An NPN bipolar transistor control circuit and battery protection chip

Abstract

The application provides an NPN bipolar transistor control circuit and a battery protection chip, and relates to the technical field of integrated circuits.The NPN bipolar transistor control circuit comprises an NPN bipolar transistor, the NPN bipolar transistor has an N-type isolation well region for isolating a P-type well region from a P-type substrate, and an emitter and a base of the NPN bipolar transistor are connected to a first voltage; a monitoring module for monitoring the first voltage; and a control module for controlling a voltage connected to the N-type isolation well region based on at least the size of the first voltage.The application adjusts the voltage connected to the N-type isolation well region through the control module, so that the leakage current of the N-type isolation well region flowing to the detection end of the first voltage caused by an interference signal is reduced or does not exist, thereby avoiding the influence of the leakage current of the PN junction caused by the interference signal on the working state represented by the first voltage, and reducing the influence of the interference signal on the working performance of the application circuit.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, specifically to an NPN bipolar transistor control circuit and a battery protection chip. Background Technology

[0002] In integrated circuit design, electrostatic discharge (ESD) protection is crucial to the reliability of integrated circuits. Therefore, integrated circuits generally incorporate ESD (electro-static discharge) protection devices. Among these, the NPN bipolar transistor (NPN) can serve as an ESD protection device. By shorting the emitter and base of the NPN bipolar transistor and grounding them, while connecting the collector to a high potential, ESD protection is achieved.

[0003] refer to Figure 1 This is a schematic diagram illustrating the connection of an example NPN bipolar transistor used as an ESD protection device. The NPN bipolar transistor is disposed on a P-type substrate (denoted as P_substrate in the figure), having a P-type well region (denoted as Pwell in the figure), a base disposed in the P-type well region, and N-type doped emitter and collector located on either side of the base. The NPN bipolar transistor also has an N-type isolation well region for isolating its P-type well region (denoted as Pwell in the figure) from the P-type substrate. Figure 1 In the diagram, the N-type isolation trap region is illustrated by two N-well trap regions and one DeepNwell.

[0004] In this application, the P-type substrate is typically grounded (VSS). In some applications, the emitter and base of the NPN bipolar transistor are shorted and no longer grounded together with the substrate. Instead, they are connected to a specific operating voltage (referred to as the first voltage in this application) to prevent electrostatic discharge to this operating voltage. In the prior art, to prevent forward conduction between the P-type well region and the N-type isolation well region, the voltage connected to the N-type isolation well region is generally the power supply voltage of the application circuit. When the NPN bipolar transistor is affected by interference signals such as radio frequency signals, such as… Figure 1 As shown, a large number of charge carriers will move between the two, forming a leakage current that flows from the high-potential N-type isolation well region to the low-potential P-type well region, and finally flows to the operating voltage, causing abnormal changes in the operating voltage and affecting the normal operating state characterized by the operating voltage, thereby affecting the relevant operating performance of the application circuit. Summary of the Invention

[0005] This application provides an NPN bipolar transistor control circuit and a battery protection chip to overcome the above-mentioned technical problems.

[0006] To address the aforementioned problems, this application discloses an NPN bipolar transistor control circuit, comprising:

[0007] An NPN bipolar transistor has an N-type isolation well region that isolates its P-type well region from the P-type substrate. The emitter and base of the NPN bipolar transistor are connected to a first voltage.

[0008] A monitoring module for monitoring the first voltage; and

[0009] A control module that controls the voltage connected to the N-type isolation trap region based at least on the magnitude of the first voltage.

[0010] In this embodiment of the invention, the first voltage is a dynamic voltage or a variable voltage, the value of which varies with the actual operation of the circuit in which the NPN bipolar transistor is applied. The manner of this variation is not limited in this application. The core concept of this invention is to control the voltage connected to the N-type isolation well region in the NPN bipolar transistor used for electrostatic discharge protection based on the magnitude of the first voltage. This effectively controls the state of the PN junction formed by the N-type isolation well region and the P-type well region, preventing leakage current generated by interference signals from affecting the operating state characterized by the first voltage (i.e., what it should normally characterize).

[0011] In one embodiment of this application, when the minimum value of the first voltage is greater than the negative Vth, the control module controls the N-type isolation well region to remain connected to the first voltage; wherein, Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region.

[0012] In one embodiment of this application, a preset threshold voltage is also included;

[0013] The control module adjusts the voltage connected to the N-type isolation well region based on the first voltage and the threshold voltage; wherein the difference between the threshold voltage and the voltage connected to the N-type isolation well region is less than Vth, where Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region.

[0014] In one embodiment of this application, when the first voltage is less than the threshold voltage, the voltage connected to the N-type isolation well region is Va, where Va≤first voltage+Vth+K, Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region, and K is a constant, so as to avoid the leakage current of the PN junction caused by interference signals affecting the working state characterized by the first voltage.

[0015] When the first voltage is greater than or equal to the threshold voltage, the voltage connected to the N-type isolation well region is switched from Va to voltage Vb, where Vb > Va, in order to avoid forward conduction of the PN junction caused by the increase of the first voltage.

[0016] In one embodiment of this application, Va is less than or equal to a first voltage, and the minimum value of Va satisfies the condition that the PN junction is not forward-biased.

[0017] In one embodiment of this application, the collector of the NPN bipolar transistor is connected to a second voltage;

[0018] Va is the common ground voltage, and Vb is the second voltage.

[0019] In one embodiment of this application, the second voltage is the power supply voltage of the NMOS control circuit.

[0020] In one embodiment of this application, the monitoring module is provided with a threshold voltage;

[0021] The monitoring module generates an indication signal based on the first voltage and the threshold voltage;

[0022] The control module adjusts the voltage connected to the N-type isolation trap region based on the indication signal.

[0023] In one embodiment of this application, the monitoring module includes a MOS element and a current source, and the control module includes a voltage switching submodule;

[0024] The threshold voltage is the turn-on voltage of the MOS element. The current source is connected to the source or drain of the MOS element to form a series circuit. The gate of the MOS element is connected to the detection terminal of the first voltage. The series circuit is controlled to conduct based on the first voltage and the turn-on threshold to output an indication signal.

[0025] The voltage switching submodule adjusts the voltage connected to the N-type isolation trap region based on the indication signal.

[0026] This application also discloses a battery protection chip, including the NMOS control circuit as described in this application embodiment, wherein the first voltage is the overcurrent detection terminal voltage of the chip.

[0027] The embodiments of this application have the following advantages:

[0028] The NPN bipolar transistor control circuit provided in this application includes: an NPN bipolar transistor having an N-type isolation well region that isolates its P-type well region from the P-type substrate, wherein the emitter and base of the NPN bipolar transistor are connected to a first voltage; a monitoring module for monitoring the first voltage; and a control module for controlling the voltage connected to the N-type isolation well region based at least on the magnitude of the first voltage. By adjusting the voltage connected to the N-type isolation well region through the control module, the leakage current generated by the interference signal in the PN junction formed by the N-type isolation well region and the P-type well region can be used to control the operating state characterized by the first voltage, thereby reducing the impact of the interference signal on the operating performance of the application circuit. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application.

[0030] Figure 1 This is a connection diagram of an example NPN bipolar transistor used as an ESD protection device;

[0031] Figure 2 This is a schematic diagram of an NPN bipolar transistor control circuit according to this application;

[0032] Figure 3 This is a schematic diagram illustrating one implementation of an NPN bipolar transistor control circuit according to this application.

[0033] Figure 4 This is a schematic diagram illustrating another implementation of the NPN bipolar transistor control circuit of this application.

[0034] Figure 5 This is a schematic diagram of the NPN bipolar transistor control circuit according to an embodiment of this application;

[0035] Figure 6 This is a schematic diagram of a battery protection chip and its peripheral circuit according to an embodiment of this application.

[0036] Explanation of reference numerals in the attached figures:

[0037] 10 - NPN bipolar transistor control circuit; 101 - NPN bipolar transistor; 1011 - P-type well region; 1012 - N-type isolation well region; 1013 - Emitter; 1014 - Base; 1015 - Collector; 102 - P-type substrate; 103 - Monitoring module; 1031 - MOS element; 1032 - Current source; 104 - Control module; 1041 - Voltage switching submodule; 20 - Battery protection chip. Detailed Implementation

[0038] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0039] refer to Figure 2 This application provides an NPN bipolar transistor control circuit 10, which includes an NPN bipolar transistor 101, wherein, as... Figure 1As shown, the NPN bipolar transistor 101 has an N-type isolation well region 1012 that isolates its P-type well region 1011 from the P-type substrate 102. The emitter 1013 and base 1014 of the NPN bipolar transistor 101 are connected to a first voltage. The NPN bipolar transistor control circuit 10 also includes a monitoring module 103 for monitoring the first voltage; and a control module 104 for controlling the voltage connected to the N-type isolation well region 1012 based at least on the magnitude of the first voltage.

[0040] The principle that the NPN bipolar transistor 101 can be used as an ESD protection device is prior art, and can be found in existing explanations such as GGNMOS, so it will not be elaborated here. In this application, when the NPN bipolar transistor 101 is applied to a certain application circuit, the first voltage can be understood as the operating voltage shown in the background art. Unlike the prior art where the N-type isolation well region 1012 is always connected to the power supply voltage, this application can adjust the voltage connected to the N-type isolation well region 1012 through the control module 104, so as to avoid the leakage current generated by the interference signal from the PN junction affecting the operating state represented by the first voltage, thereby reducing the impact of the interference signal on the operating performance of the application circuit.

[0041] In this application, a monitoring module 103 monitors the first voltage, allowing for real-time acquisition of its magnitude. The control module 104 then controls the voltage connected to the N-type isolation trap region 1012 based on the magnitude of the first voltage. Figure 2 In this context, the voltage used to connect to the N-type isolation well region 1012 can be selected and expressed as voltages Va and Vb. There are different embodiments regarding the control module 104 controlling the voltage connected to the N-type isolation well region 1012 of the NPN bipolar transistor 101 based at least on the magnitude of the first voltage. Some embodiments of this application are described below with reference to the accompanying drawings.

[0042] In one embodiment of this application, reference is made to Figure 3 When the minimum value of the first voltage is greater than the negative Vth, the control module 104 controls the N-type isolation well region 1012 to remain connected to the first voltage; where Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region 1012.

[0043] Among them, such as Figure 3 As shown, there are two PN junctions formed based on the N-type isolation well region 1012. One is the PN junction formed by the N-type isolation well region 1012 and the P-type well region 1011 (represented as PN junction ① in the various figures), and the other is the PN junction formed by the N-type isolation well region 1012 and the P-type substrate 102 (represented as PN junction ② in the various figures). In the same NPN bipolar transistor 101, the forward conduction voltage Vth of PN junction ① and PN junction ② is the same. For example, the forward conduction voltage Vth of the PN junction made of silicon is 0.7V.

[0044] In this embodiment, if the fluctuation range of the first voltage is greater than the negative Vth, the control module 104 can control the N-type isolation well region 1012 to remain connected to the first voltage, so that the voltage connected to the N-type isolation well region 1012 is always at the same potential as the voltages connected to the base 1014 and emitter 1013 in the P-type well region 1011. In this way, even if affected by interference signals such as radio frequency, there will be almost no leakage current flowing from the N-type isolation well region 1012 through the P-type well region 1011 to the detection terminal of the first voltage, thereby avoiding the leakage current generated by the interference signal from affecting the working state represented by the first voltage. At the same time, no matter how the first voltage changes, the PN junction (PN junction ①) formed by the N-type isolation well region 1012 and the P-type well region 1011 will not be forward-conductive, avoiding the first voltage fluctuation from affecting other devices on the P-type substrate 102.

[0045] Optionally, the control module 104 can use a voltage switching submodule (illustrated as switch S1 in the attached figure) to connect the lead-out terminal of the N-type isolation well region 1012 to the lead-out terminal after shorting the emitter 1013 and base 1014, or directly connect it to the detection terminal of the first voltage, so as to keep the N-type isolation well region 1012 connected to the first voltage. In practice, the minimum value of the first voltage can be determined based on the specific performance of the actual application circuit of the NPN bipolar transistor 101 or by monitoring by the monitoring module 103, etc. For example, the forward conduction voltage Vth of a PN junction device made of silicon is generally 0.7V. The monitoring module 103 is set with a threshold voltage of -0.7V. If the fluctuation range of the first voltage is detected to be above -0.7V, the control module 104 keeps the voltage connected to the N-type isolation well region 1012 as the first voltage.

[0046] It is worth noting that in this embodiment, the voltage connected to the N-type isolation well region 1012 is the first voltage. Although the first voltage may become a negative voltage, that is, less than the potential (0 voltage) connected to the P-type substrate 102, since the minimum value of the first voltage is greater than the negative Vth, the PN junction (PN junction ②) formed by the N-type isolation well region 1012 and the P-type substrate 102 will not be forward-conducted.

[0047] In another embodiment of this application, a preset threshold voltage is also included; the control module 104 adjusts the voltage connected to the N-type isolation well region 1012 of the NPN bipolar transistor 101 based on the first voltage and the threshold voltage; wherein, the preset threshold voltage must satisfy: the difference between the threshold voltage and the voltage connected to the N-type isolation well region 1012 is less than Vth, where Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region 1012.

[0048] In this embodiment, when using the comparison between a first voltage and a threshold voltage to determine whether to adjust the voltage connected to the N-type isolation well region 1012, the difference between the threshold voltage and the voltage connected to the N-type isolation well region 1012 before adjustment should be less than the forward conduction voltage of the PN junction formed based on the N-type isolation well region 1012. This is to avoid the first voltage being too large, causing the PN junction (PN junction ①) formed by the N-type isolation well region 1012 and the P-type well region 1011 to conduct forward, while the first voltage has not yet reached the threshold voltage, thus preventing the voltage connected to the N-type isolation well region 1012 from being adjusted. In short, the threshold voltage setting should consider preventing the PN junction formed based on the N-type isolation well region 1012 from conducting forward.

[0049] In one implementation, in the initial state (the first voltage is usually less than the threshold voltage after the application circuit is powered on), the N-type isolation well region 1012 is generally connected to the common ground voltage (VSS) through the lead-out terminal. The common ground voltage is basically zero voltage. Therefore, the preset threshold voltage usually only needs to be less than Vth. At this time, there will be no situation where the first voltage has not reached the threshold voltage but the PN junction ① has already been forward-conducted.

[0050] In this embodiment, the preset threshold voltage, besides preventing the forward conduction of the PN junction formed based on the N-type isolation trap region 1012, should also be set considering the operating states represented by different values ​​of the first voltage. For example, in the initial state, the first voltage is basically 0, and the operating state represented by the first voltage is "normal"; when the first voltage is greater than 0.6V, the operating state represented by the first voltage is "abnormal", Vth is 0.7V, and the set threshold voltage can be 0.6V. That is, the threshold voltage setting can be greater than or equal to the critical value of the first voltage when the operating state represented by the first voltage changes (such as the short-circuit protection threshold), so as to minimize the possibility that the leakage current generated by the PN junction due to interference signals will affect the "normal" operating state represented by the first voltage, or in other words, reduce the probability that the operating state represented by the first voltage is actually "normal" but is misjudged as "abnormal" under the influence of interference signals.

[0051] In one possible implementation of the embodiments of this application, reference is made to... Figure 4 When the first voltage is less than the threshold voltage, the voltage connected to the N-type isolation well region 1012 is Va, where Va ≤ first voltage + Vth + K, Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region 1012, and K is a constant to avoid the leakage current of the PN junction caused by interference signals affecting the working state characterized by the first voltage; when the first voltage is greater than or equal to the threshold voltage, the voltage connected to the N-type isolation well region 1012 is switched from Va to voltage Vb, Vb > Va, to avoid the PN junction from being forward conducted due to the increase of the first voltage.

[0052] Unlike existing technologies, in this implementation, such as Figure 4 As shown, when the first voltage is less than the threshold voltage, the voltage connected to the N-type isolation well region 1012 is Va. Va is a voltage value that prevents the leakage current generated by interference signals in the PN junction (PN junction ①) formed by the N-type isolation well region 1012 and the P-type well region 1011 from affecting the operating state represented by the first voltage. That is, when the N-type isolation well region 1012 is connected to voltage Va, the leakage current generated by interference signals in the PN junction ① will not cause excessive fluctuations in the first voltage, thus changing the current operating state it represents. This effectively overcomes the problem mentioned in the background art.

[0053] Since the first voltage is an operating voltage of the application circuit, such as a battery protection system, and the first voltage is the voltage at the overcurrent detection terminal, when the battery discharges excessively or the application circuit is short-circuited, the first voltage will increase. When the first voltage increases to exceed the threshold voltage, if the N-type isolation well region 1012 is still connected to voltage Va, it may cause the PN junction ① to conduct in the forward direction. Therefore, in this implementation, if... Figure 4 As shown, when the first voltage is greater than or equal to the threshold voltage, the control module 104 switches the voltage connected to the N-type isolation trap region 1012 from Va to voltage Vb, and Vb > Va, so as to avoid the PN junction from being forward-biased due to the increase of the first voltage.

[0054] Theoretically, as long as Va ≤ the first voltage, there will be virtually no leakage current flowing from the N-type isolation well region 1012 through the P-type well region 1011 to the detection terminal of the first voltage. However, since the magnitude of the leakage current is related to the magnitude of the N-terminal voltage of the PN junction, and considering that the operating state represented by the first voltage may not change within a certain range in practice, or that the value of the operating state represented by the first voltage may differ significantly from its initial value, Va can also be slightly greater than the first voltage. In this case, even if interference signals such as radio frequency are applied to the NPN bipolar transistor 101, the leakage current flowing from the N-type isolation well region 1012 through the P-type well region 1011 to the detection terminal of the first voltage will not cause a significant change in the value of the first voltage. That is, in this case, the operating state represented by the first voltage will not change abnormally due to interference signals.

[0055] For example, when the first voltage is in the range of 0-0.5V, the working state represented by the first voltage is "normal". When the first voltage is greater than 0.5V, the working state represented by the first voltage is "abnormal". In the initial state, the first voltage is 0V and Va is 0.1V. Obviously, although Va is larger than the first voltage at this time, even if there is an interference signal, the leakage current generated based on 0.1V will not cause the first voltage to exceed 0.5V. It can also effectively avoid the leakage current generated by the interference signal affecting the working state represented by the first voltage in the PN junction (PN junction ①) formed by the N-type isolation well region 1012 and the P-type well region 1011.

[0056] Since the forward conduction voltage of PN junction ① is Vth, and there is at least a voltage difference of Vth between Va and the first voltage, Va can actually be less than or equal to the sum of the first voltage and Vth. However, considering that the value of Va should avoid the leakage current generated by the interference signal affecting the working state represented by the first voltage, based on the above idea, the upper limit of Va is expressed as: Va≤first voltage+Vth+K, where the first voltage is less than the threshold voltage, and K can be positive or negative. Its value can be determined based on the range of values ​​of the first voltage corresponding to the working state represented by the first voltage in the initial state.

[0057] In practical applications, preferably, the voltage Va connected to the N-type isolation well region 1012 is less than or equal to the first voltage. It is worth emphasizing that, in any case, the minimum values ​​of Va and Vb should ensure that the PN junction formed based on the N-type isolation well region 1012 is not forward-conducting; this can be understood as ensuring that neither PN junction ① nor PN junction ② is forward-conducting. Otherwise, if the PN junction is forward-conducting, the current will affect other devices on the P-type substrate 102, rendering the N-type isolation well region 1012 meaningless. Specifically, when the first voltage is less than the threshold voltage, Va > first voltage - Vth; when the first voltage is greater than the threshold voltage, Vb > first voltage - Vth.

[0058] In this application, the collector 1015 of the NPN bipolar transistor 101 is connected to a second voltage. Since the NPN bipolar transistor 101 is an ESD protection device used to protect against the first voltage, when the collector 1015 of the NPN bipolar transistor 101 is connected to the second voltage, regardless of how the first voltage fluctuates, the second voltage must be greater than the first voltage, preventing static electricity from being released through the detection terminal of the first voltage. Simultaneously, as an ESD protection device, the NPN bipolar transistor 101 should not be reverse-biased; that is, the difference between the second voltage and the first voltage must be less than the reverse conduction voltage of the ESD device. Otherwise, ESD will break down, and the protection function will be lost.

[0059] In one example, Va is the common ground voltage (VSS), and Vb is the second voltage. Alternatively, the second voltage may be the power supply voltage (VDD) of the NPN bipolar transistor control circuit 10.

[0060] It should be noted that, in this application, the threshold voltage is used as a node. A first voltage less than the threshold voltage is considered as a "normal" working state, and a first voltage greater than the threshold voltage is considered as an "abnormal" working state. When the control module 104 controls the voltage connected to the N-type isolation trap region 1012 to the second voltage, although the second voltage is greater than the first voltage, a large amount of leakage current may flow from the N-type isolation trap region 1012 through the P-type trap region 1011 to the detection terminal of the first voltage due to interference signals. However, since the working state represented by the first voltage is already in an "abnormal" state at this time, even if the first voltage continues to increase due to leakage current, the working state represented by the first voltage is still in an "abnormal" state. The leakage current will not affect the working state represented by the first voltage.

[0061] In this embodiment, the preset threshold voltage can be set in the monitoring module 103 or the control module 104, and this application does not limit it.

[0062] In one possible implementation, the monitoring module 103 is provided with the aforementioned threshold voltage; the monitoring module 103 generates an indication signal based on the first voltage and the threshold voltage; and the control module 104 adjusts the voltage connected to the N-type isolation trap region 1012 based on the indication signal.

[0063] In the circuit, the monitoring module 103 is directly connected to the detection terminal of the first voltage to obtain the first voltage. Then, the monitoring module 103 compares the first voltage with the threshold voltage and generates an indication signal. Based on the indication signal, the control module 104 can know whether the first voltage is greater than the threshold voltage.

[0064] The monitoring module 103 can be implemented in various ways in a specific circuit.

[0065] In one implementation, the monitoring module 103 includes a comparator. The two input terminals of the comparator are connected to a first voltage and a threshold voltage, respectively, and the logic signal output by its output terminal is the indication signal.

[0066] In another implementation, the monitoring module 103 includes a MOS element 1031 and a current source 1032, and the control module 104 includes a voltage switching submodule. The threshold voltage is the turn-on voltage of the MOS element 1031. The current source 1032 is connected to the source or drain of the MOS element 1031 to form a series circuit. The gate of the MOS element 1031 is connected to the detection terminal of the first voltage. The series circuit is controlled to conduct based on the first voltage and the turn-on threshold to output an indication signal. The voltage switching submodule 1041 adjusts the voltage connected to the N-type isolation well region 1012 based on the indication signal.

[0067] In this implementation, a first voltage is input to the gate of the MOS element 1031. Based on whether the difference between the first voltage and the source of the MOS element 1031 exceeds a conduction threshold, the MOS element 1031 can be controlled to turn on, thereby controlling whether the series circuit is conducting. Since the voltage at the connection node between the MOS element 1031 and the current source 1032 will definitely be different when the series circuit is on or off, if the series circuit is off, the connection node voltage is pulled to 0 by ground. When the series circuit is on, the connection node voltage increases based on the current generated by the current source 1032 and the equivalent resistance of the MOS element 1031. Therefore, this implementation can use the voltage level signal at the connection node between the MOS element 1031 and the current source 1032 as an indication signal. In different examples, the monitoring module 103 may also include other load elements such as resistors, which are connected in series with the MOS element 1031. The indication signal can be generated through the connection node between the load element and the MOS element 1031. The voltage switching submodule 1041 of the control module 104 receives the indication signal and then switches the voltage connected to the N-type isolation trap region 1012 based on the comparison result between the first voltage indicated by the indication signal and the threshold voltage. In different circuit applications, the voltage switching submodule 1041 can be implemented using a 2-to-1 selector, an inverter circuit, a multiplexer, or multiple switches; this application does not limit this implementation.

[0068] In one example, such as Figure 5 As shown, the NPN bipolar transistor 101 serves as an ESD protection device. Its emitter 1013 and base 1014 are connected to a first voltage, and its collector 1015 is connected to the power supply voltage. The MOS element 1031 is an NMOS transistor. The drain of the NMOS transistor is connected to the current source 1032, the source is grounded, and its gate is used to connect to the detection terminal of the first voltage. The connection node between the NMOS transistor and the current source 1032 is used to output the indication signal. The voltage switching submodule 1041, by receiving the aforementioned indication signal, can obtain the comparison result between the first voltage and the threshold voltage, and then select to connect the common ground voltage VSS or the power supply voltage VDD to the N-type isolation well region 1012.

[0069] Based on the same inventive concept, this application also provides a battery protection chip 20, such as... Figure 6 As shown, it includes an NPN bipolar transistor control circuit 10 as described in the embodiments of this application, wherein the first voltage is the overcurrent detection terminal voltage of the battery protection chip 20.

[0070] In battery protection systems, such as Figure 1 The NPN bipolar transistor 101 shown is connected as an ESD protection device between the power supply voltage and the overcurrent detection terminal voltage (in Figure 6 The overcurrent detection terminal voltage is denoted as VM, i.e., the first voltage is VM), and is used for electrostatic protection of the overcurrent detection terminal. Specifically, the base 1014 and emitter 1013 are shorted and connected to the overcurrent detection terminal. The collector 1015 is connected to the power supply terminal of the battery protection chip 20, thus connecting to the power supply voltage VDD. The P-type substrate 102 is connected to the common ground terminal of the battery protection chip 20 (in...). Figure 6 (represented by the common ground voltage VSS), in the prior art, the N-type isolation trap region 1012 is a direct power supply voltage.

[0071] Those skilled in the art will know that, Figure 6 As shown, in the battery protection system, the overcurrent detection terminal is connected to a current-limiting resistor R outside the chip. The voltage VM (i.e., the first voltage) at the overcurrent detection terminal is equal to V0 + IR, where V0 is the current monitoring voltage in the peripheral circuit connected to the battery protection chip 20, and I is the current flowing from the chip to the overcurrent detection terminal. Under normal circumstances, this current I is very weak, and VM is approximately equal to V0. The operating state represented by VM at this time is the actual operating state of the battery protection system. For example, when V0 indicates a short circuit in the battery protection system, VM at this time can also effectively represent a short circuit in the battery protection system. However, when the NPN bipolar transistor 101, as an ESD protection device, is affected by interference signals such as radio frequency, the current I will increase sharply. At this time, the difference between VM and V0 will be relatively large, which may cause the battery protection chip 20 to misjudge that the battery discharge current is too large, resulting in a short circuit and thus activating the short circuit protection.

[0072] Because the battery protection chip 20 of this application has such Figure 2The NPN bipolar transistor control circuit 10 shown includes an NPN bipolar transistor 101 for ESD protection, a monitoring module 103, and a control module 104. The monitoring module 103 monitors the overcurrent detection terminal voltage VM. The control module 104 controls the voltage connected to the N-type isolation well region 1012 of the NPN bipolar transistor 101 based at least on the size of VM. This is to minimize the voltage difference between the voltage connected to the N-type isolation well region 1012 and VM under normal conditions while avoiding forward conduction of the PN junction formed by the N-type isolation well region 1012 and the P-type well region 1011. This prevents leakage current generated by interference signals from affecting the normal operating state represented by the voltage VM.

[0073] In one embodiment, in the initial state (when VM is less than the threshold voltage), the control module 104 controls the N-type isolation well region 1012 to connect to the common ground voltage VSS. Since VM is almost zero voltage in the initial state, the PN junction formed by the N-type isolation well region 1012 and the P-type well region 1011 has almost no leakage current. Therefore, even if interference signals such as radio frequency are applied to the NPN bipolar transistor 101, it will not affect the "normal" working state represented by VM. The monitoring module 103 is provided with a threshold voltage, which is less than Vth, where Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region 1012. This threshold voltage can be close to the discharge overcurrent protection threshold or short circuit protection threshold of the battery protection system. Preferably, the threshold voltage is greater than or equal to the short circuit protection threshold, because the difference between short circuit protection and discharge overcurrent protection is that the reference threshold of short circuit protection is higher, but the delay time is shorter. Generally, interference signals such as radio frequency are intermittent, and their action time is shorter than the delay time for starting the battery discharge overcurrent, so they usually do not cause the system to abnormally start the discharge overcurrent protection. When the monitoring module 103 detects that VM is greater than the threshold voltage, the indication signal output to the control module 104 is valid. Based on the indication signal, the control module 104 switches the voltage connected to the N-type isolation well region 1012 from VSS to VDD, avoiding the forward conduction of the PN junction caused by the increase of VM. At this time, even if a large amount of leakage current flows to the overcurrent detection terminal from the PN junction (PN junction ①) formed by the N-type isolation well region 1012 and the P-type well region 1011, it is not a problem, because the system has already started short-circuit protection.

[0074] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0075] The technical solutions provided in this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand this application, and the content of this specification should not be construed as a limitation of this application. Furthermore, for those skilled in the art, there will be different forms of changes in the specific implementation methods and application scope based on this application. It is neither necessary nor possible to exhaustively list all implementation methods here, and obvious changes or modifications derived therefrom are still within the protection scope of this application.

Claims

1. An NPN bipolar transistor control circuit, characterized in that, include: The NPN bipolar transistor has an N-type isolation well region that isolates its P-type well region from the P-type substrate, and the emitter and base of the NPN bipolar transistor are connected to a first voltage. A monitoring module for monitoring the first voltage; and A control module that controls the voltage connected to the N-type isolation trap region based at least on the magnitude of the first voltage.

2. The NPN bipolar transistor control circuit according to claim 1, characterized in that, When the minimum value of the first voltage is greater than the negative Vth, the control module controls the N-type isolation well region to remain connected to the first voltage; wherein, Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region.

3. The NPN bipolar transistor control circuit according to claim 1, characterized in that, It also includes a preset threshold voltage; The control module adjusts the voltage connected to the N-type isolation well region based on the first voltage and the threshold voltage; wherein the difference between the threshold voltage and the voltage connected to the N-type isolation well region is less than Vth, and Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region.

4. The NPN bipolar transistor control circuit according to claim 3, characterized in that, When the first voltage is less than the threshold voltage, the voltage connected to the N-type isolation well region is Va, where Va ≤ the first voltage + Vth + K, Vth is the forward conduction voltage of the PN junction formed based on the N-type isolation well region, and K is a constant, so as to avoid the leakage current of the PN junction caused by interference signals affecting the working state characterized by the first voltage. When the first voltage is greater than or equal to the threshold voltage, the voltage connected to the N-type isolation well region is switched from Va to Vb, where Vb > Va, in order to avoid the PN junction from being forward-biased due to the increase of the first voltage.

5. The NPN bipolar transistor control circuit according to claim 4, characterized in that, The Va is less than or equal to the first voltage, and the minimum value of Va satisfies the condition that the PN junction is not forward-biased.

6. The NPN bipolar transistor control circuit according to claim 4, characterized in that, The collector of the NPN bipolar transistor is connected to a second voltage; Va is the common ground voltage, and Vb is the second voltage.

7. The NPN bipolar transistor control circuit according to claim 6, characterized in that, The second voltage is the power supply voltage of the NPN bipolar transistor control circuit.

8. The NPN bipolar transistor control circuit according to any one of claims 3-7, characterized in that, The monitoring module is equipped with the threshold voltage; The monitoring module generates an indication signal based on the first voltage and the threshold voltage; The control module adjusts the voltage connected to the N-type isolation trap region based on the indication signal.

9. The NPN bipolar transistor control circuit according to claim 8, characterized in that, The monitoring module includes a MOS element and a current source, and the control module includes a voltage switching submodule. The threshold voltage is the turn-on voltage of the MOS element. The current source is connected to the source or drain of the MOS element to form a series circuit. The gate of the MOS element is connected to the detection terminal of the first voltage. The series circuit is controlled to conduct based on the first voltage and the turn-on threshold to output the indication signal. The voltage switching submodule adjusts the voltage connected to the N-type isolation trap region based on the indication signal.

10. A battery protection chip, characterized in that, Includes the NPN bipolar transistor control circuit as described in any one of claims 1-9, wherein the first voltage is the overcurrent detection terminal voltage of the chip.

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