Intelligent switch control device between lead-acid battery positive electrode and DCDC positive electrode

Abstract

An intelligent switch control device between a lead-acid battery positive electrode and a DCDC positive electrode comprises an MCU control unit and a plurality of driving chips connected with the MCU control unit, each driving chip is connected with a switch MOS tube, and the switch MOS tubes are connected in series between a DC / DC and a lead-acid battery BAT; the model of the driving chip is 2ED2410-EM, and the driving chip is also connected with a current acquisition circuit, a short-circuit protection circuit, an overcurrent protection circuit and an over-temperature protection circuit. According to the technical scheme of the utility model, the intelligent on-off control of the 12V, 24V and 48V vehicle-mounted power supplies is realized by adopting the driving chip and the MOS, and the intelligent on-off control circuit is mainly applied to the on-off control between the positive electrode of the lead-acid battery and the load or between the positive electrode of the lead-acid battery and the DCDC. By detecting the charging current, the discharging current, the temperature and the voltage, the state diagnosis and the fault protection of the lead-acid battery, the DCDC and the connecting wire harness are realized.

Description

Technical Field

[0001] The utility model relates to an intelligent switch control device between a positive electrode of a lead-acid battery and a positive electrode of a DCDC. Background Art

[0002] As the reliability requirements of electronic components in vehicles continue to increase, it is necessary to monitor the vehicle's current, voltage and temperature of high-current terminals in real time, and take timely protective measures when abnormalities are found.

[0003] With the popularity of pure electric vehicles, the requirements for functional safety of the whole vehicle are getting higher and higher. At present, DCDC and the positive electrode of the lead-acid battery are generally directly connected. When an abnormal short circuit occurs in the DCDC, it will affect the voltage of the lead-acid battery, thereby causing abnormal power supply of the whole vehicle, and the function of the electrical components of the whole vehicle will fail quickly, making it impossible to avoid the danger source in an emergency and achieve the functional safety goal. To avoid the above problems, the existing technology generally adopts the following two methods:

[0004] The first type: After the positive electrode of the lead-acid battery is output, a fuse and a main power relay are connected in series, and the normally open contact wiring of the relay is connected to the positive electrode of the DCDC to supply power to the subsequent electrical components;

[0005] The second type: the positive output of the lead-acid battery is directly connected to the positive pole of the DCDC after a series fuse to supply power to the subsequent electrical components.

[0006] The existing technical solutions have the following disadvantages:

[0007] 1. There is no current detection function, and the charge and discharge current of the lead-acid battery and the output current of the DCDC cannot be detected in real time. When the subsequent power-taking equipment is abnormal, causing the power current to be too large, it cannot be obtained in time and necessary protection measures cannot be taken in time.

[0008] 2. There is no voltage detection function, and the lead-acid battery voltage and relay contact pressure difference cannot be detected in real time. When the power supply voltage is abnormal, it cannot be obtained in time and necessary protective measures cannot be taken in time.

[0009] 3. There is no temperature detection function. When the terminal becomes loose, causing abnormal heating, it is impossible to obtain the information in time and take necessary protective measures in time.

[0010] 4. The reliability of the relay is not high, and it is easy to have contact erosion, adhesion, and icing failures, resulting in abnormal power supply to the entire vehicle.

[0011] 5. After an abnormal short circuit occurs in the DCDC, it cannot be quickly disconnected from the lead-acid battery, affecting the entire vehicle from entering a safe working state. Utility Model Content

[0012] The technical problem to be solved by the utility model is that the traditional main power switch is prone to contact erosion, low-temperature icing, contact adhesion, and short service life, and is unable to diagnose and protect faults, cannot meet high reliability requirements, is difficult to maintain in the later stage, and has high wiring harness costs. The utility model provides an intelligent switch control between the positive electrode of a lead-acid battery and the load, and between the positive electrode of the lead-acid battery and the positive electrode of a DCDC.

[0013] In order to achieve the above object, the utility model is realized by the following technical solutions:

[0014] An intelligent switch control device between a positive electrode of a lead-acid battery and a positive electrode of a DC / DC, characterized in that it comprises an MCU control unit and a plurality of drive chips connected thereto, each drive chip is connected to a switch MOS tube, and the switch MOS tube is connected in series between the DC / DC and the lead-acid battery BAT;

[0015] The model of the driving chip is 2ED2410-EM, and the driving chip is also connected to a current collection circuit, a short circuit protection circuit, an overcurrent protection circuit and an overtemperature protection circuit.

[0016] The current acquisition circuit adopts a differential current acquisition circuit, and the differential current acquisition input is connected to both ends of the SHUNT resistor.

[0017] The switching MOS tube uses four groups of back-to-back MOSFETs in parallel, with a total of 8 MOSFETs; the GA and SA of the driver chip control the gate and source of the four parallel MOSFETs, and GB and SB control the gate and source of another four parallel MOSFETs. By controlling the gate-source voltage of the MOS, the opening and closing of the MOS are controlled.

[0018] Compared with the prior art, the utility model has the following advantages: the utility model adopts the driver chip + MOS method to realize the intelligent switch control of 12V, 24V, and 48V vehicle power supplies, and is mainly used for on-off control between the positive electrode of the lead-acid battery and the load, or between the positive electrode of the lead-acid battery and the DCDC; by detecting the charging current, discharging current, temperature, and voltage, the status diagnosis and fault protection of the lead-acid battery, the DCDC, and the connecting harness are realized.

[0019] 1. It has current detection function, which can detect the charge and discharge current of lead-acid battery and the output current of DCDC in real time. When the downstream power-taking equipment is abnormal and the power current is too large, it can obtain the current in time and take necessary protection measures in time.

[0020] 2. It has voltage detection function, which can detect the voltages at both ends of DCDC, BAT and MOS switch in real time. When the power supply voltage is abnormal, it can be obtained in time and necessary protection measures can be taken in time.

[0021] 3. It has a temperature collection function. When the terminal is loose or the MOS switch is not fully opened, resulting in abnormal heating, the temperature can be obtained in time and necessary protective measures can be taken in time.

[0022] 4. The switch life of MOS meets the vehicle's 15-year full-operation operating conditions, reducing after-sales maintenance costs.

[0023] 5. When an abnormal short circuit occurs in DCDC, it can be quickly disconnected from the lead-acid battery and the fault can be reported. The lead-acid battery power is used to allow the vehicle to have sufficient time to park safely and avoid emergency accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the principle diagram of the utility model;

[0025] Figure 2 This is the schematic diagram of the driver chip;

[0026] Figure 3 Electrical schematics for current collection;

[0027] Figure 4 This is the electrical schematic diagram for overcurrent protection;

[0028] Figure 5 Electrical schematic diagram for temperature acquisition;

[0029] Figure 6 This is the reference power derating curve. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0032] like Figure 1 , Figure 2As shown, an intelligent switch control device between the positive electrode of a lead-acid battery and the positive electrode of a DCDC includes an MCU control unit and multiple drive chips connected thereto, each drive chip is connected to a switch MOS tube, and the switch MOS tube is connected in series between the DC / DC and the lead-acid battery BAT.

[0033] To ensure that the DC / DC and the lead-acid battery BAT support a rated continuous current of ±150A and a current capacity of 200A for 30 minutes; in the sleep state, the lead-acid battery BAT power supply switch of the distribution network remains closed, and the sleep current is less than 100uA.

[0034] In this way, since the lead-acid battery BAT has a designed current capacity of 200A, the thermal design requirements of the circuit are relatively high; and for the short-circuit protection current of 600A, the protection instantaneous surge voltage protection design requirements are relatively high; in addition, when the subsequent load power output has an instantaneous high current demand such as a short circuit, the influence of the power lead inductance on the current change rate causes an abnormal drop in the power supply voltage, which has an impact on the working state of the whole machine and is difficult to design.

[0035] To this end, in the utility model, the model of the driver chip is 2ED2410-EM, and the working voltage is 8V~36V, which meets the design requirements of bidirectional current and bidirectional switching circuit. The driver chip is also connected to a current acquisition circuit, a short-circuit protection circuit, an overcurrent protection circuit and an over-temperature protection circuit. The collected analog signal is connected to the AD pin of the MCU control unit. The MCU control unit controls the driver chip to open or close the switch MOS tube according to the collected data, thereby realizing intelligent switching control of the power supply; it perfectly replaces the traditional control method of relay plus fuse.

[0036] The driver chip has a built-in bidirectional current acquisition function, which can collect the bidirectional current flowing through the MOSFET switch. However, the error of the pre-driver built-in op amp is large; if you want to improve the current sampling accuracy, you can add an ultra-high precision op amp acquisition.

[0037] like Figure 2 As shown, in the utility model, the driving chip is connected to a current collection circuit, the current collection circuit adopts a differential current collection circuit, and the differential current collection input is connected to both ends of the SHUNT resistor.

[0038] CSOx is connected to the AD input pin of the MCU control unit to calculate the power supply current;

[0039] DG1 is connected to the GPIO pin of the MCU control unit, and the direction of the current is determined by the state of DG1;

[0040] By changing the resistance values ​​of Risx and Rcsox, the current collection gain can be adjusted;

[0041] Driver chip current acquisition gain G = Rcs0 / Ris;

[0042] Load current I f calculate:

[0043] I f = Vcs0x / (Rshunt*Rcs0 / Ris)

[0044] CSOx pin voltage Vcs0x=|Vshunt|*(Rcs0 / Ris)

[0045] Sampling resistor value Rshunt=200 / 3(uΩ)

[0046] Driver chip CSOx foot pull-down resistor Rcs0=20K

[0047] The driver chip current collection input feedback resistor Ris=213Ω.

[0048] like Figure 3 As shown, the short-circuit protection is implemented by the driver chip, and the short-circuit protection time is: maximum 10uS (short circuit and the gate voltage drops to 80%), and the short-circuit current can be set by adjusting the hardware parameters. The short-circuit current of the utility model is Ishunt=600A.

[0049] Parameter adjustment principle: When the voltage of the CSO1 port exceeds the Ven*Kcs0 value, the short-circuit protection is triggered and the chip enters a safe state. The MCU can obtain the working status of the driver chip through the INT, DG1, and DG0 pin states.

[0050] Theoretical calculation process:

[0051] Short circuit protection current I d :I d = (Ven* Kcs0 / G) / Shunt

[0052] Design voltage value Ven = 5V; (EN pin voltage, ±0.1V)

[0053] Chip design value Kcs0 = 0.74 (±0.03)

[0054] Current sampling resistor value Shunt = 67uΩ (±1%)

[0055] Driver chip current acquisition gain G = Rcs0 / Ris;

[0056] Calculation process of Gcs0:

[0057] Vshunt = 600A * 0.000067Ω = 40mV

[0058] Vcso(th) = Kcs0 * Ven = 0.74*5=3.7V

[0059] Gcs0= Vcso(th) / Vshunt = 93.25

[0060] Risp=Risn = Rcs0 / Gcs0 = 20000 / 93.25 = 214Ω

[0061] Tentative: Risp = Risn = 213Ω; Rcs0 = 20K

[0062] Gcs0 = 20K / 213Ω = 93.9

[0063] Theoretical calculation of short-circuit protection current I d = (Ven* Kcs0 / G) / Shunt = 593A.

[0064] Short circuit protection time: maximum 10uS (short circuit and gate voltage drops to 80%).

[0065] like Figure 4 As shown, the driver chip has an overcurrent protection function, and the protection time is different for different overcurrent values. The disadvantage is that it cannot be configured through software, and a protection current value can only be set through the hardware circuit.

[0066] In the utility model, the overcurrent protection of DCDC is realized by a driving chip, the driving chip sets a protection value of a larger current, and the software configures a protection value of a smaller current.

[0067] The hardware setting protection start current is 240A, and the protection time is 4S;

[0068] The hardware sets the protection point current to 375A and the protection time to 1mS; (corresponding to the red line, the sampling resistance is 67uΩ)

[0069] The software overload threshold is set to 240A, 300mS.

[0070] like Figure 5 As shown, the driver chip is connected to a temperature acquisition circuit, which implements the MOS temperature acquisition function, converts the temperature into a voltage value, and sends it to the MCU control unit for acquisition. The NTC resistor is placed close to the D pole of the MOSFET.

[0071] Calculation formula:

[0072] Vtmpo = (Ven / Ktmp+Vtmp(offset))*Rtmpo / (Rntc+Rtmp)=0.417V

[0073] Rntc = (Ven / Ktmp+Vtmp(offset))*Rtmpo / Vtmpo – Rtmp

[0074] in:

[0075] Design voltage value Ven = 5V;

[0076] Chip design value Ktmp = 10 (±0.5);

[0077] Chip temperature input offset Vtmp(offset) = 0mV (±10mV);

[0078] Chip TMP pin feedback resistor Rtmpo = 100KΩ;

[0079] NTC resistor value Rntc = 100KΩ; (25℃)

[0080] The chip TMPO pin voltage collection resistor Rtmp = 20KΩ.

[0081] According to the DCDC overcurrent protection parameter design, the Shunt resistor value is 67uΩ;

[0082] The power consumption of a single Shunt resistor at 68A is: =68A*68A*0.0002Ω =0.92W;

[0083] The utility model selects three Shunt resistors with a resistance value of 200 uΩ, an accuracy of ±1%, and a 7W to be connected in parallel.

[0084] According to the resistance derating curve, when the operating temperature is 105°C, the resistance should be derated by 60% to 4.2W.

[0085] Refer to the resistor selection specification and use it at 2.1W with a 50% derating; the power consumption requirement of 0.92W at 68A is met;

[0086] Reference power derating curve as follows Figure 6 shown.

[0087] Furthermore, the switch MOS tube uses four groups of Back to Back MOSFET in parallel, with a total of 8 MOSFETs. The GA and SA of the driver chip control the gate and source of the four parallel MOSFETs, and the GB and SB control the gate and source of the other four parallel MOSFETs. By controlling the gate-source voltage of the MOS, the MOS is controlled to be opened and closed.

[0088] The MOSFET model selected is IAUA250N04S6N005. According to the thermal simulation parameters, when the current is 150A, the maximum temperature rise of the MOSFET is 32 degrees Celsius; calculated based on the ambient temperature of 105℃, it meets the 80% derating design requirement; when the current is 200A in steady state, the maximum temperature rise of the MOSFET is 52 degrees Celsius; calculated based on the ambient temperature of 105℃, it meets the 90% derating design requirement.

[0089] The utility model uses NTC resistors to detect the temperature at the terminals of DCDC and lead-acid batteries. Through testing, the terminal temperature corresponding to the NTC resistor voltage is calibrated and pre-stored in the DFLASH of the MCU control unit. When the terminal temperature is too high, an early warning is issued, and the alarm temperature can be set. The default high temperature alarm is greater than 125°C. At the same time, the high temperature disconnection threshold can be set to prevent the wiring harness from catching fire.

[0090] The NTC resistor 1 end is in the same network as the DCDC or lead-acid battery voltage, and the entire device is copper-plated and placed close to the terminal.

[0091] The accuracy of NTC resistor and voltage divider resistor is ±1%;

[0092] Temperature detection range: -40℃-150℃.

[0093] In case of DCDC undervoltage fault, when the voltage is lower than the threshold, the power switch will be disconnected within 100us without affecting the battery power supply; DCDC undervoltage protection is determined by hardware parameters and cannot be configured.

[0094] When the DCDC fails to operate at overvoltage, the power supply switch will be disconnected within 100ms without affecting the battery power supply.

[0095] The DCDC overvoltage and DCDC undervoltage faults are recorded through fault codes, and the fault codes and the number of times the faults occur are recorded; the fault information can be reported to the entire vehicle.

[0096] The utility model provides an intelligent switch control between a positive electrode of a lead-acid battery and a load, or between a positive electrode of a lead-acid battery and a positive electrode of a DCDC.

[0097] The utility model adopts a driving chip with EFUSE, low sleep current, dual-way switch control output, current collection, and temperature collection functions, so that the intelligent switch has two-way flow, two-way switch, short circuit protection, overload protection, and over-temperature protection functions, and can perfectly replace the traditional control method of relay plus fuse between DCDC and lead-acid battery.

[0098] The intelligent switch of the utility model adopts 4 groups of back-to-back MOS in parallel, supports a rated continuous current of ±150A, and a current capacity of 200A for 30 minutes (the current capacity can be improved by adjusting some devices and circuit parameters).

[0099] The intelligent switch of the utility model meets the functional safety ASIL D requirements in terms of diagnostic function, power distribution architecture and device selection, and complies with the functional safety requirements of the entire vehicle.

[0100] The above is only a preferred embodiment of the present invention. It should be pointed out that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be regarded as the protection scope of the present invention.

Claims

1. An intelligent switch control device between the positive electrode of a lead-acid battery and the positive electrode of a DCDC, characterized in that: It includes an MCU control unit and a plurality of driver chips connected thereto, each driver chip is connected to a switch MOS tube, and the switch MOS tube is connected in series between the DC / DC and the lead-acid battery BAT; The model of the driving chip is 2ED2410-EM, and the driving chip is also connected to a current acquisition circuit, a short circuit protection circuit, an overcurrent protection circuit and an overtemperature protection circuit.

2. The intelligent switch control device between the positive electrode of a lead-acid battery and the positive electrode of a DCDC according to claim 1, characterized in that: The current acquisition circuit adopts a differential current acquisition circuit, and the differential current acquisition input is connected to both ends of the SHUNT resistor.

3. The intelligent switch control device between the positive electrode of a lead-acid battery and the positive electrode of a DCDC according to claim 1, characterized in that: The switching MOS tube uses four groups of back-to-back MOSFETs in parallel, with a total of 8 MOSFETs; the GA and SA of the driver chip control the gate and source of the four parallel MOSFETs, and GB and SB control the gate and source of another four parallel MOSFETs. By controlling the gate-source voltage of the MOS, the opening and closing of the MOS are controlled.

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