High-low voltage power supply control system and method for electric vehicle

Abstract

The invention discloses a low-voltage power supply control system and method for an electric vehicle. The system comprises a power battery pack and a low-voltage module composed of the same battery cell as a power battery. The low-voltage module is arranged in the power battery pack, and the low-voltage module is physically isolated from a high-voltage power supply cell in the power battery pack; the high-voltage output end of the power battery pack is connected with the low-voltage power supply network through the DCDC module, and the low-voltage output end of the low-voltage module is connected to the low-voltage power supply network. The system has the advantages that a low-voltage storage battery is omitted, so that the cost of the storage battery is saved; low-voltage power supply is provided through DCDC conversion of the power battery, and low-voltage power supply backup is carried out by adopting modules in the battery pack, so that redundancy reliability of low-voltage power supply is realized.

Description

Technical Field

[0001] This invention relates to the field of low-voltage power supply for automobiles, and particularly to a low-voltage power supply control system and method for electric vehicles based on a power battery pack. Background Technology

[0002] In existing new energy vehicles, the vehicle's low-voltage electrical system (such as VCU, BMS, headlights, audio system, body controller, gateway, etc.) is typically powered in two ways:

[0003] 1. Power is supplied by a high-voltage battery after being stepped down by a DC-DC converter;

[0004] 2. Powered by a separate 12V or 24V lead-acid battery, which is then charged by a DC-DC converter.

[0005] Current technologies generally employ a solution of "high-voltage power battery + DC-DC converter + lead-acid battery". In this solution, the lead-acid battery serves as a buffer and backup for the low-voltage power supply.

[0006] Disadvantages of traditional lead-acid battery solutions:

[0007] 1. High cost: Requires additional lead-acid batteries.

[0008] 2. Heavy / Large: Lead-acid batteries have low energy density, are heavy, and occupy a large amount of space in the front compartment of the vehicle.

[0009] 3. Short cycle life: The cycle life of lead-acid batteries is much shorter than that of lithium-ion power batteries, with a cycle life of only 300-500 cycles. They need to be replaced regularly, increasing the user's long-term costs.

[0010] 4. Poor environmental performance: Lead-acid batteries contain heavy metal lead and corrosive electrolytes, posing environmental pollution risks during production, use and recycling, which does not conform to the environmentally friendly development trend of "lead-free" in the automotive industry.

[0011] 5. System reliability risk: The low-voltage system relies entirely on the high-voltage DC-DC converter for power. When the high-voltage system or the DC-DC converter fails, the vehicle's low-voltage system will lose power completely, causing the vehicle to "paralyze" and unable to perform the most basic safety functions such as emergency calls, door unlocking, and hazard warning lights, posing a safety hazard. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-voltage power supply control system and method for electric vehicles. It eliminates the need for a low-voltage battery and provides low-voltage power supply through DC-DC conversion using a power battery. At the same time, it uses modules within the battery pack for low-voltage power supply backup, thereby achieving redundancy and reliability of the low-voltage power supply.

[0013] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0014] A low-voltage power supply control system for an electric vehicle includes a power battery pack and a low-voltage module identical to the power battery cells; the low-voltage module is disposed within the power battery pack and is physically isolated from the high-voltage power supply cells within the power battery pack; the high-voltage output terminal of the power battery pack is connected to a low-voltage power supply network via a DC-DC module, and the low-voltage output terminal of the low-voltage module is connected to the low-voltage power supply network.

[0015] The low-voltage module has a built-in independent BMS, which is used to monitor the low-voltage module. The independent BMS is connected to the main BMS of the power battery pack, and the main BMS is communicatively connected to the vehicle controller (VCU).

[0016] The independent BMS is connected to a voltage sensor and a temperature sensor respectively. The voltage sensor and temperature sensor are used to sample the voltage and temperature of the low-voltage module. The low-voltage module is equipped with a thermal management module. The independent BMS controls the thermal management module based on the voltage and temperature samples.

[0017] The power battery pack is provided with an independent low-voltage output port. The low-voltage module is connected to the low-voltage output port through a low-voltage switch, and the output terminal of the independent BMS is connected to the low-voltage switch.

[0018] The independent BMS has built-in SOC and SOH calculation units to monitor and calculate the remaining power and health status of the low-voltage module; when the independent BMS detects that the power of the low-voltage module is lower than the set power threshold, the independent BMS requests power replenishment from the main BMS.

[0019] The high-voltage output terminal of the power battery pack is connected to the low-voltage output terminal of the low-voltage module via a DC-DC module to charge the low-voltage module. When charging the low-voltage module, the main BMS controls the DC-DC module to convert the high voltage output of the power battery pack into low voltage to charge the low-voltage module.

[0020] A control method for a low-voltage power supply control system for an electric vehicle includes the following steps: after the vehicle starts, the main BMS of the power battery pack controls the power battery pack to output high-voltage power supply, and the vehicle controller controls the DC-DC module to convert the high-voltage power output from the power battery pack into low-voltage power supply and send it into the low-voltage power supply network. The low-voltage load obtains low-voltage power supply through the low-voltage power supply network; or an independent BMS receives the control signal from the main BMS to control the low-voltage switch to close, and the low-voltage module outputs low-voltage power to the low-voltage power supply network to achieve low-voltage power supply.

[0021] After the vehicle starts, the default control DC-DC module converts the high voltage output of the battery pack into low voltage and sends it to the low voltage power supply network to power the low voltage load of the vehicle. Only when a fault is detected in the low voltage power supply obtained by the high voltage power conversion through the DC-DC module, the low voltage switch of the low voltage module is controlled to close to provide low voltage power to the low voltage power supply network.

[0022] When the vehicle is powered on, the power level of the low-voltage module is monitored in real time. When the power level is less than the set power threshold, the power battery pack outputs high voltage, which is then converted by the DC-DC module to charge the low-voltage module.

[0023] After detecting that the vehicle is turned off or the high voltage is reduced, the independent BMS is controlled to work. After the vehicle is turned off or the high voltage is reduced, the independent BMS controls the low voltage switch to close to output low voltage power supply to the low voltage power supply network, so that the low voltage module can supply power to the low voltage load after the high voltage is reduced.

[0024] The advantages of this invention are: eliminating the low-voltage battery, saving battery costs; providing low-voltage power supply through DC-DC conversion of the power battery, and using modules within the battery pack for low-voltage power supply backup, thereby achieving redundancy and reliability of low-voltage power supply. Attached Figure Description

[0025] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0026] Figure 1 This is an electrical schematic diagram of the low-voltage power supply system of the present invention;

[0027] Figure 2 This is the control logic diagram of the low-voltage power supply system of the present invention. Detailed Implementation

[0028] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0029] To simplify the vehicle's electrical architecture, reduce system costs, achieve lead-free vehicle operation, and fully utilize the power battery's energy, this invention proposes to physically and electrically isolate a low-voltage (e.g., 12V / 24V) small-capacity module from the existing high-voltage main power battery pack. This module is specifically designed to replace the traditional 12V / 24V lead-acid battery and power the vehicle's low-voltage electrical systems (such as VCU, BMS, headlights, audio, doors and windows, gateways, etc.). The core idea of ​​this solution is to physically and electrically isolate a low-voltage, small-capacity battery module from the main power battery pack. This module is in the same system as the high-voltage module's cells, independently managed by the BMS, specifically designed to replace lead-acid batteries, and works in conjunction with the DC-DC converter to form a low-voltage power supply.

[0030] This embodiment provides a low-voltage power supply control system for electric vehicles, including a power battery pack and a low-voltage module composed of the same cells as the power battery. The low-voltage module is located inside the power battery pack, and the low-voltage module is physically isolated from the high-voltage power supply cells inside the power battery pack. The high-voltage output terminal of the power battery pack is connected to the low-voltage power supply network via a DC-DC module, and the low-voltage output terminal of the low-voltage module is connected to the low-voltage power supply network.

[0031] The low-voltage module has a built-in independent BMS, which acts as a slave BMS. This independent BMS monitors the low-voltage module and is connected to the main BMS of the power battery pack. The main BMS communicates with the vehicle control unit (VCU). The BMS within the power battery pack, acting as the master BMS, communicates directly with the VCU via the CAN network.

[0032] In this embodiment, the independent low-voltage module has complete temperature and power monitoring and thermal management modules. An independent BMS is connected to voltage and temperature sensors, which are used to sample the voltage and temperature of the low-voltage module. The low-voltage module is equipped with a thermal management module, and the independent BMS controls the thermal management module based on the voltage and temperature samples. The independent BMS enables temperature monitoring, power monitoring, and heat dissipation control of the low-voltage module.

[0033] The power battery pack has an independent low-voltage output port. The low-voltage module is connected to the low-voltage output port via a low-voltage switch, and the output of the independent BMS is connected to the low-voltage switch. The low-voltage switch is a low-voltage contactor, relay, or MOSFET switch. The independent BMS has a built-in SOC and SOH calculation unit to monitor and calculate the remaining power and health status of the low-voltage module. When the independent BMS detects that the power of the low-voltage module is lower than a set power threshold, the independent BMS requests additional power from the main BMS. The high-voltage output of the power battery pack is connected to the low-voltage output of the low-voltage module via a DC-DC converter to replenish the low-voltage module. During the replenishment of the low-voltage module, the main BMS controls the DC-DC converter to convert the high voltage output of the power battery pack into low voltage to charge the low-voltage module.

[0034] This embodiment provides a control method for a low-voltage power supply control system for an electric vehicle, which includes, after the vehicle starts, the main BMS of the power battery pack controls the power battery pack to output high-voltage power supply, and the vehicle controller controls the DC-DC module to convert the high-voltage power output from the power battery pack into low-voltage power supply and send it into the low-voltage power supply network, and the low-voltage load obtains low-voltage power supply through the low-voltage power supply network; or the independent BMS receives the control signal from the main BMS to control the low-voltage switch to close, and the low-voltage module outputs low-voltage power to the low-voltage power supply network to achieve low-voltage power supply.

[0035] After the vehicle starts, the default control DC-DC module converts the high-voltage output from the battery pack to low-voltage and supplies it to the low-voltage power supply network to power the vehicle's low-voltage loads. Only when a fault is detected in the conversion of high-voltage power to low-voltage power by the DC-DC module, will the low-voltage switch of the low-voltage module close to supply low-voltage power to the low-voltage power supply network. By default, the high-voltage output from the high-voltage battery pack is converted to low-voltage for low-voltage power supply, ensuring sufficient power supply and setting this as the default low-voltage power supply mode. The low-voltage module serves as a backup power supply mode, only supplying low-voltage power when the default power supply mode fails, malfunctions, or experiences a power outage, thus ensuring power supply reliability and redundancy. To achieve switching, switching conditions for switching to low-voltage power supply from the low-voltage module are preset. When the switching conditions are met, the system switches to low-voltage power supply from the low-voltage module, at which point the output switch of the low-voltage module closes, thus supplying low-voltage power to the outside world. The switching conditions can be preset, including but not limited to detecting DC-DC module failure, high-voltage output failure of power battery pack, high-voltage output power failure, etc. When the preset conditions are met, the power supply is switched to the low-voltage module, thereby ensuring the reliability of power supply redundancy.

[0036] In this embodiment, when the vehicle is powered on, the power level of the low-voltage module is monitored in real time. When the power level is lower than a set threshold, the power battery pack outputs high voltage, which is then converted by the DC-DC converter to charge the low-voltage module. The low-voltage module needs to maintain a certain power level; therefore, its power level is monitored in real time. When the power level falls below the set threshold, the power battery pack can output high voltage, which is then converted by the DC-DC converter to charge the low-voltage module, thus maintaining the power supply to the low-voltage module.

[0037] In this embodiment, upon detecting vehicle shutdown or high-voltage reduction, the independent BMS is activated. The independent BMS controls the low-voltage switch to close after the vehicle is shut down or the high voltage is reduced, outputting low-voltage power to the low-voltage power supply network. This allows the low-voltage module to supply power to the low-voltage load after the high voltage is reduced. Since the high-voltage power battery pack experiences high voltage reduction after the vehicle is shut down, if the high-voltage output of the power battery pack were still used for low-voltage power supply at this time, the power loss would be significant. Furthermore, if the high-voltage battery pack continues to operate, it would affect the vehicle's range upon subsequent power-up. Therefore, only the low-voltage module provides power after the high voltage is reduced. The low-voltage module's power supply can meet the low-voltage power requirements of remote control and sentry monitoring functions for a certain period without affecting the high-voltage system's power capacity.

[0038] In this embodiment, the design of the low-voltage power supply system includes:

[0039] 1. Low-voltage module design and integrated protection:

[0040] a) Cell selection: The cell chemistry system must be consistent with that of the main battery pack module (usually LFP) to ensure compatibility in charge / discharge characteristics, lifespan, and SOC estimation algorithm.

[0041] b) Structural Design: The module is physically located inside the main battery pack housing, but has an independent metal casing, an independent sampling harness (LV Harness), and an independent output port (LowVoltage Output). It should have reliable physical insulation isolation from the high-voltage main pack.

[0042] c) Thermal management of low-voltage modules: Their thermal management (liquid cooling plate or air duct) needs to be integrated with the main package to ensure uniform temperature field.

[0043] 2. Battery Management System (BMS) Design Protection: Two BMSs are required: a dedicated BMS for the low-voltage module and a BMS for the main battery pack. Master BMS: Responsible for managing the entire main battery pack; its functions remain unchanged. Slave BMS for LV Module: Dedicated to managing the independent low-voltage module.

[0044] The low-voltage module's BMS needs to have:

[0045] a) Voltage and temperature sampling.

[0046] b) SOC / SOH estimation.

[0047] c) Charge and discharge control logic (coordinated with main BMS and VCU).

[0048] d) Independent low-voltage side contactor or MOSFET switch control.

[0049] Communication and Coordination: The main BMS and independent BMS communicate via the CAN bus. The main BMS aggregates all information and reports it to the VCU. The charging and discharging strategy of the low-voltage module is decided by the vehicle's VCU.

[0050] The control methods for low-voltage power supply include: control logic for coordinated power supply of high and low voltage power sources (such as: switching strategy of DC-DC power supply during normal operation and low-voltage module power supply during faults); and intelligent charging management methods based on low-voltage module SOC.

[0051] like Figure 1 As shown, a technical solution for replacing lead-acid batteries with an independent module of the main power battery pack includes the following: an independent low-voltage module assembly 1, a main battery module assembly 4, a main battery management system (BMS) 2, a main battery high-voltage distribution box 6, and high and low voltage interfaces; the independent low-voltage module assembly 1 includes an independent BMS 1, a battery module 1, and a low-voltage output interface.

[0052] Battery Module 1: This is an independent unit physically isolated from the main battery pack. It consists of a small number of cells connected in series (e.g., 4 cells for a 12V system, 8 cells for a 24V system), and its output is directly supplied with 12V or 24V low voltage, matching different voltage requirements depending on the vehicle model. Main Battery Module Assembly 4: This typically consists of N high-voltage modules connected in series, providing the high-voltage electricity required for vehicle operation (usually 120V-800V, matching different voltage requirements depending on the vehicle model).

[0053] The independent low-voltage module assembly 1 is located inside the power battery pack housing, arranged side-by-side with the high-voltage main battery module assembly 4, separated by a physical partition. Its low-voltage output interface is directly led out to the outside of the battery pack and connected to the vehicle's low-voltage load network. The main BMS2 communicates with the independent BMS built into the low-voltage module via its internal CAN bus and exchanges information with the VCU via the vehicle's CAN bus.

[0054] like Figure 2 The diagram illustrates the core master-slave BMS architecture of this invention and the collaborative control logic under the overall coordination of the VCU. The information flow and control flow paths are as follows:

[0055] 1. Information collection and reporting:

[0056] The BMS collects voltage, temperature, and SOC / SOH status information of the independent low-voltage modules in real time. The main BMS collects total voltage, total current, insulation, and temperature information of the high-voltage main battery module in real time and monitors the status of the high-voltage distribution box. The main BMS receives low-voltage module information reported from the BMS via the CAN bus. After summarizing all status information of the high and low voltage battery systems, the main BMS reports it to the vehicle controller (VCU) via the vehicle CAN bus.

[0057] 2. Decision-making and control:

[0058] As the highest decision-making unit, the VCU (Vehicle Control Unit) integrates vehicle status (such as ignition signals, fault codes, low-voltage load requirements, etc.) and received battery information to generate energy management commands. The VCU sends commands to the main BMS (such as: enabling DC-DC operation, requesting low-voltage module discharge, setting low-voltage module charging targets, etc.) via the CAN bus.

[0059] The master BMS executes VCU commands and coordinates the charging and discharging of the high-voltage main battery module and related contactors in the high-voltage distribution box. It forwards VCU control commands regarding the low-voltage modules (e.g., closing / opening low-voltage contactors, entering charging mode, etc.) to the slave BMS via internal CAN. The slave BMS executes the commands forwarded by the master BMS, directly controlling the low-voltage contactors or MOSFET switches of the independent low-voltage modules to connect or disconnect their power supply circuits to low-voltage loads. The VCU directly controls the start / stop and operating mode of the DC-DC converter, allowing it to select whether to supply power to low-voltage loads or charge independent low-voltage modules based on commands.

[0060] The low-voltage power supply path provided in this solution includes:

[0061] Path 1 (Normal Operating Conditions): High-voltage main battery module -> DC-DC converter -> Low-voltage

[0062] Load; this path is the default mode;

[0063] Path 2 (Emergency / Backup Condition): Independent low-voltage module -> (from BMS control switch) -> low-voltage load; This path is a redundant backup mode, which switches to this path to continue providing low-voltage power supply after Path 1 fails or is abnormal.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] 1. Integration, saving space and reducing costs: Eliminating the independent lead-acid battery, the lithium battery pack is integrated into the power battery pack through modular design, using lithium batteries (usually LFP) to replace lead-acid batteries, with voltage matching (12V / 48V), saving front compartment space and reducing costs;

[0066] 2. Long lifespan, superior performance, and lighter weight: Lithium-ion batteries have a much longer cycle life than lead-acid batteries, offer superior performance, and are lighter in weight. A comparison table of lithium-ion and lead-acid batteries is shown below:

[0067]

[0068] 3. High reliability: Independent low-voltage power supply and independent BMS management system ensure emergency operation of critical low-voltage electrical components (emergency call, door unlocking, hazard warning lights, basic diagnostics) even in the event of complete failure of the main battery pack high-voltage system, thus enhancing safety.

[0069] 4. Lead-free and environmentally friendly: In line with the environmental development trend of the automotive industry.

[0070] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A low-voltage power supply control system for electric vehicles, characterized in that: It includes a power battery pack and a low-voltage module composed of the same cells as the power battery; the low-voltage module is located inside the power battery pack and is physically isolated from the high-voltage power supply cells inside the power battery pack; the high-voltage output terminal of the power battery pack is converted to low voltage by a DC-DC module and then connected to a low-voltage power supply network, and the low-voltage output terminal of the low-voltage module is connected to the low-voltage power supply network.

2. The low-voltage power supply control system for electric vehicles as described in claim 1, characterized in that: The low-voltage module has a built-in independent BMS, which is used to monitor the low-voltage module. The independent BMS is connected to the main BMS of the power battery pack, and the main BMS is communicatively connected to the vehicle controller (VCU).

3. A low-voltage power supply control system for electric vehicles as claimed in claim 2, characterized in that: The independent BMS is connected to a voltage sensor and a temperature sensor respectively. The voltage sensor and temperature sensor are used to sample the voltage and temperature of the low-voltage module. The low-voltage module is equipped with a thermal management module. The independent BMS controls the thermal management module based on the voltage and temperature samples.

4. A low-voltage power supply control system for electric vehicles as described in claim 2 or 3, characterized in that: The power battery pack is provided with an independent low-voltage output port. The low-voltage module is connected to the low-voltage output port through a low-voltage switch, and the output terminal of the independent BMS is connected to the low-voltage switch.

5. A low-voltage power supply control system for electric vehicles as described in claim 2 or 3, characterized in that: The independent BMS has built-in SOC and SOH calculation units to monitor and calculate the remaining power and health status of the low-voltage module; when the independent BMS detects that the power of the low-voltage module is lower than the set power threshold, the independent BMS requests power replenishment from the main BMS.

6. The low-voltage power supply control system for electric vehicles as described in claim 5, characterized in that: The high-voltage output terminal of the power battery pack is connected to the low-voltage output terminal of the low-voltage module via a DC-DC module to charge the low-voltage module. When charging the low-voltage module, the main BMS controls the DC-DC module to convert the high voltage output of the power battery pack into low voltage to charge the low-voltage module.

7. A control method for a low-voltage power supply control system for an electric vehicle as described in any one of claims 1-6, characterized in that: After the vehicle starts, the main BMS of the power battery pack controls the power battery pack to output high-voltage power supply. The vehicle controller controls the DC-DC module to convert the high-voltage power output from the power battery pack into low-voltage power supply and send it to the low-voltage power supply network. Low-voltage loads obtain low-voltage power supply through the low-voltage power supply network. Alternatively, the independent BMS receives the control signal from the main BMS to control the low-voltage switch to close, and the low-voltage module outputs low-voltage power to the low-voltage power supply network to achieve low-voltage power supply.

8. The control method for a low-voltage power supply control system for an electric vehicle as described in claim 7, characterized in that: After the vehicle starts, the default control DC-DC module converts the high voltage output of the battery pack into low voltage and sends it to the low voltage power supply network to power the low voltage load of the vehicle. Only when a fault is detected in the low voltage power supply obtained by the high voltage power conversion through the DC-DC module, the low voltage switch of the low voltage module is controlled to close to provide low voltage power to the low voltage power supply network.

9. The control method for a low-voltage power supply control system for an electric vehicle as described in claim 7, characterized in that: When the vehicle is powered on, the power level of the low-voltage module is monitored in real time. When the power level is less than the set power threshold, the power battery pack outputs high voltage, which is then converted by the DC-DC module to charge the low-voltage module.

10. The control method for a low-voltage power supply control system for an electric vehicle as described in claim 7, characterized in that: After detecting that the vehicle is turned off or the high voltage is reduced, the independent BMS is controlled to work. After the vehicle is turned off or the high voltage is reduced, the independent BMS controls the low voltage switch to close to output low voltage power supply to the low voltage power supply network, so that the low voltage module can supply power to the low voltage load after the high voltage is reduced.

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