Overcurrent detection module, battery protection circuit and system

Abstract

The application provides an overcurrent detection module, a battery protection circuit and a system. The overcurrent detection module comprises a reference voltage generation circuit, which is used to obtain a voltage value of a first detection terminal VDD, obtain a temperature value of a charge-discharge switch, find a corresponding reference voltage VR from a predetermined parameter table based on the obtained voltage value of the first detection terminal VDD and the temperature value of the charge-discharge switch, and output the reference voltage VR through an output terminal thereof; and a comparator, which has a first input terminal receiving the reference voltage VR output by the reference voltage generation circuit, and a second input terminal obtaining a voltage of a second detection terminal VM, and is used to compare the reference voltage VR and the voltage of the second detection terminal VM, and output a corresponding current detection signal through an output terminal thereof based on a comparison result. Compared with the prior art, the application can realize high-precision discharge or charge overcurrent detection, thereby improving the safety of a battery.

Description

[Technical Field]

[0001] This invention relates to the field of circuit design, and in particular to an overcurrent detection module, a battery protection circuit, and a system. [Background Technology]

[0002] In existing technologies, to achieve high-precision discharge overcurrent detection, a current sampling resistor R1 is generally used to obtain current detection information. Please refer to [reference needed]. Figure 1 As shown, it is a circuit diagram of a battery protection system in the prior art. Figure 1 The battery protection system shown includes cell BAT1, battery protection circuit (or battery protection chip) 110, charging power switch (or charging power transistor) FET2, discharging power switch (or discharging power transistor) FET1, and resistor R1. Generally, the voltage at the detection terminal VSS is defined as 0V. The voltage at the detection terminal VL relative to VSS, i.e., the voltage across resistor R1, reflects the discharge current. The voltage across resistor R1 (i.e., the voltage at the detection terminal VL) is proportional to the discharge current. This scheme requires a high-precision resistor R1, which is costly, occupies printed circuit board space, consumes energy, and generates heat, among other problems. If the voltage at the detection terminal VM is directly used as the current sampling information, the current detection will be inaccurate.

[0003] Therefore, it is necessary to propose an improved technical solution to overcome the above problems. [Summary of the Invention]

[0004] One of the objectives of this invention is to provide an overcurrent detection module, a battery protection circuit, and a system that can achieve high-precision overcurrent detection during discharge or charging, thereby improving battery safety.

[0005] According to one aspect of the present invention, an overcurrent detection module is provided, comprising: a reference voltage generating circuit, configured to acquire the voltage value of a first detection terminal VDD, acquire the temperature value of a charge / discharge switch, and find a corresponding reference voltage VR from a predetermined parameter table based on the acquired voltage value of the first detection terminal VDD and the temperature value of the charge / discharge switch, and output the reference voltage VR through its output terminal; a comparator, whose first input terminal receives the reference voltage VR output by the reference voltage generating circuit, and whose second input terminal acquires the voltage of a second detection terminal VM, the comparator being configured to compare the magnitude of the reference voltage VR and the voltage of the second detection terminal VM, and output a corresponding current detection signal through its output terminal based on the comparison result.

[0006] Furthermore, the predetermined parameter table includes multiple segments of the voltage value of the first detection terminal VDD, multiple segments of the temperature value of the charge / discharge switch, and multiple values ​​of the reference voltage VR. Each combination of a segment of the voltage value of the first detection terminal VDD and any segment of the temperature value of the corresponding charge / discharge switch corresponds to a value of the reference voltage VR. The reference voltage generation circuit finds the voltage segment of the first detection terminal VDD from the predetermined parameter table based on the obtained voltage value, and finds the temperature segment of the first detection terminal VDD from the predetermined parameter table based on the obtained temperature value of the charge / discharge switch, thereby finding the corresponding reference voltage VR from the predetermined parameter table and outputting the reference voltage VR through its output terminal.

[0007] Furthermore, the reference voltage VR mimics the change in the on-resistance of the charge / discharge switch as the voltage at the first detection terminal VDD changes, and also mimics the change in the on-resistance of the charge / discharge switch as its temperature changes.

[0008] Furthermore, the reference voltage generation circuit includes: a voltage analog-to-digital converter (ADC), whose input terminal is connected to the first detection terminal VDD, the ADC converting the voltage value of the first detection terminal VDD into a corresponding digital signal, and outputting a digital signal corresponding to the voltage value of the first detection terminal VDD through its output terminal; a temperature sensor, used to sense the temperature of the charge / discharge switch, and outputting a corresponding temperature value through its output terminal; a temperature analog-to-digital converter (DAC), whose input terminal is connected to the output terminal of the temperature sensor, the DAC converting the temperature value output by the temperature sensor into a corresponding digital signal, and outputting a digital signal corresponding to the temperature value of the charge / discharge switch through its output terminal; a memory, which stores corresponding information in the predetermined parameter table; and a control... The controller has a first input terminal connected to the output terminal of the voltage analog-to-digital converter (ADC), a second input terminal connected to the output terminal of the temperature analog-to-digital converter (DAC), and a third input terminal connected to the memory. Based on the digital signal output by the ADC corresponding to the voltage value of the first detection terminal VDD and the digital signal output by the ADC corresponding to the temperature value of the charge / discharge switch, the controller searches for the digital signal of the corresponding reference voltage VR from a predetermined parameter table and outputs the digital signal of the reference voltage VR through its output terminal. The DAC generates the corresponding analog voltage value of the reference voltage CR based on the digital signal output by the controller and outputs the analog voltage value of the reference voltage CR to the first input terminal of the comparator.

[0009] Furthermore, the temperature information of the charge / discharge switch can be transmitted to the temperature sensor inside the chip by conducting heat through the metal sheet on the underside of the chip package; or a metal sheet can be added to the printed circuit board, and then the temperature information of the charge / discharge switch can be transmitted to the temperature sensor inside the chip through the pins of the package.

[0010] According to another aspect of the present invention, a battery protection circuit is provided, comprising a second detection terminal connected to the negative terminal of the battery, a third detection terminal connected to the negative terminal of the battery cell, a first detection terminal connected to the positive terminal of the battery cell, a discharge control terminal connected to the control terminal of a discharge power switch, and a charging control terminal connected to the control terminal of a charging power switch. The discharge power switch and the charging power switch are connected between the third detection terminal and the second detection terminal, and are collectively referred to as a charge / discharge switch. The circuit further includes a logic circuit and an overcurrent detection module. The logic circuit generates a charging control signal or a discharge control signal based on a current detection signal output by the overcurrent detection module. The discharge control signal is output through the discharge control terminal DO, and the charging control signal is output through the discharge control terminal CO. The overcurrent detection module includes: a reference voltage generation circuit, which is used to acquire the voltage value of the first detection terminal VDD, acquire the temperature value of the charge / discharge switch, and find the corresponding reference voltage VR from a predetermined parameter table based on the acquired voltage value of the first detection terminal VDD and the temperature value of the charge / discharge switch, and output the reference voltage VR through its output terminal; a comparator, whose first input terminal receives the reference voltage VR output by the reference voltage generation circuit, and whose second input terminal acquires the voltage of the second detection terminal VM, the comparator is used to compare the magnitude of the reference voltage VR and the voltage of the second detection terminal VM, and output a corresponding current detection signal through its output terminal based on the comparison result.

[0011] According to another aspect of the present invention, a battery protection system is provided, comprising: a battery cell; a charging power switch and a discharging power switch; and a battery protection circuit. The battery protection circuit includes a second detection terminal connected to the negative terminal of the battery, a third detection terminal connected to the negative terminal of the battery cell, a first detection terminal connected to the positive terminal of the battery cell, a discharge control terminal connected to the control terminal of the discharge power switch, and a charging control terminal connected to the control terminal of the charging power switch. The discharge power switch and the charging power switch are connected between the third detection terminal and the second detection terminal, and are collectively referred to as a charge / discharge switch. The system further includes a logic circuit and an overcurrent detection module. The logic circuit generates a charging control signal or a discharging control signal based on a current detection signal output by the overcurrent detection module. The discharging control signal is output through the discharging control terminal DO, and the charging control signal is output through the discharging control terminal CO. The overcurrent detection module includes: a reference voltage generation circuit, which is used to acquire the voltage value of the first detection terminal VDD, acquire the temperature value of the charge / discharge switch, and find the corresponding reference voltage VR from a predetermined parameter table based on the acquired voltage value of the first detection terminal VDD and the temperature value of the charge / discharge switch, and output the reference voltage VR through its output terminal; a comparator, whose first input terminal receives the reference voltage VR output by the reference voltage generation circuit, and whose second input terminal acquires the voltage of the second detection terminal VM, the comparator is used to compare the magnitude of the reference voltage VR and the voltage of the second detection terminal VM, and output a corresponding current detection signal through its output terminal based on the comparison result.

[0012] Compared with existing technologies, this invention does not require a current sampling resistor R1 to obtain current detection information (or current sampling information). Instead, it uses the voltage at the detection terminal VM as the current detection information. Furthermore, as the cell voltage changes and the temperature of the discharge power switch FET1 and the charging power switch FET2 changes, the corresponding overcurrent detection voltage threshold VR is found from a predetermined parameter table. In this way, not only can high-precision charge and discharge overcurrent detection be achieved, but also the printed circuit board area can be saved and energy consumption reduced. [Attached Image Description]

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0014] Figure 1 This is a circuit diagram of a battery protection system in the prior art;

[0015] Figure 2This is a circuit diagram of the battery protection system in one embodiment of the present invention;

[0016] Figure 3 This is a circuit diagram of the discharge overcurrent detection module in the battery protection circuit of the present invention in one embodiment;

[0017] Figure 4 This is a circuit diagram of a battery protection circuit in one embodiment of the present invention.

Detailed Implementation Methods

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places throughout this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms "connected," "linked," and "connected" used herein to indicate electrical connection refer to direct or indirect electrical connection.

[0020] As mentioned in the background section, directly using the voltage at the detection terminal VM as the current sampling information leads to inaccurate current detection. This is because the voltage at the detection terminal VM reflects the voltage drop across the discharge power switch FET1 and the charging power switch FET2. During normal discharge, the voltage at the detection terminal VM is equal to I * Ron, where I is the discharge current and Ron is the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2. Generally, the gate voltages of the discharge power switch FET1 and the charging power switch FET2 are the cell voltages. When cell BAT1 discharges, the cell voltage gradually decreases; when cell BAT1 charges, the cell voltage gradually increases. Therefore, the cell voltage may change. When the cell voltage changes, the gate voltages of the discharge power switch FET1 and the charging power switch FET2 also change accordingly, and the on-resistances of the discharge power switch FET1 and the charging power switch FET2 change with their gate voltages. When a constant voltage VR is used as the voltage threshold for discharge overcurrent detection (i.e., a constant reference voltage VR is compared with the voltage at the detection terminal VM; when the voltage at the detection terminal VM exceeds this constant reference voltage VR, it is considered that a discharge overcurrent has been detected, and a corresponding discharge prohibition operation is performed), the actual corresponding discharge overcurrent detection current threshold is Ith = VR / Ron, where VR is the aforementioned constant reference voltage, and Ron is the sum of the on-resistances of the discharge power switch FET1 and the charging power switch FET2. Ron changes with the gate voltages of the discharge power switch FET1 and the charging power switch FET2. Generally, the gate voltages of the discharge power switch FET1 and the charging power switch FET2 are driven by the cell voltage. As cell BAT1 discharges, its cell voltage decreases; as cell BAT1 is charged, its cell voltage increases. In addition, as the temperature of the discharge power switch FET1 and the charging power switch FET2 changes, their on-resistance Ron also changes. When Ron changes, the discharge overcurrent detection current threshold Ith changes accordingly. In practical applications, it is best to keep the discharge overcurrent detection current threshold Ith constant.

[0021] Therefore, the present invention provides an overcurrent detection module that does not require the use of Figure 1 The current sampling resistor R1 is used to obtain current detection information, which can also save a chip pin VL (such as...). Figure 1(As shown in the diagram); instead, it uses the voltage of the detection terminal VM as the current detection information, and as the cell voltage changes and the temperature of the discharge power switch FET1 and the charging power switch FET2 changes, it finds the corresponding overcurrent detection voltage threshold VR from a predetermined parameter table, thereby achieving a precise overcurrent detection current threshold Ith. This overcurrent detection current threshold Ith does not change with the cell voltage or the temperature of the discharge power switch FET1 and the charging power switch FET2. In this way, not only can high-precision overcurrent detection be achieved, but also the printed circuit board area can be saved and energy consumption can be reduced.

[0022] Please refer to Figure 2 As shown, it is a circuit diagram of the battery protection system in one embodiment of the present invention. Figure 2 The battery protection system shown includes battery cell BAT1, battery protection circuit (or battery protection chip) 110, charging power switch 120, and discharging power switch 130. Discharging power switch 130 and charging power switch 120 are connected in series between the negative terminal B- of battery cell BAT1 and the negative terminal P- of the battery, and the positive terminal B+ of battery cell BAT1 is directly connected to the positive terminal P+ of the battery.

[0023] The charging power switch 120 includes a charging switch transistor and a diode (not shown) parasitic within it. In one embodiment of the invention, the charging switch transistor is an NMOS (N-channel Metal Oxide Semiconductor) field-effect transistor FET2. The discharging power switch 130 includes a discharging switch transistor and a diode (not shown) parasitic within it. In one embodiment of the invention, the discharging switch transistor is an NMOS field-effect transistor FET1. The drains of NMOS transistor FET1 and NMOS transistor FET2 are connected. The source of NMOS transistor FET1 is connected to the negative terminal B- of the battery cell, and the source of NMOS transistor FET2 is connected to the negative terminal P- of the battery.

[0024] The battery protection circuit 110 includes three detection terminals (or connection terminals) and two control terminals. The three detection terminals are the battery cell positive terminal B+ detection terminal VDD, the battery cell negative terminal B- detection terminal G, and the battery negative terminal P- detection terminal VM. The two control terminals are the charging control terminal CO and the discharging control terminal DO. Specifically, the detection terminal VDD is connected to the battery cell positive terminal B+, the detection terminal G is connected to the battery cell negative terminal B-, and the detection terminal VM is connected to the battery negative terminal P-. The charging control terminal CO is connected to the control terminal of the charging power switch 120 (i.e., the gate of the NMOS transistor FET2), and the discharging control terminal DO is connected to the control terminal of the discharging power switch 130 (i.e., the gate of the NMOS transistor FET1).

[0025] The battery protection circuit 110 provides charging and discharging protection for cell BAT1 by controlling the on and off states of NMOS transistors FET1 and FET2. Under normal conditions, the battery protection circuit 110 controls both NMOS transistors FET1 and FET2 to be on simultaneously, allowing for both charging and discharging. In the event of a charging anomaly, the battery protection circuit 110 controls NMOS transistor FET2 to be off, thus cutting off the charging circuit, but discharging is still possible. In the event of a discharging anomaly, the battery protection circuit 110 controls NMOS transistor FET1 to be off, thus cutting off the discharging circuit, but charging is still possible.

[0026] Please refer to Figure 3 As shown, it is a circuit diagram of the discharge overcurrent detection module in the battery protection circuit of the present invention in one embodiment.

[0027] like Figure 3 As shown, the discharge overcurrent detection module in the battery protection circuit of the present invention includes a reference voltage generation circuit 310 and a comparator Comp. Figure 3 The discharge overcurrent detection module shown performs discharge overcurrent detection by sampling the voltage of the second detection terminal VM. For ease of description, the charging power switch 120 and the discharging power switch 130 are collectively referred to as the charge-discharge switch in the following text; the sum of the on-resistances of the charging power switch 120 and the discharging power switch 130 is called the on-resistance of the charge-discharge switch.

[0028] The reference voltage generation circuit 310 is used to acquire the voltage value of the first detection terminal VDD, acquire the temperature value of the charge / discharge switch, and find the corresponding reference voltage VR from a predetermined parameter table based on the acquired voltage value of the first detection terminal VDD and the temperature value of the charge / discharge switch, and output the reference voltage VR through its output terminal. The reference voltage VR can also be referred to as the voltage threshold VR for discharge overcurrent detection.

[0029] The first input terminal of comparator Comp is connected to the output terminal of the reference voltage generation circuit 310 to receive the reference voltage VR output by the reference voltage generation circuit 310. Its second input terminal is connected to the second detection terminal VM to obtain the voltage of the second detection terminal VM. The comparator Comp is used to compare the magnitude of the reference voltage VR output by the reference voltage generation circuit 310 and the voltage of the second detection terminal VM, and based on the comparison result, outputs a corresponding current detection signal (or discharge overcurrent detection signal) EDI through its output terminal. Figure 3 In the specific embodiment shown, the first input terminal and the second input terminal of the comparator Comp are its negative input terminal and its positive input terminal, respectively.

[0030] Please refer to Table 1 below, which is a table of predetermined parameters in one embodiment of the present invention. Figure 1 The predetermined parameter table shown includes multiple segments (or ranges) of the voltage value of the first detection terminal VDD, multiple segments (or ranges) of the temperature value of the charge / discharge switch, and multiple values ​​of the reference voltage VR. Each segment of the voltage value of the first detection terminal VDD and any combination of any segment of the temperature value of the corresponding charge / discharge switch corresponds to a value of the reference voltage VR. The reference voltage VR mimics the change in the on-resistance of the charge / discharge switch (i.e., the sum of the on-resistances of the charging power switch 120 and the discharging power switch 130) as the voltage of the first detection terminal VDD (which reflects the gate drive voltage when the charge / discharge switches 120 and 130 are turned on) changes, and also mimics the change in the on-resistance of the charge / discharge switch as its temperature changes.

[0031] 2v≤VDD<2.5v 2.5v≤VDD<3v 3v≤VDD<3.5v 3.5v≤DD<4v 4v≤VDD<4.5v T<-30℃ 34.2mV 27.5mV 25.8mV 24.3mV 23.2mV -30℃≤T<-20℃ 36.0mV 28.9mV 27.2mV 25.6mV 24.5mV -20℃≤T<-10℃ 37.8mV 30.4mV 28.5mV 26.9mV 25.7mV -10℃≤T<0℃ 39.6mV 31.8mV 29.9mV 28.1mV 26.9mV 0℃≤T<10℃ 40.5mV 32.5mV 30.6mV 28.8mV 27.5mV 10℃≤T<20℃ 43.2mV 34.7mV 32.6mV 30.7mV 29.3mV 20℃≤T<30℃ 45.0mV 36.2mV 34.0mV 32.0mV 30.6mV 30℃≤T<40℃ 46.8mV 37.6mV 35.3mV 33.3mV 31.8mV 40℃≤T<50℃ 48.6mV 39.1mV 36.7mV 34.5mV 33.0mV 50℃≤T<60℃ 50.4mV 40.5mV 38.1mV 35.8mV 34.2mV 60℃≤T<70℃ 53.1mV 42.7mV 40.1mV 37.7mV 36.1mV 70℃≤T 54.0mV 43.4mV 40.8mV 38.4mV 36.7mV

[0032] Table 1

[0033] For example, when the voltage value of the first detection terminal VDD is 2V≤VDD<2.5V, and the temperature value of the charge / discharge switch is -30℃≤T<-20℃, the corresponding reference voltage VR is 36.0mV; when the voltage value of the first detection terminal VDD is 2.5V≤VDD<3V, and the temperature value of the charge / discharge switch is -10℃≤T<0℃, the corresponding reference voltage VR is 31.8mV.

[0034] Please refer to Table 2 below, which is a parameter table of one embodiment of the present invention. Figure 2 The parameter table shown includes multiple segments of the voltage value of the first detection terminal VDD, multiple segments of the temperature value of the charge / discharge switch, and multiple values ​​of the on-resistance of the charge / discharge switch. Each combination of a segment of the voltage value of the first detection terminal VDD and any segment of the corresponding temperature value of the charge / discharge switch corresponds to a value of the on-resistance of the charge / discharge switch. The multiple segments of the voltage value of the first detection terminal VDD in Tables 1 and 2 are consistent; the multiple segments of the temperature value of the charge / discharge switch in Tables 1 and 2 are also consistent.

[0035] 2v≤VG<2.5v 2.5v≤V<3v 3v≤VG<3.5v 3.5v≤V<4v 4v≤VG<4.5v T<-30℃ 34.2 mohm 27.5 mohm 25.8 mohm 24.3 mohm 23.2mohm -30℃≤T<-20℃ 36.0mohm 28.9 mohm 27.2 mohm 25.6 mohm 24.5 mohm -20℃≤T<-10℃ 37.8 mohm 30.4 mohm 28.5 mohm 26.9 mohm 25.7 mohm -10℃≤T<0℃ 39.6 mohm 31.8 mohm 29.9 mohm 28.1 mohm 26.9 mohm 0℃≤T<10℃ 40.5 mohm 32.5 mohm 30.6 mohm 28.8 mohm 27.5 mohm 10℃≤T<20℃ 43.2 mohm 34.7 mohm 32.6 mohm 30.7 mohm 29.3 mohm 20℃≤T<30℃ 45.0 mohm 36.2 mohm 34.0mohm 32.0 mohm 30.6 mohm 30℃≤T<40℃ 46.8 mohm 37.6 mohm 35.3 mohm 33.3 mohm 31.8 mohm 40℃≤T<50℃ 48.6 mohm 39.1 mohm 36.7 mohm 34.5 mohm 33.0 mohm 50℃≤T<60℃ 50.4 mohm 40.5 mohm 38.1 mohm 35.8 mohm 34.2 mohm 60℃≤T<70℃ 53.1 mohm 42.7 mohm 40.1 mohm 37.7 mohm 36.1 mohm 70℃≤T 54.0mohm 43.4 mohm 40.8 mohm 38.4 mohm 36.7 mohm

[0036] Table 2

[0037] If, according to Tables 1 and 2, each segment of the voltage value of the first detection terminal VDD and any segment of the temperature value of the corresponding charge / discharge switch are combined, the corresponding reference voltage VR and the on-resistance of the corresponding charge / discharge switch are obtained, then the current threshold Ith for discharge overcurrent detection is a constant 1A. Therefore, the effect of compensating for changes in the gate voltage and temperature of the charge / discharge switch is achieved, thus improving the accuracy of the discharge overcurrent detection threshold. In this way, the reference voltage generation circuit 310 finds the voltage value range (or segment) of the first detection terminal VDD from the predetermined parameter table (i.e., Table 1) based on the obtained voltage value of the first detection terminal VDD, and finds the temperature value range (or segment) of the charge / discharge switch from the predetermined parameter table (i.e., Table 1) based on the obtained temperature value of the charge / discharge switch, thereby finding the corresponding reference voltage VR from the predetermined parameter table (i.e., Table 1) and outputting the reference voltage VR through its output terminal.

[0038] exist Figure 3 In the specific embodiment shown, the reference voltage generation circuit 310 includes a memory 311, a voltage analog-to-digital converter 312, a temperature analog-to-digital converter 313, a temperature sensor 314, a controller 315, and a digital-to-analog converter 316.

[0039] The input terminal of the voltage analog-to-digital converter 312 is connected to the first detection terminal VDD. The voltage analog-to-digital converter 312 is used to convert the voltage value of the first detection terminal VDD into a corresponding digital signal VD[2:0], and outputs the digital signal VD[2:0] corresponding to the voltage value of the first detection terminal VDD through its output terminal. Please refer to Table 3 below, which shows the encoding method of the voltage analog-to-digital converter 312 in one embodiment of the present invention.

[0040] Table 3 shows multiple segments of the voltage value of the first detection terminal VDD and multiple digital signals VD[2:0]. Each segment of the voltage value of the first detection terminal VDD corresponds to a digital signal VD[2:0]. Where VD[2:0] = '111', the corresponding segment (or range) of the first detection terminal VDD is NA, indicating it is not applicable, meaning VD[2:0] = '111' will not occur. Table 3 is only one example of implementation; obviously, any other encoding form or other correspondence can be used. More bits can also be used for more precise quantization of the voltage of the first detection terminal VDD (i.e., the cell voltage). The digital signals VD[2:0] in Table 3 are binary numbers, but in actual implementation, they can also be other base numbers.

[0041] VD[2:0] VDD range 000 VDD<2v 001 2v≤VDD<2.5v 010 2.5v≤VDD<3v 011 3v≤VDD<3.5v 100 3.5v≤VDD<4v 101 4v≤VDD<4.5v 110 4.5V≤VDD 111 NA

[0042] Table 3

[0043] Temperature sensor 314 is used to sense the temperature of the charge / discharge switch and outputs a corresponding temperature value (which is an analog voltage signal) through its output terminal.

[0044] The input terminal of the temperature analog-to-digital converter 313 is connected to the output terminal of the temperature sensor 314. The temperature analog-to-digital converter 313 is used to convert the temperature value output by the temperature sensor 314 into a corresponding digital signal TD[3:0], and outputs the digital signal TD[3:0] corresponding to the temperature value of the charge-discharge switch through its output terminal.

[0045] Please refer to Table 4 below, which shows the encoding method of the temperature analog-to-digital converter 313 in one embodiment of the present invention.

[0046]

[0047]

[0048] Table 4

[0049] Table 4 shows multiple segments of the temperature value of the charge / discharge switch and multiple digital signals TD[3:0]. Each segment of the temperature value corresponds to one digital signal TD[3:0]. Table 4 is just one example of implementation; obviously, any other encoding form or other correspondence can be used. More bits can also be used to quantify the temperature information of the charge / discharge switch more precisely. The digital signals TD[3:0] in Table 4 are binary numbers, but in actual implementation, they can also be in other bases.

[0050] The memory 311 stores the corresponding information in the predetermined parameter table (i.e., Table 1).

[0051] The first input terminal of the controller 315 is connected to the output terminal of the voltage analog-to-digital converter 312, its second input terminal is connected to the output terminal of the temperature analog-to-digital converter 313, and its third input terminal is connected to the memory 311. Based on the digital signal (or voltage code) VD[2:0] output by the voltage analog-to-digital converter 312 corresponding to the voltage value of the first detection terminal VDD and the digital signal (or temperature code) TD[3:0] output by the voltage analog-to-digital converter 312 corresponding to the temperature value of the charge / discharge switch, the controller 315 searches for the digital code (or digital signal) MD[N:0] of the corresponding reference voltage VR from the predetermined parameter table (i.e., Table 1) stored in the memory 311, and outputs the digital code of the reference voltage VR through its output terminal. Here, N is a positive integer, indicating that the number of bits in the digital code MD[N:0] is N+1. The larger N is, the more refined the voltage value can be identified.

[0052] The digital-to-analog converter 316 generates the analog voltage value (or voltage signal) V_mimic corresponding to the reference voltage CR based on the digital code MD[N:0] output by the controller 315, and provides it to the comparator Comp. The comparator Comp compares the VM voltage with the magnitude of V_mimic. If the VM voltage is greater than the V_mimic voltage, the output signal (or current detection signal) EDI becomes high, indicating that a discharge overcurrent condition has occurred; if the VM voltage is less than the V_mimic voltage, the output signal EDI is low, indicating that a non-discharge overcurrent condition has occurred.

[0053] The preceding text is about Figure 3 This document describes the circuit structure and operation of the discharge overcurrent detection module in the battery protection circuit shown. It should be noted that the charging overcurrent detection module in the battery protection circuit of this invention has a similar structure and operating principle to the discharging overcurrent detection module; therefore, a detailed description of the charging overcurrent detection module in the battery protection circuit of this invention will not be provided here. Please refer to [link / reference needed]. Figure 4 As shown, it is a circuit diagram of the battery protection circuit in one embodiment of the present invention. Figure 4 The battery protection circuit shown includes a voltage detection module 410, an overcurrent detection module 420, and a logic module 430. The overcurrent detection module 420 includes a charging overcurrent detection module and, for example, a... Figure 3 The discharge overcurrent detection module is shown. The voltage detection module 410 can be implemented using existing technology. If the current detection signal EDI output by the overcurrent detection module 420 goes high, the logic module 430 can time it. If the discharge overcurrent protection delay time is exceeded, the discharge control terminal DO is controlled to go low, controlling the NMOS transistor FET1 to turn off, thus prohibiting discharge; if the charging overcurrent protection delay time is exceeded, the charging control terminal CO is controlled to go low, controlling the NMOS transistor FET2 to turn off, thus prohibiting charging. Alternatively, the logic circuit 430 generates a charging control signal or a discharge control signal based on the current detection signal output by the overcurrent detection module 420. The discharge control signal is output through the discharge control terminal DO, and the charging control signal is output through the discharge control terminal CO.

[0054] In one embodiment, heat can be conducted through a metal sheet on the underside of the chip package, or a large sheet of metal can be added to the printed circuit board and the temperature information of the charge / discharge switch can be transmitted to the temperature sensor 314 inside the chip through the pins of the package.

[0055] It should be noted that, according to the principle of the present invention, the multiple segments of the voltage value of the first detection terminal VDD and the multiple segments of the temperature value of the charge / discharge switch can be divided more finely to achieve better results.

[0056] It should be noted that the principle of this invention can be applied not only to single-cell lithium battery protection circuits, but also to protection circuits for dual-cell or multi-cell series-connected lithium batteries. Dual-cell or multi-cell series-connected lithium battery protection circuits simply add voltage detection functionality to the other cells, and can still be implemented according to the principle of this invention.

[0057] In summary, this invention provides an overcurrent detection module, a battery protection circuit, and a system that do not require the use of Figure 1 The current sampling resistor R1 is used to obtain current detection information, which can also save a chip pin VL (such as...). Figure 1 (As shown in the diagram); instead, it uses the voltage of the detection terminal VM as the current detection information, and as the cell voltage changes and the temperature of the discharge power switch FET1 and the charging power switch FET2 changes, it finds the corresponding overcurrent detection voltage threshold VR from a predetermined parameter table, thereby achieving a precise overcurrent detection current threshold Ith. This overcurrent detection current threshold Ith does not change with the cell voltage, nor with the temperature of the discharge power switch FET1 and the charging power switch FET2. In this way, not only can high-precision charge and discharge overcurrent detection be achieved, but also the printed circuit board area can be saved and energy consumption reduced.

[0058] In this invention, terms such as “connection,” “linked,” “connected,” and “joined” that indicate electrical connection, unless otherwise specified, indicate direct or indirect electrical connection.

[0059] It should be noted that any modifications made by those skilled in the art to the specific embodiments of the present invention do not depart from the scope of the claims. Accordingly, the scope of the claims is not limited to the foregoing specific embodiments.

Claims

1. An overcurrent detection module, characterized in that, It includes: A reference voltage generation circuit is used to obtain the voltage value of the first detection terminal VDD, obtain the temperature value of the charge-discharge switch, find the corresponding reference voltage VR from a predetermined parameter table based on the obtained voltage value of the first detection terminal VDD and the temperature value of the charge-discharge switch, and output the reference voltage VR through its output terminal. The comparator receives the reference voltage VR output by the reference voltage generation circuit at its first input terminal and acquires the voltage of the second detection terminal VM at its second input terminal. The comparator compares the magnitudes of the reference voltage VR and the voltage of the second detection terminal VM, and outputs a corresponding current detection signal based on the comparison result. The predetermined parameter table includes multiple segments of the voltage value of the first detection terminal VDD, multiple segments of the temperature value of the charge-discharge switch, and multiple values ​​of the reference voltage VR. Each segment of the voltage value of the first detection terminal VDD and any segment of the temperature value of the corresponding charge-discharge switch correspond to a value of the reference voltage VR. The reference voltage generating circuit, based on the acquired voltage value of the first detection terminal VDD, finds the voltage segment containing the acquired voltage value of the first detection terminal VDD from the predetermined parameter table, and based on the acquired temperature value of the charge / discharge switch, finds the temperature segment containing the acquired temperature value of the charge / discharge switch from the predetermined parameter table, thereby finding the corresponding reference voltage VR from the predetermined parameter table, and outputs the reference voltage VR through the output terminal of the reference voltage generating circuit. The reference voltage generation circuit includes: A voltage analog-to-digital converter (ADC) is provided, with its input terminal connected to the first detection terminal VDD. The ADC is used to convert the voltage value of the first detection terminal VDD into a corresponding digital signal and output a digital signal corresponding to the voltage value of the first detection terminal VDD through its output terminal. A temperature sensor is used to sense the temperature of the charge / discharge switch and output the corresponding temperature value through its output terminal. A temperature analog-to-digital converter, the input of which is connected to the output of the temperature sensor, is used to convert the temperature value output by the temperature sensor into a corresponding digital signal, and outputs a digital signal corresponding to the temperature value of the charge-discharge switch through its output. A memory that stores the corresponding information in the predetermined parameter table; The controller has a first input terminal connected to the output terminal of the voltage analog-to-digital converter, a second input terminal connected to the output terminal of the temperature analog-to-digital converter, and a third input terminal connected to the memory. Based on the digital signal output by the voltage analog-to-digital converter corresponding to the voltage value of the first detection terminal VDD and the digital signal output by the temperature analog-to-digital converter corresponding to the temperature value of the charge / discharge switch, the controller looks up the digital signal of the corresponding reference voltage VR from the predetermined parameter table and outputs the digital signal of the reference voltage VR through its output terminal. The digital-to-analog converter generates an analog voltage value corresponding to the reference voltage VR based on the digital signal output by the controller, and outputs the analog voltage value of the reference voltage VR to the first input terminal of the comparator through its output terminal.

2. The overcurrent detection module according to claim 1, characterized in that, The reference voltage VR mimics the change in the on-resistance of the charge / discharge switch as the voltage at the first detection terminal VDD changes, and also mimics the change in the on-resistance of the charge / discharge switch as its temperature changes.

3. The overcurrent detection module according to claim 1, characterized in that, The metal sheet on the underside of the chip is used for heat conduction so that the temperature information of the charge / discharge switch can be imported into the temperature sensor inside the chip. or A metal sheet is added to the printed circuit board, and then the temperature information of the charge / discharge switch is imported into the temperature sensor inside the chip through the package pins.

4. A battery protection circuit, comprising a second detection terminal connected to the negative terminal of the battery, a third detection terminal connected to the negative terminal of the battery cell, a first detection terminal connected to the positive terminal of the battery cell, a discharge control terminal connected to the control terminal of a discharge power switch, and a charging control terminal connected to the control terminal of a charging power switch, wherein, The discharge power switch and the charging power switch are connected between the third detection terminal and the second detection terminal. The discharge power switch and the charging power switch are collectively referred to as the charge-discharge switch. Its characteristic is that it further includes logic circuitry and an overcurrent detection module as described in any one of claims 1-3. The logic circuit generates a charging control signal or a discharging control signal based on the current detection signal output by the overcurrent detection module. The discharging control signal is output through the discharging control terminal, and the charging control signal is output through the charging control terminal.

5. A battery protection system, characterized in that, It includes: Battery cell; Charging power switch and discharging power switch; The battery protection circuit as described in claim 4.

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