A battery protection circuit

Abstract

The present invention provides a battery protection circuit, which adds a clamping circuit to the existing battery protection circuit, wherein the first end of the clamping circuit is connected to the power supply voltage sampling point, the second end is connected to the negative pole of the battery and is grounded, and the third end is connected to the loop current sampling point, which is located at the negative pole of the charging power supply or the load side. The clamping circuit receives electric energy from the power supply voltage sampling point, detects the voltage value at the loop current sampling point, and clamps the loop current sampling point when negative high voltage appears at the loop current sampling point, thereby effectively solving the problem that the negative high voltage breaks down the low-voltage switch tube and damages the chip, and realizes the high withstand voltage of the battery protection chip while using the low-voltage switch tube, and reduces the chip area and cost.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and in particular to a battery protection circuit. Background Art

[0002] The existing battery protection chip includes an over-discharge protection circuit and an over-charge protection circuit for detecting the battery voltage, a discharge over-current protection circuit, a charge over-current protection circuit and a short-circuit protection circuit for detecting the loop current, and a switch tube control module for controlling the on and off of the charge and discharge switch tube, so as to protect the battery from charging and discharging. However, the switch tubes in the existing battery protection chip mainly use low-voltage MOS tubes, and the device withstands a voltage of about 10V. When the user mistakenly inserts a high-voltage charger such as 20V or a surge voltage appears at the loop current sampling point VM, it is easy to damage the switch tube, causing the battery protection chip to fail to work properly. Replacing the switch tube with a high-voltage resistant tube will greatly increase the chip area and cost. Summary of the invention

[0003] The present invention provides a battery protection circuit to solve the problem that the existing battery protection circuit uses a low-voltage switch tube that is easily broken down and damages the chip, and uses a high-voltage switch tube to increase the chip area and cost.

[0004] The present invention is implemented in this way: a battery protection circuit comprises:

[0005] Reference and bias circuit, voltage protection circuit, current protection circuit, delay circuit, switch tube control circuit, switch tube and clamp circuit;

[0006] The first end of the voltage protection circuit is connected to the power supply voltage sampling point, and the second end is connected to the first end of the delay circuit;

[0007] The first end of the current protection circuit is connected to the loop current sampling point, and the second end is connected to the second end of the delay circuit;

[0008] The second end of the delay circuit is connected to the first end of the switch tube control circuit;

[0009] The second end of the switch tube control circuit is connected to the gate of the switch tube;

[0010] The source and drain of the switch tube are connected in series in a charge-discharge loop between the battery and the charging power source or the load;

[0011] The first end of the clamp circuit is connected to the power supply voltage sampling point, the second end and the negative electrode of the battery are connected to the ground, and the third end is connected to the loop current sampling point;

[0012] The loop current sampling point is located at the negative pole of the charging power source or the load side;

[0013] The reference and bias circuit is connected to the power supply voltage sampling point;

[0014] The reference and bias circuits are used to generate the bias voltage required by the voltage protection circuit and the bias current required by the current protection circuit; the voltage protection circuit is used to detect the power supply voltage and generate a detection reversal signal when the power supply voltage is abnormal; the current protection circuit is used to detect the charging current and the discharging current and generate a detection reversal signal when the charging current and the discharging current are abnormal; the delay circuit is used to delay the detection reversal signal; the switch tube control circuit is used to generate a control signal according to the output signal of the delay circuit, and send the control signal to the switch tube to control the start or shut down of the switch tube; the clamping circuit is used to clamp the loop current sampling point when negative high voltage appears at the loop current sampling point.

[0015] Optionally, when the clamping circuit is operating, a voltage drop between the second end and the third end thereof is smaller than a source-drain breakdown voltage of the switching tube.

[0016] Optionally, the clamping circuit includes an NMOS tube and a diode string group, and the diode string group includes a plurality of diodes connected in series;

[0017] The drain of the NMOS tube is connected to the power supply voltage sampling point, the gate and the negative electrode of the battery are connected to the ground, and the source is connected to the positive electrode of the diode string group;

[0018] The cathode of the diode string group is connected to the loop current sampling point.

[0019] Optionally, the sum of the threshold voltage of the NMOS tube and the conduction voltages of the plurality of diodes is less than the source-drain breakdown voltage of the switch tube.

[0020] Optionally, the clamping circuit includes an NMOS tube string group, and the NMOS tube string group includes a plurality of NMOS tubes connected in series;

[0021] The source of each NMOS tube is connected to the common point between the drain and the gate of the next NMOS tube;

[0022] The drain of the first NMOS tube is connected to the power supply voltage sampling point, and the gate and the negative electrode of the battery are connected to the ground;

[0023] The source of the last NMOS tube is connected to the loop current sampling point.

[0024] Optionally, the sum of the threshold voltages of the plurality of NMOS tubes is less than the source-drain breakdown voltage of the switch tube.

[0025] Optionally, the clamping circuit includes an NMOS tube and a PMOS tube string group, and the PMOS tube string group includes a plurality of PMOS tubes connected in series;

[0026] The drain of the NMOS tube is connected to the power supply voltage sampling point, the gate and the negative electrode of the battery are connected to the ground, and the source is connected to the source of the first PMOS tube in the PMOS tube string group;

[0027] In the PMOS tube string group, the common point between the gate and drain of each PMOS tube is connected to the source of the next PMOS tube, and the common point between the gate and drain of the last PMOS tube is connected to the loop current sampling point.

[0028] Optionally, the sum of the threshold voltage of the NMOS tube and the threshold voltages of the plurality of PMOS tubes is less than the source-drain breakdown voltage of the switch tube.

[0029] Optionally, the switch tube control circuit includes a logic circuit, a substrate switching circuit, and a gate control circuit;

[0030] The input end of the logic circuit is connected to the second end of the delay circuit, the first output end is connected to the first end of the substrate switching circuit, and the second output end is connected to the first end of the gate control circuit;

[0031] The second end of the substrate switching circuit is connected to the substrate of the switch tube;

[0032] The output end of the gate control circuit is connected to the gate of the switch tube;

[0033] The logic circuit is used to perform logic processing on the output signal of the delay circuit, generate a substrate switching signal, and send the substrate switching signal to the substrate switching circuit, as well as generate a control signal and send the control signal to the gate control circuit; the substrate switching circuit is used to switch the substrate polarity of the switch tube according to the substrate switching signal; the gate control circuit is used to output a gate control signal to the switch tube according to the control signal to control the start or shut down of the switch tube gate.

[0034] Optionally, the switch tube is an isolated MOSFET or a non-isolated MOSFET.

[0035] The battery protection circuit provided by the present invention adds a clamping circuit to the existing battery protection circuit, wherein the first end of the clamping circuit is connected to the power supply voltage sampling point, the second end is connected to the negative electrode of the battery and is grounded, and the third end is connected to the loop current sampling point, and the loop current sampling point is located at the negative electrode of the charging power supply or the load side. The clamping circuit receives electric energy from the power supply voltage sampling point, detects the voltage value at the loop current sampling point, and clamps the loop current sampling point when negative high voltage appears at the loop current sampling point, thereby effectively solving the problem that the negative high voltage breaks down the low-voltage switch tube and damages the chip, and realizes the high withstand voltage of the battery protection chip while using the low-voltage switch tube, and reduces the chip area and cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0037] Figure 1 is a schematic diagram of a battery protection circuit provided by an embodiment of the present invention;

[0038] Figure 2 is a schematic diagram of a switch tube in a battery protection circuit provided by an embodiment of the present invention;

[0039] Figure 3 is a schematic diagram of a clamping circuit in a battery protection circuit provided by an embodiment of the present invention;

[0040] Figure 4 is a schematic diagram of a clamping circuit in a battery protection circuit provided by another embodiment of the present invention;

[0041] Figure 5 is a schematic diagram of a clamping circuit in a battery protection circuit provided by another embodiment of the present invention;

[0042] Figure 6 It is an application schematic diagram of a battery protection circuit provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0044] The battery protection circuit provided by the present invention adds a clamping circuit to the existing battery protection circuit, wherein the first end of the clamping circuit is connected to the power supply voltage sampling point, the second end is connected to the negative electrode of the battery and is grounded, and the third end is connected to the loop current sampling point, and the loop current sampling point is located at the negative electrode of the charging power supply or the load side. The clamping circuit receives electric energy from the power supply voltage sampling point, detects the voltage value at the loop current sampling point, and clamps the loop current sampling point when negative high voltage appears at the loop current sampling point, thereby effectively solving the problem that the negative high voltage breaks down the low-voltage switch tube and damages the chip, and realizes the high withstand voltage of the battery protection chip while using the low-voltage switch tube, and reduces the chip area and cost.

[0045] Figure 1 Schematic diagram of a battery protection circuit provided by an embodiment of the present invention. Figure 1 As shown, the battery protection circuit 1 includes a reference and bias circuit 10, a voltage protection circuit 20, a current protection circuit 30, a delay circuit 40, a switch tube control circuit 50, a switch tube 60 and a clamp circuit 70;

[0046] The first end of the voltage protection circuit 20 is connected to the power supply voltage sampling point VDD, and the second end is connected to the first end of the delay circuit 40;

[0047] The first end of the current protection circuit 30 is connected to the loop current sampling point VM, and the second end is connected to the second end of the delay circuit 40;

[0048] The second end of the delay circuit 40 is connected to the first end of the switch tube control circuit 50;

[0049] The second end of the switch tube control circuit 50 is connected to the gate of the switch tube 60;

[0050] The source and drain of the switch tube 60 are connected in series in a charge-discharge loop between the battery and the charging power source or the load;

[0051] The first end of the clamp circuit 70 is connected to the power supply voltage sampling point VDD, the second end and the negative electrode of the battery are connected to the ground VSS, and the third end is connected to the loop current sampling point VM;

[0052] The loop current sampling point VM is located at the negative pole of the charging power source or the load side;

[0053] The reference and bias circuit 10 is connected to the power supply voltage sampling point VDD;

[0054] The reference and bias circuit 10 is used to generate the bias voltage required by the voltage protection circuit 20 and the bias current required by the current protection circuit 30; the voltage protection circuit 20 is used to detect the power supply voltage and generate a detection reversal signal when the power supply voltage is abnormal; the current protection circuit 30 is used to detect the charging current and the discharging current and generate a detection reversal signal when the charging current and the discharging current are abnormal; the delay circuit 40 is used to delay the detection reversal signal; the switch tube control circuit 50 is used to generate a control signal according to the output signal of the delay circuit 40, and send the control signal to the switch tube 60 to control the start or shut down of the switch tube 60; the clamping circuit 70 is used to clamp the loop current sampling point VM when negative high voltage appears at the loop current sampling point VM.

[0055] Here, the reference and bias circuit 10 is connected to the power supply voltage sampling point VDD. The power supply voltage sampling point VDD is the voltage sampling point of the positive power supply of the battery protection chip. When applied to the battery protection chip, the power supply voltage sampling point VDD is the voltage sampling point of the positive battery after passing through a preset resistor, such as Figure 1 The loop current sampling point VM is the current sampling point of the charge and discharge loop between the battery and the charging power source or the load, such as Figure 1 The VM shown in is set at the negative pole of the charging power supply or the load side. The reference and bias circuit 10 obtains the voltage sampling value of the chip power supply from the power supply voltage sampling point VDD, and then generates a bias voltage and a bias current according to the voltage sampling value. The bias voltage is the detection threshold of the voltage protection circuit 20, and the bias current is the detection threshold of the current protection circuit 30.

[0056] When the voltage protection circuit 20 is enabled, it detects the power supply voltage, compares the power supply voltage with the bias voltage to determine whether the battery is over-discharged or over-charged, and generates a detection flip signal when the power supply voltage is abnormal. When the current protection circuit 30 is enabled, it detects the charging current and the discharging current, and compares the charging current and the discharging current with the corresponding bias current to determine whether the circuit is over-discharged, over-charged or short-circuited, and generates a detection flip signal when the charging current and the discharging current are abnormal. The delay circuit 40 delays the detection flip signal issued by the voltage protection circuit 20 or the current protection circuit 30, and outputs the delayed detection flip signal to the switch tube control circuit 50. The switch tube control circuit 50 performs logic processing on the output signal of the delay circuit 40 to generate a control signal for the switch tube 60. Among them, the control signal is a switch signal of the switch tube 60 to control the start or shutdown of the switch tube 60. The switch tube 60 is connected in series in the charge and discharge circuit between the battery and the charging power source or the load. By controlling the start or shutdown of the switch tube 60, protection against voltage overcharge or overdischarge, circuit overdischarge or overcharge or short circuit is achieved.

[0057] The clamp circuit 70 receives electric energy from the power supply voltage sampling point VDD, detects the voltage information of the loop current sampling point VM, and clamps the loop current sampling point VM when a negative high voltage appears at the loop current sampling point VM. In this embodiment, when the clamp circuit 70 is working, the voltage drop between the second end and the third end is less than the source-drain breakdown voltage of the switch tube 60. Since the second end of the clamp circuit 70 and the negative electrode of the battery are connected to the ground VSS, the absolute value of the voltage at the third end of the clamp circuit 70, that is, the absolute value of the voltage at the loop current sampling point VM, is less than the breakdown voltage between the source and drain of the switch tube 60, thereby preventing the source and drain of the switch tube 60 from being broken down.

[0058] Exemplarily, for ease of understanding, a 5V low-voltage switch tube is used as an example for explanation below. The breakdown voltage VDS between the source and drain of the switch tube 60 is approximately 10V, and the battery voltage is 4V. When the battery protection chip is used normally, the potential at the loop current sampling point VM is close to the voltage VSS of the negative electrode of the battery, and the clamping circuit 70 does not work at this time. When the battery is connected to a high-voltage charger, such as a 20V charger, if the battery voltage is 4V, the voltage at the loop current sampling point VM is -16V high voltage. At this time, the potentials of the three poles of the switch tube 60 are as follows: Figure 2As shown, VSS represents the drain, VM represents the source, and SW represents the gate. The voltage difference between the drain and the source of the switch tube 60 is 16V, which is greater than the breakdown voltage VDS between the source and the drain. In the absence of the clamping circuit 70, the switch tube 60 will be broken down and burned, and the battery protection chip will fail. In the embodiment of the present invention, the clamping circuit 70 is introduced at the loop current sampling point VM. When the high-voltage charger is inserted, the negative voltage of the loop current sampling point VM is clamped, so that the absolute value of the negative voltage of the loop current sampling point VM is less than the breakdown voltage between the source and the drain of the switch tube 60, such as clamped to -4V. The voltage difference between the drain and the source of the switch tube 60 is 4V, which is much smaller than the breakdown voltage VDS between the source and the drain. The switch 60 will not be damaged due to breakdown, and the battery protection chip can still work normally.

[0059] It can be seen that the embodiment of the present invention clamps the loop current sampling point VM through the clamping circuit 70 when negative high voltage appears at the loop current sampling point VM, thereby achieving high withstand voltage of the battery protection chip while using a low-voltage switch tube, thereby reducing the area and cost of the battery protection chip while ensuring the high withstand voltage and reliability of the chip.

[0060] Optionally, as mentioned above, when the clamp circuit 70 is working, the voltage drop between the second terminal and the third terminal is less than the source-drain breakdown voltage VDS of the switch tube. As an implementation method, the clamp circuit 70 includes an NMOS tube M1 and a diode string group, and the diode string group includes a plurality of diodes connected in series;

[0061] The drain of the NMOS tube M1 is connected to the power supply voltage sampling point, the gate and the negative electrode of the battery are connected to the ground, and the source is connected to the positive electrode of the diode string group;

[0062] The cathode of the diode string group is connected to the loop current sampling point.

[0063] Here, when the clamp circuit 70 is working, the voltage drop between the gate of the NMOS tube M1 and the cathode of the diode string group is less than the source-drain breakdown voltage VDS of the switch tube. The number of diodes in the diode string group can be set according to the actual value of the source-drain breakdown voltage VDS of the switch tube, as long as the sum of the threshold voltage of the NMOS tube and the conduction voltage of the plurality of diodes is less than the source-drain breakdown voltage of the switch tube.

[0064] For ease of understanding, following the previous example, take a 5V low-voltage switch tube as an example, assuming that the breakdown voltage VDS between the source and drain of the switch tube is about 10V, and the battery voltage is 4V. Figure 3As shown, if the diode string group includes three diodes connected in series, denoted as the first diode D1, the second diode D2, and the third diode D3. Wherein the drain of the NMOS transistor M1 is connected to the power supply voltage sampling point, the gate is commonly connected to the ground with the negative electrode of the battery, and the source is connected to the positive electrode of the first diode D1; the negative electrode of the first diode D1 is connected to the positive electrode of the second diode D2, the negative electrode of the second diode D2 is connected to the positive electrode of the third diode D3, and the negative electrode of the third diode D3 is connected to the loop current sampling point VM. The on-voltage of the NMOS transistor M1, the first diode D1, the second diode D2, and the third diode D3 is all 1V, for a total of 4V. When the battery protection chip is in normal use, the potential at the loop current sampling point VM is close to the voltage VSS of the negative electrode of the battery. At this time, VM > VSS - 4V, and the NMOS transistor M1 and the diode string group in the clamping circuit 70 are not conducting. When the battery is connected to a high-voltage charger, such as a 20V charger, at this time VM = 4 - 20 = -16V, VSS - 4V = -4V, VM < VSS - 4V, the NMOS transistor M1 and the diode string group in the clamping circuit 70 conduct, and after conduction, the voltage of the loop current sampling point VM is forcibly pulled up to -4V, so that the voltage difference between the drain and source of the switching transistor is 4V, which is much smaller than the breakdown voltage VDS between the source and drain, avoiding damage to the switching transistor 60. It should be understood that the above number of diodes is only a preferred example of the present invention and can be specifically set according to actual situations.

[0065] As an implementation manner, the clamping circuit 70 includes an NMOS transistor string group, and the NMOS transistor string group includes a plurality of NMOS transistors connected in series;

[0066] Wherein, the source of each NMOS transistor is connected to the common connection point between the drain and the gate of the next NMOS transistor;

[0067] The drain of the first NMOS transistor is connected to the power supply voltage sampling point, and the gate is commonly connected to the ground with the negative electrode of the battery,

[0068] The source of the last NMOS transistor is connected to the loop current sampling point.

[0069] Here, when the clamping circuit 70 works, the voltage drop between the gate of the first NMOS transistor and the source of the last NMOS transistor is less than the source-drain breakdown voltage VDS of the switching transistor. The number of NMOS transistors in the NMOS transistor string group can be set according to the actual value of the source-drain breakdown voltage VDS of the switching transistor, as long as the sum of the threshold voltages of the NMOS transistors is less than the source-drain breakdown voltage of the switching transistor.

[0070] For ease of understanding, continuing with the previous example, taking a low-voltage switching transistor of 5V as an example, assume that the breakdown voltage VDS between the source and drain of the switching transistor is approximately 10V, and the battery voltage is 4V. As Figure 4 shown, if the NMOS transistor string group includes four NMOS transistors connected in series, denoted as the first NMOS transistor M1, the second NMOS transistor M2, the third NMOS transistor M3, and the fourth NMOS transistor M4. Among them, the drain of the first NMOS transistor M1 is connected to the power supply voltage sampling point, the gate is commonly connected to the ground with the negative electrode of the battery, and the source is connected to the common connection point between the drain and the gate of the second NMOS transistor M2; the source of the second NMOS transistor M2 is connected to the common connection point between the drain and the gate of the third NMOS transistor M3; the source of the third NMOS transistor M3 is connected to the common connection point between the drain and the gate of the fourth NMOS transistor M4; the source of the fourth NMOS transistor M4 is connected to the loop current sampling point VM. The threshold voltages of the first NMOS transistor M1, the second NMOS transistor M2, the third NMOS transistor M3, and the fourth NMOS transistor M4 are all 1V, a total of 4V. When the battery protection chip is normally used, the potential at the loop current sampling point VM is close to the voltage VSS of the negative electrode of the battery. At this time, VM > VSS - 4V, and the first NMOS transistor M1, the second NMOS transistor M2, the third NMOS transistor M3, and the fourth NMOS transistor M4 in the clamping circuit 70 are all not conducting. When the battery is connected to a high-voltage charger, such as a 20V charger, at this time VM = 4 - 20 = -16V, VSS - 4V = -4V, VM < VSS - 4V, and the first NMOS transistor M1, the second NMOS transistor M2, the third NMOS transistor M3, and the fourth NMOS transistor M4 in the clamping circuit 70 conduct. After conduction, the voltage of the loop current sampling point VM is forcibly pulled up to -4V, so that the voltage difference between the drain and the source of the switching transistor is 4V, which is much smaller than the breakdown voltage VDS between the source and the drain, avoiding damage to the switching transistor 60. It should be understood that the number of the above NMOS transistors is only a preferred example of the present invention, and can be specifically set according to actual situations.

[0071] As an implementation manner, the clamping circuit 70 includes an NMOS transistor and a PMOS transistor string group, and the PMOS transistor string group includes several PMOS transistors connected in series;

[0072] the drain of the NMOS transistor is connected to the power supply voltage sampling point, the gate is commonly connected to the ground with the negative electrode of the battery, and the source is connected to the source of the first PMOS transistor in the PMOS transistor string group;

[0073] In the PMOS tube string group, the common point between the gate and drain of each PMOS tube is connected to the source of the next PMOS tube, and the common point between the gate and drain of the last PMOS tube is connected to the loop current sampling point.

[0074] Here, when the clamp circuit 70 is working, the voltage drop between the gate of the NMOS tube and the common connection point of the gate and drain of the last PMOS tube is less than the source-drain breakdown voltage VDS of the switch tube. The number of PMOS tubes in the PMOS tube string group can be set according to the actual value of the source-drain breakdown voltage VDS of the switch tube, as long as the sum of the threshold voltage of the NMOS tube and the threshold voltages of the plurality of PMOS tubes is less than the source-drain breakdown voltage of the switch tube.

[0075] For ease of understanding, following the previous example, take a 5V low-voltage switch tube as an example, assuming that the breakdown voltage VDS between the source and drain of the switch tube is about 10V, and the battery voltage is 4V. Figure 5As shown, the clamping circuit 70 includes an NMOS transistor M1 and a PMOS transistor string group. If the PMOS transistor string group includes three PMOS transistors connected in series, denoted as the first PMOS transistor M2, the second PMOS transistor M3, and the third PMOS transistor M4. Wherein the drain of the NMOS transistor M1 is connected to the power supply voltage sampling point, the gate is commonly connected to the ground with the negative electrode of the battery, and the source is connected to the source of the first PMOS transistor M2; the common connection point between the gate and the drain of the first PMOS transistor M2 is connected to the source of the second PMOS transistor M3; the common connection point between the gate and the drain of the second PMOS transistor M3 is connected to the source of the third PMOS transistor M4; the common connection point between the gate and the drain of the third PMOS transistor M4 is connected to the loop current sampling point. The threshold voltages of the NMOS transistor M1, the first PMOS transistor M2, the second PMOS transistor M3, and the third PMOS transistor M4 are all 1V, for a total of 4V. When the battery protection chip is in normal use, the potential at the loop current sampling point VM is close to the voltage VSS of the negative electrode of the battery. At this time, VM > VSS - 4V, and the NMOS transistor M1, the first PMOS transistor M2, the second PMOS transistor M3, and the third PMOS transistor M4 in the clamping circuit 70 are all non-conductive. When the battery is connected to a high-voltage charger, such as a 20V charger, at this time VM = 4 - 20 = -16V, VSS - 4V = -4V, VM < VSS - 4V, and the NMOS transistor M1, the first PMOS transistor M2, the second PMOS transistor M3, and the third PMOS transistor M4 in the clamping circuit 70 conduct. After conduction, the voltage of the loop current sampling point VM is forcibly pulled up to -4V, so that the voltage difference between the drain and the source of the switching transistor is 4V, which is much smaller than the breakdown voltage VDS between the source and the drain, avoiding damage to the switching transistor 60. It should be understood that the number of the above PMOS transistors is only a preferred example of the present invention and can be specifically set according to actual situations.

[0076] Optionally, in this embodiment, the source and the drain of the switching transistor 60 are symmetrical. The substrate switching signal and the control signal output by the switching transistor control circuit 50 are used to indicate the startup or shutdown of the switching transistor 60. Optionally, as Figure 6 shown, it is a schematic application diagram of the battery protection circuit provided in this embodiment. After the battery passes through the preset resistor R4 and the preset capacitor C1, it provides the power supply voltage VDD to the battery protection circuit.

[0077] The switching transistor control circuit 50 includes a logic circuit 51, a substrate switching circuit 52, and a gate control circuit 53;

[0078] The input end of the logic circuit 51 is connected to the second end of the delay circuit 40, the first output end is connected to the first end of the substrate switching circuit 52, and the second output end is connected to the first end of the gate control circuit 53;

[0079] The second end of the substrate switching circuit 52 is connected to the substrate of the switch tube;

[0080] The output end of the gate control circuit 53 is connected to the gate of the switch tube;

[0081] The logic circuit 51 is used to perform logic processing on the output signal of the delay circuit 40, generate a substrate switching signal, and send the substrate switching signal to the substrate switching circuit 52, as well as generate a control signal and send the control signal to the gate control circuit 53; the substrate switching circuit 52 is used to switch the substrate polarity of the switch tube 60 according to the substrate switching signal; the gate control circuit 53 is used to output a gate control signal to the switch tube 60 according to the control signal to control the start or shut down of the gate of the switch tube 60.

[0082] Here, after receiving the output signal of the delay circuit 40, the logic circuit 51 performs logic processing on the output signal, generates a substrate switching signal and sends it to the substrate switching circuit 52, and generates a control signal and sends it to the gate control circuit 53. The substrate switching circuit 52 switches the substrate polarity of the switch tube 60 according to the substrate switching signal to select the switch tube 60 as an N-type substrate or a P-type substrate. The gate control circuit 53 controls the start or shut down of the gate of the switch tube 60 according to the control signal to protect the battery from charging and discharging.

[0083] Optionally, as a preferred example of the present invention, Figure 6 As shown, the voltage protection circuit 20 includes a first resistor R1, a second resistor R2, a third resistor R3, an over-discharge protection circuit 21, and an over-charge protection circuit 22;

[0084] The first end of the over-discharge protection circuit 21 is connected to the common point between the first resistor R1 and the second resistor R2, and the second end is connected to the delay circuit 40;

[0085] The first end of the overcharge protection circuit 22 is connected to the common point between the second resistor R2 and the third resistor R3, and the second end is connected to the delay circuit 40;

[0086] The other end of the first resistor R1 is connected to the power supply voltage sampling point; the other end of the third resistor R3 and the negative electrode of the battery are connected to the ground;

[0087] Among them, the over-discharge protection circuit 21 is used to obtain the power supply voltage from the power supply voltage sampling point, and send a detection flip signal to the delay circuit 40 when the power supply voltage is less than the first voltage threshold; the over-charge protection circuit 22 is used to obtain the power supply voltage from the power supply voltage sampling point, and send a detection flip signal to the delay circuit 40 when the power supply voltage is greater than the second voltage threshold.

[0088] Here, the first voltage threshold is a discharge protection voltage threshold, which is a standard for judging whether the battery is over-discharged. The second voltage threshold is a charge protection voltage threshold, which is a standard for judging whether the battery is over-charged.

[0089] When the over-discharge protection circuit 21 is enabled, the power supply voltage is detected and compared with the first voltage threshold to determine whether the battery is over-discharged. When the power supply voltage is less than the first voltage threshold, it is considered that the battery is over-discharged, and a detection flip signal is generated and sent to the delay circuit 40.

[0090] When the overcharge protection circuit 22 is enabled, the power supply voltage is detected and compared with the second voltage threshold to determine whether the battery is overcharged. When the power supply voltage is greater than the second voltage threshold, it is considered that the battery is over-discharged, and a detection flip signal is generated and sent to the delay circuit 40.

[0091] Optionally, as a preferred example of the present invention, Figure 6 As shown, the current protection circuit 30 includes a discharge overcurrent protection circuit 31, a short circuit protection circuit 32, and a charge overcurrent protection circuit 33;

[0092] The first ends of the discharge overcurrent protection circuit 31, the short circuit protection circuit 32, and the charge overcurrent protection circuit 33 are respectively connected to the loop current sampling point;

[0093] The second ends of the discharge overcurrent protection circuit 31, the short circuit protection circuit 32, and the charge overcurrent protection circuit 33 are respectively connected to the delay circuit 40;

[0094] The discharge overcurrent protection circuit 31 is used to obtain the discharge current from the loop current sampling point, and send a detection reversal signal to the delay circuit 40 when the discharge current is greater than the first current threshold; the charging overcurrent protection circuit 33 is used to obtain the charging current from the loop current sampling point, and send a detection reversal signal to the delay circuit 40 when the charging current is greater than the second current threshold; the short-circuit protection circuit 32 is used to obtain the short-circuit voltage from the loop current sampling point, and send a detection reversal signal to the delay circuit 40 when the short-circuit voltage is greater than the short-circuit protection voltage threshold.

[0095] Here, the first current threshold is the discharge protection current threshold, which is a standard for judging whether the loop current is too large during the battery discharge process. The second current threshold is the charge protection current threshold, which is a standard for judging whether the loop current is too large during the battery charging process. The short circuit protection voltage threshold is a standard for judging whether a short circuit occurs during the battery charging and discharging process.

[0096] When the discharge overcurrent protection circuit 31 is enabled, the loop current is detected. In practical applications, the first current threshold can be converted into a first protection voltage, and then the voltage value of the loop current sampling point VM is obtained through the current detection resistor, and the voltage value is compared with the first protection voltage. If the voltage value is greater than the first protection voltage, it is considered that the loop current is greater than the first current threshold. If the loop current is too large during battery discharge, a detection flip signal is generated and sent to the delay circuit 40.

[0097] When the charging overcurrent protection circuit 33 is enabled, the loop current is detected. In practical applications, the second current threshold can be converted into a second protection voltage, and then the voltage value of the loop current sampling point VM is obtained through the current detection resistor, and the voltage value is compared with the second protection voltage. If the voltage value is less than the second protection voltage, it is considered that the loop current is greater than the second current threshold. If the loop current is too large during battery charging, a detection flip signal is generated and sent to the delay circuit 40.

[0098] When the short-circuit protection circuit 32 is enabled, it detects whether a short circuit occurs in the battery. In practical applications, a short-circuit protection voltage threshold is preset, the voltage value of the loop current sampling point VM is obtained, and the voltage value is compared with the short-circuit protection voltage threshold. If the voltage value is less than the short-circuit protection voltage threshold, it is considered that a short circuit occurs in the battery, and a detection flip signal is generated and sent to the delay circuit 40.

[0099] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A battery protection circuit, characterized in that: include: Reference and bias circuit, voltage protection circuit, current protection circuit, delay circuit, switch tube control circuit, switch tube and clamp circuit; The first end of the voltage protection circuit is connected to the power supply voltage sampling point, and the second end is connected to the first end of the delay circuit; The first end of the current protection circuit is connected to the loop current sampling point, and the second end is connected to the second end of the delay circuit; The second end of the delay circuit is connected to the first end of the switch tube control circuit; The second end of the switch tube control circuit is connected to the gate of the switch tube; The source and drain of the switch tube are connected in series in a charge-discharge loop between the battery and the charging power source or the load; The first end of the clamp circuit is connected to the power supply voltage sampling point, the second end and the negative electrode of the battery are connected to the ground, and the third end is connected to the loop current sampling point; The loop current sampling point is located at the negative pole of the charging power source or the load side; The reference and bias circuit is connected to the power supply voltage sampling point; The reference and bias circuit is used to generate the bias voltage required by the voltage protection circuit and the bias current required by the current protection circuit; The voltage protection circuit is used to detect the power supply voltage and generate a detection flip signal when the power supply voltage is abnormal; The current protection circuit is used to detect the charging current and the discharging current, and to generate a detection flip signal when an abnormality occurs in the charging current and the discharging current; the delay circuit is used to delay the detection flip signal; The switch tube control circuit is used to generate a control signal according to the output signal of the delay circuit, and send the control signal to the switch tube to control the start or shutdown of the switch tube; the clamping circuit is used to clamp the loop current sampling point when negative high voltage appears at the loop current sampling point.

2. The battery protection circuit according to claim 1, characterized in that: When the clamp circuit is working, the voltage drop between the second end and the third end is less than the source-drain breakdown voltage of the switch tube.

3. The battery protection circuit according to claim 2, characterized in that: The clamping circuit includes an NMOS tube and a diode string group, and the diode string group includes a plurality of diodes connected in series; The drain of the NMOS tube is connected to the power supply voltage sampling point, the gate and the negative electrode of the battery are connected to the ground, and the source is connected to the positive electrode of the diode string group; The cathode of the diode string group is connected to the loop current sampling point.

4. The battery protection circuit according to claim 3, characterized in that: The sum of the threshold voltage of the NMOS tube and the conduction voltages of the plurality of diodes is less than the source-drain breakdown voltage of the switch tube.

5. The battery protection circuit according to claim 2, characterized in that: The clamping circuit includes an NMOS tube string group, and the NMOS tube string group includes a plurality of NMOS tubes connected in series; The source of each NMOS tube is connected to the common point between the drain and the gate of the next NMOS tube; The drain of the first NMOS tube is connected to the power supply voltage sampling point, and the gate and the negative electrode of the battery are connected to the ground; The source of the last NMOS tube is connected to the loop current sampling point.

6. The battery protection circuit according to claim 5, characterized in that: The sum of the threshold voltages of the plurality of NMOS tubes is less than the source-drain breakdown voltage of the switch tube.

7. The battery protection circuit according to claim 2, characterized in that: The clamp circuit includes an NMOS tube and a PMOS tube string group, and the PMOS tube string group includes a plurality of PMOS tubes connected in series; The drain of the NMOS tube is connected to the power supply voltage sampling point, the gate and the negative electrode of the battery are connected to the ground, and the source is connected to the source of the first PMOS tube in the PMOS tube string group; In the PMOS tube string group, the common point between the gate and drain of each PMOS tube is connected to the source of the next PMOS tube, and the common point between the gate and drain of the last PMOS tube is connected to the loop current sampling point.

8. The battery protection circuit according to claim 7, characterized in that: The sum of the threshold voltage of the NMOS tube and the threshold voltages of the plurality of PMOS tubes is less than the source-drain breakdown voltage of the switch tube.

9. The battery protection circuit according to any one of claims 1 to 8, characterized in that: The switch tube control circuit includes a logic circuit, a substrate switching circuit, and a gate control circuit; The input end of the logic circuit is connected to the second end of the delay circuit, the first output end is connected to the first end of the substrate switching circuit, and the second output end is connected to the first end of the gate control circuit; The second end of the substrate switching circuit is connected to the substrate of the switch tube; The output end of the gate control circuit is connected to the gate of the switch tube; The logic circuit is used to perform logic processing on the output signal of the delay circuit, generate a substrate switching signal, and send the substrate switching signal to the substrate switching circuit, as well as generate a control signal and send the control signal to the gate control circuit; the substrate switching circuit is used to switch the substrate polarity of the switch tube according to the substrate switching signal; the gate control circuit is used to output a gate control signal to the switch tube according to the control signal to control the start or shut down of the switch tube gate.

10. The battery protection circuit according to any one of claims 1 to 8, characterized in that: The switch tube is an isolated MOSFET or a non-isolated MOSFET.

Images