CN203299255U - Voltage detection circuit formed by connecting a plurality of electric core units in series and battery protection system - Google Patents

Abstract

The utility model provides a voltage detection circuit and a battery protection system in which a plurality of battery cell units are connected in series, the voltage detection circuit includes a voltage detection module, a storage module and a logic judgment module, and the voltage detection module periodically detects each battery cell one by one unit voltage, and compare the detected voltage of each cell unit with the high-voltage threshold and/or low-voltage threshold to output whether the voltage detection signal is abnormal; the storage module is used to store the current detection cycle, the voltage detection module output The voltage detection signal corresponding to each battery cell unit; the logical determination module performs logical determination according to the voltage detection signals corresponding to all the battery cell units stored in the storage module in the current detection cycle, if at least one voltage detection signal is an abnormal voltage detection signal , the logic judgment module outputs a protection signal. Compared with the prior art, the voltage detection circuit in the utility model can improve the matching of the protection voltage threshold in the battery detection circuit.

Description

Voltage detection circuit and battery protection system with multiple battery cells connected in series

【Technical field】

The utility model relates to a power management circuit, in particular to a voltage detection circuit and a battery protection system in which a plurality of electric core units are connected in series. the

【Background technique】

Due to the advantages of high energy, high battery voltage, wide working range and long storage life, lithium-ion batteries have been widely used in military and civilian small electrical appliances, such as mobile phones, portable computers, video cameras, cameras, etc., partially replacing traditional batteries. Battery. However, due to its physical characteristics, lithium batteries have very strict requirements on charging current, discharging current, voltage and temperature during use. Once exceeded, it will have serious consequences in terms of safety and life. Therefore, during the charging and discharging process of lithium-ion batteries, key parameters such as overcharge voltage, overdischarge voltage, charge limit current, and discharge limit current need to be monitored and controlled to prevent excessive battery loss and ensure safety during use. the

For a multi-cell lithium battery (or cell unit) set in series, the matching battery protection circuit needs to detect the voltage status of each cell unit to determine whether any cell unit has a charge overvoltage state or a discharge undervoltage state. the

Please refer to FIG. 1 , which is a schematic diagram of a battery protection system in the prior art in which multiple cells are connected in series. The battery protection system includes a battery pack 110 , a voltage detection circuit 120 , a control circuit 130 and a switch combination circuit 140 . the

The battery pack 110 includes a plurality of battery cell units B1, B2, Bn-1 and Bn connected in series in sequence, the positive pole of the uppermost battery cell unit Bn is connected to the positive terminal P+ of the battery, and the negative pole of the lowest battery cell unit B1 passes through the The switch combination circuit 140 is connected to the negative terminal P- of the battery. the

The voltage detection circuit 120 includes a voltage detection module 122 and a comparison module 124 . The voltage detection module 122 includes a plurality of voltage detection units, which are voltage detection unit 1, voltage detection unit 2, ..., voltage detection unit n-1 and voltage detection unit n, wherein each voltage detection unit corresponds to a voltage detection unit core unit to detect the voltage of the corresponding battery cell unit. When the battery protection system is in the charging state (that is, the charger is connected between the positive connection terminal P+ of the battery and the negative connection terminal P- of the battery to charge the battery pack 110), the comparison module 124 compares each voltage detection unit The detected voltages of the n battery cells are compared with a preset high voltage protection threshold to determine whether the battery pack 110 is in a charging overvoltage state. Specifically, when the battery protection system is in the charging state, if the detected voltages of all battery cells are less than the high voltage protection threshold, the comparison module 124 outputs a normal charging voltage signal; When the voltage is greater than the high voltage protection voltage threshold, the comparison module 124 outputs an abnormal charging signal (ie, a charging overvoltage protection signal). When the battery protection system is in the discharge state (that is, the load is connected between the battery positive connection terminal P+ and the battery negative connection terminal P-, and the battery pack 110 supplies power to the load), the comparison module 124 connects each voltage detection unit The detected voltages of the n battery cells are compared with a preset low voltage protection threshold to determine whether the battery pack 110 is in a discharge undervoltage state. Specifically, when the battery protection system is in the discharge state, if the detected voltages of all battery cells are greater than the undervoltage protection threshold, the comparison module 124 outputs a normal discharge voltage signal; if at least one battery cell If the voltage is less than the undervoltage protection threshold, the comparison module 124 outputs an abnormal discharge voltage signal (that is, a discharge undervoltage protection signal). the

The switch combination circuit 140 includes NMOS transistors MN1 and MN2, the source of the NMOS transistor MN1 is connected to the negative electrode of the battery unit B1, the drain of the NMOS transistor MN1 is connected to the drain of the NMOS transistor MN2, and the NMOS The source of the transistor MN2 is connected to the battery negative terminal P−, the gate of the NMOS transistor MN1 is the discharge control terminal DO, and the gate of the NMOS transistor MN2 is the charge control terminal CO. the

The control circuit 130 outputs a discharge control signal to the discharge control terminal DO according to the signal output by the comparison module 124 , and outputs a charge control signal to the charge control terminal CO. When the comparison module 124 outputs an abnormal charging signal, the control circuit 130 controls the NMOS transistor MN2 to be turned off and the NMOS transistor MN1 is turned on, that is, the charging circuit is turned off; when the comparison module 124 outputs an abnormal discharge signal, the control circuit 130 The circuit 130 controls the NMOS transistor MN2 to turn on and the NMOS transistor MN1 to turn off, that is, to turn off the discharge circuit. the

Since each cell unit in Figure 1 corresponds to an independent voltage detection unit, the respective deviations (offsets) of multiple voltage detections will cause the matching of each cell protection voltage threshold (for example, high voltage threshold and low voltage threshold) to decrease. Dispersion becomes larger. In addition, multiple voltage detection units are required in Fig. 1, and many devices are required, and the occupied area is relatively large. the

Therefore, it is necessary to provide an improved technical solution to overcome the above problems. the

【Content of utility model】

The purpose of the utility model is to provide a voltage detection circuit and a battery protection system in which multiple battery cells are connected in series, which can not only detect the voltage of multiple battery cells, but also determine whether any battery cells are in an overcharged state or discharge undervoltage state, and can also improve the matching of the protection voltage threshold in the battery detection circuit. the

In order to solve the above problems, according to one aspect of the utility model, the utility model provides a voltage detection circuit, which is used for voltage detection of a plurality of serially connected battery cells, which is characterized in that it includes a voltage detection module, a storage module And a logic judgment module, the voltage detection module periodically detects the voltage of each battery cell unit one by one, and compares the detected voltage of each battery cell unit with the high voltage threshold and/or the low voltage threshold to output whether it is abnormal The voltage detection signal; the storage module is used to store the voltage detection signal corresponding to each cell unit output by the voltage detection module in the current detection cycle; the logic judgment module is based on all the cells stored in the storage module The unit performs logic judgment on the voltage detection signals corresponding to the current detection cycle, and if at least one voltage detection signal is an abnormal voltage detection signal, the logic judgment module outputs a protection signal. the

Further, when charging, the voltage detection module detects the voltage of each battery unit one by one within a detection cycle, and compares the detected voltage of each battery unit with the high voltage threshold to output whether it is abnormal The charging voltage detection signal; the storage module stores the charging voltage detection signal corresponding to each battery unit output by the voltage detection module in the current detection cycle; the logic determination module stores all the battery cells according to the storage module The charging voltage detection signal corresponding to the current detection cycle is logically judged. If at least one charging voltage detection signal is an abnormal charging voltage detection signal, the logic judgment module outputs a charging overvoltage protection signal. When discharging, the voltage detection module Detect the voltage of each cell unit one by one in a detection cycle, and compare the detected voltage of each cell unit with the low-voltage threshold to output a discharge voltage detection signal whether it is abnormal; the storage module stores the current detection During the period, the discharge voltage detection signal corresponding to each cell unit output by the voltage detection module; the logic determination module performs logic based on the discharge voltage detection signals corresponding to all cell units stored in the storage module in the current detection cycle Judging, if at least one discharge voltage detection signal is an abnormal discharge voltage detection signal, the logic judgment module outputs a discharge undervoltage protection signal. the

Further, each cell unit corresponds to a clock signal, and the cycle of the clock signal corresponding to each cell unit is the same as the detection cycle, and within one detection cycle, the clock signal corresponding to each cell unit The active levels do not overlap with each other, and the voltage detection circuit also includes a control module. When the clock signal corresponding to a cell unit is at an active level, the control module connects the voltage detection module to the cell unit, so that The voltage detection module detects the battery unit; when the clock signal corresponding to a battery unit is at an invalid level, the control module prevents the voltage detection module from being connected to the battery unit. the

Further, the control module includes a plurality of pairs of switches, each cell unit corresponds to a pair of switches, each pair of switches includes a first switch and a second switch, and the first switch in each pair of switches is connected to the switch corresponding to the pair of switches. Between the positive pole of the battery unit and the first connection terminal of the voltage detection unit, the second switch in each pair of switches is connected between the negative pole of the battery unit corresponding to the pair of switches and the second connection terminal of the voltage detection unit, And the control terminal of each pair of switches is connected to the clock signal corresponding to the cell unit corresponding to the pair of switches. When the clock signal corresponding to a cell unit is at an active level, the pair of switches corresponding to the cell unit are both turned on. ; When the clock signal corresponding to a cell unit is at an inactive level, a pair of switches corresponding to the cell unit are both turned off. the

Further, the voltage detection module includes a voltage/current conversion module, a current comparison module and a reference current module, the voltage/current conversion module converts the voltage of the battery unit into a current; the reference current module is used to generate The first reference current corresponding to the high-voltage threshold and/or the second reference current corresponding to the low-voltage threshold; the current comparison module is used to compare the converted current output by the voltage/current conversion module with the corresponding high-voltage threshold generated by the reference current module The first reference current and/or the second reference current corresponding to the low-voltage threshold are compared to output a voltage detection signal indicating whether it is abnormal. the

Further, when charging, the reference current module generates a first reference current corresponding to the high-voltage threshold; the voltage/current conversion module converts the voltage of each battery cell unit into current one by one within a detection cycle, and converts each The conversion current corresponding to the voltage of each cell unit is compared with the first reference current to output a charging voltage detection signal whether it is abnormal; when discharging, the reference current module generates a second reference current corresponding to the low voltage threshold; The voltage/current conversion module converts the voltage of each cell unit one by one into a current within a detection cycle, and compares the converted current corresponding to the voltage of each cell unit with the second reference current to output whether Abnormal discharge voltage detection signal. the

Furthermore, the storage module includes a plurality of storage units, each cell unit corresponds to a storage unit, the clock terminal of each storage unit is connected to the clock signal corresponding to the corresponding cell unit, and the input terminal of each storage unit It is connected with the output end of the described current comparison module, and its output end is connected with the described logic judgment module, when the effective level of the clock signal received by the clock end of a storage unit ends, it latches the input end received by it. A voltage detection signal at the output terminal of the current comparison module. the

Furthermore, in addition to the first connection terminal and the second connection terminal, the voltage/current conversion module also includes an output terminal, a first resistor RC, a second resistor RA, a third resistor RB, a first operational amplifier OA1 and a first The PMOS transistor MP1, the second resistor RA and the third resistor RB are sequentially connected in series between the first connection terminal and the second connection terminal; the first resistor RC and the first PMOS transistor are connected in series between the first connection terminal and the output terminal ; The positive input terminal of the operational amplifier is connected to the connection node between the second resistor RA and the third resistor RB, and its negative input terminal is connected to the connection node between the first PMOS transistor and the first resistor RC , the output end of which is connected to the gate of the first PMOS transistor. the

Still further, the reference current module includes a bandgap reference voltage, a second operational amplifier, a third NMOS transistor, a second PMOS transistor, a third PMOS transistor and a resistor R0, the second PMOS transistor and the third PMOS crystal The source is connected to the power supply terminal; the gate of the second PMOS transistor is connected to the gate of the third PMOS crystal; the gate of the second PMOS transistor is connected to its drain; the third NMOS transistor is connected in series with the resistor R0 Between the drain of the second PMOS transistor and the system ground, the drain of the third PMOS transistor MP3 is the output terminal of the reference current module; the non-inverting input terminal of the second operational amplifier is connected to the bandgap reference voltage, its negative phase input terminal is connected to the connection node between the third NMOS transistor and the variable resistor, its output terminal is connected to the gate of the third NMOS transistor, and the current output by the drain of the PMOS transistor MP3 is The reference current generated by the reference current module. the

According to another aspect of the utility model, the utility model provides a battery protection system, which includes a battery pack, a switch combination circuit, a control circuit and a voltage detection circuit. The battery pack includes a plurality of battery cells connected in series in sequence, one connection end of the uppermost battery cell unit is connected to the battery positive terminal, and one connection terminal of the lowest battery cell unit is connected to the battery negative terminal through the switch combination circuit. end. The switch combination circuit includes a charge control switch and a discharge control switch connected in series. The voltage detection circuit is used to detect the voltage of a plurality of sequentially connected battery cells, which includes a voltage detection module, a storage module and a logic judgment module, and the voltage detection module periodically detects the voltage of each battery cell unit one by one , and compare the detected voltage of each cell unit with the high-voltage threshold and/or the low-voltage threshold to output whether the voltage detection signal is abnormal; the storage module is used to store the current detection cycle, the voltage detection module The output voltage detection signal corresponding to each cell unit; the logic judgment module performs a logic judgment according to the voltage detection signals corresponding to all cell units stored in the storage module in the current detection cycle, if at least one voltage detection signal is abnormal When the voltage detection signal is detected, the logic judgment module outputs a protection signal. The control circuit controls the charge control switch or the discharge control switch to be turned off according to the protection signal output by the voltage detection circuit for charge or discharge protection. the

Compared with the prior art, the voltage detection circuit and the battery protection system with multiple battery cells connected in series in the utility model periodically detect the voltage of each battery cell one by one, which can not only realize the detection of multiple battery cells The voltage of the cell is detected to determine whether there is a cell unit in a charging overvoltage state or a discharging undervoltage state, and it can also improve the matching of the protection voltage threshold in the battery detection circuit. the

【Description of drawings】

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings that need to be used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention , for those skilled in the art, other drawings can also be obtained according to these drawings on the premise of not paying creative labor. in:

Fig. 1 is a schematic diagram of a battery protection system in series with multiple cell units in the prior art;

Fig. 2 is the circuit schematic diagram in an embodiment of the battery protection system in the utility model;

Figure 3 is a schematic diagram of the voltage detection circuit in Figure 2 in one embodiment; and

FIG. 4 is a waveform diagram of each clock signal in FIG. 3 . the

【Detailed ways】

In order to make the above purpose, features and advantages of the utility model more obvious and understandable, the utility model will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. the

Reference herein to "one embodiment" or "an embodiment" refers to a specific feature, structure or characteristic that may be included in at least one implementation of the present invention. "In one embodiment" appearing in different places in this specification does not all refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments. Unless otherwise specified, the words connected, connected, and joined in this document mean that they are electrically connected directly or indirectly. In this article, n is a natural number greater than 2, and multiple means two or more. Words such as connection, connection, and series in this article can be understood as indirect or direct connection, connection, and series. the

The voltage detection circuit and battery protection system with multiple battery cells connected in series provided by the utility model can periodically detect the voltage of each battery cell one by one, not only can realize the detection of the voltage of multiple battery cells, It is determined whether any cell unit is in a charge overvoltage state or a discharge undervoltage state, and the matching of the protection voltage threshold in the battery detection circuit can also be improved. the

Please refer to FIG. 2 , which is a schematic circuit diagram of an embodiment of the battery protection system in the present invention. The battery protection system includes a battery pack 210 , a switch combination circuit 220 , a control circuit 230 and a voltage detection circuit 240 . the

The battery pack 210 includes a plurality of battery cells B1, B2, ... Bn-1 and Bn connected in series in sequence, the positive pole of the uppermost battery cell unit Bn is connected to the positive terminal P+ of the battery, and the negative pole of the lowest battery cell unit B1 The switch combination circuit 220 is connected to the negative terminal P- of the battery. the

The voltage detection circuit 240 includes a voltage detection module 242 , a storage module 244 and a logic decision module 246 . The voltage detection module 242 periodically detects the voltage of each cell unit one by one, and compares the detected voltage of each cell unit with a high-voltage threshold and/or a low-voltage threshold to output a voltage detection signal indicating whether it is abnormal . The storage module 244 is used to store the voltage detection signal corresponding to each cell unit output by the voltage detection module 242 in the current detection cycle. The logic judgment module 246 makes a logic judgment according to the voltage detection signals corresponding to all the battery cells stored in the storage module 244 in the current detection cycle. If at least one voltage detection signal is an abnormal voltage detection signal, the logic judgment module 246 output protection signal. A specific implementation of the voltage detection circuit 240 will be described in FIG. 3 . the

The working process of the voltage detection circuit 240 will be described in detail below. the

When the battery protection system is in the charging state (that is, the charger is connected between the positive connection terminal P+ of the battery and the negative connection terminal P- of the battery to charge the battery pack 210), the voltage detection module 242 in a detection cycle The voltage of each cell unit is detected one by one, and the detected voltage of each cell unit is compared with the high voltage threshold to output a charging voltage detection signal whether it is abnormal. Specifically, when the voltage detection module 242 detects that the voltage of a cell unit is lower than the high voltage threshold, the voltage detection module 242 outputs a normal charging voltage detection signal, indicating that the charging voltage of the cell unit is normal; when the When the voltage detection module 242 detects that the voltage of a cell unit is greater than the high voltage threshold, the voltage detection module 242 outputs an abnormal charging voltage detection signal, indicating that the cell unit is overcharged. The storage module 244 stores the charging voltage detection signal corresponding to each battery cell output by the voltage detection module 242 in the current detection period. The logic judgment module 246 makes a logic judgment according to the charging voltage detection signals corresponding to all battery cells stored in the storage module 244 in the current detection cycle. If at least one charging voltage detection signal is an abnormal charging voltage detection signal, the logic The judging module 246 outputs a charging overvoltage protection signal, which means that the charging protection of the battery pack 210 is required. the

When the battery protection system is in the discharge state (that is, the load is connected between the battery positive connection terminal P+ and the battery negative connection terminal P-, and the battery pack 210 supplies power to the load), the voltage detection module 242 will The voltage of each cell unit is detected one by one, and the detected voltage of each cell unit is compared with the low-voltage threshold to output a discharge voltage detection signal whether it is abnormal. During implementation, when the voltage detection module 242 detects that the voltage of a cell unit is greater than the low-voltage threshold, the voltage detection module 242 outputs a normal discharge voltage detection signal, indicating that the discharge voltage of the cell unit is normal; When the voltage detection module 242 detects that the voltage of a cell unit is lower than the low voltage threshold, the voltage detection module 242 outputs an abnormal discharge voltage detection signal, indicating that the cell unit discharges undervoltage. The storage module 244 stores the discharge voltage detection signal corresponding to each cell unit output by the voltage detection module 242 in the current detection cycle. The logic judgment module 246 makes a logic judgment according to the discharge voltage detection signals corresponding to all battery cells stored in the storage module 244 in the current detection cycle. If at least one discharge voltage detection signal is an abnormal discharge voltage detection signal, the logic The determination module 246 outputs a discharge undervoltage protection signal, which means that the battery pack 210 needs to be protected from discharge. the

Please continue to refer to FIG. 2, the switch combination circuit 220 includes a first NMOS transistor MN1 and a second NMOS transistor MN2, the source of the first NMOS transistor MN1 is connected to the negative electrode of the battery unit B1, and its drain is connected to the NMOS transistor. The drain of MN2 is connected, the source of the NMOS transistor MN2 is connected to the battery negative terminal P-, the substrate of the first NMOS transistor MN1 is connected to its source, and the substrate of the second NMOS transistor MN1 is connected to its source. The gate of the first NMOS transistor MN1 is the discharge protection control terminal of the switch combination circuit 220 , and the gate of the second NMOS transistor MN2 is the charge protection control terminal of the switch combination circuit 220 . The NMOS transistor MN1 can be turned on or off according to the control of the signal at its control terminal, thereby turning on or off the discharge circuit. The control is turned on or off, so as to turn on or turn off the charging circuit. Therefore, the NMOS transistor MN2 can also be called a charging control switch. the

The control circuit 230 is connected between the output terminal of the voltage detection circuit 240 (that is, the output terminal of the logic decision module 246 shown) and the control terminal of the switch combination circuit 220, and it is output according to the voltage detection circuit 240 The protection signal controls the switch combination circuit 220 to turn off the charging loop or the discharging loop. Specifically, when the logic determination module 246 outputs a charging overvoltage protection signal, the control circuit 230 controls the NMOS transistor MN2 to turn off and the NMOS transistor MN1 to turn on, thereby shutting down the charging circuit; when the logic determination module 246 outputs the discharge When the overvoltage protection signal is activated, the control circuit 230 controls the NMOS transistor MN2 to be turned on and the NMOS transistor MN1 to be turned off, so as to turn off the discharge circuit. the

In summary, since the voltage detection circuit 240 in the present invention only includes one voltage detection module 242, the voltage detection module 242 periodically detects the voltage of each cell unit one by one, and will detect each The voltage of the battery cell is compared with the high-voltage threshold and/or the low-voltage threshold to output a voltage detection signal indicating whether it is abnormal. In this way, it is not only possible to perform voltage detection on each cell unit to determine whether any cell unit is in a charge overvoltage or discharge undervoltage state, so as to take corresponding protection measures, but also because the same voltage detection circuit 240 is used to The detection of the voltage of each cell unit eliminates the deviation caused by multiple voltage detection units, and can improve the matching of the protection voltage thresholds (eg, the high voltage threshold and the low voltage threshold) in the battery detection circuit 240 . the

Please refer to FIG. 3 , which is a schematic diagram of an embodiment of the voltage detection circuit in FIG. 2 . The voltage detection circuit 340 includes a voltage detection module 342 , a storage module 344 , a logic decision module 346 and a control module 348 . the

In the embodiment shown in Figure 3, each cell unit corresponds to a control signal (or clock signal, such as φ1, φ2, φ3, φ4), and the period of the control signal corresponding to each cell unit is the same as the The above-mentioned detection period is the same, and within a detection period, the effective levels of the control signals corresponding to each cell unit do not overlap with each other. When the control signal corresponding to a cell unit is at an active level, the control module 348 connects the voltage detection module 342 to the cell unit, so that the voltage detection module 342 detects the cell unit; when a When the clock signal corresponding to the battery unit is at an invalid level, the control module prevents the voltage detection module from being connected to the battery unit. the

For ease of description, the battery pack 310 in FIG. 3 only exemplarily shows four battery cells connected in series in sequence, which are respectively battery cell unit B1 , battery cell unit B2 , battery cell unit B3 and battery cell unit B4 . The battery unit B1 corresponds to the clock signal φ1, the battery unit B2 corresponds to the clock signal φ2, the battery unit B3 corresponds to the clock signal φ3, and the battery unit B4 corresponds to the clock signal φ4. Please refer to Figure 4, which is a waveform diagram of each clock signal in Figure 3. In this figure, the active levels of the clock signals φ1, φ2, φ3 and φ4 are high, and the invalid signals are low, and The high levels of the clock signals φ1, φ2, φ3 and φ4 do not overlap each other, and the detection period is T. In Fig. 4, the falling edge of the previous clock signal corresponds to the rising edge of the latter clock signal, for example, the falling edge of φ1 corresponds to the rising edge of φ2, in other embodiments, the falling edge of the previous clock signal can also be separated from the latter The rising edge of the clock signal is one end of the time. Correspondingly, the falling edge of the last clock signal in the current detection cycle can also be a period of time away from the rising edge of the first clock signal in the next detection cycle, as long as the effective signals do not overlap. Can. the

In order to realize the above functions of the control module 348 . The control module 348 shown in FIG. 3 includes multiple pairs of switches, each cell unit corresponds to a pair of switches, and each pair of switches includes a first switch and a second switch. Wherein, the first switch in each pair of switches is connected between the positive pole of the cell unit corresponding to the pair of switches and the first connection terminal 1 of the voltage detection unit 342, and the second switch is connected to the electric terminal 1 corresponding to the pair of control switches. Between the negative pole of the core unit and the second connection terminal 2 of the voltage detection unit 342 , and the control terminal of each pair of control switches is connected to the corresponding clock signal of the battery unit corresponding to the pair of control switches. In a detection cycle, when the control signal corresponding to a cell unit is at an active level, a pair of control switches corresponding to the cell unit are both turned on, thereby connecting the voltage detection module 342 to the cell unit, Make the voltage detection module 342 detect whether the voltage of the battery unit is abnormal; when the control signal corresponding to a battery unit is at an invalid level, a pair of control switches corresponding to the battery unit are all turned off, thereby cutting off the The connection between the voltage detection module 342 and the battery unit. For example, the battery unit B1 corresponds to the clock signal φ1, and a pair of control switches corresponding to the battery unit B1 are the first switch K1 and the second switch K2, wherein the first switch K1 is connected to the positive pole of the battery unit B1 and the voltage Between the first connection terminal 1 of the detection unit 342, the second switch K2 is connected between the negative pole of the battery unit B2 and the second connection terminal 2 of the voltage detection unit 342, and the control of the first switch K1 and the second switch K2 Both terminals are connected to the clock signal φ1. In one detection period, when the clock signal φ1 is at an active level, both the first switch K1 and the second switch K2 are turned on, thereby connecting the voltage detection module 342 to the cell unit; when a clock signal φ1 is invalid level, both the first switch K1 and the second switch K2 are turned off, thereby cutting off the connection between the voltage detection module 342 and the battery unit B1. Since the active levels of the control signals corresponding to each battery cell unit do not overlap each other within a detection period, the voltage detection module 342 performs voltage detection on each battery cell unit one by one within a detection period. the

The voltage detection module 342 is a current-based voltage detection module, which includes a voltage/current conversion module 3422 , a current comparison module ICOMP and a reference current module 3424 . the

The voltage/current conversion module 3422 converts the voltage of the battery unit connected to it into current. the

The voltage/current conversion module 3422 includes a first input terminal 1 (which serves as the first connection terminal 1 of the voltage detection module 342), a second input terminal 2 (which serves as the second connection terminal of the voltage detection module 342 2), the output terminal 3, the voltage sampling unit, the first resistor RC, the first operational amplifier OA1 and the first PMOS transistor MP1. The voltage sampling unit is used for sampling the voltage between the first input terminal 1 and the second input terminal 2, and outputting the sampling voltage, which includes a voltage connected between the first input terminal 1 and the second input terminal 2 The second resistor RA and the third resistor RB, the voltage of the node between the second resistor RA and the third resistor RB is the sampling voltage outputted therefrom. The first resistor RC and the first PMOS transistor MP1 are connected in series between the first input terminal 1 and the output terminal 3; the connection node between the non-inverting input terminal of the operational amplifier OA1 and the second resistor RA and the third resistor RB ( That is, the output terminal of the voltage sampling unit) is connected, its negative input terminal is connected to the connection node between the first PMOS transistor MP1 and the first resistor RC, and its output terminal is connected to the first PMOS transistor MP1 connected to the grid. When the voltage/current conversion module 3422 is connected to a battery unit, it converts the voltage of the battery unit into a current (current representing the voltage of the battery unit). For example, when the control module 348 connects the voltage/current conversion module 3422 to the battery unit B1 (that is, the positive pole and the negative pole of the battery unit B1 are connected to the first input terminal 1 and the first input terminal 1 of the voltage/current conversion module 220 respectively. The second input terminal 2 is connected, and the voltage/current conversion module 3422 converts the voltage between the positive pole and the negative pole of the battery unit B1 into a current. The specific conversion process is that the positive phase input terminal of the operational amplifier OA1 samples the The voltage between the positive pole and the negative pole of the cell unit B1 (the sampling voltage is equal to B1*RA/(RA+RB)), and its output terminal is fed back to its negative phase input terminal through the PMOS transistor MP1 until the first operation The voltages of the positive phase input terminal of the amplifier OA1 and its negative phase input terminal are equal, assuming that the first operational amplifier OA1 is an ideal operational amplifier, the current value output by the drain of the first PMOS transistor MP1 (that is, the voltage/current conversion module The current output by 3422) is approximately equal to the sampling voltage at the positive-phase input terminal of the first operational amplifier OA1 divided by the resistance value of the first resistor RC, that is, the current output by the voltage/current conversion module 3422 is equal to B1*RA/((RA +RB).RC), where B1 is the voltage difference between the positive and negative electrodes of the cell unit B1 (that is, the voltage value of the cell unit B1); RA, RB, and RC are the resistance values of the resistors RA, RB, and RC, respectively. Since the resistors RA, RB, and RC are constants in the specific embodiment, the current output by the voltage/current conversion module 3422 is proportional to the voltage of the detected (or connected) cell unit, that is, the voltage/current conversion The module 3422 converts the voltage of the battery unit connected to it into a current.

In summary, the voltage/current conversion module 3422 essentially samples the voltage of the battery unit connected to it, and then converts the sampled voltage into a current. Since the sampling voltage is lower than the voltage of the cell unit connected to the voltage/current conversion module 3422 (for example, when the voltage/current conversion module 3422 is connected to the cell unit B1, the sampling voltage is equal to the voltage of the cell unit B1 Voltage value *RA/(RA+RB)), therefore, there is a voltage margin for a series of circuits between the source of the PMOS transistor MP1 and the system ground, and the voltage margin can be adjusted by adjusting the second resistor RA and the first The ratio of three resistors RB for wide range adjustment. the

The reference current module 3424 is used to generate a first reference current corresponding to a high voltage threshold and/or a second reference current corresponding to a low voltage threshold. In this embodiment, the reference current module 3424 includes a bandgap reference voltage Bandgap, a second operational amplifier OA2, a third NMOS transistor MN3, a second PMOS transistor MP2, a third PMOS transistor MP3, a nonvolatile memory NVM, and Variable resistor R0. The effective resistance data of the variable resistor R0 is stored in the non-volatile memory NVM, and the effective resistance value of the variable resistor R0 can be adjusted according to the effective resistance data. Of course, in other embodiments, the resistor R0 may also be a resistor with a fixed resistance. The sources of the PMOS transistors MP2 and MP3 are connected to the power supply terminal VCC; the gates of the PMOS transistor MP2 are connected to the gates of MP3; the gates of the PMOS transistor MP2 are connected to their drains; the NMOS transistors MN3 and The variable resistor R0 is connected in series between the drain of the PMOS transistor MP2 and the system ground, and the drain of the PMOS transistor MP3 is the output terminal of the reference current module 3424 . The bandgap reference voltage Bandgap provides a relatively stable voltage reference, and the adjustment technology is used to achieve low temperature response and high standardization. The positive phase input terminal of the second operational amplifier OA2 is connected to the bandgap reference voltage Bandgap, its negative phase input terminal is connected to the connection node between the NMOS transistor MN3 and the variable resistor R0, and its output terminal is connected to the NMOS transistor MN3 The gate of the PMOS transistor MP3 is connected to the gate, and the current output by the drain of the PMOS transistor MP3 is the reference current generated by the reference current module 3424 . the

Since the second operational amplifier OA2 and the NMOS transistor MN3 form deep negative feedback, the voltage at the drain of the NMOS transistor MN3 is equal to the bandgap reference voltage Bandgap, and it can be approximately considered that no current flows through the second operational amplifier OA2, and the NMOS transistor MN3 generates The current I1 is approximately equal to the bandgap reference voltage Bandgap divided by the resistance value of the variable resistor R0. Therefore, the current I1 can be adjusted by adjusting the variable resistor R0. And because the sources and gates of the PMOS transistors MP2 and MP3 are connected, that is, the PMOS transistors MP3 and MP2 form a current mirror, therefore, the current generated by the drain of the PMOS transistor MP3 (that is, the reference current generated by the reference current module 3424 ) is equal to or proportional to the current I1. In this way, the reference current module 340 can generate a stable first reference current corresponding to the high voltage threshold and/or a second reference current corresponding to the low voltage threshold. the

The current comparison module ICOMP is used to compare the converted current output by the voltage/current conversion module 220 with the first reference current corresponding to the high voltage threshold and/or the second reference current corresponding to the low voltage threshold generated by the reference current module 3424 The current is compared to output a voltage detection signal whether it is abnormal. the

Referring to FIG. 3 and FIG. 2 , the working principle of the voltage detection module 342 will be described in detail below. the

When the battery protection system is in the charging state (that is, the charger is connected between the battery positive connection terminal P+ and the battery negative connection terminal P- to charge the battery pack 210), the reference current module 3424 generates a corresponding high voltage threshold the first reference current. The voltage/current conversion module 3422 converts the voltage of each cell unit one by one into a current within one detection cycle, and compares the converted current corresponding to the voltage of each cell unit with the first reference current, so as to Output abnormal charging voltage detection signal. Specifically, when the conversion current corresponding to the voltage of a battery unit output by the voltage/current conversion module 3422 is less than the first reference current, it means that the voltage of the battery unit is less than the high-voltage threshold, and the current comparison module ICOMP outputs a normal charging voltage detection signal; when the conversion current corresponding to the voltage of a cell unit output by the voltage/current conversion module 3422 is greater than the first reference current, it means that the voltage of the cell unit is greater than the high voltage threshold, The current comparison module ICOMP outputs an abnormal charging voltage detection signal, indicating that the battery cell unit is over-charged. the

When the battery protection system is in a discharge state (that is, the load is connected between the battery positive connection terminal P+ and the battery negative connection terminal P-, and the battery pack 210 supplies power to the load), the reference current module 3424 generates a corresponding low voltage threshold The second reference current. The voltage/current conversion module 3422 performs current conversion on the voltage of each battery unit one by one in a detection period, and compares the converted current corresponding to the voltage of each battery unit with the second reference current, so as to Outputs a discharge voltage detection signal for abnormality. Specifically, when the conversion current corresponding to the voltage of a cell unit output by the voltage/current conversion module 3422 is greater than the second reference current, it means that the voltage of the cell unit is greater than the low-voltage threshold, and the current comparison module ICOMP outputs a normal discharge voltage detection signal; when the conversion current corresponding to the voltage of a cell unit output by the voltage/current conversion module 3422 is less than the second reference current, it means that the voltage of the cell unit is lower than the low-voltage threshold, The current comparison module ICOMP outputs an abnormal discharge voltage detection signal, indicating that the cell unit discharges undervoltage. the

The storage module 344 in FIG. 3 has the same function as the storage module 244 in FIG. 2 , that is, it is used to store the voltage detection signal corresponding to each cell unit output by the voltage detection module 342 in the current detection cycle. The storage module 344 includes a plurality of D flip-flops, each cell unit corresponds to a D flip-flop, the clock terminal CK of each D flip-flop is connected to the control signal corresponding to the corresponding cell unit, each D flip-flop The input terminal D is connected to the output terminal of the current comparison module ICOMP, and its output terminal Q is connected to the logic decision module 346 . When the active level of the clock signal received by the clock terminal CK of a D flip-flop ends, it latches (or updates) the voltage detection signal received by the input terminal D of the output terminal of the current comparison module ICOMP. The storage module 344 in FIG. 3 includes four D flip-flops, which are D flip-flops DFF1, DFF2, DFF3, and DFF4 respectively, wherein the D flip-flop DFF1 corresponds to the cell unit B1, and its clock terminal CK is connected to the clock signal φ1, and D The flip-flop DFF2 corresponds to the cell unit B2, and its clock terminal CK is connected to the clock signal φ2. The D flip-flop DFF3 corresponds to the cell unit B3, and its clock terminal CK is connected to the clock signal φ3. The D flip-flop DFF4 corresponds to the cell unit B4. The clock terminal CK is connected to the clock signal φ4. the

In a detection cycle, when the clock signal φ1 is at an active level, the voltage detection module 342 is connected to the battery unit B1, and performs voltage detection on the battery unit B1 and outputs a voltage detection signal. When the clock signal φ1 is at an active level When jumping to an invalid level, the D flip-flop DFF1 latches the voltage detection signal received by the input terminal D of the output terminal of the current comparison module ICOMP, and at the same time controls the voltage detection module 342 to be disconnected from the battery unit B1; When the clock signal Q2 is at an active level, the voltage detection module 342 is connected to the battery unit B2 to perform voltage detection on the battery unit B2 and output a voltage detection signal. When the clock signal Q2 jumps from an active level to an inactive level, The D flip-flop DFF2 latches the voltage detection signal received by the input terminal D of the output terminal of the current comparison module ICOMP, and at the same time controls the voltage detection module 342 to be disconnected from the battery unit B2. In this way, each D flip-flop DFF automatically updates its stored voltage detection signal through the corresponding clock signal, and ensures that the stored voltage detection signal is the detection output of the voltage detection module 342 for the corresponding battery unit in the current detection cycle. voltage detection signal. the

In other embodiments, other flip-flops or registers may also be used instead of D flip-flops for data storage, as long as a similar storage function can be realized, and each D flip-flop may also be called a storage unit. the

After the voltage detection module 342 completes the detection of all battery cells in the current detection cycle, the logic decision module 346 stores the corresponding voltages of all battery cells in the current detection cycle according to the D flip-flop in the storage module 344 The detection signals are logically determined, and if at least one voltage detection signal is an abnormal voltage detection signal, the logic determination module 346 outputs a protection signal. Specifically, when charging, the logic judgment module 346 makes a logic judgment according to the charging voltage detection signals corresponding to all battery cells stored in the D flip-flop in the storage module 344 in the current detection cycle, if at least one charging voltage detection signal When it is an abnormal charging voltage detection signal, the logic judgment module 346 outputs a charging overvoltage protection signal, which means that the battery pack 210 needs to be charged and protected; All battery cells stored in the trigger perform logical judgment on the discharge voltage detection signals corresponding to the current detection cycle, and if at least one discharge voltage detection signal is an abnormal charging voltage detection signal, the logic judgment module 346 outputs a discharge undervoltage protection signal, That is to say, it is necessary to perform discharge protection on the battery pack 210 . the

In the present utility model, in the present utility model, words such as "connect", "link", "connect", "connect" and the like indicate electrical connection, and unless otherwise specified, indicate direct or indirect electrical connection. the

It should be pointed out that any changes made by those skilled in the art to the specific embodiments of the present utility model do not depart from the scope of the claims of the present utility model. Correspondingly, the scope of the claims of the present utility model is not limited only to the foregoing specific embodiments. the

Claims (10)

1. A voltage detection circuit for carrying out voltage detection to a plurality of successively connected electric core units, characterized in that it comprises a voltage detection module, a storage module and a logic judgment module, The voltage detection module periodically detects the voltage of each cell unit one by one, and compares the detected voltage of each cell unit with a high-voltage threshold and/or a low-voltage threshold to output a voltage detection signal whether it is abnormal; The storage module is used to store the voltage detection signal corresponding to each cell unit output by the voltage detection module in the current detection cycle; The logic judgment module makes a logic judgment according to the voltage detection signals corresponding to all the battery cells stored in the storage module in the current detection cycle, and if at least one voltage detection signal is an abnormal voltage detection signal, the logic judgment module outputs a protection signal . the 2. voltage detection circuit according to claim 1, is characterized in that, When charging, the voltage detection module detects the voltage of each cell unit one by one within a detection cycle, and compares the detected voltage of each cell unit with the high voltage threshold to output whether the charging voltage is abnormal signal; the storage module stores the charging voltage detection signal corresponding to each cell unit output by the voltage detection module in the current detection cycle; The charging voltage detection signal corresponding to the period is logically judged, and if at least one charging voltage detection signal is an abnormal charging voltage detection signal, the logic judgment module outputs a charging overvoltage protection signal, When discharging, the voltage detection module detects the voltage of each cell unit one by one within a detection cycle, and compares the detected voltage of each cell unit with the low voltage threshold to output whether the discharge voltage detection is abnormal signal; the storage module stores the discharge voltage detection signal corresponding to each cell unit output by the voltage detection module in the current detection cycle; The discharge voltage detection signals corresponding to the period are logically judged, and if at least one discharge voltage detection signal is an abnormal discharge voltage detection signal, the logic judgment module outputs a discharge undervoltage protection signal. the 3. The voltage detection circuit according to claim 1, wherein each cell unit is corresponding to a clock signal, and the cycle of the clock signal corresponding to each cell unit is the same as the detection cycle, and in a During the detection period, the active levels of the clock signals corresponding to each cell unit do not overlap each other, The voltage detection circuit also includes a control module. When the clock signal corresponding to a cell unit is at an active level, the control module connects the voltage detection module to the cell unit so that the voltage detection module The core unit performs detection; when the clock signal corresponding to a battery unit is at an invalid level, the control module prevents the voltage detection module from being connected to the battery unit. the 4. The voltage detection circuit according to claim 3, wherein the control module includes multiple pairs of switches, each cell unit corresponds to a pair of switches, each pair of switches includes a first switch and a second switch, each pair The first switch in the switch is connected between the positive pole of the battery unit corresponding to the pair of switches and the first connection end of the voltage detection unit, and the second switch in each pair of switches is connected to the battery unit corresponding to the pair of switches Between the negative pole of the voltage detection unit and the second connection terminal of the voltage detection unit, and the control terminal of each pair of switches is connected to the clock signal corresponding to the cell unit corresponding to the pair of switches, When the clock signal corresponding to a cell unit is at an active level, a pair of switches corresponding to the cell unit are both turned on; when the clock signal corresponding to a cell unit is at an inactive level, a pair of switches corresponding to the cell unit are turned on Both switches are off. the 5. The voltage detection circuit according to claim 3, wherein the voltage detection module comprises a voltage/current conversion module, a current comparison module and a reference current module, The voltage/current conversion module converts the voltage of the battery unit into a current; The reference current module is used to generate a first reference current corresponding to a high voltage threshold and/or a second reference current corresponding to a low voltage threshold; The current comparison module is used to compare the converted current output by the voltage/current conversion module with the first reference current corresponding to the high-voltage threshold and/or the second reference current corresponding to the low-voltage threshold generated by the reference current module, so as to Outputs a voltage detection signal for abnormality. the 6. voltage detection circuit according to claim 5, is characterized in that, When charging, the reference current module generates the first reference current corresponding to the high-voltage threshold; the voltage/current conversion module converts the voltage of each cell unit one by one in a detection cycle, and converts each cell The conversion current corresponding to the voltage of the unit is compared with the first reference current to output a charging voltage detection signal whether it is abnormal; When discharging, the reference current module generates a second reference current corresponding to the low-voltage threshold; the voltage/current conversion module converts the voltage of each cell unit one by one in a detection cycle, and converts each cell The conversion current corresponding to the cell voltage is compared with the second reference current to output a discharge voltage detection signal indicating whether it is abnormal. the 7. The voltage detection circuit according to claim 5, wherein the storage module includes a plurality of storage units, each cell unit corresponds to a storage unit, and the clock terminal of each storage unit corresponds to the cell unit The corresponding clock signal is connected, the input end of each storage unit is connected with the output end of the current comparison module, and its output end is connected with the logic judgment module, When the effective level of the clock signal received by the clock terminal of a storage unit ends, it latches the voltage detection signal received by the input terminal of the output terminal of the current comparison module. the 8. The voltage detection circuit according to claim 5, wherein, in addition to the first connection terminal and the second connection terminal, the voltage/current conversion module further includes an output terminal, a first resistor RC, a second resistor RA, The third resistor RB, the first operational amplifier OA1 and the first PMOS transistor MP1, The second resistor RA and the third resistor RB are sequentially connected in series between the first connection terminal and the second connection terminal; the first resistor RC and the first PMOS transistor are connected in series between the first connection terminal and the output terminal; the operation The positive phase input terminal of the amplifier is connected to the connection node between the second resistance RA and the third resistance RB, the negative phase input terminal thereof is connected to the connection node between the first PMOS transistor and the first resistance RC, and its output terminal connected to the gate of the first PMOS transistor. the 9. The voltage detection circuit according to claim 8, wherein the reference current module comprises a bandgap reference voltage, a second operational amplifier, a third NMOS transistor, a second PMOS transistor, a third PMOS transistor and a resistor R0 , The source of the second PMOS transistor and the third PMOS crystal is connected to the power supply terminal; the gate of the second PMOS transistor is connected to the gate of the third PMOS crystal; the gate of the second PMOS transistor is connected to its drain connected; the third NMOS transistor and resistor R0 are connected in series between the drain of the second PMOS transistor and the system ground, and the drain of the third PMOS transistor MP3 is the output terminal of the reference current module; the second operation The positive-phase input terminal of the amplifier is connected to the bandgap reference voltage, the negative-phase input terminal is connected to the connection node between the third NMOS transistor and the variable resistor, and the output terminal thereof is connected to the gate of the third NMOS transistor, so The current output by the drain of the PMOS transistor MP3 is the reference current generated by the reference current module. the 10. A battery protection system, characterized in that it includes a battery pack, a switch combination circuit, a control circuit and a voltage detection circuit, The battery pack includes a plurality of battery cells connected in series in sequence, one connection end of the uppermost battery cell unit is connected to the positive terminal of the battery, and one connection end of the lowermost battery cell unit is connected to the battery negative terminal through the switch combination circuit. end, The switch combination circuit includes a charge control switch and a discharge control switch connected in series, The voltage detection circuit is the voltage detection circuit according to any one of claims 1-9, The control circuit controls the charge control switch or the discharge control switch to be turned off according to the protection signal output by the voltage detection circuit for charge or discharge protection. the

Images