WO2021179779A1 - Battery protection chip and battery protection board - Google Patents

Abstract

Disclosed are a battery protection chip and a battery protection board. The battery protection chip comprises a first starting comparator, a current source circuit and a variable delay circuit, wherein the first starting comparator is connected to an over-current detection end, and is used for forming a first control signal on the basis of a detection voltage of the over-current detection end and a first short-circuit reference voltage; the current source circuit is connected to the over-current detection end, and is used for forming a delay control current on the basis of the detection voltage of the over-current detection end; and the variable delay circuit is connected to the first starting comparator and the current source circuit, and is used for adjusting a short-circuit delay time and outputting a short-circuit protection signal on the basis of the first control signal and the delay control current. By means of the battery protection chip, the short-circuit delay time can be adjusted in real time according to the detection voltage of the over-current detection end, such that the short-circuit delay time matches the increase speed of a current during short-circuiting, thereby guaranteeing a short-circuit protection effect.

Description

Battery protection chip and battery protection board

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on March 9, 2020 with the application number of 202010158064.X and the invention title of "Battery Protection Chip and Battery Protection Board", the entire content of which is incorporated herein by reference Applying.

Technical field

This application relates to the technical field of battery protection, in particular to a battery protection chip and a battery protection board.

Background technique

Lithium batteries have the characteristics of high performance, high density, small size and light weight, making them the first choice for portable product batteries in recent years. Unlike other batteries, in order to ensure the normal and safe operation of lithium batteries, a battery connected to the lithium battery needs to be installed. The protection board is used to ensure that the lithium battery is not in abnormal conditions such as overcharge, overdischarge, overcurrent and short circuit. The battery protection board is equipped with battery protection chips, power switch tubes and surrounding resistance and capacitance components. In practical applications such as energy storage systems and electric vehicles, in order to ensure that the electrical equipment has sufficient voltage and battery life, the battery packs configured on the electrical equipment often need to be connected in parallel or in multiple strings to increase the capacity of the battery pack.

Figure 1 shows a schematic diagram of a conventional battery protection board. As shown in Figure 1, the battery protection board is arranged at both ends of the battery pack B1/B2...BN, including a battery protection chip U1, a discharge power transistor M1 connected to the over-discharge protection output terminal DO of the battery protection chip U1, and the battery The charging power transistor M2 connected to the overcharge protection output terminal CO of the protection chip U1 and the sampling resistor RS connected to the overcurrent detection terminal VINI of the battery protection chip U1. One end of the sampling resistor RS is connected to the ground terminal VSS, and the other end is connected in series. The discharging power transistor M1 is connected to the charging power transistor M2; the discharging power transistor M1 is connected to the discharging circuit (not shown in the figure), and is used to control the operation of the discharging circuit according to the drive control signal output by the over-discharge protection output terminal DO; the charging power transistor M2 is connected to a charging circuit (not shown in the figure), and is used to control the operation of the charging circuit according to the drive control signal output by the overcharge protection output terminal CO. The battery protection chip U1 includes a short-circuit comparator CMP0 connected to the overcurrent detection terminal VINI, a fixed delay circuit 11 connected to the short-circuit comparator CMP0, a logic processing circuit 12 connected to the fixed delay circuit 11, an AND logic processing circuit 12 and The overdischarge drive circuit 13 connected to the overdischarge protection output terminal DO, and the overcharge drive circuit 14 connected to the logic processing circuit 12 and the overcharge protection output terminal CO.

The above-mentioned battery protection chip U1 can realize short-circuit protection, and its realization principle is as follows: as the voltage flowing through the sampling resistor RS gradually increases, the detection voltage of the over-current detection terminal VINI of the battery protection chip U1 will gradually rise, and the comparator CMP0 is short-circuited. The detection voltage is compared with the internal preset short-circuit protection voltage threshold Vref. When the detection voltage exceeds the short-circuit protection voltage threshold Vref, the output of the short-circuit comparator CMP0 turns from high to low to start the fixed delay circuit 11 ; A short delay is formed based on the fixed delay circuit 11 (usually a preset short-circuit delay time, such as 300us); if the detection voltage is still higher than the short-circuit protection voltage threshold Vref after the short delay, the logic processing circuit 12 In addition to the role of the over-discharge drive circuit 13, the drive control signal of the over-discharge protection output terminal DO is converted from a high level to a low level, and the discharge power transistor M1 is controlled to turn off to cut off the discharge circuit, thereby realizing the purpose of short-circuit protection.

The above-mentioned battery protection chip U1 has the following shortcomings when implementing short-circuit protection: First, when a battery pack with a larger battery capacity is short-circuited, the current rises very fast, usually around 100us to reach the peak value, while the traditional battery protection chip U1 short-circuit delay time Generally, it is a fixed delay time (such as 300us), which cannot match the current rising speed, which makes the short-circuit protection effect poor; secondly, because the high current discharge needs to consider the heat dissipation requirements at the same time, the discharge power transistor M1 is generally multiple high-power MOSFETs When used in parallel, at this time, the parasitic capacitance is large, which will cause the discharge power transistor M1 to turn off for a long time. If the discharge power transistor M1 cannot be turned off in time, it will cause safety hazards such as burning of the discharge circuit or fire of the battery cell; Shortening the short-circuit delay time or removing the delay will cause the over-current detection terminal VINI to be susceptible to external signal interference, or some applications cannot start normally when a large starting current is required.

Summary of the invention

The embodiments of the present application provide a battery protection chip and a battery protection board to solve the problem that the short-circuit delay time in the existing battery protection chip cannot match the current rise speed when the battery is short-circuited.

An embodiment of the present application provides a battery protection chip, including a first startup comparator, a current source circuit, and a variable delay circuit. The first startup comparator is connected to an overcurrent detection terminal and is configured to detect The detection voltage of the terminal and the first short-circuit reference voltage form a first control signal; the current source circuit is connected to the over-current detection terminal and is used to form a delay control current based on the detection voltage of the over-current detection terminal; The variable delay circuit is connected to the first start comparator and the current source circuit, and is used to adjust the short-circuit delay time and output a short-circuit protection signal based on the first control signal and the delay control current.

Preferably, the variable delay circuit includes a delay start switch tube, a delay capacitor, a delay end comparator and a logic AND gate; the gate of the delay start switch tube is connected to the first start comparator , The source is connected to the delay capacitor, the drain is connected to the current source circuit and the delay end comparator, and is used to control conduction according to the first control signal, and the delay control current pair is used The delay capacitor is charged; the delay end comparator is connected to the drain of the delay start switch, and is used to form a second control based on the capacitor voltage corresponding to the delay capacitor and the short-circuit protection voltage threshold Signal; the logic AND gate is connected to the first start comparator and the delay end comparator, and is used to form a short circuit protection signal based on the first control signal and the second control signal.

Preferably, the current source circuit includes a fixed current branch and a variable current branch; the fixed current branch is used to output a fixed current; the variable current branch is connected to the overcurrent detection terminal for Based on the detection voltage of the overcurrent detection terminal, a variable current is output.

Preferably, the fixed current branch includes a first current source and a first voltage source; one end of the first voltage source is grounded, and the other end is connected to the first current source for outputting to the first current source A fixed voltage; the first current source is connected to the first voltage source and the variable delay circuit, and is configured to form a fixed current based on the fixed voltage and output the fixed current to the variable delay circuit .

Preferably, the variable current branch includes a second current source and a subtractor circuit; one end of the subtractor circuit is connected to the overcurrent detection terminal, and is configured to form a variable based on the detection voltage of the overcurrent detection terminal. Voltage, outputting the variable voltage to the second current source; the second current source is connected to the subtractor circuit and the variable delay circuit for forming a variable current based on the variable voltage , Output the variable current to the variable delay circuit.

Preferably, the subtractor circuit includes an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a second voltage source; one end of the first resistor is connected to the negative input terminal of the operational amplifier and The second resistor is connected, and the other end is connected to the output end of the operational amplifier; one end of the second resistor is connected to the negative input end of the operational amplifier and the first resistor, and the other end is connected to the second resistor. The voltage source is connected; one end of the third resistor is connected to the positive input end of the operational amplifier and the fourth resistor, and the other end is connected to the overcurrent detection end; one end of the fourth resistor is connected to the operation The positive input end of the amplifier is connected to the third resistor, and the other end is grounded; one end of the second voltage source is connected to the second resistor, and the other end is grounded to provide a comparison voltage to the operational amplifier.

Preferably, the battery protection chip further includes a logic processing circuit connected to the variable delay circuit, an overdischarge drive circuit arranged between the logic processing circuit and an overdischarge protection output terminal, and an overdischarge drive circuit arranged on the An overcharge drive circuit between a logic processing circuit and an overcharge protection output terminal; the logic processing circuit is used to control the overdischarge drive circuit and the overcharge drive circuit to output a turn-off drive signal according to the short circuit protection signal .

Preferably, the battery protection chip further includes a short circuit drive circuit arranged between the logic processing circuit and the over-discharge protection output terminal, and the logic processing circuit is used to control the short circuit according to the short circuit protection signal. The drive circuit outputs a short-circuit drive signal.

Preferably, the battery protection chip further includes a second start comparator connected to the overcurrent detection terminal, a fixed delay circuit connected to the second start comparator, and a logic processing circuit connected to the fixed delay circuit , An over-discharge drive circuit arranged between the logic processing circuit and the over-discharge protection output terminal, an over-charge drive circuit arranged between the logic processing circuit and the over-charge protection output terminal, and the variable delay The output driving circuit connected to the time circuit; the second start comparator is used to form a fixed start signal for controlling the fixed delay circuit based on the detection voltage of the overcurrent detection terminal and the second short-circuit reference voltage, the first The second short-circuit reference voltage is less than the first short-circuit reference voltage; the output drive circuit is connected to a peripheral short-circuit drive circuit for forming an output drive signal based on the short-circuit protection signal.

The battery protection board provided by the embodiment of the present application is arranged at both ends of the battery pack, and includes a sampling resistor connected to the battery pack, a discharging power transistor and a charging power transistor connected to the sampling resistor. For the battery protection chip connected at both ends of the battery pack, the overcharge detection end of the battery protection chip is connected to the sampling resistor.

In the battery protection chip and the battery protection board provided by the embodiments of the present application, the first start comparator connected to the overcurrent detection terminal forms a first control signal based on the detection voltage and the first short-circuit reference voltage to start based on the first control signal The variable delay circuit works to achieve the effect of controlling the variable delay circuit based on the real-time changing detection voltage; the current source circuit connected to the overcurrent detection terminal can convert the detection voltage into a delay control current, so that the delay control The current changes with the change of the detection voltage; the variable delay circuit starts the short-circuit protection work according to the first control signal output by the first start comparator, and specifically adjusts the short-circuit delay time in real time according to the delay control current, and the short-circuit delay time After the time is over, the short-circuit protection signal is output, and the short-circuit protection operation is performed based on the short-circuit protection signal to ensure the short-circuit protection effect. That is, the short-circuit delay time can be adjusted in real time according to the detection voltage of the over-current detection terminal, so that the short-circuit delay time matches the current rising speed , Guarantee the effect of short-circuit protection.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present application more clearly, the following will briefly introduce the drawings that need to be used in the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative labor.

Figure 1 is a schematic block diagram of an existing battery protection board;

FIG. 2 is a functional block diagram of a battery protection board in an embodiment of the present application;

FIG. 3 is another principle block diagram of the battery protection board in an embodiment of the present application;

FIG. 4 is a circuit diagram of the battery protection chip U1 in an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

The embodiment of the application provides a battery protection chip U1. The battery protection chip U1 can be applied to the battery protection board shown in FIG. 2 and FIG. Short-circuit detection and protection are performed on both ends of the battery pack. As shown in Figures 2 to 4, the battery protection chip U1 includes a first startup comparator CMP1, a current source circuit 15 and a variable delay circuit 16. The first startup comparator CMP1 is connected to the overcurrent detection terminal VINI for The detection voltage of the overcurrent detection terminal VINI and the first short-circuit reference voltage Vr1 form a first control signal; the current source circuit 15 is connected to the overcurrent detection terminal VINI and is used to form a delay control current based on the detection voltage of the overcurrent detection terminal VINI The variable delay circuit 16 is connected to the first start comparator CMP1 and the current source circuit 15, and is used to adjust the short-circuit delay time and output a short-circuit protection signal based on the first control signal and the delay control current.

Among them, the first startup comparator CMP1 is a comparator connected to the variable delay circuit 16 for controlling the operation of the variable delay circuit 16. The first short-circuit reference voltage Vr1 is a preset reference voltage for the first startup comparator CMP1 to determine whether or not a short-circuit. As an example, the first startup comparator CMP1 is connected to the overcurrent detection terminal VINI of the battery protection chip U1, and is used to receive the detection voltage of the overcurrent detection terminal VINI, and compare the detection voltage with the first short-circuit reference voltage Vr1, if When the detection voltage is greater than the first short-circuit reference voltage Vr1, the output of the first start comparator CMP1 changes from low level to high level, and outputs a high level first control signal.

Among them, the current source circuit 15 is a circuit formed based on a current source. In this example, the current source circuit 15 is a circuit in which the current source is controlled by the input voltage. The current source circuit 15 is connected to the overcurrent detection terminal VINI and the variable delay circuit 16, and can be formed based on the detection voltage sampled by the overcurrent detection terminal VINI A delay control current that can change with the detection voltage change, and the variable delay circuit 16 is input to the variable delay circuit 16. It is understandable that the real-time detection voltage sampled by the over-current detection terminal VINI continuously changes, so that the magnitude of the delay control current output to the variable delay circuit 16 changes in real time. In this example, the delay control current is proportional to the detection voltage. For example, when a short circuit occurs in the battery pack, the detection voltage sampled by the overcurrent detection terminal VINI in real time gradually increases, so that the corresponding delay control current increases accordingly.

Among them, the variable delay circuit 16 is a circuit that is connected to the first start comparator CMP1 and the current source circuit 15 and can realize automatic adjustment of the short-circuit delay time. As an example, the variable delay circuit 16 is connected to the first start comparator CMP1, and is used to receive the first control signal of the first start comparator CMP1, so as to determine whether to start the variable delay circuit 16 according to the first control signal. Short circuit protection. The variable delay circuit 16 is connected to the current source circuit 15, and is used to automatically adjust the short-circuit delay time based on the delay control current input by the current source circuit 15 when the variable delay circuit 16 is turned on. After the end, the short-circuit protection signal is output to perform short-circuit protection based on the short-circuit protection signal, such as controlling the charging circuit and the discharging circuit to stop working. In this example, the short-circuit delay time is inversely proportional to the delay control current. For example, when the battery pack is short-circuited, the detection voltage sampled by the over-current detection terminal VINI in real time gradually increases, so that the corresponding delay control current increases accordingly to shorten the short-circuit delay time and output a short-circuit protection signal based on the short-circuit The protection signal performs short-circuit protection to ensure the short-circuit protection effect.

In the battery protection chip U1 provided by this embodiment, the first startup comparator CMP1 connected to the overcurrent detection terminal VINI forms a first control signal based on the detection voltage and the first short-circuit reference voltage Vr1, so as to activate the variable based on the first control signal. The delay circuit 16 works to achieve the effect of controlling the operation of the variable delay circuit 16 based on the detection voltage that changes in real time; the current source circuit 15 connected to the overcurrent detection terminal VINI can convert the detection voltage into a delay control current, so that the delay When the control current changes with the detection voltage, the variable delay circuit 16 starts the short-circuit protection operation according to the first control signal output by the first start comparator CMP1, and specifically adjusts the short-circuit delay time in real time according to the delay control current, and After the short-circuit delay time is over, the short-circuit protection signal is output, and the short-circuit protection operation is performed based on the short-circuit protection signal to ensure the short-circuit protection effect. That is, the short-circuit delay time can be adjusted in real time according to the detection voltage of the over-current detection terminal VINI to make the short-circuit delay. The time and time match the rising speed of the current in the short circuit to ensure the short circuit protection effect.

In one embodiment, as shown in FIG. 4, the variable delay circuit 16 includes a delay start switch Q1, a delay capacitor C1, a delay end comparator CMP3, and a logic AND gate A1; the delay start switch Q1 The gate is connected to the first start comparator CMP1, the source is connected to the delay capacitor C1, and the drain is connected to the current source circuit 15 and the delay end comparator CMP3, which is used to control the conduction according to the first control signal. The control current charges the delay capacitor C1; the delay end comparator CMP3 is connected to the drain of the delay start switch Q1, and is used to form a second control based on the capacitor voltage corresponding to the delay capacitor C1 and the short-circuit protection voltage threshold Vref Signal; the logic AND gate A1 is connected to the first start comparator CMP1 and the delay end comparator CMP3, and is used to form a short circuit protection signal based on the first control signal and the second control signal.

Among them, the delay start switch Q1 is a switch used to control whether to start the variable delay circuit 16, and is specifically a MOS transistor. The short-circuit protection voltage threshold Vref is a preset reference voltage used for the delay end comparator CMP3 to determine whether a short-circuit.

The gate of the delay start switch Q1 is connected to the first start comparator CMP1, the source is connected to the delay capacitor C1, and the drain is connected to the current source circuit 15 and the delay end comparator CMP3; and the delay end comparator CMP3 It is connected to the drain of the delay start switch Q1. As an example, when the detection voltage is greater than the first short-circuit reference voltage Vr1, the first start comparator CMP1 outputs a high-level first control signal to the delay start switch Q1 to turn on the delay start switch Q1. Even if the drain and source of the delay start switch Q1 are turned on; at this time, the current source circuit 15 connected to the drain of the delay start switch Q1 can inject a delay control current into the delay capacitor C1 to take advantage of the delay. When the current is controlled to charge the delay capacitor C1, since the drain of the delay start switch Q1 is also connected to the delay end comparator CMP3, the delay end comparator CMP3 can collect the capacitance voltage corresponding to the delay capacitor C1 in real time. The capacitor voltage corresponding to the delay capacitor C1 is compared with the short-circuit protection voltage threshold Vref. If the capacitor voltage is greater than the short-circuit protection voltage threshold Vref, the short-circuit delay time expires, and the output of the delay end comparator CMP3 changes from low to high Level, output a high-level second control signal.

In this example, the short-circuit delay time can be calculated using the following formula: T _short =Vref*c1/lk, where T _short is the short-circuit delay time, Vref is the short-circuit protection voltage threshold Vref, and c1 is the corresponding delay capacitor C1 Capacitor voltage, lk is the delay control current. It can be seen from the above formula that the short-circuit delay time is inversely proportional to the delay control current, that is, the larger the delay control current, the smaller the short-circuit delay time, which is more conducive to ensuring the short-circuit protection effect.

In this example, the logic AND gate A1 is connected to the first start comparator CMP1 and the delay end comparator CMP3, and is used to form a short circuit protection signal based on the first control signal and the second control signal. Specifically, when the first control signal and the second control signal are both at a high level, that is, the detection voltage of the overcurrent detection terminal VINI is greater than the first short-circuit reference voltage Vr1, and the capacitance voltage of the delay capacitor C1 is greater than the short-circuit protection voltage threshold Vref At this time, the output of the logic AND gate A1 changes from low level to high level to output a high-level short-circuit signal signal, and performs short-circuit protection operation based on the short-circuit protection signal, thereby ensuring the short-circuit protection effect. Wherein, the first short-circuit reference voltage Vr1 and the short-circuit protection voltage threshold Vref may be the same or different.

In one embodiment, as shown in FIG. 4, the current source circuit 15 includes a fixed current branch 151 and a variable current branch 152; the fixed current branch 151 is used to output a fixed current; the variable current branch 152 and the overcurrent branch The detection terminal VINI is connected to output a variable current based on the detection voltage of the overcurrent detection terminal VINI.

In this example, the current source circuit 15 includes a fixed current branch 151 and a variable current branch 152. Therefore, the delay control current includes the fixed current output by the fixed current branch 151 and the variable current output by the variable current branch 152. , Is the sum of the two. In this example, when the delay start switch Q1 is turned on, the fixed current branch 151 inputs a fixed current to the delay capacitor C1, and the variable current branch 152 inputs a variable current to the delay capacitor C1 to use the fixed current and The variable current charges the delay capacitor C1 at the same time. When the capacitor voltage of the delay capacitor C1 is higher than the short-circuit protection voltage threshold Vref, the output of the delay end comparator CMP3 turns from low level to high level, and the short-circuit delay time The time is over to output the second control signal. Understandably, the delay control current includes a fixed current, so that the delay control current includes the short-circuit delay minimum current (ie, fixed current), so as to prevent the battery protection chip U1 from short-circuit protection due to occasional interference signals; The time control current includes a variable current, and the short-circuit delay time can be adjusted in real time according to the magnitude of the variable current, so as to achieve a more effective short-circuit protection effect.

Since the delay control current is the sum of the fixed current and the variable current, that is, lk=l1+l2, the short-circuit delay time can be calculated by the following formula: T _short =Vref*c1/(l1+l2), where T _short is the short-circuit delay time, Vref is the short-circuit protection voltage threshold, c1 is the capacitor voltage corresponding to the delay capacitor C1, l1 is the fixed current, and l2 is the variable current. It can be seen from the above formula that the short-circuit delay time is inversely proportional to the delay control current, that is, the larger the delay control current, the smaller the short-circuit delay time, which is more conducive to ensuring the short-circuit protection effect.

In one embodiment, as shown in FIG. 4, the fixed current branch 151 includes a first current source I1 and a first voltage source V1; one end of the first voltage source V1 is grounded, and the other end is connected to the first current source I1 for A fixed voltage is output to the first current source I1; the first current source I1 is connected to the first voltage source V1 and the variable delay circuit 16 to form a fixed current based on the fixed voltage and output a fixed current to the variable delay circuit 16.

The first voltage source V1 is a voltage source for providing a fixed voltage. The first current source I1 is a current source that is connected to the first voltage source V1 and is controlled by the first voltage source V1. The first current source I1 can convert the fixed voltage of the first voltage source V1 into a fixed current and start it at a delay. When the switch Q1 is turned on, a fixed current is input to the delay capacitor C1 to charge the delay capacitor C1 with a fixed current, which can prevent the battery protection chip U1 from being short-circuited and misprotected due to occasional interference signals.

In one embodiment, as shown in FIG. 4, the variable current branch 152 includes a second current source I2 and a subtractor circuit; one end of the subtractor circuit is connected to the overcurrent detection terminal VINI, and is used for monitoring based on the overcurrent detection terminal VINI. The voltage is detected to form a variable voltage, and the variable voltage is output to the second current source I2; the second current source I2 is connected to the subtractor circuit and the variable delay circuit 16, and is used to form a variable current based on the variable voltage, and output the variable voltage to the second current source I2. The variable delay circuit 16 outputs a variable current.

Among them, the subtractor circuit is a circuit for providing a variable current. Specifically, one end of the subtractor circuit is connected to the overcurrent detection terminal VINI, and is used to receive the detection voltage input from the overcurrent detection terminal VINI, so as to use the overcurrent detection terminal. VINI performs a subtraction operation. Since the detection voltage input from the overcurrent detection terminal VINI is a voltage that changes in real time, the voltage output by the subtractor circuit changes in real time with the detection voltage to achieve the purpose of outputting a variable voltage by the subtractor circuit.

The second current source I2 is a current source connected to the subtractor circuit and controlled by the variable voltage output from the subtractor circuit. The second current source I2 can convert the variable voltage of the subtractor circuit into a variable current, and when the delay start switch Q1 is turned on, the variable voltage is input to the delay capacitor C1 to realize the use of the variable current pair The delay capacitor C1 is charged, and the delay capacitor C1 is charged with a fixed current and a variable current. When the capacitor voltage of the delay capacitor C1 is greater than the short-circuit protection voltage threshold Vref, a short-circuit protection signal is output to achieve a variable current The purpose of real-time adjustment of the short-circuit delay time is to achieve a more effective short-circuit protection effect.

In an embodiment, as shown in FIG. 4, the subtractor circuit includes an operational amplifier OP1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a second voltage source V2; the first resistor R1 One end is connected to the negative input end of the operational amplifier OP1 and the second resistor R2, and the other end is connected to the output end of the operational amplifier OP1; one end of the second resistor R2 is connected to the negative input end of the operational amplifier OP1 and the first resistor R1, and the other One end is connected to the second voltage source V2; one end of the third resistor R3 is connected to the positive input end of the operational amplifier OP1 and the fourth resistor R4, and the other end is connected to the overcurrent detection terminal VINI; one end of the fourth resistor R4 is connected to the operational amplifier OP1 The positive input end of V2 is connected to the third resistor R3, and the other end is grounded; one end of the second voltage source V2 is connected to the second resistor R2, and the other end is grounded to provide a comparison voltage to the operational amplifier OP1.

In this example, the operational amplifier OP1, the first resistor R1, the second resistor R2, the third resistor R3, the fourth resistor R4, and the second voltage source V2 form a subtractor circuit. The positive input terminal of the subtractor circuit and the overcurrent detection terminal VINI is connected to receive the detection voltage Vin1 corresponding to the overcurrent detection terminal VINI, the negative input terminal of the subtractor circuit is connected to the second voltage source V2, used to receive the comparison voltage Vin2 of the second voltage source V2, and the output terminal of the subtractor circuit The output is a variable voltage Vo. The resistance values of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are r1, r2, r3, and r4, respectively, and the variable voltage Vo can be calculated by the following formula:

In order to eliminate the error introduced by the bias circuit at the input end of the operational amplifier OP1, it is necessary to ensure that the external output resistance at both ends of the operational amplifier OP1 is balanced, namely

at this time

Therefore, the ratio between the variable voltage Vo output by the operational amplifier OP1 and the voltage difference between the two input terminals can be changed by setting the proportional coefficient corresponding to the resistance of the first resistor R1 and the second resistor R2. This coefficient can set the short-circuit delay. The proportional operation relationship between the time and the detection voltage Vin1 corresponding to the over-current detection terminal VINI. For example, r1=r2 can be set, then Vo=Vin1-Vin2. It is understandable that when the comparison voltage Vin2 of the second voltage source V2 is fixed, the variable voltage Vo may change with the change of the detection voltage Vin1 corresponding to the overcurrent detection terminal VINI.

In this example, the larger the current flowing through the battery pack, the higher the detection voltage Vin1 of the overcurrent detection terminal VINI. When the comparison voltage Vin2 is a fixed value, the variable voltage Vo will increase accordingly; the variable voltage Vo will increase accordingly High, it will cause the variable current to increase, which will shorten the charging time of the delay capacitor C1, that is, the short-circuit delay time. Therefore, the greater the battery short-circuit current, the shorter the short-circuit delay time, and the short-circuit protection effect. So as to ensure battery safety.

In one embodiment, as shown in FIG. 2, the battery protection chip U1 further includes a logic processing circuit 12 connected to the variable delay circuit 16, and an over-discharge circuit 12 arranged between the logic processing circuit 12 and the over-discharge protection output terminal DO. The drive circuit 13 and the overcharge drive circuit 14 arranged between the logic processing circuit 12 and the overcharge protection output terminal CO; the logic processing circuit 12 is used to control the overdischarge drive circuit 13 and the overcharge drive circuit 14 according to the short circuit protection signal Output turn-off drive signal.

In this example, the short-circuit protection signal output by the variable delay circuit 16 is a signal formed by processing the first control signal and the second control signal through the logic AND gate A1. Only when the first control signal and the second control signal are both The high level short circuit protection signal will be output at high level. At this time, the short circuit protection signal is sent to the logic processing circuit 12 so that the logic processing circuit 12 controls the overdischarge drive circuit 13 and the overcharge drive circuit according to the short circuit protection signal 14 Output the turn-off drive signal to send the turn-off drive signal to the discharge power transistor M1 through the over-discharge protection output terminal DO, and use the pull-down current formed by the turn-off drive signal to control the discharge loop to stop working; and pass the turn-off drive signal through The overcharge protection output terminal CO is sent to the charging power transistor M2, and the pull-down current formed by the shutdown drive signal is used to control the charging circuit to stop working, so as to cut off the discharge circuit and the charging circuit at the same time to ensure battery safety.

In an embodiment, as shown in FIG. 4, the battery protection chip U1 further includes a short-circuit drive circuit 17 arranged between the logic processing circuit 12 and the over-discharge protection output terminal DO. The logic processing circuit 12 is used to, according to the short-circuit protection signal, The short-circuit drive circuit 17 is controlled to output a short-circuit drive signal.

Generally speaking, the pull-down current of the turn-off driving signal output by the over-discharge drive circuit 13 and the over-charge drive circuit 14 is relatively small, which makes it easy to oscillate during the normal over-discharge protection and over-charge protection. In order to overcome this phenomenon, you can A short-circuit drive circuit 17 is provided between the logic processing circuit 12 and the over-discharge protection output terminal DO, so that when the logic processing circuit 12 receives the short-circuit protection signal of the variable delay circuit 16, it controls the short-circuit drive circuit 17 to pass the over-discharge protection The output terminal DO outputs a short-circuit drive signal, and the pull-down current formed by the short-circuit drive signal is much larger than the pull-down current formed by the turn-off drive circuit, so as to realize the purpose of quickly turning off the discharge loop by using a large current.

In one embodiment, as shown in FIG. 3, the battery protection chip U1 further includes a second start comparator CMP2 connected to the overcurrent detection terminal VINI, a fixed delay circuit 11 connected to the second start comparator CMP2, and a fixed delay circuit 11 connected to the second start comparator CMP2. The logic processing circuit 12 connected to the delay circuit 11, the overdischarge drive circuit 13 arranged between the logic processing circuit 12 and the overdischarge protection output terminal DO, and the overdischarge drive circuit 13 arranged between the logic processing circuit 12 and the overcharge protection output terminal CO. The charging and driving circuit 14 and the output driving circuit connected to the variable delay circuit 16; the second start comparator CMP2 is used to control the fixed delay based on the detection voltage of the overcurrent detection terminal VINI and the second short-circuit reference voltage Vr2 The fixed start signal of the time circuit 11, the second short-circuit reference voltage Vr2 is less than the first short-circuit reference voltage Vr1; the output drive circuit is connected to the peripheral short-circuit drive circuit 17 to form an output drive signal based on the short-circuit protection signal.

Among them, the second startup comparator CMP2 is a comparator connected to the fixed delay circuit 11 for controlling the operation of the fixed delay circuit 11. The second short-circuit reference voltage Vr2 is a preset reference voltage for turning off the second startup comparator CMP2 for short-circuit, and the second short-circuit reference voltage Vr2 is less than the first short-circuit reference voltage Vr1.

In this example, the detection voltage of the overcurrent detection terminal VINI is input to the first start comparator CMP1 and the second start comparator CMP2. If the detection voltage is greater than the first short-circuit reference voltage Vr1, the output of the first start comparator CMP1 changes from low level to high level, and outputs a high level first control signal to control the operation of the variable delay circuit 16. To output the short-circuit protection signal, and the short-circuit protection signal is processed by the output drive circuit for signal enhancement, and converted into an output drive signal, so that the output drive signal can be used to control the peripheral short-circuit drive circuit 17 to quickly discharge through the peripheral short-circuit drive circuit 17 Circuit and charging circuit. If the detection voltage is not greater than the first short-circuit reference voltage Vr1 and is greater than the second short-circuit reference voltage Vr2, the output of the second start comparator CMP2 changes from low to high to form a fixed start signal for controlling the fixed delay The timing circuit 11 works so that the fixed delay circuit 11 outputs the formed short-circuit protection signal to the logic processing circuit 12, so that the logic processing circuit 12 controls the output of the over-discharge drive circuit 13 and the over-charge drive circuit 14 according to the short-circuit protection signal to turn off Drive signal, the turn-off drive signal is sent to the discharge power transistor M1 through the over-discharge protection output terminal DO, and the pull-down current formed by the turn-off drive signal is used to control the discharge loop to stop working; and the turn-off drive signal is passed through the overcharge protection output terminal CO is sent to the charging power transistor M2, and the pull-down current formed by the turn-off drive signal is used to control the charging loop to stop working, so as to cut off the discharge loop and the charging loop at the same time to ensure the safety of the battery pack.

As an example, as shown in FIG. 3, the peripheral short-circuit drive circuit 17 is connected to the output drive circuit and the discharge power transistor M1, and includes a short-circuit drive switch tube Q2 and a fifth resistor R5. The gate of the short-circuit drive switch tube Q2 and the output drive The circuit is connected, the source is connected to the ground terminal VSS, and the drain is connected to the discharging power transistor M1 through the fifth resistor R5. After the variable delay circuit 16 outputs the short-circuit protection signal, the output drive circuit forms an output drive signal, and the short-circuit drive switch Q2 is controlled to turn on according to the output drive signal to quickly pull down the gate potential of the discharge power transistor M1 to VSS The electric potential makes the discharging power transistor M1 cut off, so as to disconnect the discharging circuit, so as to achieve the purpose of battery short-circuit protection. The design of the peripheral short-circuit drive circuit 17 eliminates the need for the battery protection chip U1 to integrate the high-current drive short-circuit drive circuit 17, so that the internal components of the chip are simple; the short-circuit drive switches Q2 and the fifth can be selected reasonably according to the external drive current requirements. Resistor R5 can meet the needs of different applications and different turn-off times, making it more adaptable.

The embodiment of the application provides a battery protection board. As shown in FIG. 2 and FIG. 3, the battery protection board is arranged at both ends of the battery pack and includes a sampling resistor RS for connecting the battery pack and a discharge power transistor connected with the sampling resistor RS. M1 and the charging power transistor M2 also include the battery protection chip U1 in the above embodiment connected to both ends of the battery pack, and the overcharge detection end of the battery protection chip U1 is connected to the sampling resistor RS. In this example, the battery protection chip U1 is provided with an overdischarge protection output terminal DO connected to the discharging power transistor M1 and an overcharge protection output terminal CO connected to the charging power transistor M2.

The battery protection board provided in this embodiment integrates the battery protection chip U1 in the above embodiment, and the first start comparator CMP1 connected to the overcurrent detection terminal VINI forms a first control based on the detection voltage and the first short-circuit reference voltage Vr1 Signal to start the variable delay circuit 16 based on the first control signal, so as to achieve the effect of controlling the variable delay circuit 16 based on the detection voltage that changes in real time; the current source circuit 15 connected to the overcurrent detection terminal VINI can The detection voltage is converted into a delay control current, so that the delay control current changes with the change of the detection voltage; the variable delay circuit 16 starts the short-circuit protection operation according to the first control signal output by the first start comparator CMP1, specifically according to the delay Control the current to adjust the short-circuit delay time in real time, and output the short-circuit protection signal after the short-circuit delay time expires. The short-circuit protection operation is performed based on the short-circuit protection signal to ensure the short-circuit protection effect, which can realize the detection voltage according to the over-current detection terminal VINI Adjust the short-circuit delay time in real time, so that the short-circuit delay time matches the rising speed of the current during a short-circuit, and guarantees the effect of short-circuit protection.

As an example, as shown in FIG. 3, the battery protection board further includes a short-circuit drive circuit 17 for connecting the battery pack and the discharging power transistor M1. The short-circuit drive circuit 17 includes a short-circuit drive switch Q2 and a fifth resistor R5, and a short-circuit drive switch The gate of the tube Q2 is connected to the output driving circuit, the source is connected to the ground terminal VSS, and the drain is connected to the discharging power transistor M1 through the fifth resistor R5. After the variable delay circuit 16 outputs the short-circuit protection signal, the output drive circuit forms an output drive signal, and the short-circuit drive switch Q2 is controlled to turn on according to the output drive signal to quickly pull down the gate potential of the discharge power transistor M1 to VSS The electric potential makes the discharging power transistor M1 cut off, so as to disconnect the discharging circuit, so as to achieve the purpose of battery short-circuit protection. The design of the peripheral short-circuit drive circuit 17 eliminates the need for the battery protection chip U1 to integrate the high-current drive short-circuit drive circuit 17, so that the internal components of the chip are simple; the short-circuit drive switches Q2 and the fifth can be selected reasonably according to the external drive current requirements. Resistor R5 can meet the needs of different applications and different turn-off times, making it more adaptable.

The above embodiments are only used to illustrate the technical solutions of the present application, not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still compare the previous embodiments. The recorded technical solutions are modified, or some of the technical features are equivalently replaced; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the application, and shall be included in the application Within the scope of protection.

Claims (10)

1. A battery protection chip, which includes a first start-up comparator, a current source circuit and a variable delay circuit. The first start-up comparator is connected to an overcurrent detection terminal and is configured to be based on the detection voltage of the overcurrent detection terminal. And the first short-circuit reference voltage to form a first control signal; the current source circuit is connected to the overcurrent detection terminal, and is used to form a delay control current based on the detection voltage of the overcurrent detection terminal; the variable delay The circuit is connected to the first start comparator and the current source circuit, and is configured to adjust the short-circuit delay time and output a short-circuit protection signal based on the first control signal and the delay control current.
2. The battery protection chip of claim 1, wherein the variable delay circuit includes a delay start switch tube, a delay capacitor, a delay end comparator and a logic AND gate; the gate of the delay start switch tube The electrode is connected to the first start-up comparator, the source electrode is connected to the delay capacitor, and the drain electrode is connected to the current source circuit and the delay end comparator for controlling the conduction according to the first control signal. The delay control current is used to charge the delay capacitor; the delay end comparator is connected to the drain of the delay start switch, and is used for the capacitor voltage corresponding to the delay capacitor. And the short-circuit protection voltage threshold to form a second control signal; the logic AND gate is connected to the first start comparator and the delay end comparator, and is configured to be based on the first control signal and the second control signal Signal, forming a short-circuit protection signal.
3. The battery protection chip according to claim 2, wherein the current source circuit includes a fixed current branch and a variable current branch; the fixed current branch is used to output a fixed current; the variable current branch is connected to The overcurrent detection terminal is connected, and is used to output a variable current based on the detection voltage of the overcurrent detection terminal.
4. 8. The battery protection chip of claim 3, wherein the fixed current branch includes a first current source and a first voltage source; one end of the first voltage source is grounded, and the other end is connected to the first current source, Is used to output a fixed voltage to the first current source; the first current source is connected to the first voltage source and the variable delay circuit, and is used to form a fixed current based on the fixed voltage to the The variable delay circuit outputs the fixed current.
5. The battery protection chip of claim 3, wherein the variable current branch includes a second current source and a subtractor circuit; one end of the subtractor circuit is connected to the overcurrent detection terminal for The detection voltage of the overcurrent detection terminal forms a variable voltage, and outputs the variable voltage to the second current source; the second current source is connected to the subtractor circuit and the variable delay circuit for A variable current is formed based on the variable voltage, and the variable current is output to the variable delay circuit.
6. The battery protection chip of claim 5, wherein the subtractor circuit includes an operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a second voltage source; one end of the first resistor It is connected to the negative input terminal of the operational amplifier and the second resistor, and the other end is connected to the output terminal of the operational amplifier; one end of the second resistor is connected to the negative input terminal of the operational amplifier and the first resistor. The resistor is connected, and the other end is connected to the second voltage source; one end of the third resistor is connected to the positive input end of the operational amplifier and the fourth resistor, and the other end is connected to the overcurrent detection terminal; One end of the fourth resistor is connected to the positive input end of the operational amplifier and the third resistor, and the other end is grounded; one end of the second voltage source is connected to the second resistor, and the other end is grounded for supplying The operational amplifier provides the comparison voltage.
7. The battery protection chip according to any one of claims 1 to 6, wherein the battery protection chip further comprises a logic processing circuit connected to the variable delay circuit, and is provided in the logic processing circuit and over-discharge protection The overdischarge drive circuit between the output terminals and the overcharge drive circuit arranged between the logic processing circuit and the overcharge protection output terminal; the logic processing circuit is used to control the overcharge drive circuit according to the short circuit protection signal The discharge driving circuit and the overcharge driving circuit output turn-off driving signals.
8. The battery protection chip according to claim 7, wherein the battery protection chip further comprises a short-circuit drive circuit arranged between the logic processing circuit and the over-discharge protection output terminal, and the logic processing circuit is used for The short-circuit protection signal controls the short-circuit drive circuit to output a short-circuit drive signal.
9. The battery protection chip according to any one of claims 1-6, wherein the battery protection chip further comprises a second startup comparator connected to the overcurrent detection terminal, and a fixed extension connected to the second startup comparator. Time circuit, a logic processing circuit connected to the fixed delay circuit, an overdischarge drive circuit arranged between the logic processing circuit and the overdischarge protection output terminal, and arranged on the logic processing circuit and the overcharge protection output terminal The overcharge drive circuit between the overcharge drive circuit and the output drive circuit connected to the variable delay circuit; the second start comparator is used to form a reference voltage for Control the fixed start signal of the fixed delay circuit, the second short-circuit reference voltage is less than the first short-circuit reference voltage; the output drive circuit is connected to a peripheral short-circuit drive circuit, and is used to form a signal based on the short-circuit protection signal Output drive signal.
10. A battery protection board is arranged at both ends of a battery pack, and includes a sampling resistor connected to the battery pack, a discharging power transistor and a charging power transistor connected to the sampling resistor. The battery protection chip according to any one of claims 1-9 is connected to the terminal, and the overcharge detection terminal of the battery protection chip is connected to the sampling resistor.

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