Power conversion circuit and battery management system

Abstract

The invention relates to the technical field of new energy, in particular to a power conversion circuit and a battery management system, and the circuit comprises an input circuit which comprises a switching circuit which is connected with the output end of a power battery; the transformer comprises a primary winding and a secondary winding, and the primary winding is connected with the input circuit; the rectifying and filtering circuit is connected with the secondary winding; and the feedback control circuit is connected with the switching circuit and the rectification filter circuit, can efficiently and stably convert an input voltage into a target DC voltage, is high in conversion efficiency and small in ripple, provides reliable power supply for a battery management system, and ensures stable operation of the system.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a power conversion circuit and a battery management system. Background Technology

[0002] The Battery Management System (BMS) is the "brain" of the battery system. It is responsible for real-time monitoring of key parameters such as battery voltage, current, and temperature, accurate estimation of battery state of charge (SOC) and state of health (SOH), and activating protection mechanisms when the battery is overcharged, over-discharged, or overheated.

[0003] Traditional electric vehicles typically require an additional 12V lead-acid battery as the core power source for their low-voltage power supply system to ensure a stable low-voltage power supply for the BMS and other vehicle controllers (such as the vehicle control unit (VCU) and motor controller (MCU)). This 12V lead-acid battery needs to be set up independently of the main battery system, resulting in a dual-battery architecture of "main battery + 12V lead-acid battery". This dual-battery architecture not only significantly increases the structural complexity of the vehicle's electrical system, increasing the difficulty of system integration and the cost of troubleshooting, but also, due to the weight and volume of the 12V lead-acid battery itself, adversely affects the lightweight design goals pursued by new energy vehicles, thus restricting the improvement of the vehicle's range to some extent.

[0004] Furthermore, due to the significant difference between the supply voltage of the 12V lead-acid battery and the output voltage of the power battery (typically several hundred volts), a DC-DC converter needs to be additionally configured in the vehicle's circuitry to continuously charge the 12V lead-acid battery. This DC-DC converter steps down the high-voltage DC output from the power battery to a low-voltage DC suitable for the 12V lead-acid battery. However, during this energy conversion process, energy loss is inevitable due to the limited conversion efficiency of the DC-DC converter (usually difficult to reach 100%), leading to a decrease in the overall vehicle energy utilization efficiency. Simultaneously, the introduction of the DC-DC converter increases the vehicle's hardware cost and circuit complexity, and its long-term operational stability can potentially impact the reliability of the vehicle's power supply system.

[0005] In summary, the current low-voltage power supply architecture based on 12V lead-acid batteries in new energy vehicles has significant shortcomings in terms of system complexity, vehicle lightweighting, energy utilization efficiency, and cost control. It has become a key technical bottleneck restricting the performance improvement and industrialization of new energy vehicles. There is an urgent need to propose a new low-voltage power supply solution to overcome the defects and shortcomings of the existing technology. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, the present invention provides a power conversion circuit and a battery management system, which aims to efficiently and stably convert the input voltage into a voltage compatible with the battery management system, without the need for an additional 12V lead-acid battery or DC-DC converter, thereby reducing the hardware cost and circuit complexity of the vehicle.

[0007] To address at least one of the aforementioned technical problems, in a first aspect, the present invention provides a power conversion circuit disposed in a battery management system, the power conversion circuit comprising: The input circuit includes a switching circuit, which is connected to the output terminal of the power battery and is used to convert the initial DC voltage output by the power battery into a first alternating voltage. A transformer includes a primary winding and a secondary winding, the primary winding being connected to the input circuit, and the transformer being used to step down the first alternating voltage output by the input circuit to a second alternating voltage; A rectifier and filter circuit, connected to the secondary winding, is used to convert the second alternating voltage into a first direct current voltage and to filter the first direct current voltage. A feedback control circuit, connected to the switching circuit and the rectifier-filter circuit, is used to generate a first target control signal and send it to the switching circuit when the voltage difference between the first DC voltage output by the rectifier-filter circuit and the first target voltage required by the battery management system is greater than a preset difference threshold. The switching circuit is used to adjust the on-time of the switching circuit based on the first target control signal, so as to adjust the voltage value of the first alternating voltage, such that the voltage difference is less than or equal to the difference threshold.

[0008] Optionally, the feedback control circuit includes a detection circuit, an optocoupler, and a switch control circuit; The input terminal of the detection circuit is connected to the output terminal of the rectifier and filter circuit, the output terminal of the detection circuit is connected to the input terminal of the switch control circuit through the optocoupler, and the output terminal of the switch control circuit is connected to the switch circuit. The detection circuit is used to send a first feedback signal to the switch control circuit through the optocoupler when it detects that the voltage difference between the first DC voltage and the first target voltage is greater than a preset difference threshold; the switch control circuit is used to generate the first target control signal based on the first feedback signal.

[0009] Optionally, the detection circuit includes a reference voltage source and a voltage divider circuit, wherein, The voltage divider circuit is connected to the output terminal of the rectifier and filter circuit, and is used to divide the first DC voltage by a fixed ratio to obtain a feedback voltage, and apply the feedback voltage to the reference terminal of the reference voltage source. The feedback voltage is less than the first DC voltage. The reference voltage source is connected to the voltage divider circuit. The reference voltage source is used to generate a first feedback signal that matches the direction and magnitude of the feedback voltage deviation when the feedback voltage received at the reference terminal deviates from the reference voltage inside the reference voltage source. The voltage value of the first target voltage after being divided according to the fixed ratio is consistent with the reference voltage.

[0010] Optionally, the switch control circuit is used for: When the first feedback signal indicates that the feedback voltage is greater than the reference voltage, a first target control signal is generated to indicate a reduction in the on-time of the switching circuit. When the first feedback signal indicates that the feedback voltage is less than the reference voltage, a first target control signal is generated to indicate an increase in the on-time of the switching circuit.

[0011] Optionally, the switching circuit includes a switching transistor, a drive current-limiting resistor, and a gate discharge circuit; The gate of the switching transistor is connected to the signal output terminal of the switching control circuit through the driving current limiting resistor, the drain of the switching transistor is connected to one end of the primary winding, and the source of the switching transistor is grounded. The gate discharge circuit includes a discharge resistor and a discharge diode. The anode of the discharge diode is connected to the gate of the switching transistor, the cathode of the discharge diode is connected to one end of the discharge resistor, and the other end of the discharge resistor is connected to the signal output terminal of the switch control circuit.

[0012] Optionally, the transformer includes a plurality of secondary windings coupled to the primary winding, and the rectifier and filter circuit includes a plurality of rectifier and filter units, each of which is connected to one of the secondary windings, and the plurality of rectifier and filter units are used to output DC voltages of different magnitudes.

[0013] Optionally, the transformer further includes: An auxiliary winding is connected to the feedback control circuit and is used to supply power to the feedback control circuit.

[0014] Optionally, the input circuit further includes: An input filter circuit is provided, wherein the input terminal of the input filter circuit is connected to the output terminal of the power battery, and the output terminal of the input filter circuit is connected to the primary winding through the switching circuit. The input filter circuit is used to filter the initial DC voltage output by the power battery.

[0015] Optionally, the power conversion circuit further includes: The power status indicator module includes a current-limiting resistor and a light-emitting unit. One end of the current-limiting resistor is connected to the output terminal of the rectifier filter circuit, and the other end is connected to the anode of the light-emitting unit. The cathode of the light-emitting unit is grounded.

[0016] To achieve the above objectives, according to a second aspect of the present invention, a battery management system is provided, including the power conversion circuit as described in any of the preceding claims.

[0017] By employing the above technical solution, the power conversion circuit and battery management system provided by this invention, through the inclusion of an input circuit containing a switching circuit, a transformer, a rectifier and filter circuit, and a feedback control circuit, can directly step down and filter the high-voltage DC power from the power battery into the stable low-voltage DC power required by the BMS, providing a reliable power supply for the core module of the battery management system and ensuring stable system operation. Furthermore, this power conversion circuit, integrated into the BMS, eliminates the need for a traditional 12V lead-acid battery and a dedicated DC-DC converter. This breaks the limitations of a dual-battery architecture, simplifies the vehicle's electrical system, reduces integration and troubleshooting costs as well as hardware costs, reduces additional weight and volume to fit lightweight design, reduces energy loss to improve energy efficiency, and simultaneously ensures power supply stability through feedback control, providing reliable support for the core functions of the BMS and effectively overcoming the technical bottlenecks of traditional low-voltage power supply architectures.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can also be implemented according to the contents of the specification. Furthermore, in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0019] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A frame diagram of a power conversion circuit provided in an embodiment of the present invention is shown; Figure 2 A circuit diagram of a power conversion circuit provided in an embodiment of the present invention is shown; Figure 3 A frame diagram of another power conversion circuit provided by an embodiment of the present invention is shown. Detailed Implementation

[0020] To better understand the technical solutions provided in the embodiments of this specification, the technical solutions of the embodiments of this specification will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this specification and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this specification, rather than limitations on the technical solutions of this specification. In the absence of conflict, the embodiments of this specification and the technical features in the embodiments can be combined with each other.

[0021] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. The term "two or more" includes two or more cases.

[0022] As mentioned above, in order to efficiently and stably convert the input voltage into a voltage that is compatible with the vehicle controller, this invention provides a power conversion circuit, which is installed in the BMS battery management system, to convert the initial DC voltage (typically a DC voltage of 230-850V) output by the power battery into the first target voltage (typically a DC voltage of 12V) required by the BMS.

[0023] Figure 1 A framework diagram of a power conversion circuit according to an embodiment of the present invention is shown, as follows. Figure 1 As shown, the power conversion circuit includes: an input circuit 10, a transformer 20, a rectifier and filter circuit 30, and a feedback control circuit 40.

[0024] The input circuit 10 includes a switching circuit 11 connected to the output terminal of the power battery, used to convert the initial DC voltage output by the power battery into a first alternating voltage. A transformer 20 includes a primary winding and a secondary winding. The primary winding is connected to the input circuit 10, and the transformer 20 is used to step down the first alternating voltage output by the input circuit 10 to a second alternating voltage. A rectifier-filter circuit 30 is connected to the secondary winding, used to convert the second alternating voltage into a first DC voltage and filter the first DC voltage. A feedback control circuit 40 is connected to the switching circuit 10 and the rectifier-filter circuit 30. The feedback control circuit 40 generates a first target control signal and sends it to the switching circuit 11 when the voltage difference between the first DC voltage output by the rectifier-filter circuit 30 and the first target voltage required by the battery management system (BMS) is greater than a preset difference threshold. The switching circuit 11 adjusts its conduction time based on the first target control signal to adjust the voltage value of the first alternating voltage, making the voltage difference less than or equal to the difference threshold.

[0025] Through the power conversion circuit provided in the above embodiments, the initial DC voltage output by the power battery is converted into a suitable second alternating voltage through the input circuit 10 and the transformer 20. Then, the second alternating voltage is rectified into a first DC voltage by the rectifier and filter circuit 30 to obtain a preliminary voltage output. Next, the feedback control circuit 40 monitors the first DC voltage in real time. When the first DC voltage deviates from the first target voltage required by the battery management system (BMS), a first target control signal is generated and sent to the switching circuit 11 to adjust the conduction time of the switching circuit 11. The longer the conduction time of the switching circuit 11 in one working cycle, the longer the energy input time of the primary winding, and the more electrical energy (stored in the form of magnetic energy) received by the primary winding in one working cycle; the shorter the conduction time of the switching circuit 11 in one working cycle, the less energy is input. The first alternating voltage is essentially the "equivalent voltage value" of the high-frequency pulse signal generated by the switching circuit 11, which is determined by the energy input time of the primary winding: the longer the energy input time, the higher the "effective amplitude" of the pulse signal (i.e., the larger the equivalent voltage value of the first alternating voltage); conversely, the smaller the equivalent voltage value. Therefore, by changing the on-time of the switching circuit 11 within one working cycle, the voltage value of the first alternating voltage can be changed. When the voltage value of the first alternating voltage changes, the magnitude of the change in magnetic flux induced in the secondary winding coupled to the primary winding also changes, and the voltage value of the corresponding output second alternating voltage will also be adjusted synchronously, ultimately making the voltage difference between the first DC voltage output by the rectifier filter circuit 30 and the first target voltage less than or equal to the difference threshold, thereby achieving a stable output of the voltage required by the BMS.

[0026] Figure 2 The circuit diagram shown is a power conversion circuit according to an embodiment of the present invention, as follows: Figure 2As shown, in one embodiment, the feedback control circuit 40 includes a detection circuit 41, an optocoupler U2, and a switch control circuit 42.

[0027] The input terminal of the detection circuit 41 is connected to the output terminal of the rectifier filter circuit 30, and the output terminal of the detection circuit 41 is connected to the input terminal of the switch control circuit 42 through the optocoupler U2. The output terminal of the switch control circuit 42 is connected to the switch circuit 11. The detection circuit 41 is used to send a first feedback signal to the switch control circuit 42 through the optocoupler U2 when the voltage difference between the first DC voltage and the first target voltage is detected to be greater than a preset difference threshold. The switch control circuit 42 is used to generate a first target control signal based on the first feedback signal.

[0028] Among them, optocoupler U2 can be a PC817 optocoupler. Optocoupler U2 is an isolation device that realizes electro-optical-electrical signal conversion. It contains a light-emitting diode (input terminal) and a phototransistor (output terminal), which are coupled through an optical path. Through electro-optical-electrical signal conversion, U2 transmits the voltage deviation information (first feedback signal) output by the detection circuit 41 to the switch control circuit 42. At the same time, it realizes electrical isolation between the high-voltage side of the primary winding and the low-voltage side of the secondary winding, preventing high-voltage interference from entering the low-voltage control terminal and ensuring circuit safety and signal stability.

[0029] For example, the light-emitting diode (LED) is connected to the output terminal of the detection circuit 41. If the first DC voltage is greater than the first target voltage, the current flowing through the LED increases accordingly, and the LED's luminous intensity increases; if the first DC voltage is less than the first target voltage, the current flowing through the LED decreases accordingly, and the LED's luminous intensity decreases. The collector of the phototransistor is connected to the switch control circuit 42, and the emitter is grounded. The phototransistor changes its conduction state according to the light intensity of the LED: the stronger the light, the higher the conduction degree of the phototransistor, the smaller the equivalent resistance between the collector and emitter, and the lower the voltage of the first feedback signal fed back to the switch control circuit 42; the weaker the light, the lower the conduction degree of the phototransistor, the larger the equivalent resistance, and the higher the voltage of the first feedback signal. The current transfer ratio (CTR) of the optocoupler U2 satisfies: I LED *CTR=I PC Among them, I LED I represents the current of the light-emitting diode in the optocoupler U2. PC This represents the current of the phototransistor. Matching resistor R16 stabilizes the feedback loop gain, ensuring output voltage accuracy.

[0030] In some embodiments, the detection circuit 41 includes a reference voltage source U3 and a voltage divider circuit 411. The voltage divider circuit 411 is connected to the output terminal of the rectifier-filter circuit 30 and is used to divide the first DC voltage by a fixed ratio to obtain a feedback voltage, and apply the feedback voltage to the reference terminal of the reference voltage source U3. The feedback voltage is less than the first DC voltage. The reference voltage source U3 is connected to the voltage divider circuit 411 and is used to generate a first feedback signal that matches the direction and magnitude of the feedback voltage deviation when the feedback voltage received at the reference terminal deviates from the internal reference voltage of the reference voltage source U3; wherein, the voltage value of the first target voltage after being divided by a fixed ratio is consistent with the internal reference voltage.

[0031] The cathode of the reference voltage source U3 is connected to the cathode of the light-emitting diode in the optocoupler U2, and the anode of the reference voltage source U3 is grounded. The anode of the light-emitting diode in the optocoupler U2 is connected to the output terminal of the rectifier-filter circuit 30 via a current-limiting resistor R16. By setting the reference voltage source U3 and the voltage divider circuit 411, accurate sampling of the first DC voltage can be achieved. Combined with the optocoupler U2, the first feedback signal is transmitted to the switch control circuit 42 without loss. The first DC voltage output by the rectifier-filter circuit 30 is divided by the voltage divider circuit 411 and compared with the reference voltage of the reference voltage source U3 to generate an error voltage. The error voltage controls the input current of the optocoupler, causing the conduction degree of the phototransistor to change, and the first feedback signal is output to the switch control circuit 42.

[0032] For example, the reference voltage source U3 can be a TL431 reference voltage source, which internally consists of a precision reference source, a high-gain operational amplifier, and an NPN high-power transistor. The reference voltage inside the reference voltage source U3 is 2.5V, which is the voltage value after the first target voltage is divided according to a fixed ratio. If the feedback voltage is greater than 2.5V, the operational amplifier inside the reference voltage source U3 outputs a high level, driving the NPN high-power transistor to increase its conduction, increasing the input current of the optocoupler U2, and thus increasing the conduction of the phototransistor. If the feedback voltage is less than 2.5V, the operational amplifier inside the reference voltage source U3 outputs a low level, driving the NPN high-power transistor to decrease its conduction, decreasing the input current of the optocoupler, and thus decreasing the conduction of the phototransistor.

[0033] In some embodiments, the anode of the reference voltage source U3 is also connected to terminal 6 of the secondary winding Ns3 via resistor R12, and the cathode is grounded together with terminal 5 of the secondary winding Ns3. Resistor R12 can act as a voltage divider, ensuring stable operation of the reference voltage source U3 and preventing it from being broken down.

[0034] In some embodiments, the voltage divider circuit 411 includes resistors R13, R18, and R23. One end of resistor R13 is connected to the output terminal VOUT3 of the rectifier filter circuit 30, and the other end of resistor R13 is connected to one end of resistor R18 and the reference stage of the reference voltage source U3; the other end of resistor R18 is connected to one end of resistor R23, and the other end of resistor R23 is grounded.

[0035] The end where resistors R13 and R18 are connected serves as the output terminal of the feedback voltage. The reference terminal (REF terminal) of the reference voltage source U3 is connected in parallel to the anode (ground terminal) of U3 through resistor R14 and capacitor C15, forming an RC filter network to filter out high-frequency interference in the feedback signal. The reference voltage Uref of the reference voltage source U3 is 2.5V. The feedback voltage after the first target voltage is divided according to a fixed ratio is mainly determined by the voltage dividing resistors R13 and R18. Uout = Uref * (1 + R13 / R18) In this example, R13 = 2kΩ and R18 = 1kΩ, so the feedback voltage Uout = 2.5V × (1 + 2kΩ / 1kΩ) = 7.5V > 2.5V. Therefore, the operational amplifier inside the reference voltage source U3 outputs a high level, increasing the conduction of the NPN high-power transistor, increasing the input current of the optocoupler, and thus increasing the conduction of the phototransistor.

[0036] In some embodiments, the switch control circuit 42 is used for: When the first feedback signal indicates that the feedback voltage is greater than the reference voltage, a first target control signal is generated to indicate that the conduction time of the control switch circuit 11 is reduced; when the first feedback signal indicates that the feedback voltage is less than the reference voltage, a first target control signal is generated to indicate that the conduction time of the control switch circuit 11 is increased.

[0037] When the feedback voltage equals the reference voltage, it indicates that the first DC voltage output by the rectifier-filter circuit 30 is equal to the first target voltage required by the BMS, which satisfies the normal operation of the BMS. When the feedback voltage is greater than the reference voltage, it indicates that the first DC voltage output by the rectifier-filter circuit 30 is greater than the first target voltage required by the BMS. Therefore, by reducing the conduction time of the control switch circuit 11, the voltage value of the first alternating voltage can be reduced, so that the voltage difference between the first DC voltage output by the rectifier-filter circuit 30 and the first target voltage required by the BMS is less than or equal to a preset difference threshold. When the feedback voltage is less than the reference voltage, it indicates that the first DC voltage output by the rectifier-filter circuit 30 is less than the first target voltage required by the BMS. Therefore, by increasing the conduction time of the control switch circuit 11, the voltage value of the first alternating voltage can be increased, so that the voltage difference between the first DC voltage output by the rectifier-filter circuit 30 and the first target voltage required by the BMS is less than or equal to a preset difference threshold.

[0038] Optionally, the switch control circuit 42 includes a control chip U1, which receives a first feedback signal sent by the detection circuit 41 through the optocoupler U2 and generates a first target control signal based on the first feedback signal.

[0039] For example, the control chip U1 is a UC2844 chip. Pin 1 of the control chip U1 is connected to the collector of the phototransistor; pin 2 of the control chip U1 is connected to the emitter of the phototransistor and is used to receive the first feedback signal; pin 6 of the control chip U2 is connected to the switching circuit 11 and generates the first target control signal for adjusting the switching circuit 11.

[0040] The switch control circuit 42 also includes capacitor C18, resistor R17, capacitor C19, capacitor C20, capacitor C21, and resistor R21. Pin 1 of control chip U1 is grounded through capacitor C18; pins 2 and 5 of control chip U1 are directly grounded; pin 3 of control chip U1 is grounded through capacitor C19; pin 4 of control chip U1 is connected to one end of capacitor C20 and resistor R21; the other end of resistor R21 is connected to one end of capacitor C21 and pin 8 of control chip U1; and the other ends of capacitors C20 and C21 are grounded.

[0041] The operating frequency f of the control chip U1 is determined by resistor R17 and capacitor C19: f = 1.8 / (R17 * C19).

[0042] In a specific embodiment of this application, R17=1kΩ, C19=1nF, then the operating frequency of the control chip U1 is f=1.8 / (1kΩ*1nF)=1.8MHz, which ensures the high efficiency of the switch control circuit 42.

[0043] In one embodiment, the transformer 20 further includes: The auxiliary winding Ncc is connected to the feedback control circuit 40 and is used to power the feedback control circuit 40.

[0044] In this design, the auxiliary winding Ncc is wound on the same iron core as the secondary and primary windings Np. When a high-frequency pulse current is applied to the primary winding Np, the changing magnetic field generated in the iron core is simultaneously coupled to the secondary windings Ns1, Ns2, and Ns3, and the auxiliary winding Ncc, inducing corresponding voltages in these windings. The number of turns in the auxiliary winding Ncc must be designed to match the operating voltage required by the control chip U1.

[0045] For example, such as Figure 2As shown, pin 7 of control chip U1 is connected to the auxiliary winding Ncc through a series diode D10 and resistor R10, receiving the operating voltage provided by the auxiliary winding Ncc. Pin 7 of control chip U1 is also grounded through parallel capacitors C14 and C13, used to receive the output voltage of the auxiliary winding Ncc after rectification by diode D10 and current limiting by resistor R10.

[0046] In one embodiment, the transformer 20 includes a plurality of secondary windings Ns coupled to the primary winding Np, and the rectifier filter circuit 30 includes a plurality of rectifier filter units, each of which is connected to a secondary winding Ns. The plurality of rectifier filter units are used to output DC voltages of different magnitudes.

[0047] At least one rectifier and filter unit is used to output the first target voltage required by the BMS, which is 12V. Other rectifier and filter units can be used to output the 3.5V or 5V voltage required by low-voltage modules in the BMS, such as sampling and detection modules. Alternatively, they can be used to output the DC voltage (e.g., 15V) required by other external structures besides the BMS, without limitation.

[0048] In other embodiments, the output voltages of multiple rectifier and filter units may also be equal, for example, all 12V, to power different modules that require the same voltage.

[0049] For example, each rectifier-filter unit includes a rectifier diode, a current-limiting resistor, a first filter capacitor, and a second filter capacitor. The positive terminal of the rectifier diode is connected to one end of the secondary winding, and the negative terminal of the rectifier diode is connected to one end of the current-limiting resistor and one end of the first filter capacitor, respectively. The other end of the current-limiting resistor is connected to the input terminal of the feedback control circuit 40 and one end of the second filter capacitor. The other ends of the first filter capacitor and the other ends of the second filter capacitor are connected to the other end of the secondary winding.

[0050] In one specific embodiment, such as Figure 2As shown, the first rectifier-filter unit is connected to the first primary winding Ns1 and includes a rectifier diode D1, a current-limiting resistor R1, filter capacitors C1, C3, and C4, a current-limiting resistor R4, and a Zener diode D2. The anode of the rectifier diode D1 is connected to one end of the first primary winding Ns1, and the cathode of the rectifier diode D1 is connected to one end of the current-limiting resistor R1. The other end of the current-limiting resistor R1 serves as the output terminal VOUT1 of the first rectifier-filter unit. One end of the filter capacitor C3 is connected to the cathode of the rectifier diode D1, and the other end of the filter capacitor C3 is connected to the other end (reference ground) of the first primary winding Ns1. One end of each of the filter capacitors C4, C1, R4, and D2 is connected to the other end of the current-limiting resistor R1, and the other ends of each of the filter capacitors C4, C1, R4, and D2 are connected to the other end (reference ground) of the first primary winding Ns1.

[0051] The rectifier diode D1 converts the alternating voltage of the secondary winding into unidirectional pulsating DC. Filter capacitors C3 and C4 are solid-state capacitors used to filter out low-frequency ripple. Filter capacitor C1 is a ceramic capacitor used to filter out high-frequency noise. Together, these three components output a stable DC voltage. Furthermore, filter capacitors C3 and C4, along with the current-limiting resistor R1, form a π-type filter network, resulting in a more stable DC voltage output. The current-limiting resistor R4 limits the Zener diode current, and the Zener diode D2 clamps the output voltage to achieve stable power supply.

[0052] The second rectifier-filter unit is connected to the second-stage winding Ns2 and includes a rectifier diode D6, a current-limiting resistor R5, filter capacitors C9, C12, and C11, and a Zener diode D7. The anode of rectifier diode D6 is connected to one end of the second-stage winding Ns2, and the cathode of rectifier diode D6 is connected to one end of the current-limiting resistor R5. The other end of the current-limiting resistor R5 serves as the output terminal VOUT2 of the second rectifier-filter unit. One end of filter capacitor C12 is connected to the cathode of rectifier diode D6, and the other end of filter capacitor C12 is connected to the other end (reference ground) of the second-stage winding Ns2. One end of filter capacitors C11, C9, R9, and D7 is connected to the other end of the current-limiting resistor R5, and the other ends of filter capacitors C11, C9, R9, and D7 are all connected to the other end (reference ground) of the second-stage winding Ns2.

[0053] The rectifier diode D6 is used to convert the alternating voltage of the secondary winding into unidirectional pulsating DC. Filter capacitors C11 and C12 are solid-state capacitors used to filter out low-frequency ripple. Filter capacitor C9 is a ceramic capacitor used to filter out high-frequency noise. Together, these three components output a stable DC voltage. Furthermore, filter capacitors C11 and C12, along with the current-limiting resistor R5, form a π-type filter network, resulting in a more stable DC voltage output. The current-limiting resistor R9 limits the Zener diode current, and the Zener diode D7 clamps the output voltage to achieve stable power supply.

[0054] The third rectifier-filter unit is connected to the third stage winding Ns3 and includes a rectifier diode D11, a current-limiting resistor R11, filter capacitors C17, C16, and C22, as well as a current-limiting resistor R25. The anode of rectifier diode D11 is connected to one end of the third stage winding Ns2, and the cathode of rectifier diode D11 is connected to one end of the current-limiting resistor R11. The other end of the current-limiting resistor R11 serves as the output terminal VOUT3 of the third rectifier-filter unit. One end of filter capacitor C17 is connected to the cathode of rectifier diode D11, and the other end of filter capacitor C17 is connected to the other end (reference ground) of the third stage winding Ns3. One end of filter capacitor C16 is connected to the other end of the current-limiting resistor R11, and the other end of filter capacitor C16 is grounded. Resistor R11, filter capacitor C17, and filter capacitor C16 form a π-type filter network to make the output DC voltage more stable. One end of the filter capacitor C22 is connected to the cathode of the rectifier diode D11 through resistor R12, and the other end of the filter capacitor C22 is connected to the other end (reference ground) of the third winding Ns3. One end of the current-limiting resistor R25 is connected to the other end of the current-limiting resistor R11, and the other end of the current-limiting resistor R25 is connected to the other end (reference ground) of the third winding Ns3.

[0055] The rectifier diode D11 is used to convert the alternating voltage of the secondary winding into unidirectional pulsating DC. Filter capacitors C16 and C17 are solid-state capacitors used to filter out low-frequency ripple. Filter capacitor C22 is a ceramic capacitor used to filter out high-frequency noise. These three components work together to output a stable DC output. The current-limiting resistor R25 is used to limit the current of the Zener diode.

[0056] For example, rectifier diodes D1, D6 and D11 are all Schottky diodes with a reverse withstand voltage of 100V and a forward current of 20A.

[0057] It should be noted that, Figure 2 The rectifier filter circuit 30 in the diagram only outlines two rectifier filter units (the first rectifier filter unit and the second filter unit), but in reality, the rectifier filter circuit 30 also includes a third filter unit. Furthermore... Figure 2Only the detection circuit 41 in the feedback control circuit 40 is shown connected to the third rectifier filter unit. In fact, both the first rectifier filter unit and the second rectifier filter unit are connected to a detection circuit 41. Figure 2 (Not shown). Accordingly, the feedback control circuit 40 may include multiple detection circuits 41, each connected to a corresponding rectifier and filter unit, for acquiring the actual DC voltage output by each rectifier and filter unit, and based on the DC voltage output by each rectifier and filter unit, sending a corresponding feedback signal to the switch control circuit 42 through the optocoupler U2. This allows the switch control circuit 42 to adjust the conduction time of the switch circuit based on the target control signal generated by the corresponding feedback signal, thereby adjusting the first alternating voltage input to the primary winding, so that each rectifier and filter unit can ultimately output the required target DC voltage.

[0058] For example, a first rectifier and filter unit is used to output a first DC voltage, a second rectifier and filter unit is used to output a second DC voltage, and a third rectifier and filter unit is used to output a third DC voltage. The magnitudes of the first, second, and third DC voltages can be different. The DC voltage output by each rectifier and filter unit is related to the turns ratio of the secondary winding to the primary winding to which each rectifier and filter unit is connected.

[0059] For example, the ripple ΔU of the DC voltage output by each filter unit is related to the switching cycle of the switching circuit, the turns ratio of the secondary winding to the primary winding, and the total capacitance value of the filter capacitor, and is usually controlled within 50mV.

[0060] ΔU can be estimated by the following formula: ΔU=(Iout*T) / (2*C 总 ).

[0061] Where Iout is the output current required by the load, which can be obtained by adjusting the conduction time of the switching circuit and the turns ratio of the transformer. T is the switching cycle of the switching circuit 11, and C... 总 This represents the total capacitance of the filter capacitors.

[0062] For example, Iout = 1A, C 总 =147μF, T=f1=1 / 1.8MHz≈0.556μs, then we can obtain: ΔU=(1A×0.556μs) / (2×147μF)≈1.88mV.

[0063] For example, transformer 20 uses an EE16 type ferrite core transformer with an operating frequency of 65kHz. The primary winding Np of transformer 20 has 200 turns and uses 0.2mm enameled wire; the first primary winding Ns1 has 10 turns, the second primary winding Ns2 has 15 turns, and the third primary winding Ns3 has 5 turns, all using 0.3mm enameled wire; the auxiliary winding Nec has 8 turns and is used to provide operating voltage for the feedback control circuit 40. The primary and secondary insulation strength of transformer 20 is greater than 2500VAC.

[0064] In some embodiments, such as Figure 2 As shown, the switching circuit 11 includes a switching transistor Q1, a drive current-limiting resistor R19, and a gate discharge circuit.

[0065] The gate of the switching transistor Q1 is connected to the signal output terminal of the switching control circuit 42 through the driving current limiting resistor R19, the drain of the switching transistor Q1 is connected to one end of the primary winding, and the source of the switching transistor Q1 is grounded.

[0066] The gate discharge circuit includes a discharge resistor R15 and a discharge diode D12. The anode of the discharge diode D12 is connected to the gate of the switching transistor Q1, the cathode of the discharge diode D12 is connected to one end of the discharge resistor R15, and the other end of the discharge resistor R15 is connected to the signal output terminal of the switch control circuit 42.

[0067] The drive current-limiting resistor R19 is used to limit the drive current flowing into the gate of the switching transistor Q1, preventing excessive current from damaging the gate of Q1. It also controls the switching speed of Q1 and optimizes electromagnetic interference during the switching process. When the signal output of the switch control circuit 42 is turned off, the bleeder diode D12 conducts, and the bleeder resistor R15 provides a discharge path for the residual charge on the gate of Q1, accelerating the turn-off process of Q1 and preventing residual gate charge from causing false turn-on of Q1.

[0068] For example, both the bleeder resistor R15 and the drive current-limiting resistor R19 are connected to pin 6 of the control chip U1. The control chip U1 outputs a first target control signal through pin 6. The first target control signal is a PWM drive signal used to control the on / off state of the switching transistor Q1. The duty cycle D (the ratio of conduction time to period) of the switching transistor Q1 is: D = ton / T.

[0069] The switching circuit also includes resistors R22 and R24. One end of resistor R22 is connected to the gate of the switching transistor Q1. The other end of resistor R22 and one end of resistor R24 ​​are connected to pin 3 of the control chip U1 via resistor R17. One end of resistor R24 ​​is connected to the source of the switching transistor Q1, and the other end of resistor R24 ​​is grounded. Resistor R22 acts as a pull-down resistor for the gate of the switching transistor Q1, pulling the gate potential of Q1 low to ground when there is no drive signal, ensuring reliable turn-off of Q1 and preventing malfunctions caused by a floating gate. Resistor R24 ​​acts as a source sampling resistor for the switching transistor Q1, used to detect the source current of Q1 and provide an overcurrent protection signal to the control chip U1. When the current exceeds a set threshold, U1 will turn off the drive signal for the switching transistor, protecting Q1 and the entire circuit.

[0070] In one exemplary embodiment, the switching transistor Q1 is a 2N60 type N-channel MOSFET with a withstand voltage of 600V and an on-resistance of 10Ω.

[0071] For example, the turns ratio of transformer 20 is U secondary / U primary = N secondary / N primary. The turns ratio of the transformer (i.e., the turns ratio of the primary winding and the secondary winding) can be determined based on the first target voltage required by the BMS, the initial DC voltage output by the power battery, and the maximum duty cycle of the switching transistor.

[0072] Taking a first DC voltage of 12V as an example, if the minimum value of the first AC voltage U min =230V, the maximum duty cycle D of the switching transistor Q1 is 0.45, then the turns ratio of the primary winding Np and the secondary winding Ns2 of transformer 20 must satisfy: Np / Ns2=(U min *D) / (U out +U D6 ) Among them, U out =12V is the first DC voltage, U D6 The forward voltage drop of rectifier diode D6 is 0.5V. Substituting this into the equation, we get: (230*0.45) / (12+0.5)≈8.28. Therefore, in the actual design, taking the primary winding Np of transformer 20 to be 83 turns and the secondary winding Ns2 to be 10 turns is sufficient to meet the turns ratio requirement.

[0073] In one embodiment, the power conversion circuit further includes a power status indication module. For example... Figure 2 As shown, the power status indicator module includes a current-limiting resistor R20 and a light-emitting unit D13. One end of the current-limiting resistor R20 is connected to the output terminal of the rectifier filter circuit, and the other end is connected to the anode of the light-emitting unit D13. The cathode of the light-emitting unit D13 is grounded.

[0074] Optionally, the light-emitting unit D13 is a light-emitting diode (LED). The power status indicator module can visually display whether the power module is working properly. When the circuit is powered on and operating normally, the LED D13 will light up, allowing users or maintenance personnel to quickly determine the power status and promptly detect power failures.

[0075] Figure 3 A framework diagram of another power conversion circuit provided by an embodiment of the present invention is shown, as follows. Figure 3 As shown, in one embodiment, the input circuit 10 further includes: The input filter circuit 12 is connected to the output terminal of the power battery, and the output terminal of the input filter circuit 12 is connected to the primary winding through the switching circuit 40. The input filter circuit 12 is used to filter the initial DC voltage output by the power battery.

[0076] See Figure 2 As shown, the input filter circuit 12 includes capacitors C25, C7, and C8, and resistors R26 and R27. One end of capacitors C25, C7, and C8 is connected in parallel to the output terminal of the power battery and the primary winding, while the other end is grounded. Resistors R26 and R27 are connected in series and then in parallel with capacitors C25, C7, and C8.

[0077] Among them, capacitor C25 is a high-voltage ceramic capacitor used to suppress low-frequency interference of the input voltage; capacitors C7 and C8 are film capacitors used to suppress high-frequency interference of the input voltage.

[0078] The impedance characteristics of a capacitor satisfy Z c =jωC, where ω is the angular frequency, ω=2πf, f is the frequency of the interference signal, and C is the capacitance value. By selecting a suitable capacitor, the interference signal can form a low-impedance path on the capacitor and thus be filtered out.

[0079] Optionally, capacitor C25 has a capacitance of 10μF and a rated voltage of 1000V; capacitor C7 has a capacitance of 100nF and a rated voltage of 1000V; and capacitor C8 has a capacitance of 100nF and a rated voltage of 1000V. The input voltage range is 230-850V DC. After input filtering, high-frequency interference in the input voltage can be suppressed by more than 30dB.

[0080] Resistors R26 and R27 are both 200KΩ, used to limit the input inrush current during the initial power-on phase to prevent capacitors C25, C7, and C8 from being damaged by the instantaneous large current.

[0081] In some embodiments, resistors R3, R7, R6, capacitor C2, resistor R8, diode D5, diode D10, and resistor R10 are also provided between the input filter circuit 12 and the transformer 10.

[0082] In this circuit, resistor R6 and capacitor C2 are connected in parallel and then through resistor R8 and diode D5 to the primary winding of transformer 10 and the drain of switching transistor Q1. Capacitor C2, resistor R8, and diode D5 form an RCD spike absorption circuit to suppress voltage spikes when the transformer primary winding or the switching transistor is turned off, ensuring circuit reliability. Resistors R3 and R7 are connected in series to form a voltage divider starting circuit. One end is connected to the output terminal of the power battery, and the other end is connected to pin 7 of control chip U1 to provide the initial starting voltage for control chip U1.

[0083] This application also provides a battery management system, including the power conversion circuit described above. The power conversion circuit can be integrated into the battery management system.

[0084] The power conversion circuit and battery management system provided by this invention, by setting up an input circuit including a switching circuit, a transformer, a rectifier and filter circuit, and a feedback control circuit, can directly step down and filter the high-voltage DC power from the power battery into the stable low-voltage DC power required by the BMS, providing a reliable power supply for the core module of the battery management system and ensuring stable system operation. Furthermore, this power conversion circuit is integrated into the BMS, eliminating the need for a traditional 12V lead-acid battery and a dedicated DC-DC converter. This breaks the limitations of a dual-battery architecture, simplifies the vehicle's electrical system, reduces integration and troubleshooting costs as well as hardware costs, reduces additional weight and volume to fit lightweight design, reduces energy loss to improve energy efficiency, and simultaneously ensures power supply stability through feedback control, providing reliable support for the core functions of the BMS and effectively overcoming the technical bottlenecks of traditional low-voltage power supply architectures.

[0085] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A power conversion circuit, characterized in that, The power conversion circuit, located in the battery management system, includes: The input circuit includes a switching circuit, which is connected to the output terminal of the power battery and is used to convert the initial DC voltage output by the power battery into a first alternating voltage. A transformer includes a primary winding and a secondary winding, the primary winding being connected to the input circuit, and the transformer being used to step down the first alternating voltage output by the input circuit to a second alternating voltage; A rectifier and filter circuit, connected to the secondary winding, is used to convert the second alternating voltage into a first direct current voltage and to filter the first direct current voltage. A feedback control circuit, connected to the switching circuit and the rectifier-filter circuit, is used to generate a first target control signal and send it to the switching circuit when the voltage difference between the first DC voltage output by the rectifier-filter circuit and the first target voltage required by the battery management system is greater than a preset difference threshold. The switching circuit is used to adjust the on-time of the switching circuit based on the first target control signal, so as to adjust the voltage value of the first alternating voltage, such that the voltage difference is less than or equal to the difference threshold.

2. The power conversion circuit according to claim 1, characterized in that, The feedback control circuit includes a detection circuit, an optocoupler, and a switch control circuit. The input terminal of the detection circuit is connected to the output terminal of the rectifier and filter circuit, the output terminal of the detection circuit is connected to the input terminal of the switch control circuit through the optocoupler, and the output terminal of the switch control circuit is connected to the switch circuit. The detection circuit is used to send a first feedback signal to the switch control circuit through the optocoupler when it detects that the voltage difference between the first DC voltage and the first target voltage is greater than a preset difference threshold. The switch control circuit is used to generate the first target control signal based on the first feedback signal.

3. The power conversion circuit according to claim 2, characterized in that, The detection circuit includes a reference voltage source and a voltage divider circuit, wherein, The voltage divider circuit is connected to the output terminal of the rectifier and filter circuit, and is used to divide the first DC voltage by a fixed ratio to obtain a feedback voltage, and apply the feedback voltage to the reference terminal of the reference voltage source. The feedback voltage is less than the first DC voltage. The reference voltage source is connected to the voltage divider circuit. The reference voltage source is used to generate a first feedback signal that matches the direction and magnitude of the feedback voltage deviation when the feedback voltage received at the reference terminal deviates from the reference voltage inside the reference voltage source. The voltage value of the first target voltage after being divided according to the fixed ratio is consistent with the reference voltage.

4. The power conversion circuit according to claim 3, characterized in that, The switch control circuit is used for: When the first feedback signal indicates that the feedback voltage is greater than the reference voltage, a first target control signal is generated to indicate a reduction in the on-time of the switching circuit. When the first feedback signal indicates that the feedback voltage is less than the reference voltage, a first target control signal is generated to indicate an increase in the on-time of the switching circuit.

5. The power conversion circuit according to claim 2, characterized in that, The switching circuit includes a switching transistor, a drive current-limiting resistor, and a gate discharge circuit. The gate of the switching transistor is connected to the signal output terminal of the switching control circuit through the driving current limiting resistor, the drain of the switching transistor is connected to one end of the primary winding, and the source of the switching transistor is grounded. The gate discharge circuit includes a discharge resistor and a discharge diode. The anode of the discharge diode is connected to the gate of the switching transistor, the cathode of the discharge diode is connected to one end of the discharge resistor, and the other end of the discharge resistor is connected to the signal output terminal of the switch control circuit.

6. The power conversion circuit according to claim 1, characterized in that, The transformer includes a plurality of secondary windings coupled to the primary winding, and the rectifier and filter circuit includes a plurality of rectifier and filter units, each of which is connected to one of the secondary windings. The plurality of rectifier and filter units are used to output DC voltages of different magnitudes.

7. The power conversion circuit according to claim 1, characterized in that, The transformer also includes: An auxiliary winding is connected to the feedback control circuit and is used to supply power to the feedback control circuit.

8. The power conversion circuit according to claim 1, characterized in that, The input circuit also includes: An input filter circuit is provided, wherein the input terminal of the input filter circuit is connected to the output terminal of the power battery, and the output terminal of the input filter circuit is connected to the primary winding through the switching circuit. The input filter circuit is used to filter the initial DC voltage output by the power battery.

9. The power conversion circuit according to claim 1, characterized in that, The power conversion circuit further includes: The power status indicator module includes a current-limiting resistor and a light-emitting unit. One end of the current-limiting resistor is connected to the output terminal of the rectifier filter circuit, and the other end is connected to the anode of the light-emitting unit. The cathode of the light-emitting unit is grounded.

10. A battery management system, comprising the power conversion circuit as described in any one of claims 1-9.

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