Rechargeable battery short circuit protection device

Abstract

The utility model discloses a rechargeable battery short circuit protection device, including discharge switch, voltage sampler, comparator and controller, one end of voltage sampler is connected with the node on power bus, for obtaining sampling voltage, and the other end is electrically connected with one input of comparator, and the other input of comparator is electrically connected with reference voltage source, and discharge switch sets up on power bus, when sampling voltage is less than first threshold value, voltage sampler is in the following state, to make the voltage that voltage sampler exports to comparator follow sampling voltage and change, when sampling voltage is greater than or equal to first threshold value, voltage sampler is in the clamping state, to make the voltage that voltage sampler exports to comparator be the fixed clamping voltage, and clamping voltage is greater than the reference voltage that reference voltage source provided, the above-mentioned protection device, effectively realized the quick protection of short circuit time and the false triggering of normal start time to avoid, avoid the device burnout caused by response delay.

Description

Technical Field

[0001] This utility model relates to the field of battery management circuit technology, and in particular to a short-circuit protection device for rechargeable batteries. Background Technology

[0002] With the widespread application of lithium batteries in electric vehicles, portable electronic devices, and energy storage systems, their safety has become an increasingly important concern. During operation, a short circuit in a lithium battery can lead to equipment damage, malfunction, and even vehicle loss of control in high-risk scenarios such as electric vehicles, seriously threatening the lives of users. Therefore, effectively implementing short-circuit protection for lithium batteries has become a pressing technical challenge that needs to be addressed.

[0003] In existing battery management systems (BMS), short-circuit protection mechanisms typically trigger protection actions by detecting abnormal current or voltage in the circuit. However, existing technologies have significant drawbacks in implementing short-circuit protection. On the one hand, to avoid misinterpreting a large instantaneous current generated when a capacitive load is powered on as a short circuit, the trigger delay for short-circuit protection is often set to be relatively long. While this design reduces false triggers, it also leads to a delayed protection action when a real short circuit occurs, resulting in excessive shutdown current and potential damage to critical components such as the discharge MOSFET, thus causing the short-circuit protection function to fail. On the other hand, if the trigger threshold for short-circuit protection is set too sensitively to improve safety, a sudden current may be misinterpreted as a short circuit when a high-capacitive load is powered on, preventing the system from starting normally and affecting the user experience.

[0004] To address the aforementioned issues, existing technologies have proposed some improvement solutions, such as optimizing delay settings through software algorithms or adding auxiliary detection circuits to distinguish between real short circuits and false short circuits. However, these methods often increase the complexity and cost of the system, and under certain extreme conditions, it is still difficult to completely avoid the problems of false triggering or protection failure. Utility Model Content

[0005] The purpose of this invention is to provide a rechargeable battery short-circuit protection device that can quickly respond to real short-circuit protection while ensuring safety, in order to solve the above-mentioned technical problems.

[0006] To achieve the above objectives, this utility model provides a short-circuit protection device for a rechargeable battery, including a discharge switch, a voltage sampler, a comparator, and a controller;

[0007] One end of the voltage sampler is connected to a node on the power bus between the battery and the load to obtain the sampled voltage. The other end of the voltage sampler is electrically connected to one of the input terminals of the comparator, and the other input terminal of the comparator is electrically connected to a reference voltage source.

[0008] A discharge switch is installed on the power bus to control the discharge state of the battery;

[0009] The input terminal of the controller is electrically connected to the output terminal of the comparator, and the output terminal of the controller is electrically connected to the discharge switch;

[0010] When the sampled voltage is less than a first threshold, the voltage sampler is in a following state, so that the voltage output by the voltage sampler to the comparator changes in accordance with the sampled voltage; the first threshold is related to the voltage level when the load is short-circuited;

[0011] When the sampled voltage is greater than or equal to the first threshold, the voltage sampler is in a clamped state, so that the voltage output by the voltage sampler to the comparator is a fixed clamped voltage, and the clamped voltage is greater than the reference voltage provided by the reference voltage source.

[0012] Preferably, it further includes a shunt, and the power bus includes a positive bus for electrically connecting the positive terminal of the battery and the positive terminal of the load, and a negative bus for electrically connecting the negative terminal of the battery and the negative terminal of the load. The shunt and the discharge switch are connected in series on the negative bus. The sampling voltage is the voltage signal of the shunt and / or the discharge switch relative to the negative terminal of the battery.

[0013] Preferably, it also includes a charging switch connected in series with the negative bus and electrically connected to the controller, the charging switch being used to control the charging state of the battery.

[0014] Preferably, the discharge switch is electrically connected to the negative terminal of the load through the charging switch, the discharge switch is electrically connected to the negative terminal of the battery through the shunt, and the node on the negative bus that is electrically connected to the voltage sampler is located between the discharge switch and the charging switch.

[0015] Preferably, the controller is electrically connected to the charging switch and the discharging switch via a charging / discharging drive circuit.

[0016] Preferably, the voltage sampler includes an electronic switch transistor, which includes a first conducting terminal, a second conducting terminal, and a control terminal. The first conducting terminal is electrically connected to a node on the power bus to acquire the sampled voltage; the second conducting terminal is electrically connected to one of the input terminals of a comparator; and the control terminal is electrically connected to a controller.

[0017] When the sampling voltage is less than the first threshold, the electronic switch is in the on state, and the second on terminal follows the first on terminal to output a voltage signal to the comparator;

[0018] When the sampling voltage is greater than or equal to the first threshold, the electronic switch is in saturation, and the second conducting terminal outputs the clamping voltage to the comparator. The clamping voltage and the first threshold are the difference between the voltage of the control terminal and the threshold voltage of the electronic switch.

[0019] Preferably, the electronic switch includes an NMOS transistor or a PMOS transistor.

[0020] Preferably, the clamping voltage is 1-2V.

[0021] Preferably, the controller also controls the electronic switch to be in an off state to shield short-circuit protection.

[0022] Compared to existing technologies, the aforementioned short-circuit protection device, through its dual-mode design of voltage sampler following and clamping, combined with the fast response mechanism of comparator and controller, effectively achieves rapid protection during short circuits and avoidance of false triggering during normal startup. On the one hand, it can quickly disconnect the discharge switch when a short circuit occurs, preventing device burnout due to response delay; on the other hand, it can operate stably under normal load or high capacitive load, ensuring normal device startup and operation. This short-circuit protection scheme, which balances safety and practicality, is significantly superior to existing short-circuit protection schemes with excessively long delays or frequent false triggering, providing a more reliable guarantee for the safe application of battery systems. Attached Figure Description

[0023] Figure 1 This is a circuit diagram of a short-circuit protection device in one embodiment of the present invention.

[0024] Figure 2 This is a circuit diagram of a short-circuit protection device in another embodiment of the present invention. Detailed Implementation

[0025] To explain in detail the technical content, structural features, objectives and effects of this utility model, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0026] This embodiment discloses a short-circuit protection device for rechargeable batteries, applicable to rechargeable battery systems such as lithium batteries. It is used to quickly respond and protect the battery and related circuits when a short circuit occurs, avoiding device damage or system failure, and preventing false triggering when powered on under normal load or high capacitive load.

[0027] like Figure 1 The short-circuit protection device consists of discharge switch Q1, voltage sampler 10, comparator U1, and controller U2.

[0028] One end of the voltage sampler 10 is connected to a node D0 on the power bus between the battery and the load to obtain the sampled voltage. The other end of the voltage sampler 10 is electrically connected to one of the input terminals (such as the inverting terminal) of the comparator U1, and the other input terminal (such as the non-inverting terminal) of the comparator U1 is electrically connected to the reference voltage source 20.

[0029] The discharge switch Q1 is located on the power bus and is used to control the battery's discharge state. When the discharge switch Q1 is in the ON state, the power circuit of the power bus is connected; when the discharge switch Q1 is in the OFF state, the power circuit of the power bus is disconnected.

[0030] The input terminal of controller U2 is electrically connected to the output terminal of comparator U1, and the output terminal of controller U2 is electrically connected to discharge switch Q1.

[0031] When the sampled voltage is less than the first threshold, the voltage sampler 10 is in a following state, so that the voltage output by the voltage sampler 10 to the comparator U1 changes with the sampled voltage. The first threshold is related to the voltage level when the load is short-circuited.

[0032] When the sampled voltage is greater than or equal to the first threshold, the voltage sampler 10 is in a clamping state, so that the voltage output by the voltage sampler 10 to the comparator U1 is a fixed clamping voltage, and the clamping voltage is greater than the reference voltage provided by the reference voltage source 20.

[0033] The short-circuit protection device in this embodiment, through the coordinated operation of the voltage sampler 10, comparator U1 and controller U2, can quickly detect abnormal voltage changes and take protective measures when a short circuit occurs in the load.

[0034] Specifically, when a load short circuit causes the sampling voltage to rise sharply and exceed the first threshold, the voltage sampler 10 enters a clamping state, outputting a fixed clamping voltage (higher than the reference voltage). This causes the comparator U1 to continuously output a signal, and the controller U2 then drives the discharge switch Q1 to disconnect the circuit. This mechanism avoids the continuous flow of short-circuit current due to excessive response delay, significantly reducing the risk of overcurrent burnout of critical components such as the discharge switch Q1 and the load. Compared with the problem of excessive shutdown current due to long protection delay settings in existing technologies, this device greatly improves the timeliness and reliability of short-circuit protection through a fast response mechanism at the hardware level, effectively protecting circuit components.

[0035] Furthermore, when the sampling voltage rises sharply due to a short circuit (potentially reaching the positive terminal voltage of the battery), the clamping function of the voltage sampler 10 ensures that the voltage output to the comparator U1 is fixed at the clamping voltage, avoiding the risk of damaging the comparator U1 due to excessively high voltage input. This design not only protects the core circuit components but also further enhances the stability and durability of the entire short-circuit protection device under extreme operating conditions.

[0036] Under normal operating conditions or when a high-capacitive load is powered on, the sampled voltage is typically below the first threshold. At this time, the voltage sampler 10 is in follower mode, and the output voltage dynamically changes with the sampled voltage. According to the parameter design, when the sampled voltage is below the reference voltage, comparator U1 will not output a trigger signal, and controller U2 will not drive discharge switch Q1 to open, thus ensuring that discharge switch Q1 remains on and the circuit is powered normally. This design effectively avoids the misjudgment problem caused by the overly sensitive short-circuit protection trigger threshold in existing technologies. Especially in scenarios where a high-capacitive load generates a large instantaneous current, this device can accurately distinguish between normal load and short-circuit conditions, ensuring normal equipment startup and operation without affecting the user experience.

[0037] On the other hand, the short-circuit protection device in this embodiment also includes a shunt 30. The power bus includes a positive bus X1 for electrically connecting the positive terminal of the battery and the positive terminal of the load, and a negative bus X2 for electrically connecting the negative terminal of the battery and the negative terminal of the load. The shunt 30 and the discharge switch Q1 are connected in series on the negative bus X2. The sampling voltage is the voltage signal of the shunt 30 and / or the discharge switch Q1 relative to the negative terminal of the battery.

[0038] In this embodiment, the shunt 30 specifically employs a low-resistance, high-precision resistor element with a resistance range of 1mΩ to 10mΩ; for example, a 5mΩ resistor can be selected as the shunt 30. The function of the shunt 30 is to convert the current flowing through the negative bus X2 into a measurable voltage signal so that the subsequent voltage sampler 10 can acquire the sampling voltage. The discharge switch Q1 uses an N-type MOSFET (NMOS transistor), and the discharge path is turned on or off via a control signal output by the controller U2.

[0039] The input terminal of the voltage sampler 10 is connected to a node D0 on the negative bus X2. This node D0 is located between the shunt 30 and the discharge switch Q1. Alternatively, when the shunt 30 is directly connected to the positive terminal of the battery and the discharge switch Q1 is directly connected to the negative terminal of the load, this node D0 is located at the end of the discharge switch Q1 closest to the negative terminal of the battery.

[0040] Specifically, when a short circuit occurs in the load, the current increases sharply, and the voltage drop across the shunt 30 and the discharge switch Q1 increases significantly, thus forming a sampling voltage signal related to the short circuit state.

[0041] In this embodiment, the series connection of the shunt 30 and the discharge switch Q1 ensures the accuracy of current detection and the reliability of discharge control. By setting the shunt 30 on the negative bus X2, changes in the current flowing through the load can be effectively monitored, thereby providing timely voltage signal feedback for short-circuit protection. At the same time, the fast response capability of the discharge switch Q1 ensures that the circuit can be quickly cut off when a short circuit occurs, avoiding the risk of device overheating or burnout.

[0042] On the other hand, such as Figure 2 The short-circuit protection device also includes a charging switch Q2 connected in series with the negative bus X2 and electrically connected to the controller U2. The charging switch Q2 is used to control the charging state of the battery. Thus, during the charging process, if the charging current on the power bus is too large, it may cause the sampled voltage to exceed the first threshold, thereby controlling the charging switch Q2 to open through the controller U2, thereby further improving the safety performance of the protection device.

[0043] In this regard, the discharge switch Q1 is electrically connected to the negative terminal of the load through the charging switch Q2, and the discharge switch Q1 is electrically connected to the negative terminal of the battery through the shunt 30. The node D0 on the negative bus that is electrically connected to the voltage sampler 10 is located between the discharge switch Q1 and the charging switch Q2.

[0044] In this embodiment, the voltage sampler 10 collects the common voltage across the shunt 30 and the discharge switch Q1. During battery discharge, if a short circuit occurs in the load, the voltage across the shunt 30 and the discharge switch Q1 rises rapidly, causing the sampled voltage to exceed a first threshold. Based on this signal, the controller U2 controls the discharge switch Q1 to open. After the discharge switch Q1 opens, due to the load short circuit, the voltage at the negative terminal of the load is equivalent to the voltage at the positive terminal of the battery. Therefore, the sampled voltage is equal to the voltage at the positive terminal of the battery (e.g., 50V). At this time, under the clamping action of the voltage sampler 10, only the clamping voltage (e.g., 1.3V) enters the comparator U1.

[0045] On the other hand, the controller U2 is electrically connected to the charging switch Q2 and the discharging switch Q1 through the charging and discharging drive circuit 40.

[0046] On the other hand, the voltage sampler 10 includes an electronic switch tube, which includes a first conducting terminal, a second conducting terminal, and a control terminal.

[0047] The first conducting terminal is electrically connected to node D0 on the power bus to acquire the sampling voltage. The second conducting terminal is electrically connected to one of the input terminals of comparator U1, and the control terminal is electrically connected to controller U2.

[0048] When the sampled voltage is less than the first threshold, the electronic switch is in the on state, and the second on terminal follows the first on terminal to output a voltage signal to the comparator U1.

[0049] When the sampling voltage is greater than or equal to the first threshold, the electronic switch is in saturation. The second conducting terminal outputs a clamping voltage to the comparator U1. The clamping voltage and the first threshold are the difference between the voltage at the control terminal and the threshold voltage of the electronic switch.

[0050] The electronic switch in this embodiment includes an NMOS transistor or a PMOS transistor, and the clamping voltage is 1-2V.

[0051] Taking an NMOS transistor as an example, its drain serves as the first conduction terminal, the source as the second conduction terminal, and the gate as the control terminal. The drain is electrically connected to node D0 on the power bus. The source is electrically connected to the positive input terminal of comparator U1, used to output a voltage signal to comparator U1. The gate is electrically connected to the output terminal of controller U2. Controller U2 adjusts the gate voltage by outputting a control signal, thereby controlling the operating state of the NMOS transistor.

[0052] For an electronic switch using an NMOS transistor, assuming a threshold voltage of 2V, the voltage applied to the gate by the controller U2 is 3.3V.

[0053] The operating states of an NMOS transistor include follower state and clamp state, and its state behavior depends on the relationship between the sampling voltage Vd and the gate voltage Vg and the threshold voltage Vth.

[0054] The operating region (linear region vs. saturation region) of an NMOS transistor switches according to changes in Vd.

[0055] Specifically:

[0056] In the linear region, Vd < (Vg - Vth), the NMOS transistor is fully turned on, which is equivalent to a low-impedance switch, and Vs ≈ Vd.

[0057] In the saturation region, Vd ≥ (Vg - Vth), the NMOS transistor cannot be fully turned on, and the output Vs is clamped at Vg - Vth ≈ 1.3V. At this time, the NMOS transistor limits the current and voltage transfer, thus playing a protective role.

[0058] Therefore, it can be seen that the switching condition between the linear region and the saturation region depends on the size of Vd.

[0059] Therefore, under normal load conditions:

[0060] The battery is supplying power normally, and there is no short circuit in the load. The sampled voltage Vd comes from shunt 30 and discharge switch Q1, and is usually very low; assuming a normal Vd = 0.1V.

[0061] The controller U2 sets the gate voltage Vg to 3.3V, turns on the electronic switch (NMOS transistor), and allows the sampling voltage to be passed to the comparator U1.

[0062] Under load short-circuit conditions:

[0063] If Vd increases to 20V, then Vd > (Vg - Vth), and the electronic switch enters the saturation region.

[0064] At this point, Vs = Vg - Vth = 1.3V (clamped, 20V not passed).

[0065] Comparator U1 compares the 1.3V voltage with the reference voltage. If the reference voltage is 1V, then 1.3V > 1V, and sends a protection signal to controller U2. Controller U2 then controls the discharge switch Q1 to open.

[0066] After the discharge switch Q1 is turned off, Vd remains at the positive terminal voltage level of the battery, such as 50V. This keeps the electronic switch in the saturation region and in a clamped state, thus protecting the comparator U1 from damage by a higher sampling voltage.

[0067] On the other hand, the controller U2 also controls the electronic switch to be in the off state to shield short-circuit protection.

[0068] In this embodiment, the electronic switch is controlled to be in the off state by the controller U2, which can temporarily disable the short-circuit protection function of the power circuit where the battery is located as needed, so as to meet the different usage needs of users and effectively improve the user experience.

[0069] The above-disclosed embodiments are merely preferred embodiments of the present utility model and should not be construed as limiting the scope of the present utility model. Therefore, any equivalent variations made in accordance with the scope of the present utility model application shall still fall within the scope of the present utility model.

Claims

1. A short circuit protection device for a rechargeable battery, characterized in that Includes a discharge switch, voltage sampler, comparator, and controller; One end of the voltage sampler is connected to a node on the power bus between the battery and the load to obtain the sampled voltage. The other end of the voltage sampler is electrically connected to one of the input terminals of the comparator, and the other input terminal of the comparator is electrically connected to a reference voltage source. A discharge switch is installed on the power bus to control the discharge state of the battery; The input terminal of the controller is electrically connected to the output terminal of the comparator, and the output terminal of the controller is electrically connected to the discharge switch; When the sampled voltage is less than a first threshold, the voltage sampler is in a following state, so that the voltage output by the voltage sampler to the comparator changes in accordance with the sampled voltage; the first threshold is related to the voltage level when the load is short-circuited; When the sampled voltage is greater than or equal to the first threshold, the voltage sampler is in a clamped state, so that the voltage output by the voltage sampler to the comparator is a fixed clamped voltage, and the clamped voltage is greater than the reference voltage provided by the reference voltage source.

2. The rechargeable battery short circuit protection device of claim 1, wherein, It also includes a shunt, and the power bus includes a positive bus for electrically connecting the positive terminal of the battery and the positive terminal of the load, and a negative bus for electrically connecting the negative terminal of the battery and the negative terminal of the load. The shunt and the discharge switch are connected in series on the negative bus. The sampling voltage is the voltage signal of the shunt and / or the discharge switch relative to the negative terminal of the battery.

3. The rechargeable battery short circuit protection device of claim 2, wherein, It also includes a charging switch connected in series with the negative bus and electrically connected to the controller, the charging switch being used to control the charging state of the battery.

4. The rechargeable battery short circuit protection device of claim 3, wherein, The discharge switch is electrically connected to the negative terminal of the load through the charging switch, and the discharge switch is electrically connected to the negative terminal of the battery through the shunt. The node on the negative bus that is electrically connected to the voltage sampler is located between the discharge switch and the charging switch.

5. The rechargeable battery short circuit protection device of claim 3, wherein, The controller is electrically connected to the charging switch and the discharging switch via a charging and discharging drive circuit.

6. The rechargeable battery short circuit protection device of claim 1, wherein, The voltage sampler includes an electronic switch transistor, which has a first conducting terminal, a second conducting terminal, and a control terminal. The first conducting terminal is electrically connected to a node on the power bus to acquire the sampled voltage. The second conducting terminal is electrically connected to one of the input terminals of a comparator, and the control terminal is electrically connected to a controller. When the sampling voltage is less than the first threshold, the electronic switch is in the on state, and the second on terminal follows the first on terminal to output a voltage signal to the comparator; When the sampling voltage is greater than or equal to the first threshold, the electronic switch is in saturation, and the second conducting terminal outputs the clamping voltage to the comparator. The clamping voltage and the first threshold are the difference between the voltage of the control terminal and the threshold voltage of the electronic switch.

7. The rechargeable battery short circuit protection device of claim 6, wherein, The electronic switching transistor includes an NMOS transistor or a PMOS transistor.

8. The rechargeable battery short circuit protection device of claim 6, wherein, The clamping voltage is 1-2V.

9. The rechargeable battery short circuit protection device of claim 6, wherein, The controller also controls the electronic switch to be in an off state to shield against short circuit protection.

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