Battery charging and discharging circuit, circuit board and battery charging and discharging device

Abstract

The utility model discloses a battery charging and discharging circuit, a circuit board and a battery charging and discharging device, and relates to the field of power electronic control. A bidirectional direct current source; the input filter capacitor is connected with two poles of the bidirectional direct-current source; the first converter circuit is respectively connected with two poles of the bidirectional direct current source and the positive pole of the load cell; the second converter circuit is respectively connected with two electrodes of the bidirectional direct current source and the negative electrode of the load cell; when the load cell is in a charging state, the first converter circuit is used for performing voltage reduction conversion on the voltage output by the bidirectional direct current source; and when the load cell is in a zero-volt discharge state, the first converter circuit is used for carrying out boost conversion on the voltage output by the load cell, and the second converter circuit is used for carrying out buck conversion on the output voltage of the bidirectional direct current source so as to provide voltage compensation for the load cell. According to the invention, under the extreme condition that the voltage of the load cell is close to zero volt, the energy of the load cell can be effectively and completely released.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power electronic control, in particular to a battery charging and discharging circuit, a circuit board and a battery charging and discharging device. BACKGROUND

[0002] With the wide application of lithium ion batteries and sodium ion batteries in electric vehicles, renewable energy storage, portable electronic devices and other fields, the safety and performance requirements of battery charging and discharging equipment are increasingly improved. In the research, testing and recycling process of batteries, it is often necessary to charge and discharge the battery under extreme conditions, such as reducing the battery voltage to zero volts. Achieving zero-volt discharge of the battery is of great significance for evaluating the performance and safety of the battery, and ensuring the safety of the recycling process.

[0003] However, the existing charging and discharging circuit faces many challenges in achieving zero-volt discharge of the battery. The traditional DC-DC converter cannot continuously discharge at the rated current when the input voltage is extremely low due to the duty cycle limit and loop impedance. This results in a significant decrease in discharge efficiency when the battery voltage approaches zero volts, and the equipment cannot effectively release electrical energy, resulting in the battery being unable to completely empty, which cannot meet the needs of experiments and industrial applications. Therefore, there is an urgent need for a circuit design that can efficiently and safely achieve zero-volt discharge of the battery. CONTENT OF THE INVENTION

[0004] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a battery charging and discharging circuit, a circuit board and a battery charging and discharging device, which can realize battery charging and zero-volt discharge.

[0005] The battery charging and discharging circuit according to the first aspect of the present application comprises: a load cell; a bidirectional DC source; an input filter capacitor connected to both poles of the bidirectional DC source; a first converter circuit connected to both poles of the bidirectional DC source and the positive pole of the load cell; and a second converter circuit connected to both poles of the bidirectional DC source and the negative pole of the load cell. When the load cell is in a charging state, the first converter circuit is used to step-down convert the voltage output by the bidirectional DC source, and the second converter circuit is in a straight-through state to communicate the negative pole of the load cell with the negative pole of the bidirectional DC source; when the load cell is in a zero-volt discharge state, the first converter circuit is used to step-up convert the voltage output by the load cell, and the second converter circuit is used to step-down convert the voltage across the bidirectional DC source to provide voltage compensation for the load cell.

[0006] The battery charging and discharging circuit according to the embodiments of the present application has at least the following beneficial effects: in the charging process, the first converter circuit can perform step-down conversion on the voltage of the bidirectional DC source during charging, so that the circuit can adapt to the charging requirements of load battery cells with different voltage specifications, thereby realizing safe and efficient charging of the load battery cells; meanwhile, the second converter circuit is in a straight-through state, so that the current can pass through the second converter circuit from the negative electrode of the bidirectional DC source to the negative electrode of the load battery cell, ensuring the integrity of the charging loop. In the zero-volt discharging process, through the step-up conversion of the first converter circuit and the voltage compensation of the second converter circuit, the small amount of residual power in the battery cell can be effectively transmitted back to the bidirectional DC source, and the battery cell can complete discharging under relatively mild conditions, which helps to protect the internal structure of the battery cell and prolong the service life of the battery cell, and is of great significance for the research and development, testing and recycling of lithium-ion batteries. The same circuit can be used to realize flexible switching of charging and zero-volt discharging functions in the present application, and the circuit can work effectively whether it is normal discharging or special low-voltage discharging, thereby improving the overall reliability and adaptability of the system and reducing system failures caused by abnormal battery cell voltage.

[0007] According to some embodiments of the present application, the second converter circuit comprises a third switch tube, a fourth switch tube, a second inductor, a second capacitor and a second driver, a first output end of the second driver is connected with a control end of the third switch tube, a second output end of the second driver is connected with a control end of the fourth switch tube, an input end of the third switch tube and an output end of the fourth switch tube are connected with a positive electrode and a negative electrode of the bidirectional DC source respectively, an output end of the third switch tube and an input end of the fourth switch tube are connected, one end of the second inductor is connected between the output end of the third switch tube and the input end of the fourth switch tube, the other end of the second inductor is connected with one end of the second capacitor, the other end of the second capacitor is connected with the negative electrode of the bidirectional DC source, and the connection end of the second inductor and the second capacitor is connected with the negative electrode of the load battery cell.

[0008] According to some embodiments of the present application, the first converter circuit comprises a first switch tube, a second switch tube, a first inductor, a first capacitor and a first driver, a first output terminal of the first driver is connected with a control terminal of the first switch tube, a second output terminal of the first driver is connected with a control terminal of the second switch tube, an input terminal of the first switch tube and an output terminal of the second switch tube are connected with a positive pole and a negative pole of the bidirectional direct current source respectively, an output terminal of the first switch tube and an input terminal of the second switch tube are connected, one end of the first inductor is connected between the output terminal of the first switch tube and the input terminal of the second switch tube, the other end of the first inductor is connected with one end of the first capacitor, the other end of the first capacitor is connected with the negative pole of the bidirectional direct current source, and the connection end of the first inductor and the first capacitor is connected with a positive pole of the load cell.

[0009] According to some embodiments of the present application, the control circuit is further connected with the first driver and the second driver, and is used for controlling the level state of the first output terminal and the second output terminal of the first driver and the level state of the first output terminal and the second output terminal of the second driver.

[0010] According to some embodiments of the present application, the control circuit comprises a controller, a current sensor and a voltage sensor, the current sensor is arranged at one end of the load cell, an output terminal of the current sensor is connected with the controller, an input terminal of the voltage sensor is connected between two ends of the load cell, an output terminal of the voltage sensor is connected with the controller, a first output terminal of the controller is connected with the first driver, and a second output terminal of the controller is connected with the second driver.

[0011] According to some embodiments of the present application, the controller comprises an analog-to-digital conversion module, a control module and a modulation signal generation module, the analog-to-digital conversion module is connected with the current sensor and the voltage sensor respectively, and is used for converting the detected analog current signal and analog voltage signal into digital signals, the control module is connected with the analog-to-digital conversion module, and is used for generating a control instruction according to the digital signals, and the modulation signal generation module is connected with the control module, and is used for generating a modulation signal according to the control instruction and outputting to the first driver and the second driver.

[0012] According to some embodiments of the present application, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are metal oxide semiconductor field effect tubes.

[0013] The circuit board according to the second aspect of the present application comprises the battery charging and discharging circuit according to the first aspect of the present application.

[0014] The battery charging and discharging device according to the third aspect of the present application comprises the circuit board according to the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0015] The present application will be further described below in conjunction with the drawings and embodiments, wherein:

[0016] Figure 1 A schematic block diagram of the battery charging and discharging circuit according to the embodiments of the present application;

[0017] Figure 2 A circuit diagram of the battery charging and discharging circuit according to the embodiments of the present application;

[0018] Figure 3 A current trend diagram of the battery charging and discharging circuit according to the embodiments of the present application in a charging state;

[0019] Figure 4 A current trend diagram of the battery charging and discharging circuit according to the embodiments of the present application in a zero-volt discharging state;

[0020] Figure 5 A schematic diagram of the connection relationship of the control circuit of the battery charging and discharging circuit according to the embodiments of the present application.

[0021] REFERENCE SIGNS

[0022] Load cell 100; bidirectional direct current source 200; input filter capacitor 300; first converter circuit 400; second converter circuit 500; control circuit 600. DETAILED DESCRIPTION

[0023] The embodiments of the present application will be described in detail below, examples of which are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation to the present application.

[0024] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application.

[0025] In the description of the present application, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, within, etc. are understood as including the number. If it is described as first, second, it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0026] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and those skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0027] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0028] The conventional DC-DC converter cannot continuously discharge at rated current due to duty cycle limitation and loop impedance and other factors when the input voltage is extremely low. This results in a significant decrease in discharge efficiency when the battery voltage approaches zero volts, and the device cannot effectively release electrical energy.

[0029] Therefore, the battery charging and discharging circuit provided by the present application can solve the problems existing in the prior art. The technical solutions provided by the present application are described in detail one by one as follows.

[0030] In a first aspect, the present application provides a battery charging and discharging circuit, which comprises Figure 1As shown, the embodiment battery charging and discharging circuit includes a load battery 100, a bidirectional DC source 200, an input filter capacitor 300, a first converter circuit 400, and a second converter circuit 500. The load battery 100 serves as an energy storage unit of the circuit and is responsible for storing and releasing electric energy; the bidirectional DC source 200 can charge the load battery 100 and also allows the load battery 100 to discharge to the bidirectional DC source 200; the first converter circuit 400 is connected to the positive and negative poles of the bidirectional DC source 200 and the positive pole of the load battery 100 and is responsible for step-down conversion of the output voltage of the bidirectional DC source 200 in a charging state; the second converter circuit 500 is connected to the positive and negative poles of the bidirectional DC source 200 and the negative pole of the load battery 100 and is responsible for step-up conversion of the output voltage of the load battery 100 in a zero-volt discharging state and step-down conversion of the output voltage of the bidirectional DC source 200 to provide voltage compensation for the load battery 100.

[0031] When the load battery 100 is in a charging state, the first converter circuit 400 works in a step-down mode (BUCK), and the first converter circuit 400 converts the voltage of the bidirectional DC source 200 to a charging voltage suitable for the load battery 100 by step-down conversion, while the second converter circuit 500 is in a pass-through state, in which the second converter circuit 500 connects the negative pole of the bidirectional DC source 200 to the negative pole of the load battery 100 to provide a current loop and does not participate in voltage conversion. In this state, energy flows from the bidirectional DC source 200 to the load battery 100, and the load battery 100 can be safely and effectively charged.

[0032] When the load battery 100 is in a zero-volt discharging state, the first converter circuit 400 works in a step-up mode (BOOST) and is responsible for increasing the output voltage of the load battery 100, while the second converter circuit 500 works in a step-down mode (BUCK) and is responsible for reducing the voltage across the bidirectional DC source 200. In this state, energy flows from the load battery 100 to the bidirectional DC source 200. Since the output end of the second converter is connected to the negative pole of the load battery 100, it is equivalent to connecting a DC source in series with the load battery 100 to provide necessary voltage compensation for the load battery 100. Through such a design, when the voltage of the load battery 100 is insufficient, the positive pole of the load battery 100 still has sufficient voltage to overcome the loop impedance problem in the circuit, so that the load battery 100 can maintain the rated discharging current even at a low voltage (close to 0V), and finally reduce the voltage of the load battery 100 to zero volts.

[0033] As shown in FIG. 1, the embodiment battery charging and discharging circuit includes a load battery 100, a bidirectional DC source 200, an input filter capacitor 300, a first converter circuit 400, and a second converter circuit 500. Figure 2In some embodiments, the first converter circuit 400 includes a first switch Q1, a second switch Q2, a first inductor L1, a first capacitor C1, and a first driver DRV1. The first output terminal of the first driver DRV1 is connected to the control terminal of the first switch Q1, the second control terminal of the first driver DRV1 is connected to the control terminal of the second switch Q2, the input terminal of the first switch Q1 and the output terminal of the second switch Q2 are connected to the positive and negative poles of the bidirectional DC source DC respectively, the output terminal of the first switch Q1 and the input terminal of the second switch Q2 are connected, one end of the first inductor L1 is connected between the output terminal of the first switch Q1 and the input terminal of the second switch Q2, the other end of the first inductor L1 is connected to one end of the first capacitor C1, the other end of the first capacitor C1 is connected to the negative pole of the bidirectional DC source DC, and the connection end of the first inductor L1 and the first capacitor C1 is connected to the positive pole of the load battery BAT. The second converter circuit 500 includes a third switch Q3, a fourth switch Q4, a second inductor L2, a second capacitor C2, and a second driver DRV2. The first output terminal of the second driver DRV2 is connected to the control terminal of the third switch Q3, the second control terminal of the second driver DRV2 is connected to the control terminal of the fourth switch Q4, the input terminal of the third switch Q3 and the output terminal of the fourth switch Q4 are connected to the positive and negative poles of the bidirectional DC source DC respectively, the output terminal of the third switch Q3 and the input terminal of the fourth switch Q4 are connected, one end of the second inductor L2 is connected between the output terminal of the third switch Q3 and the input terminal of the fourth switch Q4, the other end of the second inductor L2 is connected to one end of the second capacitor C2, the other end of the second capacitor C2 is connected to the negative pole of the bidirectional DC source DC, and the connection end of the second inductor L2 and the second capacitor C2 is connected to the negative pole of the battery.

[0034] It can be understood that, as Figure 3 In the charging state of the load battery BAT, the first converter circuit 400 works in the buck mode (BUCK) to reduce the voltage of the bidirectional DC source DC to a charging voltage suitable for the load battery BAT, and to provide a stable charging current for the battery. The second converter circuit 500 is in a pass-through state, connecting the negative pole of the bidirectional DC source DC to the negative pole of the load battery BAT to provide a current loop and not participating in voltage conversion.

[0035] In the charging state, the first converter circuit 400 works in the step-down mode (BUCK), the first switch Q1 is the main switch controlled by the first output of the first driver DRV1, and the second switch Q2 is the synchronous rectifier controlled by the second output of the first driver DRV1, which is complementary to the first switch Q1. In a complete working cycle of the first converter circuit 400 in the step-down mode (BUCK), it can be divided into a first energy storage stage and a first freewheeling stage. In the first energy storage stage, the first switch Q1 is turned on and the second switch Q2 is turned off. In this stage, the current flows through the first switch Q1, the first inductor L1, the positive electrode of the load battery BAT, the negative electrode of the load battery BAT, the second converter circuit 500, and the negative electrode of the DC source in turn, forming a loop. In this process, the first inductor L1 continuously stores energy, and the current in the loop gradually increases. In the first freewheeling stage, the first switch Q1 is turned off and the second switch Q2 is turned on. At this time, the first inductor L1 begins to release energy gradually. In this stage, the current flows through the first inductor L1, the positive electrode of the load battery BAT, the negative electrode of the load battery BAT, the second switch Q2 circuit, and the first inductor L1, forming a loop. In this process, the current in the loop gradually decreases due to the gradual decrease of the energy stored in the inductor. By controlling the on and off states of the first switch Q1 and the second switch Q2 through the first driver DRV1, the first converter circuit 400 continuously alternates between the first energy storage stage and the first freewheeling stage, so that the current in the loop presents a triangular waveform. In a working cycle (control cycle), the current first rises and then falls. In the rising stage (the first switch Q1 is turned on and the second switch Q2 is turned off), the current rises from the minimum value to the maximum value. In the falling stage (the first switch Q1 is turned off and the second switch Q2 is turned on), the current falls from the minimum value to the minimum value. Finally, the average value of the current loop is the output current of the first converter circuit 400. By adjusting the duty cycle (the ratio of the first energy storage stage to the entire working cycle), the output voltage or current of the first converter circuit 400 can be stabilized at the required current and voltage level when the load battery BAT is charging. At the same time, since the first capacitor C1 is also provided and the switching frequency of the first switch Q1 and the second switch Q2 is usually high, the output ripple of the first converter circuit 400 is usually small.

[0036] During charging, the second converter circuit 500 is in a direct-on state, the third switch Q3 is controlled by the first output of the second driver DRV2 and is in a turned-off state, and the fourth switch Q4 is controlled by the second output of the second driver DRV2 and is in a turned-on state. In this state, current flows from the negative terminal of the load cell BAT, through the second inductor L2, the fourth switch Q4, and the negative terminal of the bidirectional DC source. Ultimately, the battery charging and discharging circuit in this embodiment achieves a closed loop during charging. That is, the bidirectional DC source releases energy, which is then stepped down by the first converter circuit 400 to a suitable voltage level for the load cell BAT, inputting to the positive terminal of the load cell BAT. Finally, the current flows from the negative terminal of the load cell BAT through the second converter circuit 500 and back to the negative terminal of the bidirectional DC source.

[0037] Understandable, such as Figure 4 When the load cell BAT is in a zero-volt discharge state, the first converter circuit 400 operates in boost mode to increase the voltage of the load cell BAT, overcoming the limitation of the loop impedance and providing discharge current to the bidirectional DC source. The second converter circuit 500 operates in buck mode, reducing the voltage of the bidirectional DC source and connecting it in series with the negative terminal of the load cell BAT to provide auxiliary voltage to the load cell BAT, thereby indirectly increasing the input voltage of the first converter.

[0038] In the zero-volt discharge state, the first converter circuit 400 operates in boost mode, with the first switch Q1 and the second switch Q2 alternately and complementaryly turning on and off. A complete operating cycle of the first converter circuit 400 in boost mode can be divided into a second energy storage stage and a second freewheeling stage. In the second energy storage stage, the first switch Q1 is off, and the second switch Q2 is on. The current flow at this time is as follows: Figure 4 As shown, the load cell BAT begins charging the first inductor L1. At this time, the current output to the bidirectional DC source is entirely provided by the input filter capacitor C3. During the second freewheeling phase, the first switch Q1 is turned on, and the second switch Q2 is turned off. The current flow direction at this time is as follows... Figure 4 As shown, at this time, the first inductor L1 releases energy, and the voltage output by the load cell BAT is connected in series with the inductive voltage of the first inductor L1 to supply power to the bidirectional DC source, while simultaneously charging the input filter capacitor C3. By controlling the on and off states and times of the first switch Q1 and the second switch Q2 through the first driver DRV1, and in conjunction with the input filter capacitor C3, the output voltage of the load cell BAT can be boosted and discharged to the bidirectional DC source.

[0039] In the zero-volt discharge state, the second converter circuit 500 works in the buck mode (BUCK), and the working states of each element and the current flow in the second converter circuit 500 are similar to those when the first converter circuit 400 works in the buck mode (BUCK). Therefore, the specific working conditions of the second converter circuit 500 in the zero-volt discharge state are not described herein.

[0040] As Figure 5 The battery charging and discharging circuit of the embodiment further includes a control circuit 600 connected with the first driver DRV1 and the second driver DRV2, which is used to coordinate the working states of the first driver DRV1 and the second driver DRV2 to realize accurate control of the battery charging and discharging process.

[0041] Further, as Figure 5 The control circuit 600 includes a controller CTRL, a current sensor CT and a voltage sensor VS. The current sensor CT is arranged at one end of the load battery BAT, and the output end of the current sensor CT is connected with the controller CTRL, which is used to detect the current change flowing through the load battery BAT in real time. The input end of the voltage sensor VS is connected to both ends of the load battery BAT, and the output end of the voltage sensor VS is connected with the controller CTRL, which is used to monitor the voltage state at both ends of the load battery BAT in real time. The first output end of the controller CTRL is connected with the first driver DRV1, and the second output end of the controller CTRL is connected with the second driver DRV2. The controller CTRL serves as the core control unit, receives the analog signals of the current sensor CT and the voltage sensor VS, then filters, amplifies and digitizes the analog signals to obtain digitized current and voltage data, calculates the required control parameters according to the preset control strategy combined with real-time data, and finally generates control signals which are sent to the first driver DRV1 and the second driver DRV2 through the first and second output ends respectively. The control circuit 600 can realize accurate charging and discharging control of the load battery BAT, especially in extreme working conditions such as zero-volt discharge, to ensure the safe and stable operation of the battery.

[0042] It can be understood that the controller CTRL includes an analog-to-digital conversion module, a control module and a modulated signal generation module. The analog-to-digital conversion module samples the input analog current and voltage signals through a multi-channel ADC, and converts the sampled analog signals into digital signals transmitted to the control module. The control module obtains the digital current and voltage data transmitted by the ADC module, filters and corrects the data, eliminates noise and error, and calculates whether the current and voltage are within the set range; according to the preset control target (such as constant current charging, constant voltage discharging, etc.), the required control amount is calculated, and the calculation result is converted into a control instruction and transmitted to the modulated signal generation module. The modulated signal generation module generates appropriate modulated signals (such as PWM signals) according to the control instruction, adjusts the duty cycle and frequency, controls the on and off time of the power switch device, and ensures that the output signal meets the requirements of the driver.

[0043] In a second aspect, the application further provides a circuit board comprising the battery charging and discharging circuit according to any one of the embodiments of the first aspect of the application. The functions and principles of the circuit board of the present embodiment are based on the above-mentioned battery charging and discharging circuit, so the circuit board of the present embodiment has the same beneficial effects as the above-mentioned battery charging and discharging circuit. In order to save space, the same beneficial effects will not be repeated here.

[0044] In a third aspect, the application further provides a battery charging and discharging device comprising a circuit board according to the embodiment of the second aspect of the application. The functions and principles of the battery charging and discharging device of the present embodiment are based on the above-mentioned battery charging and discharging circuit, so the battery charging and discharging device of the present embodiment has the same beneficial effects as the above-mentioned battery charging and discharging circuit. In order to save space, the same beneficial effects will not be repeated here.

[0045] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application. In addition, the embodiments of the application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A battery charging and discharging circuit, characterized by comprising: The battery charging and discharging circuit comprises: a load cell; a bidirectional DC source; an input filter capacitor connected to two poles of the bidirectional DC source; a first converter circuit connected to two poles of the bidirectional DC source and a positive pole of the load cell respectively; a second converter circuit connected to two poles of the bidirectional DC source and a negative pole of the load cell respectively; when the load cell is in a charging state, the first converter circuit is used to step-down convert the voltage output by the bidirectional DC source, and the second converter circuit is in a pass-through state to communicate the negative pole of the load cell with the negative pole of the bidirectional DC source; when the load cell is in a zero-volt discharging state, the first converter circuit is used to step-up convert the voltage output by the load cell, and the second converter circuit is used to step-down convert the voltage across the bidirectional DC source to provide voltage compensation for the load cell.

2. The battery charging and discharging circuit according to claim 1, wherein: the second converter circuit comprises a third switch tube, a fourth switch tube, a second inductor, a second capacitor and a second driver, a first output end of the second driver is connected to a control end of the third switch tube, a second output end of the second driver is connected to a control end of the fourth switch tube, an input end of the third switch tube and an output end of the fourth switch tube are connected to a positive pole and a negative pole of the bidirectional DC source respectively, an output end of the third switch tube and an input end of the fourth switch tube are connected, one end of the second inductor is connected between the output end of the third switch tube and the input end of the fourth switch tube, the other end of the second inductor is connected to one end of the second capacitor, the other end of the second capacitor is connected to the negative pole of the bidirectional DC source, and the negative pole of the load cell is connected between the second inductor and the second capacitor.

3. The battery charging and discharging circuit according to claim 2, wherein: the first converter circuit comprises a first switch tube, a second switch tube, a first inductor, a first capacitor and a first driver, a first output end of the first driver is connected to a control end of the first switch tube, a second output end of the first driver is connected to a control end of the second switch tube, an input end of the first switch tube and an output end of the second switch tube are connected to a positive pole and a negative pole of the bidirectional DC source respectively, an output end of the first switch tube and an input end of the second switch tube are connected, one end of the first inductor is connected between the output end of the first switch tube and the input end of the second switch tube, the other end of the first inductor is connected to one end of the first capacitor, the other end of the first capacitor is connected to the negative pole of the bidirectional DC source, and the positive pole of the load cell is connected between the first inductor and the first capacitor.

4. The battery charging and discharging circuit according to claim 3, wherein: The control circuit is connected with the first driver, the second driver and the load cell, and is used for controlling the level state of the first output end and the second output end of the first driver and the level state of the first output end and the second output end of the second driver.

5. The battery charging and discharging circuit of claim 4, wherein: The control circuit comprises a controller, a current sensor and a voltage sensor, the current sensor is arranged at one end of the load cell, the output end of the current sensor is connected with the controller, the input end of the voltage sensor is connected at both ends of the load cell, the output end of the voltage sensor is connected with the controller, the first output end of the controller is connected with the first driver, and the second output end of the controller is connected with the second driver.

6. The battery charging and discharging circuit of claim 5, wherein: The controller comprises an analog-to-digital conversion module, a control module and a modulation signal generation module, the analog-to-digital conversion module is connected with the current sensor and the voltage sensor respectively, and is used for converting the detected analog current signal and analog voltage signal into digital signals, the control module is connected with the analog-to-digital conversion module, and is used for generating a control instruction according to the digital signals, and the modulation signal generation module is connected with the control module, and is used for generating a modulation signal according to the control instruction and outputting to the first driver and the second driver.

7. The battery charging and discharging circuit according to any one of claims 3 to 6, characterized in that: The first switch tube, the second switch tube, the third switch tube and the fourth switch tube are metal oxide semiconductor field effect tubes.

8. A wiring board, characterized by The battery charging and discharging circuit comprises any one of claims 1-7.

9. A battery charging and discharging device, characterized by The circuit board comprises claim 8.

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