CN121663998A

CN121663998A - Power conversion circuit and battery management system

Info

Publication number: CN121663998A
Application number: CN202511764927.7A
Authority: CN
Inventors: 任强; 张坤华; 胡文锦
Original assignee: Dongfeng Motor Group Co Ltd
Current assignee: Dongfeng Motor Group Co Ltd
Priority date: 2025-11-27
Filing date: 2025-11-27
Publication date: 2026-03-13

Abstract

This invention relates to the field of new energy technology, specifically to a power conversion circuit and a battery management system. The circuit includes: an input circuit, including a switching circuit connected to the output terminal of a power battery; a transformer, including a primary winding and a secondary winding, the primary winding being connected to the input circuit; a rectifier and filter circuit connected to the secondary winding; and a feedback control circuit connected to the switching circuit and the rectifier and filter circuit. It can efficiently and stably convert the input voltage into a target DC voltage, with high conversion efficiency and low ripple, providing a reliable power supply for the battery management system and ensuring stable system operation.

Description

Power conversion circuit and battery management system

Technical Field

The invention relates to the technical field of new energy, in particular to a power supply conversion circuit and a battery management system.

Background

A Battery Management System (BMS) serves as a "brain" of the Battery system, and performs real-time monitoring on key parameters such as voltage, current, temperature, etc. of the Battery, accurate estimation on a State of Charge (SOC) and a State of Health (SOH), and an important function of starting a protection mechanism when abnormal conditions such as overcharge, overdischarge, and overtemperature occur in the Battery.

In order to ensure that a BMS and other vehicle controllers (such as a vehicle controller VCU and a motor controller MCU) can obtain stable low-voltage power supply, a set of 12V lead-acid batteries needs to be additionally configured as a core power supply of a low-voltage power supply system, and the 12V lead-acid batteries need to be set independently of a power battery system, so that a vehicle electrical appliance architecture presents a double-battery architecture mode of 'power battery+12v lead-acid batteries'. The double-battery architecture not only greatly improves the structural complexity of the whole vehicle electrical system and increases the system integration difficulty and the fault investigation cost, but also has adverse effects on the pursuit light-weight design target of the new energy automobile due to certain weight and volume of the 12V lead-acid battery, thereby restricting the improvement of the whole vehicle cruising ability to a certain extent.

Further, because there is a great difference between the power supply voltage of the 12V lead-acid battery and the output voltage (usually hundreds of volts) of the power battery, in order to realize continuous charging of the 12V lead-acid battery, a DC-DC converter needs to be additionally configured in the whole vehicle circuit, and the high-voltage direct current output by the power battery is down-converted into the low-voltage direct current adapted to the 12V lead-acid battery through the DC-DC converter (direct current-direct current converter). However, in the energy conversion process, the conversion efficiency of the DC-DC converter is limited (generally, the conversion efficiency is difficult to reach 100%), energy loss is inevitably generated, the energy utilization efficiency of the whole vehicle is reduced, meanwhile, the introduction of the DC-DC converter also increases the hardware cost and the circuit complexity of the whole vehicle, and the stability of the DC-DC converter in the long-term operation process can also have potential influence on the reliability of the whole vehicle power supply system.

In summary, the low-voltage power supply architecture based on the 12V lead-acid battery in the current new energy automobile has obvious defects in the aspects of system complexity, overall light weight, energy utilization efficiency, cost control and the like, and becomes a key technical bottleneck for restricting the performance improvement and industrialization development of the new energy automobile, and a novel low-voltage power supply solution is needed to be provided so as to overcome the defects and the defects of the prior art.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a power supply conversion circuit and a battery management system, which aim to efficiently and stably convert input voltage into voltage suitable for a battery management system, and a 12V lead-acid battery or a DC-DC converter is not required to be additionally arranged, so that the hardware cost and the circuit complexity of the whole vehicle are reduced.

To solve at least one of the above problems, in a first aspect, the present invention provides a power conversion circuit, which is disposed in a battery management system, and includes:

The input circuit comprises a switch circuit, and the switch circuit is connected with the output end of the power battery and is used for converting the initial direct-current voltage output by the power battery into a first alternating voltage;

The transformer comprises a primary winding and a secondary winding, the primary winding is connected with the input circuit, and the transformer is used for reducing the first alternating voltage output by the input circuit into a second alternating voltage;

The rectification filter circuit is connected with the secondary winding and used for converting the second alternating voltage into a first direct voltage and filtering the first direct voltage;

the feedback control circuit is connected with the switching circuit and the rectifying and filtering circuit and is used for generating a first target control signal and sending the first target control signal to the switching circuit when the voltage difference between the first direct current voltage output by the rectifying and filtering circuit and the first target voltage required by the battery management system is larger than a preset difference threshold value;

The switching circuit is used for adjusting 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, so that the voltage difference value is smaller than or equal to the difference value threshold value.

Optionally, the feedback control circuit includes a detection circuit, a photo coupler, and a switch control circuit;

The input end of the detection circuit is connected with the output end of the rectifying and filtering circuit, the output end of the detection circuit is connected with the input end of the switch control circuit through the photoelectric coupler, and the output end of the switch control circuit is connected with the switch circuit;

The detection circuit is used for sending a first feedback signal to the switch control circuit through the photoelectric coupler when detecting that the voltage difference between the first direct-current voltage and the first target voltage is larger than a preset difference threshold value, and the switch control circuit is used for generating the first target control signal based on the first feedback signal.

Optionally, the detection circuit comprises a reference voltage source and a voltage divider circuit, wherein,

The voltage dividing circuit is connected with the output end of the rectifying and filtering circuit and is used for dividing the first direct-current voltage in a fixed proportion to obtain a feedback voltage, and applying the feedback voltage to the reference end of the reference voltage source, wherein the feedback voltage is smaller than the first direct-current voltage;

The reference voltage source is connected with the voltage dividing circuit and is used for generating a first feedback signal matched with the deviation direction and the deviation of the feedback voltage when the feedback voltage received by the reference voltage source deviates from the reference voltage in the reference voltage source, wherein the voltage value of the first target voltage after being divided according to the fixed proportion is consistent with the reference voltage.

Optionally, the switch control circuit is configured to:

Generating the first target control signal for indicating a decrease in on-time for controlling the switching circuit when the first feedback signal indicates that the feedback voltage is greater than the reference voltage;

When the first feedback signal indicates that the feedback voltage is smaller than the reference voltage, the first target control signal for indicating to control the increase of the on time of the switching circuit is generated.

Optionally, the switching circuit comprises a switching tube, a driving current limiting resistor and a grid bleeder circuit;

The grid electrode of the switching tube is connected with the signal output end of the switching control circuit through the driving current limiting resistor, the drain electrode of the switching tube is connected with one end of the primary winding, and the source electrode of the switching tube is grounded;

the grid bleeder circuit comprises a bleeder resistor and a bleeder diode, wherein the anode of the bleeder diode is connected with the grid of the switching tube, the cathode of the bleeder diode is connected with one end of the bleeder resistor, and the other end of the bleeder resistor is connected with the signal output end of the switching control circuit.

Optionally, the transformer includes a plurality of secondary windings coupled with the primary winding, the rectifying and filtering circuit includes a plurality of rectifying and filtering units, each rectifying and filtering unit is correspondingly connected with one secondary winding, and the plurality of rectifying and filtering units are respectively used for outputting direct-current voltages with different voltage magnitudes.

Optionally, the transformer further includes:

and the auxiliary winding is connected with the feedback control circuit and is used for supplying power to the feedback control circuit.

Optionally, the input circuit further includes:

The input end of the input filter circuit is connected with the output end of the power battery, the output end of the input filter circuit is connected with the primary winding through the switch circuit, the input filter circuit is used for filtering the initial direct-current voltage output by the power battery.

Optionally, the power conversion circuit further includes:

the power state indicating module comprises a current limiting resistor and a light emitting unit, wherein one end of the current limiting resistor is connected with the output end of the rectifying and filtering circuit, the other end of the current limiting resistor is connected with the anode of the light emitting unit, and the cathode of the light emitting unit is grounded.

In order to achieve the above object, according to a second aspect of the present invention, there is provided a battery management system including the power conversion circuit as described in any one of the above.

By means of the technical scheme, the power supply conversion circuit and the battery management system can directly step down and filter the high-voltage direct current of the power battery into stable low-voltage direct current required by the BMS through the input circuit comprising the switch circuit, the transformer, the rectifying and filtering circuit and the feedback control circuit, so that reliable power supply is provided for a core module of the battery management system, and stable operation of the system is guaranteed. And this power conversion circuit sets up in BMS, saves traditional 12V lead acid battery and special DC-DC converter, has both broken the limit of double cell framework, has simplified whole car electrical system, reduced integration and troubleshooting cost and hardware cost, reduces extra weight volume again in order to agree with lightweight design, reduce the energy loss in order to promote energy utilization efficiency, simultaneously with the help of feedback control guarantee power supply stability, provides reliable support for BMS core function, has effectively broken through the technical bottleneck of traditional low pressure power supply framework.

The foregoing description is only an overview of the present invention, and is intended to provide a better understanding of the technical means of the present invention, as well as to provide a better understanding of the present invention with reference to the following detailed description of the invention, when read in light of the above and other objects, features and advantages of the present invention.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:

Fig. 1 shows a frame diagram of a power conversion circuit according to an embodiment of the present invention;

Fig. 2 shows a schematic circuit diagram of a power conversion circuit according to an embodiment of the present invention;

Fig. 3 is a block diagram of another power conversion circuit according to an embodiment of the present invention.

Detailed Description

In order to better understand the technical solutions provided by the embodiments of the present specification, the following detailed description of the technical solutions of the embodiments of the present specification is made through the accompanying drawings and the specific embodiments, and it should be understood that the specific features of the embodiments of the present specification are detailed descriptions of the technical solutions of the embodiments of the present specification, and not limit the technical solutions of the present specification, and the technical features of the embodiments of the present specification may be combined with each other without conflict.

In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises an element. The term "two or more" includes two or more cases.

As described above, in order to efficiently and stably convert an input voltage into a voltage adapted to a vehicle controller, the present invention provides a power conversion circuit provided in a BMS battery management system for converting an initial dc voltage (typically 230-850V dc voltage) output from a power battery into a first target voltage (typically 12V dc voltage) required for the BMS.

Fig. 1 shows a frame diagram of a power conversion circuit according to an embodiment of the present invention, and as shown in fig. 1, the power conversion circuit includes an input circuit 10, a transformer 20, a rectifying and filtering circuit 30, and a feedback control circuit 40.

The input circuit 10 comprises a switching circuit 11, the switching circuit 11 being connected to the output of the power cell for converting an initial dc voltage output by the power cell into a first alternating voltage. The transformer 20 comprises a primary winding and a secondary winding, the primary winding being connected to the input circuit 10, the transformer 20 being arranged to step down a first alternating voltage output by the input circuit 10 to a second alternating voltage. The rectifying and filtering circuit 30 is connected to the secondary winding for converting the second alternating voltage into a first direct voltage and filtering the first direct voltage. The feedback control circuit 40 is connected to the switching circuit 10 and the rectifying and filtering circuit 30, and the feedback control circuit 40 is configured to generate a first target control signal and send the first target control signal to the switching circuit 11 when a voltage difference between the first dc voltage output by the rectifying and filtering circuit 30 and a first target voltage required by the BMS is greater than a preset difference threshold. The switching circuit 11 is configured to adjust the on time of the switching circuit 11 based on the first target control signal to adjust the voltage value of the first alternating voltage such that the voltage difference is less than or equal to the difference threshold.

Through the power conversion circuit provided by the embodiment, the initial direct current 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 direct current voltage through the rectification filter circuit 30 to obtain a preliminary voltage output, then the feedback control circuit 40 monitors the first direct current voltage in real time, and when the first direct current voltage deviates from a first target voltage required by the battery management system BMS, a first target control signal is generated and sent to the switch circuit 11 to adjust the on time of the switch circuit 11. The longer the on-time of the switching circuit 11 in one working cycle, the longer the energy input duration of the primary winding, the more electric energy (stored in the form of magnetic energy) the primary winding receives in one working cycle, and the shorter the on-time of the switching circuit 11 in one working cycle, the less the input energy. The first alternating voltage is essentially an 'equivalent voltage value' of a high-frequency pulse signal generated by switching the switching circuit 11, and is determined by the energy input duration of the primary winding, namely, the longer the energy input duration is, the higher the 'effective amplitude' of the pulse signal is (namely, the larger the equivalent voltage value of the first alternating voltage is), and otherwise, the smaller the equivalent voltage value is. Thus, by varying the on-time of the switching circuit 11 in one duty cycle, the voltage value of the first alternating voltage can be varied. When the voltage value of the first alternating voltage changes, the change amplitude of the magnetic flux induced by the secondary winding coupled with the primary winding also changes, and the voltage value of the corresponding output second alternating voltage is synchronously adjusted, so that the voltage difference value between the first direct voltage output by the rectifying and filtering circuit 30 and the first target voltage is smaller than or equal to the difference threshold value, and stable output of the voltage required by the BMS is realized.

Fig. 2 shows a schematic circuit diagram of a power conversion circuit according to an embodiment of the present invention, and as shown in fig. 2, in one embodiment, a feedback control circuit 40 includes a detection circuit 41, a photo coupler U2, and a switch control circuit 42.

The input end of the detection circuit 41 is connected with the output end of the rectifying and filtering circuit 30, the output end of the detection circuit 41 is connected with the input end of the switch control circuit 42 through the photoelectric coupler U2, the output end of the switch control circuit 42 is connected with the switch circuit 11, the detection circuit 41 is used for sending a first feedback signal to the switch control circuit 42 through the photoelectric coupler U2 when detecting that the voltage difference between the first direct current voltage and the first target voltage is larger than a preset difference threshold value, and the switch control circuit 42 is used for generating a first target control signal based on the first feedback signal.

The photo coupler U2 may be a PC817 photo coupler, where the photo coupler U2 is an isolation device for implementing electro-optical-electrical signal conversion, and includes a light emitting diode (input end) and a phototransistor (output end) coupled through an optical path. Through the conversion of the electric-optical-electric signals, the U2 transmits the voltage deviation information (first feedback signal) output by the detection circuit 41 to the switch control circuit 42, and meanwhile, the electric isolation between the high-voltage side of the primary winding and the low-voltage side of the secondary winding is realized, the high-voltage interference is avoided from entering the low-voltage control end, and the circuit safety and the signal stability are ensured.

The light emitting diode is illustratively connected to the output of the detection circuit 41, and the current flowing through the light emitting diode increases if the first direct voltage is greater than the first target voltage, and decreases if the first direct voltage is less than the first target voltage. The collector of the phototransistor is connected to the switch control circuit 42 and the emitter is grounded. The phototransistor changes its on state according to the light intensity of the light emitting diode, the stronger the light, the higher the conduction degree of the phototransistor, the smaller the equivalent resistance between the collector and the emitter, the lower the voltage of the first feedback signal fed back to the switch control circuit 42, and 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 photo coupler U2 satisfies I _LED*CTR=I_PC. Wherein I _LED is the led current in the optocoupler U2, and I _PC is the phototransistor current. The feedback loop gain is stabilized through the matching resistor R16, and the output voltage precision is ensured.

In some embodiments, detection circuit 41 includes a reference voltage source U3 and a voltage divider circuit 411. The voltage dividing circuit 411 is connected to an output end of the rectifying and filtering circuit 30, and is configured to divide the first dc voltage by a fixed ratio to obtain a feedback voltage, and apply the feedback voltage to a reference end of the reference voltage source U3, where the feedback voltage is smaller than the first dc voltage. The reference voltage source U3 is connected to the voltage dividing circuit 411, and the reference voltage source U3 is configured to generate a first feedback signal that matches the deviation direction and the deviation of the feedback voltage when the feedback voltage received by the reference terminal deviates from the reference voltage inside the reference voltage source U3, where the voltage value of the first target voltage after being divided by a fixed ratio is consistent with the internal reference voltage.

The cathode of the reference voltage source U3 is connected with the cathode of the light emitting diode in the photoelectric coupler U2, and the anode of the reference voltage source U3 is grounded. The anode of the light emitting diode in the photocoupler U2 is connected to the output end of the rectifying and filtering circuit 30 through the current limiting resistor R16. Accurate sampling of the first direct current voltage can be achieved by setting the reference voltage source U3 and the voltage dividing circuit 411, and the first feedback signal is transmitted to the switch control circuit 42 in a lossless manner in combination with the optocoupler U2. The first direct current voltage output by the rectifying and filtering circuit 30 is divided by the voltage dividing circuit 411 and then compared with the reference voltage of the reference voltage source U3 to generate an error voltage, the input current of the photoelectric coupler is controlled by the error voltage to change the conduction degree of the phototransistor, and a first feedback signal is output to the switch control circuit 42.

The reference voltage source U3 may be a TL431 reference voltage source, and the reference voltage source is internally composed of a precision reference source, a high-gain operational amplifier and an NPN high-power tube. The reference voltage in the reference voltage source U3 is 2.5V, and the voltage value of the corresponding first target voltage divided according to the fixed proportion is 2.5V. If the feedback voltage is smaller than 2.5V, the operational amplifier in the reference voltage source U3 outputs a low level, the NPN high-power tube is driven to be weakened, the input current of the photoelectric coupler is weakened, and the conduction degree of the phototriode is weakened.

In some embodiments, the anode of the reference voltage source U3 is also connected to the terminal 6 of the secondary winding Ns3 through a resistor R12, and the cathode is commonly grounded to the terminal 5 of the secondary winding Ns 3. The resistor R12 can have the voltage division effect, so that the reference voltage source U3 works stably and is prevented from being broken down.

In some embodiments, voltage divider circuit 411 includes resistor R13, resistor R18, and resistor R23. One end of the resistor R13 is connected with the output end VOUT3 of the rectifying and filtering circuit 30, the other end of the resistor R13 is connected with one end of the resistor R18 and the reference level of the reference voltage source U3, the other end of the resistor R18 is connected with one end of the resistor R23, and the other end of the resistor R23 is grounded.

The end of the resistor R13 connected to the resistor R18 is the output end 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 a resistor R14 and a capacitor C15, forming an RC filter network for filtering high frequency interference in the feedback signal. The reference voltage uref=2.5v of the reference voltage source U3, and the feedback voltage of the first target voltage after being divided by the fixed ratio is mainly determined by the voltage dividing resistors R13 and R18:

Uout=Uref*(1+R13/R18)

In this example, r13=2kΩ, r18=1kΩ, and the feedback voltage uout=2.5v× (1+2kΩ/1kΩ) =7.5v >2.5v. The operational amplifier in the reference voltage source U3 outputs high level to drive the NPN high-power tube to be conducted to be enhanced, and the input current of the photoelectric coupler is enhanced, so that the conduction degree of the phototriode is enhanced.

In some embodiments, the switch control circuit 42 is configured to:

When the first feedback signal indicates that the feedback voltage is greater than the reference voltage, a first target control signal for indicating that the on-time of the control switch circuit 11 is reduced is generated, and when the first feedback signal indicates that the feedback voltage is less than the reference voltage, a first target control signal for indicating that the on-time of the control switch circuit 11 is increased is generated.

When the feedback voltage is greater than the reference voltage, the first direct current voltage output by the rectifying and filtering circuit 30 is greater than the first target voltage required by the BMS, so that the voltage value of the first alternating voltage can be reduced by controlling the conduction time of the switching circuit 11 to reduce, so that the voltage difference between the first direct current voltage output by the rectifying and filtering circuit 30 and the first target voltage required by the BMS is less than or equal to a preset difference threshold value, and when the feedback voltage is less than the reference voltage, the first direct current voltage output by the rectifying and filtering circuit 30 is less than the first target voltage required by the BMS, so that the voltage difference between the first direct current voltage output by the rectifying and filtering circuit 30 and the first target voltage required by the BMS is less than or equal to the preset difference threshold value by controlling the conduction time of the switching circuit 11 to increase.

Optionally, the switch control circuit 42 includes a control chip U1, where the control chip U1 is configured to send the first feedback signal by the receiving detection circuit 41 through the photocoupler U2, and generate the first target control signal based on the first feedback signal.

The control chip U1 is an UC2844 chip, a pin1 of the control chip U1 is connected to a collector of a phototransistor, a pin2 of the control chip U1 is connected to an emitter of the phototransistor and is configured to receive a first feedback signal, and a pin6 of the control chip U2 is connected to the switch circuit 11 and is configured to generate a first target control signal for adjusting the switch circuit 11.

The switch control circuit 42 further includes a capacitor C18, a resistor R17, a capacitor C19, a capacitor C20, a capacitor C21, and a resistor R21. The pin1 of the control chip U1 is grounded through the capacitor C18, the pin2 and the pin5 of the control chip U1 are directly grounded, the pin3 of the control chip U1 is grounded through the capacitor C19, the pin4 of the control chip U1 is connected with one end of the capacitor C20 and one end of the resistor R21, the other end of the resistor R21 is connected with one end of the capacitor C21 and the pin8 of the control chip U1, and the other ends of the capacitor C20 and the capacitor C21 are grounded.

The operating frequency f of the control chip U1 is determined by the resistor R17 and the capacitor C19, f=1.8/(R17C 19).

In an embodiment of the present application, r17=1kΩ and c19=1nf, the operating frequency f=1.8/(1kΩ×1nf) =1.8 MHz of the control chip U1, which ensures the high efficiency of the switch control circuit 42.

In one embodiment, the transformer 20 further comprises:

the auxiliary winding Ncc is connected to the feedback control circuit 40 for powering the feedback control circuit 40.

The auxiliary winding Ncc and the secondary winding Np are wound on the same iron core, and when the primary winding Np is fed with high-frequency pulse current, a changing magnetic field generated in the iron core is coupled to the secondary windings Ns1, ns2, ns3 and the auxiliary winding Ncc at the same time, so that the windings all induce corresponding voltages. The number of turns of the auxiliary winding Ncc is designed to match the operating voltage required by the control chip U1.

Illustratively, as shown in fig. 2, pin7 of control chip U1 is connected to auxiliary winding Ncc through a series diode D10 and a resistor R10, and receives an operating voltage supplied from auxiliary winding Ncc. The pin7 of the control chip U1 is grounded through capacitors C14 and C13 connected in parallel, and is used for receiving the output voltage of the auxiliary winding Ncc rectified by the diode D10 and limited by the resistor R10.

In one embodiment, the transformer 20 includes a plurality of secondary windings Ns coupled to the primary winding Np, and the rectifying and filtering circuit 30 includes a plurality of rectifying and filtering units, each of which is correspondingly connected to one secondary winding Ns, and the plurality of rectifying and filtering units are respectively configured to output dc voltages with different voltage magnitudes.

Wherein, at least one rectifying and filtering unit is used for outputting a first target voltage required by the BMS to be 12V, and other rectifying and filtering units can be used for outputting a voltage of 3.5 or 5V required by a low-voltage module such as a sampling module, a detection module and the like in the BMS. Or a direct current voltage (e.g., 15V) required for other external structures except the BMS, is not limited thereto.

In other embodiments, the voltages output by the rectifying and filtering units may be equal, for example, all 12V, so as to supply power to different modules with the same required voltage.

Illustratively, each rectifying and filtering unit includes a rectifying diode, a current limiting resistor, a first filtering capacitor, and a second filtering capacitor. The positive pole of the rectifier diode is connected with one end of the secondary winding, the negative pole of the rectifier diode is respectively connected with one end of the current-limiting resistor and one end of the first filter capacitor, the other end of the current-limiting resistor is connected with the input end of the feedback control circuit 40 and one end of the second filter capacitor, and the other end of the first filter capacitor and the other end of the second filter capacitor are connected with the other end of the secondary winding.

In a specific embodiment, as shown in fig. 2, the first rectifying and filtering unit is connected to the first secondary winding Ns1, and includes a rectifying diode D1, a current-limiting resistor R1, a filter capacitor C3, a filter capacitor C4, a current-limiting resistor R4, and a zener diode D2. An anode of the rectifying diode D1 is connected with one end of the first secondary winding Ns1, a cathode of the rectifying diode D1 is connected with one end of the current-limiting resistor R1, and the other end of the current-limiting resistor R1 serves as an output end VOUT1 of the first rectifying and filtering 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 (ground) of the first secondary winding Ns 1. One end of the filter capacitor C4, one end of the filter capacitor C1, one end of the current-limiting resistor R4 and one end of the voltage-stabilizing diode D2 are connected with the other end of the current-limiting resistor R1, and the other ends of the filter capacitor C4, the filter capacitor C1, the current-limiting resistor R4 and the voltage-stabilizing diode D2 are connected with the other end (referenced to the ground) of the first secondary winding Ns 1.

The rectifier diode D1 is used for converting alternating voltage of the secondary winding into unidirectional pulsating direct current. The filter capacitors C3 and C4 are solid capacitors and are used for filtering low-frequency ripples. The filter capacitor C1 is a ceramic capacitor and is used for filtering high-frequency noise, and the three components are cooperated to output stable direct current. And the filter capacitors C3 and C4 and the current limiting resistor R1 can form a pi-type filter network to output more stable direct current voltage. The current limiting resistor R4 is used for limiting the current of the voltage stabilizing tube, and the voltage stabilizing diode D2 is used for clamping the output voltage to realize stable power supply.

The second rectifying and filtering unit is connected with the second secondary winding Ns2 and comprises a rectifying diode D6, a current-limiting resistor R5, a filter capacitor C9, a filter capacitor C12, a filter capacitor C11, a current-limiting resistor R9 and a zener diode D7. An anode of the rectifying diode D6 is connected to one end of the second secondary winding Ns2, a cathode of the rectifying diode D6 is connected to one end of the current limiting resistor R5, and the other end of the current limiting resistor R5 serves as an output end VOUT2 of the second rectifying and filtering unit. One end of the filter capacitor C12 is connected to the cathode of the rectifier diode D6, and the other end of the filter capacitor C12 is connected to the other end (ground) of the second secondary winding Ns 2. One end of the filter capacitor C11, the filter capacitor C9, the current-limiting resistor R9 and the zener diode D7 are all connected with the other end of the current-limiting resistor R5, and the other ends of the filter capacitor C11, the filter capacitor C9, the current-limiting resistor R9 and the zener diode D7 are all connected with the other end (ground) of the second secondary winding Ns 2.

The rectifier diode D6 is used for converting the alternating voltage of the secondary winding into unidirectional pulsating direct current. The filter capacitors C11 and C12 are solid-state capacitors for filtering low-frequency ripple waves. The filter capacitor C9 is a ceramic capacitor and is used for filtering high-frequency noise, and the three are cooperated to output stable direct current. And the filter capacitors C11 and C12 and the current limiting resistor R5 can form a pi-type filter network to output more stable direct current voltage. The current limiting resistor R9 is used for limiting the current of the voltage stabilizing tube, and the voltage stabilizing diode D7 is used for clamping the output voltage to realize stable power supply.

The third rectifying and filtering unit is connected to the third secondary winding Ns3, and includes a rectifying diode D11, a current limiting resistor R11, a filter capacitor C17, a filter capacitor C16, a filter capacitor C22, and a current limiting resistor R25. An anode of the rectifying diode D11 is connected to one end of the third secondary winding Ns2, a cathode of the rectifying diode D11 is connected to one end of the current limiting resistor R11, and the other end of the current limiting resistor R11 serves as an output terminal VOUT3 of the third rectifying and filtering unit. One end of the filter capacitor C17 is connected to the cathode of the rectifier diode D11, and the other end of the filter capacitor C17 is connected to the other end (ground) of the third secondary winding Ns 3. One end of the filter capacitor C16 is connected with the other end of the current limiting resistor R11, and the other end of the filter capacitor C16 is grounded. The resistor R11, the filter capacitor C17 and the filter capacitor C16 form a pi-type filter network, so that the output direct-current voltage is smoother. One end of the filter capacitor C22 is connected to the cathode of the rectifier diode D11 through the resistor R12, and the other end of the filter capacitor C22 is connected to the other end (ground) of the third secondary winding Ns 3. 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 (ground) of the third secondary winding Ns 3.

The rectifier diode D11 is used for converting the alternating voltage of the secondary winding into unidirectional pulsating direct current. The filter capacitors C16 and C17 are solid-state capacitors for filtering low-frequency ripples. The filter capacitor C22 is a ceramic capacitor and is used for filtering high-frequency noise, and the three components are cooperated to output stable direct current. The current limiting resistor R25 is used to limit the voltage regulator current.

Illustratively, the rectifying diodes D1, D6, and D11 are schottky diodes, which withstand 100V in reverse and 20A in forward direction.

It should be noted that, in fig. 2, the rectifying and filtering circuit 30 only frames two rectifying and filtering units (the first rectifying and filtering unit and the second rectifying and filtering unit), and in fact, the rectifying and filtering circuit 30 further includes a third filtering unit. And fig. 2 only shows that the detection circuit 41 in the feedback control circuit 40 is connected to the third rectifying and filtering unit, and in fact, one detection circuit 41 (not shown in fig. 2) is connected to each of the first rectifying and filtering unit and the second rectifying and filtering unit. Correspondingly, the feedback control circuit 40 may include a plurality of detection circuits 41, where each detection circuit 41 is respectively connected to a corresponding rectifying and filtering unit, and is configured to obtain a dc voltage actually output by each rectifying and filtering unit, and send, based on the dc voltage output by each rectifying and filtering unit, a corresponding feedback signal to the switch control circuit 42 through the photo coupler U2, so that the switch control circuit 42 may adjust the on time of the switch circuit based on a target control signal generated by the corresponding feedback signal, so as to adjust the first alternating voltage input by the primary winding, and enable each rectifying and filtering unit to finally output a required target dc voltage.

The first rectifying and filtering unit is used for outputting a first direct current voltage, the second rectifying and filtering unit is used for outputting a second direct current voltage, and the third rectifying and filtering unit is used for outputting a third direct current voltage. The first dc voltage, the second dc voltage, and the third dc voltage may have different voltage levels. The voltage value of the direct-current voltage output by each rectifying and filtering unit is related to the turn ratio of the secondary winding and the primary winding connected with each rectifying and filtering unit.

Illustratively, the ripple Δu of the dc voltage output by each filter unit is related to the switching period of the switching circuit, the turns ratio of the secondary winding to the primary winding, and the total capacitance value of the filter capacitor, which is typically controlled to be within 50 mV.

ΔU can be estimated by:

ΔU=(Iout*T)/(2*C_{Total (S)})。

The Iout is an output current required by a load, and can be obtained by adjusting the on time of a switch circuit and the turns ratio of a transformer. T is the switching period of the switching circuit 11, and C _{Total (S)} is the total capacitance of the filter capacitor.

For example iout=1a, c _{Total (S)} =147 μf, t=f1=1/1.8 mhz≡0.556 μs, then it is possible to:

ΔU=(1A×0.556μs)/(2×147μF)≈1.88mV。

The transformer 20 is an EE16 type ferrite core transformer with an operating frequency of 65kHz, a primary winding Np of the transformer 20 is 200 turns, 0.2mm enameled wire is adopted, a first secondary winding Ns1 is 10 turns, a second secondary winding Ns2 is 15 turns, a third secondary winding Ns3 is 5 turns, all 0.3mm enameled wire is adopted, and an auxiliary winding Nec is 8 turns for providing an operating voltage for the feedback control circuit 40. The primary-secondary insulation strength of the transformer 20 is greater than 2500VAC.

In some embodiments, as shown in fig. 2, the switching circuit 11 includes a switching tube Q1, a drive current limiting resistor R19, and a gate bleed circuit.

The grid of the switching tube Q1 is connected with the signal output end of the switch control circuit 42 through the driving current limiting resistor R19, the drain electrode of the switching tube Q1 is connected with one end of the primary winding, and the source electrode of the switching tube Q1 is grounded.

The grid bleeder circuit includes bleeder resistor R15 and bleeder diode D12, and bleeder diode D12's positive pole is connected with the grid of switch tube Q1, and bleeder diode D12's negative pole is connected with bleeder resistor R15's one end, and bleeder resistor R15's the other end is connected with the signal output part of switch control circuit 42.

The driving current limiting resistor R19 is used for limiting the driving current flowing into the gate of the switching tube Q1, preventing the gate of the switching tube Q1 from being damaged due to overlarge current, controlling the switching speed of the switching tube Q1, and optimizing electromagnetic interference in the switching process. When the signal output end of the switch control circuit 42 is turned off, the bleeder diode D12 is turned on, the bleeder resistor R15 provides a bleeder path for residual charges on the gate of the switching tube Q1, so as to accelerate the turn-off process of the switching tube Q1 and avoid misleading of the switching tube Q1 due to residual charges on the gate.

Illustratively, the bleeder resistor R15 and the driving current limiting resistor R19 are both connected to pin6 of the control chip U1. The control chip U1 outputs a first target control signal through a pin6, wherein the first target control signal is a PWM driving signal and is used for controlling the on-off of the switching tube Q1, and the duty ratio D (the ratio of the on time to the period) of the switching tube Q1 is D=ton/T.

The switching circuit further includes a resistor R22 and a resistor R24. One end of a resistor R22 is connected with the grid electrode of the switching tube Q1, the other end of the resistor R22 is connected with one end of a resistor R24 through a resistor R17 commonly connected with a pin3 of the control chip U1, one end of the resistor R24 is connected with the source electrode of the switching tube Q1, and the other end of the resistor R24 is grounded. The resistor R22 can be used as a gate pull-down resistor of the switching tube Q1, and pulls down the gate potential of the switching tube Q1 to ground when no driving signal is generated, so as to ensure the reliable turn-off of the switching tube Q1 and prevent misoperation caused by gate suspension. The resistor R24 can be used as a source sampling resistor of the switching tube Q1 and is used for detecting the source current of the switching tube Q1 and providing an overcurrent protection signal for the control chip U1, and when the current exceeds a set threshold value, the U1 can turn off the driving signal of the switching tube and protect the switching tube Q1 and the whole circuit.

In an exemplary embodiment, the switching transistor Q1 is a 2N60 type N channel MOS transistor, and has a withstand voltage of 600V and an on-resistance of 10Ω.

Illustratively, the transformer 20 has a transformation ratio relationship of urest/urest=nsend/nrst, and the transformation ratio of the transformer (i.e., the turns ratio of the primary winding and the secondary winding) may be determined based on the first target voltage required by the BMS, the initial direct current voltage output from the power battery, and the maximum duty ratio of the switching tube.

Taking the first dc voltage as 12V for example, if the minimum value of the first ac voltage U _min =230v and the maximum duty ratio d=0.45 of the switching tube Q1, the transformation ratio of the primary winding Np and the secondary winding Ns2 of the transformer 20 needs to be satisfied that Np/ns2= (U _min*D)/(U_out+U_D6)

Wherein, U _out =12v is the first dc voltage, U _D6 is the forward voltage drop of the rectifying diode D6, which is 0.5V, and substituted by (230×0.45)/(12+0.5) ≡8.28. In practical design, the primary winding np=83 turns of the transformer 20 and the second secondary winding Ns2 is 10 turns, so as to meet the transformation ratio requirement.

In one embodiment, the power conversion circuit further comprises a power state indication module. As shown in fig. 2, the power status indication module includes a current limiting resistor R20 and a light emitting unit D13, wherein one end of the current limiting resistor R20 is connected to the output end of the rectifying and filtering circuit, and the other end is connected to the anode of the light emitting unit D13, and the cathode of the light emitting unit D13 is grounded.

Optionally, the light emitting unit D13 is a light emitting diode. Through the power state indicating module, whether the power module works normally can be visually displayed, when the circuit is electrified and works normally, the light emitting diode D13 can emit light, so that a user or maintainer can conveniently and quickly judge the power state, and a power failure can be timely found.

Fig. 3 shows a frame diagram of another power conversion circuit according to an embodiment of the present invention, as shown in fig. 3, in one embodiment, the input circuit 10 further includes:

The input filter circuit 12, the input end of the input filter circuit 12 is connected with the output end of the power battery, the output end of the input filter circuit 12 is connected with the primary winding through the switch circuit 40, and the input filter circuit 12 is used for filtering the initial direct current voltage output by the power battery.

Referring to fig. 2, the input filter circuit 12 includes a capacitor C25, a capacitor C7, a capacitor C8, a resistor R26, and a resistor R27. One end of the capacitor C25, the capacitor C7 and the capacitor C8 are connected in parallel, the other end of the capacitor C8 is connected with the output end and the primary winding of the power battery, the resistor R26 and the resistor R27 are connected in series and then connected with the capacitor C25, the capacitor C7 and the capacitor C8 in parallel.

The capacitor C25 adopts a high-voltage ceramic capacitor for inhibiting low-frequency interference of input voltage, and the capacitors C7 and C8 adopt film capacitors for inhibiting high-frequency interference of input voltage.

The impedance characteristic of the capacitor meets the condition that Z _c = jωC, wherein ω is an angular frequency, ω = 2pi f, f is an interference signal frequency, and C is a capacitance value of the capacitor, and an appropriate capacitor is selected to enable the interference signal to form a low-impedance path on the capacitor so as to be filtered.

Alternatively, the capacitance of the capacitor C25 is 10 μF, the rated voltage is 1000V, the capacitance of the capacitor C7 is 100nF, the rated voltage is 1000V, and the capacitance of the capacitor C8 is 100nF, the rated voltage is 1000V. The input voltage range is 230-850V direct current voltage, and after input filtering, the high-frequency interference in the input voltage can be restrained by more than 30 dB.

The resistance values of the resistor R26 and the resistor R27 are 200KΩ, and the resistor R is used for limiting the input impact current at the initial stage of power-up, so as to avoid the damage of the capacitor C25, the capacitor C7 and the capacitor C8 due to instantaneous large current.

In some embodiments, a resistor R3, a resistor R7, a resistor R6, a capacitor C2, a resistor R8, a diode D5, a diode D10, and a resistor R10 are further disposed between the input filter circuit 12 and the transformer 10.

The resistor R6 and the capacitor C2 are connected in parallel and then connected to the primary winding of the transformer 10 and the drain of the switching tube Q1 through the resistor R8 and the diode D5. The capacitor C2, the resistor R8 and the diode D5 can form an RCD peak absorption circuit, so that voltage peaks when the primary winding of the transformer or the switching tube is turned off are suppressed, and the reliability of the circuit is ensured. And after the resistor R3 and the resistor R7 are connected in series, a voltage division starting circuit is formed, one end of the voltage division starting circuit is connected with the output end of the power battery, and the other end of the voltage division starting circuit is connected with a pin7 pin of the control chip U1 and is used for providing initial starting voltage for the control chip U1.

The embodiment of the application also provides a battery management system which comprises the power supply conversion circuit. The power conversion circuit may be integrated in the battery management system.

According to the power supply conversion circuit and the battery management system, the input circuit comprising the switch circuit, the transformer, the rectifying and filtering circuit and the feedback control circuit are arranged, so that the high-voltage direct current of the power battery can be directly reduced in voltage and filtered into the stable low-voltage direct current required by the BMS, reliable power supply is provided for a core module of the battery management system, and stable operation of the system is ensured. And this power conversion circuit sets up in BMS, saves traditional 12V lead acid battery and special DC-DC converter, has both broken the limit of double cell framework, has simplified whole car electrical system, reduced integration and troubleshooting cost and hardware cost, reduces extra weight volume again in order to agree with lightweight design, reduce the energy loss in order to promote energy utilization efficiency, simultaneously with the help of feedback control guarantee power supply stability, provides reliable support for BMS core function, has effectively broken through the technical bottleneck of traditional low pressure power supply framework.

The foregoing embodiments are merely for illustrating the technical solution of the present application, but not for limiting the same, and although the present application has been described in detail with reference to the foregoing embodiments, it will be understood by those skilled in the art that modifications may be made to the technical solution described in the foregoing embodiments or equivalents may be substituted for parts of the technical features thereof, and that such modifications or substitutions do not depart from the spirit and scope of the technical solution of the embodiments of the present application in essence.

Claims

1. A power conversion circuit provided in a battery management system, the power conversion circuit comprising:

2. The power conversion circuit of claim 1, wherein the feedback control circuit comprises a detection circuit, a photo coupler, and a switch control circuit;

3. The power conversion circuit of claim 2, wherein the detection circuit comprises a reference voltage source and a voltage divider circuit, wherein,

4. A power conversion circuit according to claim 3, wherein the switch control circuit is configured to:

5. The power conversion circuit of claim 2, wherein the switching circuit comprises a switching tube, a drive current limiting resistor, and a gate bleed circuit;

6. The power conversion circuit according to claim 1, wherein the transformer comprises a plurality of secondary windings coupled to the primary windings, the rectifying and filtering circuit comprises a plurality of rectifying and filtering units, each rectifying and filtering unit is correspondingly connected to one secondary winding, and the rectifying and filtering units are respectively used for outputting direct-current voltages with different voltage magnitudes.

7. The power conversion circuit of claim 1, wherein the transformer further comprises:

8. The power conversion circuit of claim 1, wherein the input circuit further comprises:

9. The power conversion circuit according to claim 1, wherein the power conversion circuit further comprises:

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