Series battery pack, electric quantity active equalization circuit, control method and expansion topology

Abstract

The invention provides a series battery pack, an electric quantity active equalization circuit, a control method and an expansion topology. The device mainly comprises 2-16 battery cells connected in series, each battery cell corresponds to one set of flyback transformers and one optocoupler relay, and all the flyback transformers multiplex a single high-frequency chopper tube; the input side of the flyback transformer is connected with a plurality of series cells, and the output side is connected with a single cell for voltage reduction and energy transmission; one side of the optocoupler relay is connected with the positive electrode of the series battery cell, and the other side of the optocoupler relay is connected with the corresponding flyback transformer and is used for gating charging of the single battery cell and controlling the equalization time of the battery cell; the high-frequency chopper tube is connected with the flyback transformers, receives PWM signals sent by an external microcontroller, adjusts voltage of the output sides of all the flyback transformers, and controls the battery cells to balance current. According to the invention, the battery pack formed by serially connecting the battery cells with poor consistency is effectively handled, the active equalization work of the battery cells in multiple modes is ensured, and the potential safety hazard caused by overcharge and overdischarge of a single battery cell is obviously reduced.

Description

Technical Field

[0001] The present invention relates to the field of battery management technology, and in particular to a series battery pack, an active power balancing circuit, a control method and an extended topology. Background Art

[0002] Since the voltage provided by a single lithium battery cell is about 4V, in order to meet the battery supply voltage in actual use, such as the 300V platform of electric vehicles, a multi-stage series topology is usually used to combine the cells into a battery pack. However, due to manufacturing process errors, the same batch of batteries has inconsistent parameters such as self-discharge rate, capacity, and internal resistance, resulting in a large number of high-quality batteries that do not meet the consistency standards being hoarded or sold at a low price because they cannot be packaged. At the same time, during the use of the battery pack, due to the different aging degrees of the internal cells, the consistency of the cells will also deteriorate.

[0003] Therefore, due to the inherent differences in battery cells and differences in acquired usage, there is always a problem of poor consistency in the series topology battery pack. When charging, some cells in the series topology battery pack are fully charged while the remaining cells are not fully charged; when discharging, some cells are fully discharged while the remaining cells still have some power left.

[0004] To solve the above problems, reliable battery charge balancing technology must be developed to ensure battery safety and improve energy utilization. Currently, most balancing research is limited to constructing circuit topologies of energy storage components such as inductors and capacitors, and less attention is paid to modular circuit applications. Among the technologies related to active charge balancing of series-connected battery packs, fast, efficient, economical, and scalable charge balancing methods and modular applications have become an important direction for battery management optimization. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide a series battery pack, an active power balancing circuit, a control method and an extended topology.

[0006] According to one aspect of the present invention, there is provided a series battery pack, comprising 2 to 16 battery cells connected in series, each battery cell corresponds to a set of flyback transformers and an optocoupler relay, and all the flyback transformers reuse a single high-frequency chopper tube;

[0007] The flyback transformer is connected to a plurality of battery cells in series on its input side and to a single battery cell on its output side to achieve voltage reduction and energy transmission; the optocoupler relay receives a 0 / 1 signal from an external microcontroller MCU to implement the gating task of charging a single battery cell and control the balancing time of the battery cell; the high-frequency chopper receives a PWM signal from the MCU to adjust the voltage on the output side of the flyback transformer and control the balancing current of the corresponding battery cell.

[0008] Preferably, the optical coupler relay is a photocell output type photoelectric coupler, the internal structure of which includes a light-emitting diode LED, a photocell and a MOS tube, and is connected to the positive terminal of the primary side of the flyback transformer;

[0009] The diode LED is controlled to light up and turn off by inputting a driving signal, that is, when the diode LED emits light to illuminate the PN junction group and the photoelectron energy is greater than the bandgap width, the entire array of photocells is stimulated to generate a photogenerated voltage, so that the MOS tube is turned on, and a photogenerated current is generated after the load is connected; when the diode LED is turned off, the photocurrent disappears, the charge on the internal load capacitor of the optocoupler relay is released, and the MOS tube is turned off.

[0010] According to a second aspect of the present invention, there is provided a circuit for active power balancing of a series-connected battery pack, comprising a detection chip, a microcontroller MCU and a control circuit;

[0011] The detection chip collects and detects the voltage, current, and temperature of all battery cells to obtain the battery cell status, charger status, and load status;

[0012] The microcontroller MCU receives the battery cell status, the charger status and the load status, and uses them as a basis to determine the working mode, and obtains the corresponding balancing time and balancing current; and converts them into control signals;

[0013] The control circuit inputs the control signal to the series-connected battery pack, and controls the battery cells with a high state of charge (SOC) to charge the battery cells with a low state of charge (SOC), so that the states of charge (SOC) tend to be consistent.

[0014] Preferably, the detection chip comprises:

[0015] The battery pack connection unit detects whether the chip port is connected to the battery cell;

[0016] Multiple ADC units to obtain the current voltage;

[0017] Overvoltage detection unit detects the current voltage. If it exceeds the specified range, it will issue an overvoltage warning, stop balancing, and cut off the charging pile;

[0018] The temperature detection unit obtains the battery cell temperature and detects the current temperature of each battery cell. If the temperature exceeds the specified range, a high temperature warning is issued and balancing is stopped, and the charging pile or load is disconnected;

[0019] The overcurrent detection unit obtains the cell current and detects the current cell charge and discharge current. If the current exceeds the specified range, an overcurrent warning is issued and the charging pile or load is cut off.

[0020] The pre-charge and discharge unit controls the initial rate of change of the charge inside the battery cell.

[0021] Preferably, the microcontroller MCU comprises:

[0022] A mode determination unit, which identifies four cell operation modes according to the cell state, the charger state and the load state, namely, a charge balance mode, a discharge balance mode, a sleep balance mode and a stop balance mode;

[0023] The active balancing calculation unit takes the SOC of each battery cell as input and obtains the balancing time and balancing current based on the current, voltage and temperature characteristics of the working mode determined.

[0024] Preferably, the charging equalization mode means that when the battery cell is connected to the charger, it is charged and equalized at the same time;

[0025] The discharge balancing mode means that when the battery cell is connected to a load and is in a discharging state, it is discharged and balanced at the same time;

[0026] The sleep balancing mode means that the battery cell is not connected to a load or a charger and is in a state without an external circuit. After a certain time countdown ends, the balancing circuit is awakened to balance the battery cells only when each battery cell meets the balancing requirements.

[0027] The stop balancing mode means that the battery cell is currently limited by the safety indicators of voltage, current or temperature, and balancing is strictly prohibited at the next moment.

[0028] Preferably, the control circuit comprises:

[0029] The photoelectric switch selection unit outputs multiple control signals to control the photorelay to select the battery cell and determine the charging and discharging time;

[0030] MOS gate drive unit, outputs a control signal to improve the gate drive capability of the MOS tube on the primary side of the flyback transformer;

[0031] The high-frequency spike absorption unit absorbs the oscillation spikes generated when the high-frequency chopper tube is quickly turned on and off.

[0032] According to a third aspect of the present invention, a method for controlling an active charge balancing circuit of a series-connected battery pack is provided, comprising:

[0033] Collect and test the voltage, current, and temperature of all cells to obtain the cell status, charger status, and load status;

[0034] Receiving the cell state, the charger state and the load state, judging the working mode based on the state, and obtaining the corresponding balancing time and balancing current;

[0035] The balancing time and the balancing current are converted into control signals and input into an active power balancing circuit to control the battery cells with a high state of charge SOC to charge the battery cells with a low state of charge SOC, so as to achieve a uniform state of charge SOC.

[0036] According to a fourth aspect of the present invention, there is provided an extended topology, comprising an N-layer stacked structure, N≤3;

[0037] The n-th layer structure includes the n-th layer battery topology part and the n-th layer active power balancing circuit;

[0038] The n-th layer battery topology part includes 2 to 16 n-1-th layer structures connected in series, each of the n-1-th layer structures corresponds to a set of flyback transformers and a photocoupler relay; all the flyback transformers reuse a single high-frequency chopper tube;

[0039] The n-th layer control balancing circuit controls the charge state SOC of 2 to 16 structures of the n-1-th layer to be consistent;

[0040] Each layer of the structure includes any one of the series-connected battery packs and any one of the active power balancing circuits described.

[0041] Compared with the prior art, the embodiments of the present invention have at least one of the following beneficial effects:

[0042] The series battery pack (Pack) and the active power balancing circuit in the embodiment of the present invention are proposed based on the flyback converter circuit and are used to achieve active balancing of series cells. The series cell active balancing topology structure can quickly and efficiently transfer energy from high saturation cells to low saturation cells when the cells are charging, discharging, or sleeping.

[0043] The series-connected battery pack and active power balancing circuit in the embodiment of the present invention replaces the expensive topology of multiple high-frequency chopper tubes with the topology of a single high-frequency chopper tube and multiple optocoupler relays, effectively reducing the cost of components; and optimizes multiple high-frequency PWMs to only one high-frequency PWM and multiple ordinary high and low level signals, reducing the requirements for MCU performance.

[0044] The active equalization circuit and control method of the battery pack in series in the embodiment of the present invention combines the three steps of data collection, mode judgment and equalization decision method, and finally outputs accurate equalization time and equalization current. This equalization circuit and method can effectively deal with battery packs composed of battery cells with poor consistency in series, ensuring that the active equalization of battery cells in multiple modes can be implemented, thereby significantly reducing the safety hazards caused by overcharging and over-discharging of a single battery cell.

[0045] The active charge balancing circuit of the series-connected battery pack in the embodiment of the present invention is extended to a two-stage series topology, thereby reducing the difficulty of modular design of the multi-stage series-connected battery pack balancing circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0047] Figure 1 is a general structural diagram of an active charge balancing circuit for a series-connected battery pack in one embodiment of the present invention;

[0048] Figure 2 It is a schematic diagram of an expanded topological structure of an active power balancing circuit based on a series-connected battery pack in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0049] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0050] like Figure 1 As shown, in one embodiment of the present invention, a series battery pack is provided, which specifically includes 2 to 16 battery cells connected in series; each battery cell corresponds to a set of flyback transformers and an optocoupler relay; all flyback transformers reuse a single high-frequency chopper. The flyback transformer input side is connected to multiple series battery cells, and the output side is connected to a single battery cell for voltage reduction and energy transmission; the optocoupler relay is connected to the positive pole of the series battery cells on one side, and the other side is connected to the corresponding flyback transformer, which is used to select the charging of a single battery cell and control the battery cell balancing time; the high-frequency chopper is connected to the flyback transformer, receives a PWM signal from an external microcontroller MCU, adjusts the output side voltage of all the flyback transformers, and controls the battery cell balancing current.

[0051] In a preferred embodiment of the present invention, the photocoupler relay is a photoelectric cell output type photoelectric coupler, the internal structure includes a light emitting diode LED, a photocell and a MOS tube, and is connected to the positive terminal of the primary side of the flyback transformer. The light emitting diode LED is controlled to light up and turn off by inputting a driving signal, that is, when the light emitting diode LED emits light to illuminate the PN junction group and the photoelectron energy is greater than the bandgap width, the entire array of photocells is stimulated to generate a photogenerated voltage, the MOS tube is turned on, and a photogenerated current is generated after the load is connected; when the light emitting diode LED is turned off, the photocurrent disappears, the charge on the load capacitor inside the photocoupler relay is released, and the MOS tube is turned off.

[0052] In order to better provide energy storage, in a preferred embodiment, each battery cell includes one battery chip or several parallel-connected battery chips.

[0053] The series battery pack in the above embodiment is based on a flyback converter, an optocoupler relay and a high-frequency chopper circuit, which can quickly and efficiently transfer energy from a high-saturation cell to a low-saturation cell when the cell is charging, discharging or sleeping.

[0054] Based on the same inventive concept, in one embodiment of the present invention, an active charge balancing circuit for a series battery pack is provided. The circuit adopts a valley-filling active balancing control strategy to control the battery cells with a high state of charge (SOC) to charge the battery cells with a low state of charge (SOC), thereby achieving a consistent state of charge (SOC).

[0055] from Figure 1 It can be seen that the active power balancing circuit includes three parts: detection chip, microcontroller MCU and control circuit. Among them, the detection chip collects and detects the voltage, current and temperature of all cells to obtain the cell status, charger status and load status; the microcontroller MCU receives the cell status, charger status and load status, and uses them as a basis to determine the working mode, and obtains the corresponding balancing time and balancing current and converts them into control signals; the control circuit inputs the control signal to the series battery pack to control the cells with high state of charge SOC to charge the cells with low state of charge SOC, so as to achieve the consistency of state of charge SOC.

[0056] In some specific embodiments, a process of converting the balancing time and the balancing current into a control signal is provided:

[0057] The balancing time (16 cells have 16 balancing times) corresponds to the time when the MCU outputs high and low levels. For example, if cell 1 needs to be turned off for 2000 seconds, the MCU's I / O output port is kept at a low level for 2000 seconds in the program, and then the optocoupler relay is kept off for 2000 seconds.

[0058] During software and hardware debugging, the reference value of the battery's balancing current when PWM takes a certain duty cycle can be obtained, that is, the PWM-current table. The balancing current can be found by consulting the reference value table to find the initial setting value of the PWM duty cycle. After starting to run, the PWM duty cycle will be adjusted at every moment due to feedback from current, voltage, and temperature.

[0059] Furthermore, in order to better complete the detection task, in some preferred embodiments, the detection chip includes a battery pack detection unit, an overcurrent detection unit, an overvoltage detection unit, a temperature detection unit, a pre-charge and pre-discharge unit, and an ADC voltage sampling unit.

[0060] The battery pack detection unit is used to detect whether the chip port is connected to a battery cell; the overcurrent detection unit is used to detect the current battery cell charging and discharging current. If it exceeds the specified range, an overcurrent warning will be issued and the charging pile or load will be cut off; the overvoltage detection unit is used to detect the current battery cell charging and discharging voltage. If it exceeds the specified range, an overvoltage warning will be issued, balancing will be stopped, and the charging pile will be cut off; the temperature detection unit is used to detect the current temperature of each battery cell. If it exceeds the specified range, an overtemperature warning will be issued, balancing will be stopped, and the charging pile or load will be cut off; the pre-charge and pre-discharge unit is used to control the initial change rate of the charge inside the battery cell, smooth the startup process of charging and discharging, and improve the life of the battery cell; the ADC voltage sampling unit is used to obtain the voltage of the battery cell at the current moment.

[0061] In some specific embodiments, the detection chip can be selected from the BQ76940 or BQ76952 series. Connecting to the PCHG pin of the BQ76952 can pre-charge the battery with a series resistor, which can be used to reduce the charging current of the undervoltage battery; connecting to the PDSG pin of the BQ76952 can pre-discharge the battery with a series resistor, so that the load can be charged slowly, which can be used to reduce the inrush current when the load is initially powered.

[0062] Furthermore, in order to better complete the balancing task, in a preferred embodiment, the microcontroller MCU is composed of a mode determination unit and an active balancing algorithm unit.

[0063] The mode judgment unit includes a data processing subunit and a balancing mode judgment subunit. The data processing subunit uses IIC communication to obtain voltage, current, temperature and other data from the BQ series chip, and then calculates the average value and standard deviation value. The corresponding data is compared with the known battery cell data curve or table to update the battery cell status information at the current moment, such as comparing the voltage data with the OCV-SOC fitting curve to obtain the SOC value of the battery cell at the current moment. The balancing mode judgment subunit identifies four working modes of the battery cell according to the battery cell status and the detection results of the charger / load detection circuit, including: charging balancing mode, discharging balancing mode, sleep balancing mode and stop balancing mode (safe mode). Generally, when the battery cell state is in an abnormal state such as overvoltage, overcurrent, or over-high temperature, the stop balancing mode is entered. When the charge and discharge detection circuit flag returns to 1, the corresponding balancing mode is entered. When the charge and discharge balancing is not entered for a long time or the balancing current remains at a low level, the sleep balancing mode is entered.

[0064] Furthermore, in some specific embodiments, the current working mode can be judged in combination with Table 1.

[0065] Table 1

[0066]

[0067] The charging balancing mode refers to the process of charging and balancing the battery cells when they are connected to the charger. The overall system of active balancing of the battery pack in series (the system includes active balancing circuit, load, and charger) needs to quickly balance the battery cell modules, and at the same time ensure that all the batteries are fully charged at the end of charging, even if the capacity of each battery cell is different, each battery cell must reach its own saturation state. In the charging mode, 4.2V is assumed to be the highest charging voltage of the battery cell; 10mV is defined as the balancing standard (that is, the voltage difference of the battery cell is less than 10mV at any time, that is, the battery cell module is considered to be in a balanced state at this time); the charging end standard is defined as: the voltage difference between the battery cells is less than 10mV, and the charging current is less than 0.01C. When the battery cell module is first connected to the charger, the battery cell module not only charges the battery cell, but also balances the battery cells; if the difference between the batteries is too large, and one battery cell reaches the highest voltage first, it enters the safe mode.

[0068] The discharge mode refers to the process of discharging and balancing when the battery is connected to the load and is in the discharge state. Balancing will cause additional energy loss, so the system requires that the discharge balancing should ensure that the battery can fully utilize the energy of all the batteries, while not over-activating the balancing circuit to reduce the energy loss during the balancing process; the dual balancing standard method is used to reduce the balancing time of the battery (that is, define the battery voltage extreme difference at any time to be less than 10mV or 20mV), reduce the balancing loss, and prevent the battery from being always on the boundary of the balancing condition and always in the balancing state.

[0069] Sleep mode refers to the process in which the battery cell is neither connected to the load nor to the charger, and is in a state without an external circuit, and only performs cell balancing. The system needs to ensure that when the battery cell is not used for a long time, the battery cell is regularly tested and the battery cell is balanced, while also focusing on saving the energy of the battery cell. It should be noted that the battery cell may be stored in the warehouse for a long time after it is produced and shipped. Due to the different self-discharge rates of the battery cells, when the user uses the battery cell module for the first time, the battery cell may be seriously unbalanced, which will lead to a poor user experience. Therefore, the software system also needs to regularly test the battery cell when it is not in use. When an imbalance is found, the battery cell is balanced in time to correct the difference. It should be noted that the balancing in sleep mode needs to strictly control the cycle of battery cell detection to prevent excessive battery cell energy from being consumed due to frequent activation of battery cell detection. In order to reduce energy consumption, before the detection cycle is reached, the sampling circuit and the balancing circuit will be in sleep mode, waiting for the corresponding trigger condition to wake up.

[0070] Safety mode means that the battery cell is currently limited by safety indicators (voltage, current, temperature), and balancing is strictly prohibited at the next moment. Since the battery cell balancing current will affect the temperature and battery cell current of the battery cell module; when the temperature of some batteries is too high, balancing of the battery cell should be avoided or a lower current should be used for balancing; when the charge and discharge current is large, high current balancing should be avoided to avoid the danger of overcurrent in the battery cell.

[0071] The active balancing algorithm unit is burned into the MCU. When the working mode of the battery cell is confirmed to be charge balancing, discharge balancing, or sleep balancing, and the battery cell is considered to need balancing, the active balancing control algorithm is called to calculate the balancing time and balancing current.

[0072] In some specific embodiments, the microcontroller MCU may adopt the STM32G030x6 series.

[0073] Furthermore, in order to better realize circuit control, in a preferred embodiment of the present invention, the control circuit is composed of a photoelectric switch gating unit, a MOS gate driving unit and a high-frequency spike absorption unit.

[0074] Among them, the photoelectric switch selection unit outputs multiple control signals to control the photorelay to select the battery cell and determine the charging and discharging time;

[0075] MOS gate drive unit, outputs a control signal to improve the gate drive capability of the MOS tube on the primary side of the flyback transformer;

[0076] The high-frequency spike absorption unit absorbs the oscillation spikes generated when the high-frequency chopper tube is quickly turned on and off.

[0077] In some specific embodiments, the MCU sends out 17 control signals in total, 1-16 are 0 / 1 signals output by the MCU's common I / O port, which are used to control the on / off of the optocoupler relay, and the photoelectric switch selection unit receives 1-16 signals and operates. The 17th channel is the PWM output port of the MCU, and the output high-frequency PWM signal passes through the MOS gate drive unit to become a high-quality chopper tube drive signal (such as the voltage is increased from 3.3V output by the MCU to 5V, the signal is inverted, etc.), and then the MOS gate drive unit outputs the high-quality signal as the gate signal of the high-frequency chopper tube.

[0078] In some specific embodiments, in the control circuit, the high-frequency spike absorption unit uses a filter to filter out the high-frequency oscillation spikes on the primary side of the transformer caused by the rapid switching on and off of the high-frequency chopper tube, so as to improve the waveform quality on the primary side of the flyback converter.

[0079] The control circuit includes 17 control signals, among which relays 1 to 16 are used to select cells with balancing requirements; and there is another drive for improving the gate drive capability of the MOS tube on the primary side of the flyback converter.

[0080] The control circuit in the above embodiment outputs a control signal to the series-connected battery pack to control the battery cell with a high state of charge SOC to charge the battery cell with a low state of charge SOC, so that the state of charge SOC tends to be consistent. In addition, the operating efficiency of the battery cell is effectively guaranteed, and the corresponding charging, discharging and balancing requirements are met for the four working modes of the battery cell.

[0081] In some specific embodiments, the detection chip, the microcontroller MCU and the control circuit are compatible with SPI, I2C, and mainstream serial port communication for communicating with the host computer. The detection chip is connected to the microcontroller MCU. The microcontroller MCU (STM32G030x6) performs ADC sampling data according to the detection chip (BQ76952) and runs the on-chip balancing algorithm. Subsequently, the microcontroller MCU inputs the balancing time and balancing current into the control circuit, and the control circuit outputs a high-frequency PWM control signal of 3.3V output from an I / O port to control the chopper tube M, and there are 2 to 16 I / O ports, which output a selection signal to control the optocoupler relay of the primary side of the transformer to select the battery cell with a balancing demand. Finally, the balancing time and balancing current calculated by the MCU are adjusted to realize active balancing and charge and discharge control of 2 to 16 battery cells by adjusting the duty cycle of the high-frequency PWM and the on-off time of the photoelectric switch.

[0082] Based on the same inventive concept, in another embodiment of the present invention, a method for controlling an active charge balancing circuit of a series-connected battery pack is provided, comprising:

[0083] Step 1, collect and detect the voltage, current, and temperature of all battery cells to obtain the battery cell status, charger status, and load status;

[0084] Step 2, receiving the cell state, the charger state and the load state, judging the working mode based on the state, and obtaining the corresponding balancing time and balancing current;

[0085] Step 3, converting the balancing time and the balancing current into a control signal, inputting the control signal into an active power balancing circuit, controlling the battery cell with a high state of charge SOC to charge the battery cell with a low state of charge SOC, so as to achieve a uniform state of charge SOC.

[0086] The various steps in the above-mentioned examples of the present invention may refer to the implementation technology of the module / unit of the active charge balancing circuit of the series-connected battery pack in the above-mentioned embodiment, and will not be described in detail here.

[0087] Based on the same inventive concept, in other embodiments of the present invention, an extended topology is also provided, such as Figure 2 As shown, it includes an N-layer stacked structure, N≤3;

[0088] The n-th layer structure includes the n-th layer battery topology part and the n-th layer active power balancing circuit;

[0089] The n-th layer battery topology part includes 2 to 16 n-1-th layer structures connected in series, each of the n-1-th layer structures corresponds to a set of flyback transformers and a photocoupler relay; all the flyback transformers reuse a single high-frequency chopper tube;

[0090] The n-th layer control balancing circuit controls the charge state SOC of 2 to 16 structures of the n-1-th layer to be consistent;

[0091] Each layer of the structure includes a series-connected battery pack as described in any one of claims 1-3 and an active charge balancing circuit as described in any one of claims 4-8.

[0092] The above-mentioned extended structure is applicable in the fields of electric vehicles, power system power battery energy storage, etc., especially for battery packs composed of battery cells through a multi-stage series topology structure. This extended topology effectively prevents potential safety risks caused by overcharging and over-discharging of a single battery cell, ensuring the stable operation of the battery system.

[0093] In one specific embodiment, N is 2 layers, that is, Figure 2 As shown, it includes a master-slave two-stage structure, the master stage structure includes: 2 to 16 battery modules connected in series, each battery module corresponds to a set of flyback transformers and an optocoupler relay; all flyback transformers reuse a single high-frequency chopper tube; each battery module includes the series battery pack and the active power balancing circuit in the above embodiment. Each battery module is a slave stage structure.

[0094] After each voltage sampling of the slave structure is completed, the voltage data will be transmitted to the master structure chip; the master structure replenishes energy for all battery modules according to the total voltage of each slave structure.

[0095] In order to more clearly and completely understand the active charge balancing circuit and control method applicable to the series topology battery pack in the above-mentioned embodiment, an embodiment of the present invention is combined with Figure 1 and Figure 2 , explain again. Figure 2As shown, the battery module contains 6 battery cells (B1~B6), and the battery cell voltage value is represented by the green area. The larger the area, the higher the SOC. First, based on the ADC sampling of the BQ series detection chip, all the battery cell voltage values ​​are obtained. According to the mature voltage-SOC conversion algorithm, it is found that the SOC of battery cells B2, B3, and B5 is relatively low. The fuzzy control active balancing algorithm determines that B2, B3, and B5 need to be balanced. Close the photoelectric switches K2, K3, and K5 corresponding to B2, B3, and B5, and the high-frequency chopper tube M gate inputs an adjustable PWM wave.

[0096] The embodiment of the present invention adopts a structure in which multiple flyback transformers reuse a single high-frequency chopper tube M to achieve unified control of the charging current of each battery cell. In the figure, the sum of the series voltages of B1 to B6 is the input voltage of the circuit, so the balance is achieved by transferring part of the energy from the "battery cell module" as a whole to some of the "battery cells". Specifically, in the high-level stage of the PWM wave, a part of the energy in each battery cell is transferred to the transformer core. There is current flowing through the thick line loop in the figure, where the battery cell charging current is I0, and B2, B3, and B5 correspond to the primary currents of the transformer, respectively, I2, I3, and I5; the secondary side of the transformer is charged evenly by the capacitor to the battery cell; in the low-level stage of the PWM wave, the energy stored in the magnetic core is released to charge B2, B3, and B5 evenly, and at the same time charge the capacitor to compensate for the energy lost in the high-level stage of the PWM wave.

[0097] It should be noted that B2, B3, and B5 also send out part of their own energy. The reason why this circuit can achieve energy replenishment is that the energy obtained by B2, B3, and B5 is far greater than the energy they send out.

[0098] The active balancing circuit is scalable, and each layer of the circuit can meet the active balancing requirements of 2 to 16 groups of cells. Figure 2 As shown in the figure, after each voltage sampling of the Slave layer, the data will be sent to the Master layer chip through communication. Therefore, the Master layer can provide energy to 2 to 16 battery modules according to the total voltage of each subsystem.

[0099] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A series battery pack, characterized in that: It comprises 2 to 16 battery cells connected in series, each battery cell corresponds to a set of flyback transformers and a photocoupler relay, and all the flyback transformers reuse a single high-frequency chopper tube; The flyback transformer has a plurality of battery cells connected in series on its input side and a single battery cell connected on its output side for voltage reduction and energy transmission; the optocoupler relay has one side connected to the positive pole of the battery cells connected in series and the other side connected to the corresponding flyback transformer for gating the charging of a single battery cell and controlling the battery cell balancing time; the high-frequency chopper is connected to the flyback transformer, receives a PWM signal from an external microcontroller MCU, adjusts the output side voltage of all the flyback transformers, and controls the battery cell balancing current.

2. The series battery pack according to claim 1, characterized in that: The optical coupler relay is a photoelectric coupler with a photoelectric output, and its internal structure includes a light-emitting diode (LED), a photoelectric cell and a MOS tube; The diode LED is controlled to light up and turn off by inputting a driving signal; when the diode LED emits light to illuminate the PN junction group and the photoelectron energy is greater than the bandgap width, the entire array of photocells is stimulated to generate a photovoltage, so that the MOS tube is turned on, and a photocurrent is generated after the load is connected; when the diode LED is turned off, the photocurrent disappears, the charge on the internal load capacitor of the optocoupler relay is released, and the MOS tube is turned off.

3. The series-connected battery pack according to claim 1, characterized in that: Each battery cell includes one battery chip or several battery chips connected in parallel.

4. An active charge balancing circuit applicable to a series-connected battery pack according to any one of claims 1 to 3, characterized in that: Including detection chip, microcontroller MCU and control circuit; The detection chip collects and detects the voltage, current, and temperature of all battery cells to obtain the battery cell status, charger status, and load status; The microcontroller MCU receives the battery cell status, the charger status and the load status, and uses them as a basis to determine the working mode, calculates the corresponding balancing time and balancing current, and converts them into control signals; The control circuit inputs the control signal to the series-connected battery pack.

5. The active charge balancing circuit for a series-connected battery pack according to claim 4, characterized in that: The detection chip comprises: The battery pack connection unit detects whether the chip port is connected to the battery cell; Multiple ADC units to obtain the current voltage; Overvoltage detection unit detects the current voltage. When it exceeds the threshold range, it issues an overvoltage warning, stops balancing, and cuts off the charging pile. The temperature detection unit obtains the battery cell temperature and detects the current temperature of each battery cell. If the temperature exceeds the threshold, a high temperature warning is issued and balancing is stopped, and the charging pile or load is disconnected; The overcurrent detection unit obtains the cell current and detects the current cell charge and discharge current. If the current exceeds the threshold, an overcurrent warning is issued and the charging pile or load is cut off. The pre-charge and discharge unit controls the initial rate of change of the charge inside the battery cell.

6. The active charge balancing circuit for a series-connected battery pack according to claim 4, characterized in that: The microcontroller MCU comprises: A mode determination unit, which identifies four cell operation modes according to the cell state, the charger state and the load state, namely, a charge balance mode, a discharge balance mode, a sleep balance mode and a stop balance mode; The active balancing calculation unit takes the SOC of each battery cell as input and obtains the balancing time and balancing current based on the current, voltage and temperature characteristics of the working mode determined.

7. The active charge balancing circuit for a series-connected battery pack according to claim 6, characterized in that: The charging equalization mode means that when the battery cell is connected to the charger, it is charged and equalized at the same time; The discharge balancing mode means that when the battery cell is connected to a load and is in a discharging state, it is discharged and balanced at the same time; The sleep balancing mode means that the battery cell is not connected to a load or a charger and is in a state without an external circuit. After a certain time countdown ends, the balancing circuit is awakened to balance the battery cells only when the battery cells meet the balancing requirements. The stop balancing mode means that the battery cell is currently limited by the safety indicators of voltage, current or temperature, and balancing is strictly prohibited at the next moment.

8. The active charge balancing circuit for a series-connected battery pack according to claim 4, characterized in that: The control circuit comprises: The photoelectric switch selection unit outputs multiple control signals to control the photorelay to select the battery cell and determine the charging and discharging time; MOS gate drive unit, outputs a control signal to improve the gate drive capability of the MOS tube on the primary side of the flyback transformer; The high-frequency spike absorption unit absorbs the oscillation spikes generated when the high-frequency chopper tube is quickly turned on and off.

9. A method for controlling an active charge balancing circuit of a series-connected battery pack, characterized in that: include: Collect and test the voltage, current, and temperature of all cells to obtain the cell status, charger status, and load status; Receiving the cell state, the charger state and the load state, judging the working mode based on the state, and obtaining the corresponding balancing time and balancing current; The balancing time and the balancing current are converted into control signals and input into an active power balancing circuit to control the battery cells with a high state of charge SOC to charge the battery cells with a low state of charge SOC, so as to achieve a uniform state of charge SOC.

10. An extended topology, characterized in that: Including N-layer stacking structure, N≤3; The n-th layer structure includes the n-th layer battery topology part and the n-th layer active power balancing circuit; The n-th layer battery topology part includes 2 to 16 n-1-th layer structures connected in series, each of the n-1-th layer structures corresponds to a set of flyback transformers and a photocoupler relay; all the flyback transformers reuse a single high-frequency chopper tube; The n-th layer control balancing circuit controls the charge state SOC of 2 to 16 structures of the n-1-th layer to be consistent; Each layer of the structure includes a series-connected battery pack as described in any one of claims 1-3 and an active charge balancing circuit as described in any one of claims 4-8.

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