti-backflow unit is arranged between the second field effect transistor and the backup power supply 500, and is used to prohibit the current of the backup power supply 500 from flowing to the main power supply. For example, the anti-backflow unit is a diode D1. In the absence of the main power supply 600, due to the unidirectional conduction characteristics of the diode D1, the current of the backup battery is prevented from flowing back into the main power supply 600.

[0056] Furthermore, a current limiting resistor R2 is also provided in series between the second field effect transistor and the backup power supply 500 on the charging circuit. The current limiting resistor R2 serves to limit the charging current, and the maximum charging current is limited to within 100mA. Generally, the over-discharge protection voltage of the backup battery is 2.8V, the current limiting resistor R2 is 22R, and the charging current I CHRG =(5V-2.8VV F ) / 22R≈100mA. The maximum power consumption of the current limiting resistor R2 is P R2 =I CHRG 2 *R2=100mA2 *22R = 0.22W, where V F Represents the forward voltage of the Schottky diode, for example, V F is 0.2V.

[0057] Furthermore, the charging switch circuit 210 further includes a first resistor R1 and a fourth resistor R4, wherein one end of the first resistor R1 is connected to the source of the second field effect transistor Q2, and the other end is connected to the gate of the second field effect transistor Q2. One end of the fourth resistor R4 is connected to the source of the third field effect transistor Q3, and the other end is connected to the gate of the third field effect transistor Q3.

[0058] Specifically, when the main control unit 100 detects that the backup battery is under-voltage, the main control unit 100 outputs a charging control signal BAT_CHRG_EN to control the third field effect transistor Q3 to be turned on, the drain of the third field effect transistor Q3 is pulled low, and at the same time, the gate of the second field effect transistor Q2 is pulled low, and the gate-source voltage of the second field effect transistor Q2 is greater than the turn-on voltage V GS2 , the second field effect transistor Q2 is turned on, and the 5V voltage of the main power supply 600 flows through the current limiting resistor R2 to charge the battery pack of the backup battery. In addition, the main control unit 100 is also used to monitor the current, charging voltage, and discharging voltage of the charging circuit to achieve overcharge, overcurrent, and overdischarge protection for the backup battery.

[0059] In one embodiment, if Figure 2 As shown, the overvoltage monitoring circuit 400 includes a first voltage dividing resistor R8 and a second voltage dividing resistor R9.

[0060] One end of the first voltage-dividing resistor R8 is used to connect to the backup power supply 500, and the other end is connected to one end of the second voltage-dividing resistor R9; the other end of the second voltage-dividing resistor R9 is used to be grounded;

[0061] The main control unit 100 is connected to the series node between the first voltage-dividing resistor R8 and the second voltage-dividing resistor R9 via a voltage sampling pin, so as to collect and obtain the open-circuit voltage V1 or the discharge voltage V2.

[0062] Furthermore, the overvoltage monitoring circuit 400 further includes a low-pass filter, which is connected in parallel with the second voltage-dividing resistor. The low-pass filter may be a capacitor C1.

[0063] Specifically, the voltage division values ​​of the two voltage division resistors R8 and R9 are sent to the main control unit 100 for ADC sampling, and the main control unit 100 identifies the current voltage value of the backup battery and determines whether it is overcharged or undervoltage. Capacitor C1 acts as a low-pass filter to prevent the main control unit 100 from misjudging due to unstable ADC sampling voltage.

[0064] In one embodiment, if Figure 2 As shown, the life monitoring circuit 300 includes a first field effect transistor Q1 and a discharge resistor R7;

[0065] One end of the discharge resistor R7 is used to connect the backup power supply 500, and the other end is used to connect the drain of the first field effect transistor Q1, and the source of the first field effect transistor Q1 is used to ground; the gate of the first field effect transistor Q1 is connected to a test pin of the main control unit 100; the main control unit 100 is used to send the battery life test signal BAT_TEST through the test pin. The first field effect transistor Q1 can be an NMOS tube, because the conduction internal resistance of NMOS is small, while if a bipolar transistor is used, the internal resistance is large in the saturated conduction state, and the loss is large.

[0066] The backup battery life monitoring circuit 300 is implemented using the principle that the battery life is accompanied by the increase of the battery internal resistance. The battery capacity is a key indicator of the battery life. When the capacity is less than 60%, it is generally considered that the battery life has expired. By calculating the size of the battery internal resistance value, the battery capacity at the current temperature is analyzed by looking up the table and judging whether the battery life has expired.

[0067] I TEST is the instantaneous discharge test current (instantaneous discharge current), the test current I TEST =V2 / R7, substitute into the above formula back, The instantaneous discharge is composed of a discharge resistor R7 and an NMOS tube Q1. The main control unit 100 outputs a battery life test signal BAT_TEST, which is responsible for controlling the conduction of the NMOS tube Q1. The battery actively discharges to the ground instantaneously through the discharge resistor R7. At the same time, the backup battery V1 and the backup power supply instantaneous discharge voltage V2 are calculated through the overvoltage monitoring circuit 400. The relationship between the battery internal resistance and the battery capacity at different ambient temperatures is shown in Table 1. In addition, in addition to providing an active discharge circuit, the discharge resistor R7 also plays a role in current limiting. The backup battery of the present application has a built-in over-discharge short-circuit protection function.

[0068] Table 1 Relationship between battery internal resistance and battery capacity at different ambient temperatures

[0069]

[0070] In one embodiment, if Figure 3 As shown, the over-temperature protection circuit 700 is also included; the backup power supply 500 includes a built-in temperature sensor. The temperature sensor can be a thermistor R NTC .

[0071] The over-temperature protection circuit 700 includes a pull-up resistor R10, one end of which is used to connect to a working power supply, and the other end of which is connected to the temperature sensor. The working power supply can be used to power the IO pin of the main control unit 100 (MCU), and the pull-up voltage is 3.3V.

[0072] The main control unit 100 is connected to the series node between the pull-up resistor and the temperature sensor via a voltage division collection pin, so as to collect the voltage division of the temperature sensor.

[0073] Thermistor R NTC The voltage division value of the pull-up resistor R10 is sent to the main control unit for ADC sampling. The negative temperature characteristic of the thermistor is used. When the temperature rises, the resistance value decreases. The main control unit 100 calculates the resistance value of the thermistor to look up the table to determine the current temperature of the thermistor, that is, the battery pack temperature, so as to diagnose whether the battery pack is overheated. The thermistor values ​​of the backup battery at different temperatures are shown in Table 2.

[0074] Table 2 Examples of thermistor values ​​of backup batteries at different temperatures

[0075]

[0076] Further, the over-temperature protection circuit 700 includes a transient voltage suppression diode and a capacitor;

[0077] One end of the transient voltage suppression diode and the capacitor are both connected to the series node between the pull-up resistor and the temperature sensor, and the other ends are grounded. The transient voltage suppression diode D2 prevents static electricity from being introduced from the battery pack to damage the IO pins of the main control unit (MCU).

[0078] This application utilizes the existing software and hardware resources of the main control unit (MCU), adopts discrete devices, and simply builds field effect tubes and resistors to meet the basic requirements of backup battery charging overcharge, overcurrent, overdischarge and overtemperature, and realizes reliable backup battery charging management functions at low cost. Combined with the technical parameters of the backup battery, overtemperature monitoring and battery life monitoring functions are realized.

[0079] The present application also provides an emergency call system, which includes a backup battery and a power charging circuit of the emergency call system, which charges and discharges the backup power supply 500, and monitors and protects the backup power supply 500. The power charging circuit is connected to the battery (main power supply 600) of the vehicle.

[0080] It can be understood that the options in the above embodiment are also applicable to this embodiment, so they will not be described again here.

[0081] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A power charging circuit for an emergency call system, characterized in that: include: Main control unit, charging unit, life monitoring circuit and overvoltage monitoring circuit; The charging unit is used to control the connection between the main power supply of the vehicle and the backup power supply of the emergency call system; The overvoltage monitoring circuit is used to detect the open circuit voltage and discharge voltage of the backup power supply; The life monitoring circuit is used to detect the instantaneous discharge current of the backup power supply according to the battery life test signal; The main control unit is used to send the battery life test signal, and obtain the internal resistance of the backup power supply according to the acquired open circuit voltage, the discharge voltage and the instantaneous discharge current according to a pre-stored formula, and then determine the life of the backup power supply according to the battery internal resistance.

2. The power charging circuit of the emergency call system according to claim 1, characterized in that: The life monitoring circuit includes a first field effect transistor and a discharge resistor; One end of the discharge resistor is used to connect the backup power supply, and the other end is used to connect the drain of the first field effect transistor, and the source of the first field effect transistor is used to be grounded; the gate of the first field effect transistor is connected to a test pin of the main control unit; the main control unit is used to send the battery life test signal through the test pin.

3. The power charging circuit of the emergency call system according to claim 1, characterized in that: The charging unit includes a charging circuit and a charging switch circuit; the charging circuit is connected between the main power supply and the backup power supply; the charging switch circuit is used to control the on and off of the charging circuit.

4. The power charging circuit of the emergency call system according to claim 3, characterized in that: The charging switch circuit includes a second field effect transistor and a third field effect transistor; an anti-backflow unit is serially connected to the charging line; The source of the second field effect transistor is connected to the main power supply, and the drain is connected to the backup power supply; the gate of the second field effect transistor is connected to the drain of the third field effect transistor; The source of the third field effect tube is used for grounding, and the gate of the third field effect tube is used for connecting to the charging control pin of the main control unit; the main control unit is used for sending a charging control signal through the charging control pin to control the conduction of the charging circuit; The backflow prevention unit is arranged between the second field effect transistor and the backup power supply, and is used to prohibit the current of the backup power supply from flowing to the main power supply.

5. The power charging circuit of the emergency call system according to claim 4, characterized in that: A current limiting resistor is also serially arranged between the second field effect transistor and the backup power supply on the charging circuit.

6. The power charging circuit of the emergency call system according to claim 1, characterized in that: The overvoltage monitoring circuit includes a first voltage-dividing resistor and a second voltage-dividing resistor; One end of the first voltage-dividing resistor is used to connect to the backup power supply, and the other end is connected to one end of the second voltage-dividing resistor; the other end of the second voltage-dividing resistor is used to ground; The main control unit is connected to the series node between the first voltage-dividing resistor and the second voltage-dividing resistor via a voltage sampling pin, so as to collect and obtain the open-circuit voltage or the discharge voltage.

7. The power charging circuit of the emergency call system according to claim 6, characterized in that: The overvoltage monitoring circuit also includes a low-pass filter; the low-pass filter is connected in parallel with the second voltage-dividing resistor.

8. The power charging circuit of the emergency call system according to claim 1, characterized in that: Also includes an over-temperature protection circuit; the backup power supply includes a built-in temperature sensor; The over-temperature protection circuit comprises a pull-up resistor; one end of the pull-up resistor is used to connect to the working power supply; the other end of the pull-up resistor is connected to the temperature sensor; The main control unit is connected to the series node between the pull-up resistor and the temperature sensor through a voltage division collection pin, so as to collect the voltage division of the temperature sensor.

9. The power charging circuit of the emergency call system according to claim 8, characterized in that: The over-temperature protection circuit includes a transient voltage suppression diode and a capacitor; One end of the transient voltage suppression diode and the capacitor are both connected to the series node between the pull-up resistor and the temperature sensor, and the other ends are both grounded.

10. An emergency call system, characterized in that: The emergency call system includes a backup power supply and also includes: a power charging circuit for the emergency call system according to any one of claims 1 to 9.

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