Low-voltage power supply and vehicle electrical system

Abstract

The present invention relates to a low-voltage power supply and an on-board electrical system. The low-voltage power supply includes a first DC / DC converter and a microprocessor. The input terminal of the first DC / DC converter is electrically connected to the positive terminal of a high-voltage power supply, and the output terminal of the first DC / DC converter is electrically connected to a low-voltage load. The microprocessor is configured to activate the first DC / DC converter only when the high-voltage power supply is electrically decoupled from the load circuit.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle technology, and more particularly to a low-voltage power supply and on-board electrical system for electric vehicles. Background Technology

[0002] Electric vehicles typically have both high-voltage and low-voltage power supplies. The high-voltage power supply is mainly used to drive the motor to rotate and propel the vehicle. The low-voltage power supply is usually used for the vehicle's low-power electrical equipment, such as power windows, power doors, lights, windshield wipers, multimedia equipment, dashboard, and controllers.

[0003] Low-voltage power supplies, such as 12V, currently primarily use lead-acid batteries. However, as vehicles become increasingly electrified and intelligent, the use of sensors, controllers, and actuators increases the power supply load, rendering low-voltage lead-acid batteries inadequate for the requirements of modern new energy vehicles. For modern electric vehicles, existing lead-acid batteries suffer from drawbacks such as large size, heavy weight, short lifespan, and the need for multiple replacements throughout the vehicle's lifespan. Furthermore, due to their lead content, their use is subject to increasingly stringent environmental regulations in various countries and regions.

[0004] In addition, there are alternatives using 12V lithium batteries. However, 12V lithium batteries are currently expensive, making them difficult to promote and apply, especially in low- and mid-range vehicles.

[0005] Therefore, there is an urgent need to further improve the existing onboard electrical systems and power supply methods of electric vehicles. Summary of the Invention

[0006] This invention proposes an improved low-voltage power supply and on-board electrical system for electric vehicles. In this low-voltage power supply or on-board electrical system, the high capacity and high reliability of the high-voltage power supply of electric vehicles are utilized. A low-power DC / DC converter is used to directly utilize the high-voltage power supply to achieve long-term low-voltage energy supply in parking mode, eliminating the need for existing low-voltage lead-acid batteries and reducing the overall vehicle material and maintenance costs.

[0007] According to one aspect of the invention, a low-voltage power supply is provided, the low-voltage power supply including a first DC / DC converter and a microprocessor, the input terminal of the first DC / DC converter being electrically connected to the positive terminal of a high-voltage power supply, the output terminal of the first DC / DC converter being electrically connected to a low-voltage load, wherein the microprocessor is configured to enable the first DC / DC converter only when the high-voltage power supply is electrically decoupled from the load circuit.

[0008] The present invention also proposes an on-board electrical system having a high-voltage power supply, a load circuit, and a main relay connected between the high-voltage power supply and the load circuit. The load circuit includes a high-voltage load and a low-voltage load. The first terminal of the main relay is connected to the positive terminal of the high-voltage power supply, and the second terminal of the main relay is electrically connected to the high-voltage load on one side and to the low-voltage load on the other side via a third DC / DC converter. The on-board electrical system also includes the aforementioned low-voltage power supply, which is electrically connected between the first terminal of the main relay and the low-voltage load.

[0009] The low-voltage power supply and vehicle electrical system proposed in this invention can replace the original low-voltage lead-acid battery to provide power for extended periods when the vehicle is stationary. Specifically, it utilizes a low-power high-voltage / low-voltage DC / DC converter to directly supply low-voltage, low-power power from the high-voltage power supply. The input of this DC / DC converter is connected before the main relay, maintaining a continuous electrical connection with the high-voltage power supply. Therefore, it reduces overall vehicle material and maintenance costs. Furthermore, this type of low-voltage power supply can be flexibly installed within the high-voltage battery pack, high-voltage junction box, or other locations, allowing for flexible placement according to vehicle requirements. Attached Figure Description

[0010] The above and other features and advantages of the present invention will become more apparent from a detailed description of exemplary embodiments thereof with reference to the accompanying drawings.

[0011] Figure 1 This is an exemplary topology diagram of a low-voltage power supply according to the present invention;

[0012] Figure 2 This is another exemplary topology diagram of a low-voltage power supply according to the present invention;

[0013] Figure 3 This is a circuit diagram of one embodiment of the vehicle electrical system according to the present invention. Detailed Implementation

[0014] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to make the content of the invention comprehensive and complete, and to fully convey the concept of the exemplary embodiments to those skilled in the art. In the drawings, the dimensions of some elements may be exaggerated or modified for clarity. The same reference numerals in the drawings denote the same or similar structures, and therefore their detailed description will be omitted.

[0015] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a full understanding of embodiments of the invention. However, those skilled in the art will recognize that the invention can be practiced without one or more of the specific details described, or other methods, elements, etc. In other instances, well-known structures, methods, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0016] The low-voltage power supply includes at least a first DC / DC converter and a microprocessor. The input of the first DC / DC converter is electrically connected to the positive terminal of the high-voltage power supply, and the output of the first DC / DC converter is electrically connected to the low-voltage load. The microprocessor is configured to enable the first DC / DC converter only when the high-voltage power supply is electrically decoupled from the load circuit.

[0017] Figure 1 An exemplary topology diagram of a low-voltage power supply is shown. Figure 1 In the example shown, the low-voltage power supply includes a first DC / DC converter, a supercapacitor module, a switching assembly, and a microprocessor. The positive terminal of the supercapacitor module is electrically connected to the output terminal of the first DC / DC converter, and the negative terminal of the supercapacitor module is grounded. A switching assembly consisting of two metal-oxide-semiconductor field-effect transistors (MOSFETs) connected back-to-back is provided between the positive terminal of the supercapacitor module and the output terminal of the first DC / DC converter. The switching assembly is used to control the charging or discharging of the supercapacitor module under the control of the microprocessor. Here, the supercapacitor module consists of six individual supercapacitors connected in series. However, in specific applications, more or fewer individual supercapacitors can be used depending on specific needs. When designing the supercapacitor module, the operating voltage of the supercapacitor module, the parameters of the individual supercapacitors, and the safety factor need to be considered. Taking a 12V low-voltage power supply system as an example, if the typical operating voltage of the individual supercapacitors is 3V, and the upper limit of the safe operating voltage is 90% of the typical operating voltage, then the upper limit of the safe operating voltage of the supercapacitor module consisting of six individual supercapacitors connected in series is 3*6*0.9 = 16.2V. The microprocessor pre-charges the supercapacitor module by controlling a low-power first DC / DC converter, bringing the module's voltage to the specified operating voltage, such as 14V. The actual voltage of the supercapacitor module can be flexibly adjusted according to the vehicle's requirements, as long as it remains below the safe voltage upper limit.

[0018] In this context, the use of overcapacity modules is particularly advantageous. Low-voltage loads on the vehicle, especially inductive loads such as water pumps, thermal management valves, and motors, can cause fluctuations in the power network during switching or under certain special operating conditions. Overcapacity modules can compensate for insufficient peak power from the first high-voltage to low-voltage DC / DC converter, while also absorbing peak (wave) interference on the power network, maintaining voltage stability in the low-voltage network.

[0019] In addition to the microprocessor, the low-voltage power supply also includes a supercapacitor module monitoring module, a low-voltage power management chip, and a drive circuit in the form of a gate drive circuit, among other control and detection devices. The microprocessor is connected to the supercapacitor module monitoring module, the low-voltage power management chip, the drive circuit, and the first DC / DC converter. The supercapacitor module monitoring module monitors the operating parameters (such as current, voltage, and temperature) of the supercapacitor module and individual supercapacitors, and based on this, supports passive balancing of the individual supercapacitors, thereby extending the lifespan of the supercapacitor module. In other words, the supercapacitor module monitoring module monitors the operating parameters of the supercapacitor module in real time during charging and discharging, and based on the monitored operating parameters, enables the supercapacitor module to perform balancing operations on the supercapacitor cells. In addition, based on parameters collected by the supercapacitor module monitoring module (such as the voltage level, current level, and / or temperature of the supercapacitor module or individual supercapacitor), the microprocessor drives the metal-oxide-semiconductor field-effect transistor through the gate drive circuit to disconnect the connection between the supercapacitor module and the output terminal of the first DC / DC converter, thereby stopping the supercapacitor module from charging or discharging; or drives the metal-oxide-semiconductor field-effect transistor through the gate drive circuit to connect the supercapacitor module and the output terminal of the first DC / DC converter or the low-voltage load, thereby charging or discharging the supercapacitor module.

[0020] The low-voltage management chip can communicate with the vehicle controller via a CAN bus. For example, it can obtain the status of the main relay from the vehicle controller. When the main relay is in the off state, the low-voltage management chip provides an input signal to the microprocessor, which, in response, activates a low-power first DC / DC converter to supply power to the low-voltage load. When the main relay is in the on state, the first DC / DC converter does not operate, and the low-voltage load is supplied by a high-voltage power supply via a third DC / DC converter. The low-voltage management chip can also provide a corresponding signal to the microprocessor based on the voltage at the positive terminal of the overcapacitor module. In response to this signal, the microprocessor can drive the gate circuit to connect or disconnect the connection between the overcapacitor module and the output of the first DC / DC converter or the low-voltage load. Furthermore, the microprocessor is further configured to monitor the operating status of the first DC / DC converter in real time and feed the monitoring results back to the vehicle controller via the CAN bus. For example, the microprocessor can also monitor the voltage and / or current of the first DC / DC converter for monitoring and diagnostic purposes.

[0021] Here, the supercapacitive module and the low-power high-voltage low-voltage first DC / DC converter share a microprocessor, low-voltage power management chip and communication module, etc., which improves efficiency while reducing module development cost and component cost.

[0022] Figure 2 Another exemplary topology diagram of a low-voltage power supply is shown. (Compared to...) Figure 2 Compared to the aforementioned embodiments, the number of individual supercapacitors is reduced under the same design requirements. Figure 2 The supercapacitor module consists of only three individual supercapacitors connected in series. However, a bidirectional boost / buck second DC / DC converter is connected between the positive terminal of the supercapacitor module, the low-voltage load, and the first DC / DC converter. This second DC / DC converter enables the supercapacitor module to perform boost discharge and step-down charging from an external voltage source. The advantages are that, through a reasonable number of individual supercapacitors and the bidirectional DC / DC design, the size and cost can be further reduced. Simultaneously, the bidirectional second DC / DC converter can actively manage the power during supercapacitor charging and discharging, minimizing the impact on the 12V power grid.

[0023] Although a supercapacitor module consisting of three individual supercapacitors is shown, other numbers of individual supercapacitors can also be considered. In practical design, the number of supercapacitors and the operating voltage range of the bidirectional second DC / DC converter can be reasonably defined according to specific requirements to achieve the best cost-effectiveness. For example, the lower limit of the supercapacitor module's operating voltage can be defined based on the power requirements of the 12V low-voltage power supply network. The supercapacitor module does not have over-discharge safety limitations, but the lower the lower limit of the supercapacitor module's operating voltage, the greater the boost power required by the bidirectional second DC / DC converter, and the higher the cost. For example, reducing the six series-connected supercapacitors in the above embodiment to three results in a safe operating voltage upper limit of 3*3*0.9 = 8.1V for the supercapacitor module. In this case, the total cost of the individual supercapacitors and the bidirectional second DC / DC converter is optimal.

[0024] Figure 3 A circuit diagram of a preferred embodiment of the vehicle electrical system according to the present invention is shown. Figure 3 The vehicle electrical system shown mainly includes a high-voltage power supply and a load circuit. The high-voltage power supply is also referred to here as a high-voltage battery pack or power battery. A main relay is provided between the high-voltage power supply and the load circuit to connect or disconnect the connection between them as needed. Here, the load includes high-voltage loads and low-voltage loads. High-voltage loads include, for example, motor 1, compressor 2, etc.; low-voltage loads include, for example, in-vehicle entertainment systems, control units, lighting systems, controllers, etc. Downstream of the main relay, that is, starting from the positive terminal of the high-voltage power supply and looking along the current direction, the high-voltage load circuit and the low-voltage load circuit are connected in parallel. The low-voltage load circuit is connected to the positive terminal of the high-voltage power supply via a third DC / DC converter.

[0025] The input of the third DC / DC converter is connected to the high-voltage output of the high-voltage power supply, and its output is connected to a low-voltage load circuit or a low-voltage load. This third DC / DC converter is used to convert a certain value of the DC power supply voltage output from the high-voltage power supply into a lower value, thus regulating the power supply output and stabilizing the power supply voltage. DC / DC converters are generally classified into three types: high-voltage to high-voltage DC / DC converters, high-voltage to low-voltage DC / DC converters, and low-voltage regulated DC / DC converters. Here, the third DC / DC converter is a high-voltage to low-voltage DC / DC converter. Furthermore, Figure 3It is also shown that the third DC / DC converter and the on-board charger (OBC) are integrated together. The on-board charger (OBC) enables slow charging of electric vehicles. Installed on the electric vehicle, the OBC connects to an AC charging station during charging, converting AC power to DC power and slowly charging the high-voltage power source. Integrating the third DC / DC converter and the on-board charger reduces the overall weight of the power supply unit, achieving weight reduction and improving driving range; it also reduces costs and the number of parts requiring final assembly during vehicle production, thereby lowering manufacturing costs.

[0026] Depend on Figure 3 It can also be seen that high-voltage power supplies can be charged using either AC or DC charging. DC charging, also known as "fast charging," uses an external DC charging station to directly charge the high-voltage power supply without the need for an on-board charger. AC charging, also known as "slow charging," involves the AC charging station supplying 220V single-phase AC or 380V three-phase AC current from the AC grid to the on-board charger (OBC) installed in the vehicle. The on-board charger then converts the AC power into DC power to charge the electric vehicle.

[0027] A low-voltage power supply 3 is connected upstream of the main relay, upstream of the high-voltage power supply, following the current direction. When the vehicle control unit (VCU) does not receive a high-voltage signal—that is, when the vehicle is off or the main relay is disconnected—low-voltage power supply 3 supplies power to the low-voltage load. When the VCU receives a high-voltage signal, the third DC / DC converter starts, and the high-voltage electricity output from the high-voltage power supply is converted by the third DC / DC converter to output a stable low-voltage electricity. Here, low-voltage power supply 3 is connected across the positive and negative terminals of the high-voltage power supply and remains electrically connected to it. Therefore, it can provide a stable low-voltage power supply to the low-voltage load when needed. Figure 3 The diagram also shows that motor 1 is connected to the power supply line via an inverter.

[0028] Here, the power distribution process of the vehicle's electrical system includes, for example:

[0029] S1: Detect the status of the main relay;

[0030] S2: When the main relay is disconnected, power is supplied to the low-voltage load by means of a low-voltage power supply.

[0031] The status of the main relay can be detected directly by a status sensor, or indirectly by detecting the current and / or voltage on the main circuit. For example, when the main relay is on (vehicle started), the high-voltage power supply outputs a stable low-voltage power supply after being converted by the third DC / DC converter. At this time, the low-voltage power supply is not in operation. When the vehicle is off and the main relay is off, the low-voltage power supply supplies power to the low-voltage load.

[0032] Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solution of the power distribution method according to this application can be embodied in the form of a software product. This software product can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, or external hard drive) or on a network, and includes several instructions to cause a computing device (such as a personal computer, server, or network device, etc.) to execute the power distribution process according to this application.

[0033] Overall, the solution described in this application allows for the application of the vehicle's electrical system to the current vehicle architecture without requiring major modifications to the overall vehicle's electronic and electrical architecture or power topology. Furthermore, the low-voltage power supply in this application offers the following advantages compared to traditional lead-acid low-voltage batteries or low-voltage lithium batteries:

[0034] 1. Supercapacitor modules can stabilize low-voltage networks. Compared with lead-acid batteries and lithium batteries, they have advantages such as small size, light weight and long life. At the same time, supercapacitor modules still maintain good power characteristics in low-temperature environments.

[0035] 2. Fully utilize the large capacity and high reliability of existing high-voltage power supplies to enable them to provide low-voltage energy for extended periods in parking mode via low-power DC / DC converters, eliminating the need for low-voltage batteries and reducing overall vehicle material and maintenance costs.

[0036] 3. Integrated design: The supercapacitive module and the low-power high-voltage and low-voltage first DC / DC converter share the same microprocessor, power management chip, etc., which can improve efficiency and reduce costs;

[0037] 4. The low-voltage power supply can be flexibly installed in the high-voltage battery pack, the high-voltage junction box, or other locations, and can be arranged flexibly according to the needs of the vehicle.

[0038] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A low voltage power supply, characterized by The low-voltage power supply includes a first DC / DC converter and a microprocessor. The input of the first DC / DC converter is electrically connected to the positive terminal of the high-voltage power supply, and the output of the first DC / DC converter is electrically connected to the low-voltage load. The microprocessor is configured to enable the first DC / DC converter only when the high-voltage power supply is electrically decoupled from the load circuit.

2. The low voltage power supply of claim 1, wherein, The low-voltage power supply also includes a supercapacitor module and a switching assembly. The supercapacitor module consists of at least one single supercapacitor. The switching assembly is located between the positive terminal of the supercapacitor module and the output terminal of the first DC / DC converter, and is used to control the charging or discharging of the supercapacitor module under the control of the microprocessor.

3. The low voltage power supply of claim 2, wherein, The switching assembly includes two metal-oxide-semiconductor field-effect transistors connected back-to-back, and the microprocessor is configured to control the charging or discharging of the supercapacitor module by controlling the on / off state of the two metal-oxide-semiconductor field-effect transistors.

4. A low voltage power supply according to claim 2 or 3, characterized in that The supercapacitor module is formed by six individual supercapacitors connected in series.

5. A low voltage power supply according to claim 2 or 3, characterized in that, The low-voltage power supply also includes a second DC / DC converter disposed between the positive terminal of the supercapacitor module and the switching assembly. The second DC / DC converter is configured to perform a boost operation on the discharge voltage of the supercapacitor module during the discharge process and a buck operation on the externally input charging voltage during the charging process of the supercapacitor module.

6. A low voltage power supply according to claim 2 or 3, characterized in that The low-voltage power supply also includes a supercapacitor module monitoring module, which is used to monitor the operating parameters of the supercapacitor module in real time during the charging and discharging process of the supercapacitor module, and to enable the supercapacitor module to perform equalization operation of the supercapacitor cells based on the monitored operating parameters.

7. The low voltage power supply of claim 6, wherein, The operating parameters include the operating current of the supercapacitor module, the operating temperature, and the voltage of the supercapacitor cell.

8. The low-voltage power supply according to claim 2 or 3, characterized in that, The microprocessor is further configured to monitor the operating status of the first DC / DC converter in real time and feed the monitoring results back to the vehicle controller via the CAN bus.

9. A vehicle-mounted electrical system comprising a high-voltage power supply, a load circuit, and a main relay connected between the high-voltage power supply and the load circuit, wherein the load circuit includes a high-voltage load and a low-voltage load, a first terminal of the main relay is connected to the positive terminal of the high-voltage power supply, and a second terminal of the main relay is electrically connected to the high-voltage load on one side and to the low-voltage load on the other side via a third DC / DC converter, characterized in that... The vehicle electrical system also includes a low-voltage power supply according to any one of claims 1 to 8, the low-voltage power supply being electrically connected between a first terminal of the main relay and a low-voltage load.

10. The vehicle electrical system according to claim 9, characterized in that, The third DC / DC converter is integrated with the on-board charger.

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