Passive equalization control protection circuit and large-current passive equalization control protection circuit

Abstract

This invention relates to the field of battery management system technology, and in particular to a passive balancing control and protection circuit and a high-current passive balancing control and protection circuit. It includes a current-limiting resistor, LED chips, a balancing MOSFET, and a MOSFET control circuit. The battery cell is interconnected with the current-limiting resistor, LED chips, and balancing MOSFET. The MOSFET control circuit is connected to the gate of the balancing MOSFET. The advantages of this invention are: using LED chips instead of balancing resistors protects the battery cell from over-discharge damage even in the event of a short circuit due to balancing MOSFET failure, reducing losses; eliminating the need for a heat sink, reducing costs; simplifying the software control logic; and in applications requiring higher balancing current, simply connecting one or more identical balancing branches in parallel eliminates concerns about balancing MOSFET failure and heat dissipation, simplifying design and facilitating rapid product launch.

Description

Technical Field

[0001] This invention relates to the field of battery management system technology, and in particular to passive equalization control and protection circuits and high-current passive equalization control and protection circuits. Background Technology

[0002] Lithium-ion battery storage packs typically consist of multiple cells connected in series. The more cells connected in series, the higher the requirement for cell consistency is, in order to fully utilize the capacity performance of the battery pack. To address this need, various battery management systems (BMS) based on balancing control have emerged, mainly divided into two categories: passive balancing and active balancing. Passive balancing, due to its simple circuit structure, ease of control, and low cost, has been integrated into chips by major battery management chip manufacturers and is widely used.

[0003] The mainstream passive balancing scheme consists of a balancing resistor and a balancing MOSFET connected in parallel across the battery cell. When cells in a series-connected battery pack need balancing, the balancing MOSFET in this branch conducts, and the balancing resistor, connected in parallel across the cell, consumes excess charge, making the capacity of each cell in the battery pack more consistent. After balancing, the battery management chip controls the balancing MOSFET to turn off, disconnecting the balancing branch from the cell and ceasing to consume battery charge. This requires the balancing MOSFET to have high reliability, withstand voltage and current surges, and provide electrostatic discharge protection. When the balancing MOSFET fails, the drain and source of the MOSFET are shoot-through, and the balancing resistor remains connected in parallel across the cell, continuously consuming the cell's charge, eventually leading to over-discharge damage. Some manufacturers add a passive balancing circuit failure detection circuit, but if the balancing MOSFET fails, the balancing branch is not disconnected; timely maintenance is required, otherwise, over-discharge damage to the cell will still occur. Passive balancing is an energy-consuming process. Figure 3 As shown, the battery cell consumes power through heating via resistors. This requires selecting resistors with appropriate power and a reasonable PCB layout, and may even require adding heat sinks to control the temperature rise within an acceptable range, which increases complexity and cost. Summary of the Invention

[0004] This invention addresses the problems of existing technologies by providing a passive equalization control protection circuit and a high-current passive equalization control protection circuit.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a passive equalization control and protection circuit, including a current-limiting resistor, an LED, an equalization MOSFET, and a MOSFET control circuit. The battery cell is interconnected with the current-limiting resistor, the LED, and the equalization MOSFET. The MOSFET control circuit is connected to the gate of the equalization MOSFET.

[0007] In this circuit, the current-limiting resistor is R4, the LED bead is LED1, the equalizing MOSFET is MOSFET Q2, the positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor R4, the other end of the current-limiting resistor R4 is connected to the anode of LED1, the cathode of LED1 is connected to the drain of MOSFET Q2, the negative terminal BAT- of the battery cell is connected to the source of MOSFET Q2, the MOSFET control circuit includes a battery management chip, and the gate of MOSFET Q2 is connected to the equalization control pin EQ of the battery management chip.

[0008] The passive equalization control protection circuit further includes resistors R5 and R6. One end of resistor R5 is connected to the gate of MOSFET Q2 and one end of resistor R6. The other end of resistor R5 is connected to the equalization control pin EQ of the battery management chip. The other end of resistor R6 is connected to the source of MOSFET Q2 and the negative terminal BAT- of the battery cell.

[0009] In this circuit, the current-limiting resistor is R4, the LED bead is LED1, the balancing MOSFET is MOSFET Q2, the positive terminal BAT+ of the battery cell is connected to the anode of LED1, the cathode of LED1 is connected to one end of the current-limiting resistor R4, the other end of the current-limiting resistor R4 is connected to the drain of MOSFET Q2, the negative terminal BAT- of the battery cell is connected to the source of MOSFET Q2, the MOSFET control circuit includes a battery management chip, and the gate of MOSFET Q2 is connected to the balancing control pin EQ of the battery management chip.

[0010] The passive equalization control protection circuit further includes resistors R5 and R6. One end of resistor R5 is connected to the gate of MOSFET Q2 and one end of resistor R6. The other end of resistor R5 is connected to the equalization control pin EQ of the battery management chip. The other end of resistor R6 is connected to the source of MOSFET Q2 and the negative terminal BAT- of the battery cell.

[0011] The present invention also provides a high-current passive equalization control and protection circuit, including multiple passive equalization control and protection circuits connected in parallel at both ends of the battery cell.

[0012] Among them, multiple passive equalization control and protection circuits include a first equalization branch and a second equalization branch connected in parallel at both ends of the cell, and the MOS transistor control circuit includes a battery management chip;

[0013] The first equalization branch includes a current-limiting resistor RA1, an LED bead LEDA1, an equalization MOSFET QA1, a resistor RB1, and a resistor RC1;

[0014] The second equalization branch includes a current-limiting resistor RB1, an LED bead LEDB2, an equalization MOSFET QA2, a resistor RB2, and a resistor RC2;

[0015] The positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor RA1. The other end of the current-limiting resistor RA1 is connected to the anode of the LED bead LEDA1. The cathode of the LED bead LEDA1 is connected to the drain of the equalizing MOSFET QA1. The source of the equalizing MOSFET QA1 is connected to the negative terminal BAT- of the battery cell and one end of the resistor RC1. The other end of the resistor RC1 is connected to the gate of the equalizing MOSFET QA1 and one end of the resistor RB1. The other end of the resistor RB1 is connected to the equalization control pin EQ of the battery management chip.

[0016] The positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor RA2. The other end of the current-limiting resistor RA2 is connected to the anode of the LED bead LEDA2. The cathode of the LED bead LEDA2 is connected to the drain of the equalizing MOSFET QA2. The source of the equalizing MOSFET QA2 is connected to the negative terminal BAT- of the battery cell and one end of the resistor RC2. The other end of the resistor RC2 is connected to the gate of the equalizing MOSFET QA2 and one end of the resistor RB2. The other end of the resistor RB2 is connected to the equalization control pin EQ of the battery management chip. The beneficial effects of this invention are:

[0017] 1. By replacing the balancing resistor with LED beads and adding only one current-limiting resistor, the battery cell can be protected from over-discharge damage even if the balancing MOSFET fails and short-circuits, as long as the cell voltage is higher than the LED bead's turn-on voltage, thus reducing losses.

[0018] 2. Replacing the equalization resistor with LED beads effectively reduces the temperature rise caused by the balancing branch being turned on by emitting light, eliminating the need for a heat sink, reducing costs, and improving BMS reliability.

[0019] 3. Since temperature rise is no longer the bottleneck, the equalization function activation method no longer requires gap control; only equalization enable control needs to be considered, which simplifies the software control logic.

[0020] 4. In applications requiring increased balancing current, simply connect one or more identical balancing branches in parallel. There is no need to worry about balancing MOSFET failure or heat dissipation issues, which simplifies the design and facilitates rapid product launch. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the passive equalization control and protection circuit of the present invention.

[0022] Figure 2 This is a circuit diagram of the high-current passive equalization control and protection circuit of the present invention.

[0023] Figure 3 This is a circuit diagram of a traditional passive equalization control and protection circuit.

[0024] exist Figures 1 to 3 The reference numerals in the figures include:

[0025] 101—First balanced branch; 102—Second balanced branch. Detailed Implementation

[0026] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0027] Example 1

[0028] A passive equalization control and protection circuit, such as Figure 1 As shown, it includes a current-limiting resistor, an LED chip, a balancing MOSFET, and a MOSFET control circuit. The battery cell is interconnected with the current-limiting resistor, the LED chip, and the balancing MOSFET. The MOSFET control circuit is connected to the gate of the balancing MOSFET.

[0029] In this circuit, the current-limiting resistor is R4, the LED bead is LED1, the equalizing MOSFET is MOSFET Q2, the positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor R4, the other end of the current-limiting resistor R4 is connected to the anode of LED1, the cathode of LED1 is connected to the drain of MOSFET Q2, the negative terminal BAT- of the battery cell is connected to the source of MOSFET Q2, the MOSFET control circuit includes a battery management chip, and the gate of MOSFET Q2 is connected to the equalization control pin EQ of the battery management chip.

[0030] The passive equalization control protection circuit further includes resistors R5 and R6. One end of resistor R5 is connected to the gate of MOSFET Q2 and one end of resistor R6. The other end of resistor R5 is connected to the equalization control pin EQ of the battery management chip. The other end of resistor R6 is connected to the source of MOSFET Q2 and the negative terminal BAT- of the battery cell.

[0031] The beneficial effects of this embodiment are as follows:

[0032] 1. By replacing the balancing resistor with LED beads and adding only one current-limiting resistor, the battery cell can be protected from over-discharge damage even if the balancing MOSFET fails and short-circuits, as long as the cell voltage is higher than the LED bead's turn-on voltage, thus reducing losses.

[0033] 2. Replacing the equalization resistor with LED beads effectively reduces the temperature rise caused by the balancing branch being turned on by emitting light, eliminating the need for a heat sink, reducing costs, and improving BMS reliability.

[0034] 3. Since temperature rise is no longer the bottleneck, the equalization function activation method no longer requires gap control; only equalization enable control needs to be considered, which simplifies the software control logic.

[0035] 4. In applications requiring increased balancing current, simply connect one or more identical balancing branches in parallel. There is no need to worry about balancing MOSFET failure or heat dissipation issues, which simplifies the design and facilitates rapid product launch.

[0036] Specifically, this embodiment uses LED chips as the passive equalization energy conversion device, converting the excess electrical energy stored in the battery cells into light energy, replacing the mainstream equalization resistor heating method. LEDs generate less heat, preventing localized overheating of the equalization circuitry on the BMS PCB, eliminating the need for a heat sink and thus reducing BMS costs. Because no excess heat is generated, the ambient temperature does not rise significantly, thereby improving BMS reliability.

[0037] The function of the current-limiting resistor is to limit the current in the balancing branch within the allowable range, preventing excessive current from the battery cell voltage from burning out the LED. The selection of the current-limiting resistor needs to consider the battery cell's maximum voltage Ubat, the LED's on-state voltage Uled, and the LED's forward rated operating current If, i.e., the current-limiting resistor R = (Ubat - Uled) / If. The maximum balancing current is mainly determined by the normal rated operating current of the LED. If there are strict requirements for the PCB board size, 2835 surface-mount LEDs can be selected, which can achieve a maximum balancing current of 180mA, meeting the requirements of mainstream passive balancing current specifications.

[0038] The selection of LED chips as energy conversion devices is also due to the fact that LED chips require a certain forward voltage to operate normally. This ensures that in the event of a MOSFET failure, the balancing circuit will not continuously consume the battery cell's energy. Before the battery cell voltage drops below the safe voltage, the LED chips will stop working due to insufficient forward voltage, thus preventing irreparable damage from over-discharge. 2835 LED chips can be selected, with a minimum forward voltage of 2.5V, which is significantly higher than the safe voltage of 1.8V for lithium iron phosphate batteries. This ensures that the battery cell remains within the safe voltage range, preventing over-discharge damage and unnecessary losses.

[0039] After the LED beads of this invention replace the equalization resistor, the local heat generation caused by equalization is no longer a bottleneck. Therefore, there is no need to control the equalization MOSFET to be in an intermittent on-off state. When equalization is required, the equalization MOSFET can be controlled to be continuously on, which simplifies the software control logic.

[0040] This embodiment also provides a high-current passive equalization control and protection circuit, such as Figure 2As shown, it includes multiple passive equalization control and protection circuits connected in parallel at both ends of the battery cell.

[0041] Among them, multiple passive equalization control and protection circuits include a first equalization branch 101 and a second equalization branch 102 connected in parallel at both ends of the battery cell, and the MOS transistor control circuit includes a battery management chip.

[0042] The first equalization branch 101 includes a current-limiting resistor RA1, an LED bead LEDA1, an equalization MOSFET QA1, a resistor RB1, and a resistor RC1;

[0043] The second equalization branch 102 includes a current-limiting resistor RB1, an LED bead LEDB2, an equalization MOSFET QA2, a resistor RB2, and a resistor RC2;

[0044] The positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor RA1. The other end of the current-limiting resistor RA1 is connected to the anode of the LED chip LEDA1. The cathode of the LED chip LEDA1 is connected to the drain of the equalizing MOSFET QA1. The source of the equalizing MOSFET QA1 is connected to the negative terminal BAT- of the battery cell and one end of the resistor RC1. The other end of the resistor RC1 is connected to the gate of the equalizing MOSFET QA1 and one end of the resistor RB1. The other end of the resistor RB1 is connected to the equalization control pin EQ of the battery management chip. Specifically, the current-limiting resistor RA1 and the LED chip LEDA1 can be interchanged without affecting the operation and performance of the circuit.

[0045] The positive terminal (BAT+) of the battery cell is connected to one end of the current-limiting resistor RA2. The other end of the current-limiting resistor RA2 is connected to the anode of the LED chip LEDA2. The cathode of the LED chip LEDA2 is connected to the drain of the equalizing MOSFET QA2. The source of the equalizing MOSFET QA2 is connected to the negative terminal (BAT-) of the battery cell and one end of resistor RC2. The other end of resistor RC2 is connected to the gate of the equalizing MOSFET QA2 and one end of resistor RB2. The other end of resistor RB2 is connected to the equalization control pin (EQ) of the battery management chip. Specifically, the current-limiting resistor RA2 and the LED chip LEDA2 can be interchanged without affecting the operation and performance of the circuit.

[0046] Furthermore, the multiple passive equalization control and protection circuits can include N equalization branches, and the connection method of the N equalization branches is as described above. They are connected in parallel at both ends of the battery cell, which can achieve a larger equalization current and shorten the equalization time. Figure 2The multiple passive balancing branches shown are connected in parallel and controlled by the same balancing control pin (EQ) of the same battery management chip. The signal controlling the balancing MOSFETs of multiple balancing branches can be from TI's BQ series battery management chips. Using a single balancing control signal to control the balancing MOSFETs of multiple balancing branches simplifies the MOSFET drive circuit, improves reliability, and reduces PCB size. The high-current passive balancing control and protection circuit of this invention can increase the balancing current. As long as the PCB size allows, it avoids the problems of localized overheating and cell over-discharge damage caused by balancing MOSFET failure, common in mainstream passive balancing circuits, resulting in a reliable structure.

[0047] Example 2

[0048] The difference between Example 2 and Example 1 is that the positions of the LED1 and the current-limiting resistor R4 are interchanged, which does not affect the operation and performance of the circuit in this example, and the structure is flexible; that is, the current-limiting resistor is R4, the LED1 is the LED, the equalizing MOSFET is Q2, the positive terminal BAT+ of the battery cell is connected to the anode of the LED1, the cathode of the LED1 is connected to one end of the current-limiting resistor R4, the other end of the current-limiting resistor R4 is connected to the drain of the MOSFET Q2, the negative terminal BAT- of the battery cell is connected to the source of the MOSFET Q2, the MOSFET control circuit includes a battery management chip, and the gate of the MOSFET Q2 is connected to the equalization control pin EQ of the battery management chip.

[0049] The passive equalization control protection circuit further includes resistors R5 and R6. One end of resistor R5 is connected to the gate of MOSFET Q2 and one end of resistor R6. The other end of resistor R5 is connected to the equalization control pin EQ of the battery management chip. The other end of resistor R6 is connected to the source of MOSFET Q2 and the negative terminal BAT- of the battery cell.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the present invention without departing from the scope of the present invention are within the scope of the present invention.

Claims

1. A passive equalization control and protection circuit, characterized in that: The device includes a current-limiting resistor, an LED chip, an equalizing MOSFET, and a MOSFET control circuit. The battery cell is interconnected with the current-limiting resistor, the LED chip, and the equalizing MOSFET. The MOSFET control circuit is connected to the gate of the equalizing MOSFET. The device is characterized by: the current-limiting resistor being R4; the LED chip being LED1; the equalizing MOSFET being MOSFET Q2; the positive terminal BAT+ of the battery cell being connected to the anode of LED1; the cathode of LED1 being connected to one end of the current-limiting resistor R4; the other end of the current-limiting resistor R4 being connected to the drain of MOSFET Q2; and the negative terminal BAT- of the battery cell being connected to the source of MOSFET Q2. The MOSFET control circuit includes a battery management chip, and the gate of MOSFET Q2 is connected to the equalization control pin EQ of the battery management chip.

2. The passive equalization control and protection circuit according to claim 1, characterized in that: The passive equalization control and protection circuit also includes resistors R5 and R6. One end of resistor R5 is connected to the gate of MOSFET Q2 and one end of resistor R6. The other end of resistor R5 is connected to the equalization control pin EQ of the battery management chip. The other end of resistor R6 is connected to the source of MOSFET Q2 and the negative terminal BAT- of the battery cell.

3. A high-current passive equalization control and protection circuit, characterized in that: It includes multiple passive equalization control and protection circuits as described in any one of claims 1-2, which are respectively connected in parallel at both ends of the battery cell.

4. The high-current passive equalization control and protection circuit according to claim 3, characterized in that: Multiple passive equalization control and protection circuits include a first equalization branch and a second equalization branch connected in parallel at both ends of the battery cell, and the MOSFET control circuit includes a battery management chip; the first equalization branch includes a current-limiting resistor RA1, an LED bead LEDA1, an equalization MOSFET QA1, a resistor RB1, and a resistor RC1; The second equalization branch includes a current-limiting resistor RB1, an LED bead LEDB2, an equalization MOSFET QA2, a resistor RB2, and a resistor RC2; The positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor RA1. The other end of the current-limiting resistor RA1 is connected to the anode of the LED LED1. The cathode of the LED LED1 is connected to the drain of the equalizing MOSFET QA1. The source of the equalizing MOSFET QA1 is connected to the negative terminal BAT- of the battery cell and one end of the resistor RC1. The other end of the resistor RC1 is connected to the gate of the equalizing MOSFET QA1 and one end of the resistor RB1. The other end of the resistor RB1 is connected to the equalization control pin EQ of the battery management chip. The positive terminal BAT+ of the battery cell is connected to one end of the current-limiting resistor RA2. The other end of the current-limiting resistor RA2 is connected to the anode of the LED LED2. The cathode of the LED LED2 is connected to the drain of the equalizing MOSFET QA2. The source of the equalizing MOSFET QA2 is connected to the negative terminal BAT- of the battery cell and one end of the resistor RC2. The other end of the resistor RC2 is connected to the gate of the equalizing MOSFET QA2 and one end of the resistor RB2. The other end of the resistor RB2 is connected to the equalization control pin EQ of the battery management chip.

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