Lithium battery charging overvoltage secondary protection circuit and lithium battery charging system

Abstract

The present invention relates to the field of lithium battery protection technology, and specifically discloses a lithium battery charging overvoltage secondary protection circuit and a lithium battery charging system, comprising: a first charging overvoltage protection module, a second charging overvoltage protection module, and at least one bypass filter module; the first charging overvoltage protection module is used to monitor the charging voltage and the current lithium battery voltage in real time, and output a charging start signal when it is determined that the lithium battery voltage is less than the charging voltage, and output a charging shutdown signal when it is determined that the lithium battery voltage is not less than the charging voltage; the second charging overvoltage protection module is used to output the charging voltage to the first charging overvoltage protection module according to the output voltage of the charging power supply when receiving the charging start signal, and stop outputting the charging voltage to the first charging overvoltage protection module when receiving the charging shutdown signal. The lithium battery charging overvoltage secondary protection circuit provided by the present invention has the advantages of simple structure and low cost.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery protection, and in particular to a lithium battery charging overvoltage secondary protection circuit and a lithium battery charging system. Background Art

[0002] The application of lithium battery protection boards can improve the safety and stability of batteries, thereby protecting devices and users from potential safety risks. With the popularity and increasing demand for smart devices, the power consumption and accuracy requirements of lithium battery protection boards are becoming increasingly higher.

[0003] Currently, most lithium battery protection boards use external MOS tubes, but this solution has the disadvantages of high cost, low integration, complex periphery and high safety risks.

[0004] Therefore, how to provide a lithium battery protection solution with a simple structure and low cost has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0005] The present invention provides a lithium battery charging overvoltage secondary protection circuit and a lithium battery charging system, which solve the problems of complex structure and high cost of lithium battery charging protection boards existing in the related art.

[0006] As a first aspect of the present invention, a secondary charging overvoltage protection circuit for a lithium battery is provided, comprising: a first charging overvoltage protection module, a second charging overvoltage protection module, and at least one bypass filter module, wherein the first charging overvoltage protection module is electrically connected to the second charging overvoltage protection module, the first charging overvoltage protection module is further configured to be connected to a positive electrode of a lithium battery, the second charging overvoltage protection module is further configured to be connected to a positive electrode of a charging power supply, and the bypass filter module is electrically connected to at least the first charging overvoltage protection module and / or the second charging overvoltage protection module;

[0007] The first charging overvoltage protection module is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and output a charging start signal when it is determined that the voltage of the lithium battery is less than the charging voltage, and output a charging shutdown signal when it is determined that the voltage of the lithium battery is not less than the charging voltage;

[0008] The second charging overvoltage protection module is configured to output a charging voltage to the first charging overvoltage protection module according to the output voltage of the charging power supply when receiving the charging start signal, and stop outputting the charging voltage to the first charging overvoltage protection module when receiving the charging shutdown signal;

[0009] The bypass filter module is used to filter the charging voltage.

[0010] Furthermore, the first charging overvoltage protection module at least includes: a charging voltage detection unit, a signal processing unit, a charging unit, an overcharge detection unit and a first charging switch unit;

[0011] The first input end of the charging voltage detection unit is connected to the output end of the second charging overvoltage protection module, the second input end of the charging voltage detection unit is connected to the positive electrode of the lithium battery, and the output end of the charging voltage detection unit is connected to the signal processing unit. The charging voltage detection unit is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and generate a corresponding detection signal according to the relationship between the charging voltage and the current voltage of the lithium battery;

[0012] The input end of the signal processing unit is connected to the charging voltage detection unit, and the output end of the signal processing unit is connected to the charging unit and the overcharge detection unit respectively. The signal processing unit is configured to directly output a high-level detection signal when the detection signal is at a high level, and to delay outputting a low-level detection signal when the detection signal is at a low level;

[0013] The charging unit is connected to the signal processing unit and the first charging switch unit respectively, and the charging unit is used to generate a charging start driving signal according to the high level detection signal or generate a charging shutdown driving signal according to the low level detection signal;

[0014] The overcharge detection unit is respectively connected to the signal processing unit, the positive electrode of the lithium battery, and the second charging overvoltage protection module. The overcharge detection unit is used to start overcharge detection according to the high-level detection signal, and output a low-level overcharge signal when the voltage of the lithium battery is not greater than the overcharge voltage threshold, or output a high-level overcharge signal when the voltage of the lithium battery is greater than the overcharge voltage threshold; or output a low-level overcharge signal according to the low-level detection signal to turn off overcharge detection;

[0015] The first charging switch unit is configured to be turned on according to the charging start driving signal to transmit the charging voltage to the lithium battery, or to be turned off according to the charging stop driving signal to block the charging voltage from being transmitted to the lithium battery.

[0016] Furthermore, the first charging switch unit includes a P-type MOS tube.

[0017] Furthermore, the charging voltage detection unit includes: a first comparator, the positive input end of the first comparator is used to connect to the output end of the second charging overvoltage protection module, the inverting input end of the first comparator is used to connect to the positive electrode of the lithium battery, and the output end of the first comparator is the output end of the charging voltage detection unit.

[0018] Furthermore, the signal processing unit includes: a first trigger, a second trigger, a third trigger, a fourth trigger and a first NOT gate, the first trigger, the second trigger, the third trigger and the fourth trigger are connected in series in sequence, the D input end of the first trigger is the input end of the signal processing unit, the input end of the first NOT gate is connected to the D input end of the first trigger, the output end of the first NOT gate is respectively connected to the SN end of the first trigger, the second trigger, the third trigger and the fourth trigger, and the Q output end of the second trigger and the Q output end of the fourth trigger are both output ends of the signal processing unit.

[0019] Furthermore, the overcharge detection unit includes: a second comparator and a first AND gate, the non-inverting input of the second comparator is connected to the positive electrode of the lithium battery, the inverting input of the second comparator is used to input the overcharge voltage threshold, the output of the second comparator is connected to the first input of the first AND gate, the second input of the first AND gate is connected to the output of the signal processing unit, and the output of the first AND gate is used to connect to the second charging overvoltage protection module.

[0020] Furthermore, the first charging overvoltage protection module also includes: an LED driving unit, which is connected to the signal processing unit, and the LED driving unit can generate a charging state flashing driving signal according to the high-level detection signal output by the signal processing unit or generate an overcharging state flashing driving signal according to the low-level detection signal output by the signal processing unit.

[0021] Furthermore, the second charging overvoltage protection module includes: a charge pump and a second charging switch unit, the charge pump is connected to the second charging switch unit, and the second charging switch unit and the charge pump are respectively connected to the charging power supply and the first charging overvoltage protection module;

[0022] The charge pump is configured to generate a switch driving signal according to the output voltage of the charging power supply and the overcharge detection signal of the first charging overvoltage protection module;

[0023] The second charging switch unit is configured to be turned on according to the switch driving signal to output a charging voltage to the first charging overvoltage protection module, or to be turned off according to the switch driving signal to stop outputting a charging voltage to the first charging overvoltage protection module.

[0024] Furthermore, the second charging switch unit includes an N-type MOS transistor.

[0025] As another aspect of the present invention, a lithium battery charging system is provided, which includes a lithium battery, a charging power supply and the lithium battery charging overvoltage secondary protection circuit mentioned above, the lithium battery charging overvoltage secondary protection circuit is respectively connected to the output end of the charging power supply and the positive electrode of the lithium battery, the lithium battery charging overvoltage secondary protection circuit is used to provide a charging voltage to the lithium battery according to the output voltage of the charging power supply, and to activate the overvoltage protection function when the voltage of the lithium battery is not less than the charging voltage.

[0026] The lithium battery charging overvoltage secondary protection circuit provided by the present invention realizes control of lithium battery charging by connecting a first charging overvoltage protection module and a second charging overvoltage protection module, and can stop the charging process when the lithium battery is charged with overvoltage. The lithium battery charging overvoltage secondary protection circuit realizes charging management control and charging protection functions by separating charging detection and charging overvoltage functions from the charging power supply, which can effectively improve the safety of lithium battery charging and has the advantages of simple structure, low cost and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention, but do not constitute a limitation of the present invention.

[0028] Figure 1 This is a structural block diagram of the lithium battery charging overvoltage secondary protection circuit provided by the present invention.

[0029] Figure 2 This is a structural block diagram of the first charging overvoltage protection module and the second charging overvoltage protection module provided by the present invention.

[0030] Figure 3 This is a circuit schematic diagram of the first charging overvoltage protection module and the second charging overvoltage protection module provided by the present invention.

[0031] Figure 4a This is a specific circuit schematic diagram of the charging voltage detection unit provided by the present invention.

[0032] Figure 4b This is a schematic diagram of a specific circuit of the signal processing unit provided by the present invention.

[0033] Figure 4c This is a schematic diagram of the specific circuit of the charging unit provided by the present invention.

[0034] Figure 4d This is a schematic diagram of a specific circuit of the overcharge detection unit provided by the present invention.

[0035] Figure 4e This is a schematic diagram of the specific circuit of the charge pump provided by the present invention.

[0036] Figure 5 This is a schematic diagram of a specific circuit of the LED driving unit provided by the present invention. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate for the embodiments of the present invention described herein. In addition, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatuses.

[0040] In this embodiment, a secondary protection circuit for overvoltage of a lithium battery is provided. Figure 1 FIG. 1 is a structural block diagram of a lithium battery charging overvoltage secondary protection circuit 10 according to an embodiment of the present invention. Figure 1 As shown, it includes: a first charging overvoltage protection module U1, a second charging overvoltage protection module U2 and at least one bypass filter module, the first charging overvoltage protection module U1 is electrically connected to the second charging overvoltage protection module U2, the first charging overvoltage protection module U1 is also used to connect to the positive electrode BAT+ of the lithium battery, the second charging overvoltage protection module U2 is also used to connect to the positive electrode CHARGER+ of the charging power supply, and the bypass filter module is electrically connected to at least the first charging overvoltage protection module U1 and / or the second charging overvoltage protection module U2;

[0041] The first charging overvoltage protection module U1 is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and output a charging start signal when it is determined that the voltage of the lithium battery is less than the charging voltage, and output a charging shutdown signal when it is determined that the voltage of the lithium battery is not less than the charging voltage;

[0042] The second charging overvoltage protection module U2 is configured to output a charging voltage to the first charging overvoltage protection module according to the output voltage of the charging power supply when receiving the charging start signal, and stop outputting the charging voltage to the first charging overvoltage protection module when receiving the charging shutdown signal;

[0043] The bypass filter module is used to filter the charging voltage.

[0044] In an embodiment of the present invention, the first charging overvoltage protection module U1 can monitor the relationship between the current voltage of the lithium battery and the charging voltage in real time, and generate a charging start signal when the current voltage of the lithium battery is lower than the charging voltage. The charging start signal can connect the charging circuit between the first charging overvoltage protection module and the second charging overvoltage protection module, so that the output voltage of the charging power supply can be transmitted to the lithium battery through the second charging overvoltage protection module and the first charging overvoltage protection module to realize charging of the lithium battery. When it is monitored that the current voltage of the lithium battery is higher than the charging voltage, a charging shutdown signal will be generated to block the charging process of the charging power supply.

[0045] It should be noted here that the first charging overvoltage protection module can also monitor the relationship between the voltage of the lithium battery and the overcharge voltage threshold in real time during the charging process of the lithium battery, and can block the charging process of the charging power supply when the voltage of the lithium battery is greater than the overcharge voltage threshold.

[0046] It should also be noted that the bypass filter module in the embodiment of the present invention is used to filter the charging voltage to reduce noise signals of the charging voltage.

[0047] Therefore, the lithium battery charging overvoltage secondary protection circuit provided by the present invention realizes the control of lithium battery charging by connecting the first charging overvoltage protection module and the second charging overvoltage protection module, and can stop the charging process when the lithium battery is charged with overvoltage. The lithium battery charging overvoltage secondary protection circuit separates the charging detection and charging overvoltage functions from the charging power supply to realize the charging management control and charging protection functions, which can effectively improve the safety of lithium battery charging, and has the advantages of simple structure, low cost and easy implementation.

[0048] In the embodiment of the present invention, Figure 2As shown, the first charging overvoltage protection module U1 at least includes: a charging voltage detection unit 110 , a signal processing unit 120 , a charging unit 130 , an overcharge detection unit 140 and a first charging switch unit 150 .

[0049] The first input end of the charging voltage detection unit 110 is connected to the output end of the second charging overvoltage protection module U2, the second input end of the charging voltage detection unit 110 is connected to the positive electrode BAT+ of the lithium battery, and the output end of the charging voltage detection unit 110 is connected to the signal processing unit 120. The charging voltage detection unit 110 is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and generate a corresponding detection signal according to the relationship between the charging voltage and the current voltage of the lithium battery.

[0050] In the embodiment of the present invention, Figure 3 and Figure 4a As shown, the charging voltage detection unit 110 includes: a first comparator A1, the non-inverting input terminal of the first comparator A1 is used to connect the output terminal OUT of the second charging overvoltage protection module U2, the inverting input terminal of the first comparator A1 is used to connect the positive electrode BAT+ of the lithium battery, and the output terminal of the first comparator A1 is the output terminal of the charging voltage detection unit 110.

[0051] Specifically, the output end of the second charging overvoltage protection module U2 is connected to the voltage end VCC of the first charging overvoltage protection module U1, and the charging voltage detection unit 110 can monitor the charging voltage and the voltage of the positive electrode BAT+ of the lithium battery in real time, and output a high-level detection signal when the voltage of the lithium battery is lower than the charging voltage, and output a low-level detection signal when the voltage of the lithium battery is higher than the charging voltage.

[0052] In an embodiment of the present invention, the input end of the signal processing unit 120 is connected to the charging voltage detection unit, and the output end of the signal processing unit 120 is respectively connected to the charging unit 130 and the overcharge detection unit 140. The signal processing unit 120 is used to directly output a high-level detection signal when the detection signal is at a high level, and to delay outputting a low-level detection signal when the detection signal is at a low level.

[0053] Specifically, if Figure 3 and Figure 4bAs shown, the signal processing unit 120 includes: a first trigger D1, a second trigger D2, a third trigger D3, a fourth trigger D4 and a first NOT gate NG1. The first trigger D1, the second trigger D2, the third trigger D3 and the fourth trigger D4 are connected in series in sequence. The D input end of the first trigger D1 is the input end of the signal processing unit 120. The input end of the first NOT gate NG1 is connected to the D input end of the first trigger D1. The output end of the first NOT gate NG1 is respectively connected to the SN end of each of the first trigger D1, the second trigger D2, the third trigger D3 and the fourth trigger D4. The Q output end of the second trigger D2 and the Q output end of the fourth trigger D4 are both output ends of the signal processing unit 120.

[0054] In an embodiment of the present invention, when the charge voltage detection unit 110 outputs a high level, the first NOT gate NG1 outputs a low level. The output of the first NOT gate NG1 is connected to the SN terminal of each flip-flop. Therefore, at this time, the SN terminal of each flip-flop is at a low level. When the SN terminal of the flip-flop is at a low level, regardless of how the clock signal CLK changes, the Q output terminal of the flip-flop directly outputs the level signal of the D input terminal of the flip-flop. That is, at this time, the Q output terminal of each flip-flop directly outputs a high-level signal. Therefore, when the charge voltage detection unit 110 outputs a high-level detection signal, the signal processing unit 120 directly outputs a high-level detection signal.

[0055] When the charging voltage detection unit 110 outputs a low-level signal, the first NOT gate NG1 outputs a high-level signal. At this time, the SN terminal of each trigger is a high-level signal, and the output terminal of the trigger needs to be output according to the clock signal CLK. In the embodiment of the present invention, specifically, when the charging voltage detection unit 110 outputs a low-level detection signal, the signal processing unit 120 needs to delay the clock cycle before outputting the low-level detection signal. Therefore, if Figure 3 As shown, the overcharge detection unit 140 is connected to the Q output terminal of the second flip-flop, that is, the low-level detection signal is output to the overcharge detection unit 140 after the duration of the low-level detection signal is greater than two clock signal CLK cycles. The Q output terminal of the fourth flip-flop needs to output a low-level detection signal after the duration of the low-level detection signal is greater than four clock signal CLK cycles.

[0056] In the embodiment of the present invention, Figure 3 As shown, the charging unit 130 is connected to the signal processing unit 110 and the first charging switch unit 150 respectively, and the charging unit 130 is used to generate a charging start driving signal according to the high level detection signal or generate a charging shutdown driving signal according to the low level detection signal.

[0057] Specifically, if Figure 3 and Figure 4c As shown, the charging unit 130 includes: a second NOT gate NG2, a second AND gate AND2, a third comparator A3, a fourth comparator A4, a first resistor R1, a second resistor R2, a third resistor R3, a second P-type MOS transistor P2, and a third P-type MOS transistor P3. One end of the first resistor R1 and the second resistor R2 connected in series is connected to the positive electrode of the lithium battery, and the other end of the first resistor R1 and the second resistor R2 connected in series is connected to the negative electrode of the lithium battery and to a signal ground. A positive input end of the third comparator A3 is connected to the connection end of the first resistor R1 and the second resistor R2. A negative input end of the third comparator A3 is used to input a charging stop voltage threshold VREF_1. An output end of the third comparator A3 is connected to an input end of the second NOT gate NG2. An output end of the second NOT gate NG2 is connected to one input end of the second AND gate AND2. The other input end of the second AND gate AND2 is connected to the output end of the signal processing unit. An output end of the second AND gate AND2 is connected to a gate drive end of the third P-type MOS transistor P3. The negative input terminal of the fourth comparator A4 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to signal ground, the positive input terminal of the fourth comparator A4 is used to input the charging current threshold VREF_2, and the output terminal of the fourth comparator A4 is connected to the gate drive terminal of the second P-type MOS transistor P2. The gate drive terminal of the second P-type MOS transistor P2 is connected to the drive terminal of the first charging switch unit 150 (i.e., the P-type MOS transistor P1). The source of the second P-type MOS transistor P2, the source of the third P-type MOS transistor P3, and the source terminal of the first charging switch unit 150 are connected and are all connected to the charging voltage. The drain of the second P-type MOS transistor P2 and the drain of the third P-type MOS transistor P3 are both connected to the gate drive terminal of the second P-type MOS transistor P2.

[0058] according to Figure 3 and Figure 4cAs shown, when the signal processing unit outputs a high level (i.e., the charging voltage detection unit 110 outputs a high level) and the current voltage of the lithium battery is less than the charge stop voltage threshold VREF_1, the gate voltage of the third P-type MOS transistor P3 is VCC. At this time, the third P-type MOS transistor P3 is in a high-impedance state. The gate drive of the second P-type MOS transistor P2 and the gate drive of the first charging switch unit (i.e., the first P-type MOS transistor P1) are controlled by the fourth comparator A4. That is, the charging unit 130 is turned on. The fourth comparator A4 (the fourth comparator here acts as an operational amplifier) ​​outputs a varying current signal to control the operating current of the second P-type MOS transistor P2. Since the current between the second P-type MOS transistor P2 and the first charging switch unit 150 is proportional, the operating current of the first charging switch unit 150 is controlled by controlling the operating current of the second P-type MOS transistor P2, thereby controlling the degree of activation of the second P-type MOS transistor P2 and the first charging switch unit 150. It should be understood here that, since the charging between the charging power supply and the lithium battery is continuously connected when the first charging switch unit 150 is turned on, and since the charging current is a fixed value (for example, 500 mA), the operating current of the second P-type MOS tube P2 is controlled to control the operating current of the first charging switch unit 150, thereby ultimately achieving charging control of the lithium battery.

[0059] When the signal processing unit outputs a low level and / or the current voltage of the lithium battery is greater than the charge stop voltage threshold VREF_1, the three-level drive voltage of the third P-type MOS transistor P3 is low. At this time, the gate drive terminals of the second P-type MOS transistor and the first charging switch unit 150 are both pulled to VCC, that is, the charging unit 130 is turned off.

[0060] In an embodiment of the present invention, the overcharge detection unit 140 is respectively connected to the signal processing unit 120, the positive electrode BAT+ of the lithium battery and the second charging overvoltage protection module U2. The overcharge detection unit 140 is used to start overcharge detection according to the high-level detection signal, and output a low-level overcharge signal when the voltage of the lithium battery is not greater than the overcharge voltage threshold VREF, or output a high-level overcharge signal when the voltage of the lithium battery is greater than the overcharge voltage threshold VREF; or output a low-level overcharge signal according to the low-level detection signal to turn off overcharge detection.

[0061] Specifically, if Figure 3 and Figure 4dAs shown, the overcharge detection unit 140 includes: a second comparator A2 and a first AND gate AND1, the non-inverting input terminal of the second comparator A2 is connected to the positive electrode BAT+ of the lithium battery, the inverting input terminal of the second comparator A2 is used to input the overcharge voltage threshold, the output terminal of the second comparator is connected to the first input terminal of the first AND gate AND1, the second input terminal of the first AND gate AND1 is connected to the output terminal of the signal processing unit 120, and the output terminal of the first AND gate AND1 is used to connect to the second charging overvoltage protection module U2.

[0062] In the embodiment of the present invention, Figure 3 and Figure 4d As shown, the overcharge detection unit 140 also includes a fourth resistor R4 and a fifth resistor R5. One end of the fourth resistor R4 and the fifth resistor R5 connected in series is connected to the positive electrode BAT+ of the lithium battery, and the other end of the fourth resistor R4 and the fifth resistor R5 connected in series is connected to the negative electrode of the lithium battery and to the signal ground. The non-inverting input end of the second comparator A2 is connected to the connection end between the fourth resistor R4 and the fifth resistor R5.

[0063] according to Figure 3 and Figure 4d As shown, when the signal processing unit 120 outputs a high-level detection signal, the overcharge detection unit is turned on. At this time, when the lithium battery voltage at the non-inverting input terminal of the second comparator A2 is less than the overcharge voltage threshold, the second comparator A2 outputs a low-level signal, and at this time the first AND gate AND1 outputs a low-level signal. When the signal processing unit 120 outputs a high-level detection signal, and at this time the lithium battery voltage at the non-inverting input terminal of the second comparator A2 is greater than the overcharge voltage threshold, the second comparator A2 outputs a high-level signal, and at this time the first AND gate AND1 outputs a high-level signal. When the signal processing unit 120 outputs a low-level detection signal, the overcharge detection unit is turned off, and the first AND gate AND1 outputs a low-level signal.

[0064] In an embodiment of the present invention, the first charging switch unit 150 is configured to be turned on according to the charging start drive signal to transmit the charging voltage to the lithium battery, or turned off according to the charging shutdown drive signal to block the charging voltage from being transmitted to the lithium battery.

[0065] Specifically, the first charging switch unit 150 includes a P-type MOS transistor P1.

[0066] In the embodiment of the present invention, Figure 5As shown, the first charging overvoltage protection module U1 also includes: an LED driving unit 160, which is connected to the signal processing unit 120. The LED driving unit 160 can generate a charging state flashing driving signal according to the high-level detection signal output by the signal processing unit 120 or generate an overcharging state flashing driving signal according to the low-level detection signal output by the signal processing unit 120.

[0067] Specifically, Figure 5 The circuit diagram of the LED driving unit 160 is shown as follows. Figure 5 As shown, when the overcharge detection unit 140 outputs a low level, the signal processing unit 120 outputs a high level, and the charging voltage detection unit 110 outputs a high level, the bias current circuit of IBIAS of the LED driving unit 160 is turned on, and the LED lamp is always on; when the overcharge detection unit 140 outputs a high level, the signal processing unit outputs a high level, and the charging voltage detection unit outputs a high level, the driving tube connected to the LED lamp is mainly driven by the clock signal, and is therefore in a flashing state; when the overcharge detection unit 140 outputs a low level, the signal processing unit outputs a low level, and the charging voltage detection unit outputs a low level, the bias current circuit of IBIAS of the LED driving unit 160 is short-circuited, and therefore the LED lamp is in an off state.

[0068] In the embodiment of the present invention, Figure 2 As shown, the second charging overvoltage protection module U2 includes: a charge pump 210 and a second charging switch unit 220, the charge pump 210 is connected to the second charging switch unit 220, and the second charging switch unit 220 and the charge pump 210 are respectively connected to the charging power supply and the first charging overvoltage protection module U1;

[0069] The charge pump 210 is used to generate a switch driving signal according to the output voltage of the charging power supply and the overcharge detection signal of the first charging overvoltage protection module U1;

[0070] The second charging switch unit 220 is configured to be turned on according to the switch driving signal to output a charging voltage to the first charging overvoltage protection module U1 , or turned off according to the switch driving signal to stop outputting a charging voltage to the first charging overvoltage protection module U1 .

[0071] It should be understood that the charge pump 210 can be controlled and adjusted according to the output result of the overcharge detection unit in the first charging overvoltage protection module U1 so that the driving voltage of the second charging switch unit 220 is equal to twice the output voltage of the charging power supply, thereby enabling the output voltage of the second charging overvoltage protection module U2 to be equal to the output voltage of the charging power supply.

[0072] In the embodiment of the present invention, the specific working principle diagram of the charge pump 210 is as follows: Figure 3 and Figure 4e As shown, according to Figure 3 and Figure 4e As can be seen, the input signal EN of the charge pump 210 is derived from the output of the overcharge detection unit. It should be noted that when the input signal EN of the charge pump 210 is low, the structure formed by the switch combination can ensure that the output voltage VOUT of the second charging overvoltage protection module U2 is equal to the input voltage VIN of the second charging overvoltage protection module U2. The input voltage terminal of the second charging overvoltage protection module U2 is connected to the output terminal of the charging power supply. Therefore, the structure formed by the switch combination can ensure that the output voltage VOUT of the second charging overvoltage protection module U2 is equal to the output voltage of the charging power supply. When the input signal EN of the charge pump 210 is high, the output of the second charging overvoltage protection module U2 is pulled low, that is, the output of the second charging overvoltage protection module U2 is low.

[0073] In the embodiment of the present invention, the second charging switch unit 220 includes an N-type MOS transistor N1.

[0074] In addition, in the embodiment of the present invention, the bypass filter module includes a filter capacitor, such as Figure 1 As shown, at least three filter capacitors are included, namely C0, C1 and C2. Among them, filter capacitor C0 is located between the output end of the charging power supply and the signal ground, filter capacitor C2 is located between the output end of the first charging overvoltage protection module and the signal ground, and filter capacitor C3 is located between the positive electrode of the lithium battery and the signal ground.

[0075] The following combination Figures 1 to 5 The working principle of the lithium battery charging overvoltage secondary protection circuit according to the embodiment of the present invention is described.

[0076] when Figure 1 When the circuit shown is connected and ready for charging, when the input voltage VCC of the first charging overvoltage protection module is greater than the voltage of the lithium battery, the charging voltage detection unit 110 outputs a high level. At this time, the trigger SN terminal signal of the signal processing unit 120 is low. Therefore, the output of the signal processing unit 120 is a high level, and both the output terminal of the second D trigger and the output terminal of the fourth D trigger are high. At this time, the overcharge detection unit 140 is turned on (because the current lithium battery voltage in the overcharge detection unit 140 is less than the overcharge voltage threshold, the overcharge detection unit output is a low level at this time), and the charging unit 130 enters the charging state. Based on Figure 5 It can be seen from the working principle of the LED driving unit 160 shown that the LED light is in a constant-on charging state at this time.

[0077] When the first charging overvoltage protection module U1 enters the charging state, and at this time the voltage of the lithium battery in the overcharge detection unit 140 is greater than the overcharge voltage threshold, the overcharge detection unit 140 outputs a high level. At this time, the input signal EN of the charge pump 210 is a high level, so the second charging overvoltage protection module U2 outputs a low level. At this time, if the charging power supply is not released, the input voltage VCC of the first charging overvoltage protection module will be re-established after being low for a moment, that is, the output of the second charging overvoltage protection module will be high again, that is, the input voltage VCC of the first charging overvoltage protection module is still high, and the outputs of the charging voltage detection unit and the signal processing unit are both high. At this time, the LED light driven by the LED driving unit is in an overcharge flashing state.

[0078] like Figure 3 As shown, when the input voltage VCC of the first charging overvoltage protection module U1 is at a low level, that is, less than the lithium battery voltage, the charging voltage detection unit 110 outputs a low level. When the duration of the level signal is greater than 2 clock CLK cycles, the overcharge detection unit 140 is turned off. At this time, the overcharge detection unit 140 outputs a low level. After the charge pump 210 is started again, the output voltage of the second charging overvoltage protection module is re-established. Therefore, the input voltage VCC of the first charging overvoltage protection module U1 re-enters a high level state. At this time, the signal processing unit and the overcharge detection unit output a high level again, driving the LED light to be in a flashing overcharge state.

[0079] Therefore, when the lithium battery voltage is greater than the overcharge voltage threshold, if the charging power supply is still connected to the VIN terminal of the second charging overvoltage protection module U2, such as Figure 1 As shown, the FAIL pin (output end of the overcharge detection unit) of the first charging overvoltage protection module U1 is connected to the EN pin of the second charging overvoltage protection module U2. When the FAIL pin output is low, that is, the EN pin (input end of the charge pump) of the second charging overvoltage protection module U2, the output voltage of the second charging overvoltage protection module U2 is high, the input voltage VCC pin of the first charging overvoltage protection module U1 becomes high, and the charging voltage detection unit output is high. At this time, the trigger SN terminal signal of the signal processing unit is low, the signal processing unit output is high, and the overcharge detection unit output is high. At this time, the FAIL output is high, and the LED light is in a flashing overcharge state; if the charging power supply is not connected to the VIN terminal of the second charging overvoltage protection module U2 at this time, VIN is low, as shown Figure 1As shown, the FAIL pin of the first charging overvoltage protection module U1 is connected to the EN pin of the second charging overvoltage protection module U2. When the FAIL pin output is low, VIN is low, the OUT output is still low, and the VCC pin of the second charging overvoltage protection module U1 is low. When the VCC voltage is lower than the battery voltage, the charging voltage detection unit output is low. When the low signal lasts for more than 4 CLK cycles, the signal processing unit output is low, the charging unit is turned off, and the LED light is turned off, that is, the charging release state is entered.

[0080] Therefore, in an embodiment of the present invention, a charging P-type MOS tube is integrated inside the first charging overvoltage protection module U1, and a charging N-type MOS tube is integrated inside the second charging overvoltage protection module U2. The first charging overvoltage protection module U1 and the second charging overvoltage protection module U2 are connected in series between the positive pole B+ of the lithium battery and the positive pole CHARGE+ of the charging power supply; the first charging overvoltage protection module U1 monitors the voltage of the lithium battery, and when the lithium battery is fully charged, the charging tube P1 inside the first charging overvoltage protection module U1 is turned off; the first charging overvoltage protection module U1 monitors the voltage of the lithium battery, and when the lithium battery is overvoltage, the first charging overvoltage protection module U1 transmits a signal to the second charging overvoltage protection module U2, and the charging tube inside the second charging overvoltage protection module U2, namely the N-type MOS tube N1, is turned off; and the first charging overvoltage protection module U1 drives the LED according to different states of BAT and VCC. When the first charging overvoltage protection module U1 detects that the voltage of the lithium battery reaches the charging voltage threshold and the duration reaches or exceeds the full charge stop delay time, the full charge stop state is activated, the charging P-type MOS tube inside the first charging overvoltage protection module U1 is turned off, and the LED enters the full charge flashing state.

[0081] When the voltage of the lithium battery decreases and is lower than the overcharge voltage threshold and the duration reaches or exceeds the recharge delay time, the first charging overvoltage protection module U1 is released from the full state to the normal mode, and the LED enters the charging constant light state.

[0082] In the embodiment of the present invention, when the charging P-type MOS tube of the first charging overvoltage protection module U1 is damaged and the voltage of the lithium battery rises to above the overcharge voltage threshold +50mV and lasts for the overcharge protection delay time or longer, the overvoltage protection is activated, the output of the FAIL pin of the first charging overvoltage protection module U1 becomes high, the gate voltage of the charging N-type MOS tube of the second charging overvoltage protection module U2 is pulled down, the charging N-type MOS tube is turned off, and the LED enters the overcharge flashing state.

[0083] When the charging P-type MOS tube of the first charging overvoltage protection module U1 is damaged and the voltage of the lithium battery rises above the overcharge voltage threshold +50mV and lasts for the overcharge protection delay time or longer, the overvoltage protection is activated. At this time, the charging power supply is unplugged, VCC is lower than the voltage BAT of the lithium battery and the duration is greater than the charging release delay time, and the LED enters the charging release state.

[0084] It should be understood that, in the embodiment of the present invention, the operating voltage of the first charging overvoltage protection module U1 is provided by the second charging overvoltage protection module U2 ; and the operating voltage of the second charging overvoltage protection module U2 is provided by the charging power supply.

[0085] In summary, the lithium battery charging overvoltage secondary protection circuit provided in the embodiment of the present invention uses a separate charging overvoltage protection module to protect the battery when it is overcharged, and the charging power supply is not directly connected to the first charging overvoltage protection module. The first charging overvoltage protection module U1 can detect the plug-in status of the charging power supply and send different signals to drive the LED according to different statuses, thereby improving the charging safety of the lithium battery and enhancing the user experience.

[0086] As another embodiment of the present invention, a lithium battery charging system is provided, wherein Figure 1 As shown, it includes a lithium battery 20, a charging power supply 30 and the lithium battery charging overvoltage secondary protection circuit 10 mentioned above, the lithium battery charging overvoltage secondary protection circuit 10 is respectively connected to the output end of the charging power supply 30 and the positive electrode of the lithium battery, the lithium battery charging overvoltage secondary protection circuit 10 is used to provide a charging voltage to the lithium battery according to the output voltage of the charging power supply, and to turn on the overvoltage protection function when the voltage of the lithium battery is not less than the charging voltage.

[0087] The lithium battery charging system provided by the present invention adopts the lithium battery charging overvoltage secondary protection circuit mentioned above. By connecting the first charging overvoltage protection module and the second charging overvoltage protection module, it can control the charging of the lithium battery and stop the charging process when the lithium battery is over-voltage. The lithium battery charging overvoltage secondary protection circuit separates the charging detection and charging overvoltage functions from the charging power supply to realize the charging management control and charging protection functions, which can effectively improve the safety of lithium battery charging and has the advantages of simple structure, low cost and easy implementation.

[0088] The working principle of the lithium battery charging system according to the embodiment of the present invention can be referred to the description of the lithium battery charging overvoltage secondary protection circuit above, which will not be repeated here.

[0089] It will be understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present invention, and the present invention is not limited thereto. Those skilled in the art will appreciate that various modifications and improvements can be made without departing from the spirit and substance of the present invention, and such modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A secondary protection circuit for lithium battery charging overvoltage, characterized in that: include: a first charging overvoltage protection module, a second charging overvoltage protection module, and at least one bypass filter module, wherein the first charging overvoltage protection module is electrically connected to the second charging overvoltage protection module, the first charging overvoltage protection module is further used to connect to the positive electrode of the lithium battery, the second charging overvoltage protection module is further used to connect to the positive electrode of the charging power supply, and the bypass filter module is electrically connected to at least the first charging overvoltage protection module and / or the second charging overvoltage protection module; The first charging overvoltage protection module is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and output a charging start signal when it is determined that the voltage of the lithium battery is less than the charging voltage, and output a charging shutdown signal when it is determined that the voltage of the lithium battery is not less than the charging voltage; The second charging overvoltage protection module is configured to output a charging voltage to the first charging overvoltage protection module according to the output voltage of the charging power supply when receiving the charging start signal, and stop outputting the charging voltage to the first charging overvoltage protection module when receiving the charging shutdown signal; The bypass filter module is used to filter the charging voltage; Wherein, the first charging overvoltage protection module at least includes: a charging voltage detection unit, a signal processing unit, a charging unit, an overcharge detection unit and a first charging switch unit; The first input end of the charging voltage detection unit is connected to the output end of the second charging overvoltage protection module, the second input end of the charging voltage detection unit is connected to the positive electrode of the lithium battery, and the output end of the charging voltage detection unit is connected to the signal processing unit. The charging voltage detection unit is used to monitor the charging voltage and the current voltage of the lithium battery in real time, and generate a corresponding detection signal according to the relationship between the charging voltage and the current voltage of the lithium battery; The input end of the signal processing unit is connected to the charging voltage detection unit, and the output end of the signal processing unit is connected to the charging unit and the overcharge detection unit respectively. The signal processing unit is configured to directly output a high-level detection signal when the detection signal is at a high level, and to delay outputting a low-level detection signal when the detection signal is at a low level; The charging unit is connected to the signal processing unit and the first charging switch unit respectively, and the charging unit is used to generate a charging start driving signal according to the high level detection signal or generate a charging shutdown driving signal according to the low level detection signal; The overcharge detection unit is respectively connected to the signal processing unit, the positive electrode of the lithium battery, and the second charging overvoltage protection module. The overcharge detection unit is used to start overcharge detection according to the high-level detection signal, and output a low-level overcharge signal when the voltage of the lithium battery is not greater than the overcharge voltage threshold, or output a high-level overcharge signal when the voltage of the lithium battery is greater than the overcharge voltage threshold; or output a low-level overcharge signal according to the low-level detection signal to turn off overcharge detection; The first charging switch unit is configured to be turned on according to the charging start driving signal to transmit the charging voltage to the lithium battery, or to be turned off according to the charging stop driving signal to block the charging voltage from being transmitted to the lithium battery.

2. The lithium battery charging overvoltage secondary protection circuit according to claim 1, characterized in that: The first charging switch unit includes a P-type MOS tube.

3. The lithium battery charging overvoltage secondary protection circuit according to claim 2, characterized in that: The charging voltage detection unit includes: a first comparator, the non-inverting input end of the first comparator is used to connect to the output end of the second charging overvoltage protection module, the inverting input end of the first comparator is used to connect to the positive electrode of the lithium battery, and the output end of the first comparator is the output end of the charging voltage detection unit.

4. The lithium battery charging overvoltage secondary protection circuit according to claim 2, characterized in that: The signal processing unit includes: a first trigger, a second trigger, a third trigger, a fourth trigger and a first NOT gate. The first trigger, the second trigger, the third trigger and the fourth trigger are connected in series in sequence. The D input end of the first trigger is the input end of the signal processing unit. The input end of the first NOT gate is connected to the D input end of the first trigger. The output end of the first NOT gate is respectively connected to the SN end of each of the first trigger, the second trigger, the third trigger and the fourth trigger. The Q output end of the second trigger and the Q output end of the fourth trigger are both output ends of the signal processing unit.

5. The lithium battery charging overvoltage secondary protection circuit according to claim 2, characterized in that: The overcharge detection unit includes: a second comparator and a first AND gate, the non-inverting input of the second comparator is connected to the positive electrode of the lithium battery, the inverting input of the second comparator is used to input the overcharge voltage threshold, the output of the second comparator is connected to the first input of the first AND gate, the second input of the first AND gate is connected to the output of the signal processing unit, and the output of the first AND gate is used to connect to the second charging overvoltage protection module.

6. The lithium battery charging overvoltage secondary protection circuit according to claim 1, characterized in that: The first charging overvoltage protection module also includes: an LED driving unit, which is connected to the signal processing unit, and the LED driving unit can generate a charging state flashing driving signal according to the high-level detection signal output by the signal processing unit or generate an overcharging state flashing driving signal according to the low-level detection signal output by the signal processing unit.

7. The lithium battery charging overvoltage secondary protection circuit according to claim 1, characterized in that: The second charging overvoltage protection module includes: a charge pump and a second charging switch unit, the charge pump is connected to the second charging switch unit, and the second charging switch unit and the charge pump are respectively connected to the charging power supply and the first charging overvoltage protection module; The charge pump is configured to generate a switch driving signal according to the output voltage of the charging power supply and the overcharge detection signal of the first charging overvoltage protection module; The second charging switch unit is configured to be turned on according to the switch driving signal to output a charging voltage to the first charging overvoltage protection module, or to be turned off according to the switch driving signal to stop outputting a charging voltage to the first charging overvoltage protection module.

8. The lithium battery charging overvoltage secondary protection circuit according to claim 7, characterized in that: The second charging switch unit includes an N-type MOS transistor.

9. A lithium battery charging system, characterized in that: It includes a lithium battery, a charging power supply and a lithium battery charging overvoltage secondary protection circuit as described in any one of claims 1 to 8, wherein the lithium battery charging overvoltage secondary protection circuit is respectively connected to the output end of the charging power supply and the positive electrode of the lithium battery, and the lithium battery charging overvoltage secondary protection circuit is used to provide a charging voltage to the lithium battery according to the output voltage of the charging power supply, and to turn on the overvoltage protection function when the voltage of the lithium battery is not less than the charging voltage.

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