Voltage protection circuit for lithium ion single-section positive end secondary overcharge protection

Abstract

The utility model provides a voltage protection circuit for lithium ion single-section positive end secondary overcharge protection, which relates to the technical field of lithium ion battery protection and comprises a primary protection unit, a secondary protection unit and a fusing protection unit. The primary protection unit is connected with the positive pole of the power supply and is connected with the current detection resistor to provide primary overcharge protection; the secondary protection unit is connected with the field effect transistor, and when the primary protection unit fails, overcharge protection is started; and the fusing protection unit is connected in series in the charging loop, and when the secondary protection is activated and fused, the charging loop is cut off. Under the condition that the first-stage protection fails, the second-stage protection is started to cut off the charging loop in time, so that the safety of the battery is ensured, reliable overcharge protection is provided, and dangerous conditions such as explosion or combustion of the lithium ion battery in an overcharge state are prevented.

Description

TECHNICAL FIELD

[0001] The utility model relates to lithium ion battery protection technical field, especially a voltage protection circuit for lithium ion single section positive end two level overcharge protection for preventing battery explosion or combustion under overcharge state. BACKGROUND

[0002] Lithium ion batteries are widely used in various portable electronic devices, and their high energy density and long life make them popular. However, lithium ion batteries will produce high internal temperature under overcharge state, which may cause uncontrolled chemical reaction inside the battery, thus causing fire or even explosion. To suppress and prevent this risk, a multi-level protection strategy is usually adopted in the battery management system.

[0003] The common protection strategy includes first level protection and second level protection. The existing lithium ion single section two level overcharge protection voltage on the market, the existing IC without dedicated single section two level overcharge protection voltage, now using the original lithium battery single section full protection IC (overcharge, overdischarge, overcurrent, etc.) needs to use two level lithium protection IC negative end protection and MOS tube mode (this mode is designed), which is expensive and has small utilization space. The first level protection is usually realized by a protection IC (integrated circuit) with functions of power display, overcharge protection, overdischarge protection, overcurrent protection, overtemperature protection, etc. However, when the first level protection fails due to fault or other reasons, a high-reliability second level overcharge protection mechanism is needed to further ensure the safety of the battery. SUMMARY

[0004] Therefore, the utility model aims at providing a voltage protection circuit for lithium ion single section positive end two level overcharge protection, which can start the second level protection and cut off the charging circuit in time to ensure the safety of the battery and provide reliable overcharge protection, preventing the lithium ion battery from exploding or burning under overcharge state.

[0005] To achieve the above purpose, the utility model provides the following technical scheme:

[0006] Based on the above purpose, the utility model provides a voltage protection circuit for lithium ion single section positive end two level overcharge protection, which includes a first level protection unit, a second level protection unit and a fuse protection unit. The first level protection unit is connected with the positive pole of the power supply and connected with the current detection resistor, providing first level overcharge protection. The second level protection unit is connected with the field effect transistor, starting overcharge protection when the first level protection unit fails. The fuse protection unit is connected in series in the charging circuit, cutting off the charging circuit when the second level protection is activated and fused.

[0007] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0008] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0009] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0010] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0011] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0012] As a further scheme of the utility model, the first protection IC (U2) is connected with the positive pole B+ of power supply through VDD pin, grounded (GND) through VSS pin, connected with the positive pole B+ of power supply through BAT pin, connected with current detection resistance R5, R7 respectively through SRP pin and SRN pin, current detection resistance R5 and R7 are connected in series, connected with the positive pole B+ and negative pole B- of power supply, form closed loop.

[0013] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0014] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0015] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0016] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0017] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0018] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0019] As a further scheme of the utility model, the secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0020] Compared with the prior art, the utility model provides a kind of voltage protection circuit for lithium ion single section positive end secondary overcharge protection, with the following beneficial effects:

[0021] The utility model discloses a threefold protection mechanism of primary protection, secondary protection and fuse protection, which ensures the safety of the battery during charging, the primary protection unit (U2) provides basic overcharge protection, ensures timely cut-off when the battery voltage reaches the set overcharge voltage, prevents the battery from being damaged due to overcharge, the secondary protection unit (U1) serves as secondary protection, when the primary protection unit fails or fails to respond in time, the secondary protection will intervene to further protect the battery from overcharge damage, and the fuse protection unit will fuse when the secondary protection starts, completely cutting off the charging circuit to ensure that the battery will not continue to charge in extreme conditions, thereby effectively avoiding the risk of battery damage or explosion.

[0022] The utility model discloses accurate voltage and current protection, through the cooperation of current detection resistance and protection unit pin, can accurately monitor charging current, ensures timely reaction when current exceeds the safe range, prevents excessive current from causing battery overheating or internal damage, and the current protection circuit is configured with detailed current monitoring and voltage regulating resistance, ensures that the current during battery charging does not exceed the set range, avoids overcurrent phenomenon during battery charging, and reduces the security risk.

[0023] The voltage protection circuit of the utility model greatly improves the safety and reliability of the charging system through multiple protection mechanisms, accurate voltage and current monitoring, temperature protection, automatic fuse protection and auxiliary protection of protection diodes. These designs not only effectively prevent battery overcharge, overcurrent and overheating risks, but also deal with various extreme conditions, ensuring long-term stable operation of the battery and charging equipment.

[0024] These aspects or other aspects of the present application will be more apparent in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the utility model or related technologies, the following will briefly introduce the drawings needed to be used in the exemplary embodiments or related technology description, the drawings are used to provide further understanding of the utility model, and constitute a part of the specification, and are used together with the embodiments of the utility model to explain the utility model, and do not constitute the limitation to the utility model. In the drawings:

[0026] Figure 1 The utility model discloses a circuit diagram of a voltage protection circuit for lithium ion single section positive end secondary overcharge protection. DETAILED DESCRIPTION

[0027] The application will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments described below or technical features among the embodiments can be combined with each other to form new embodiments without conflicts.

[0028] To make the objectives, technical solutions and advantages of the present application clearer, the embodiments of the present application are further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0029] It should be noted that all the expressions of "first" and "second" in the embodiments of the present application are used to distinguish two non-identical entities or non-identical parameters with the same name. It can be seen that "first" and "second" are only used for the convenience of description and should not be understood as a limitation of the embodiments of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, other steps or units inherent to the process, method, system, product or equipment containing a series of steps or units.

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The flowchart shown in the accompanying drawings is only an example and does not necessarily include all the contents and operations / steps, nor does it necessarily be executed in the described order. For example, some operations / steps can be further divided, combined or partially merged, so that the actual execution order can be changed according to the actual situation.

[0032] Some embodiments of the present application will be described in detail below in conjunction with the accompanying drawings. The following embodiments and features in the embodiments can be combined with each other without conflicts.

[0033] Referring to Figure 1 The embodiments of the present application provide a voltage protection circuit for lithium ion single-section positive terminal secondary overcharge protection, which comprises a primary protection unit, a secondary protection unit and a fuse protection unit. The primary protection unit is connected with a positive electrode of a power supply and connected with a current detection resistor to provide primary overcharge protection. The secondary protection unit is connected with a field effect transistor to start overcharge protection when the primary protection unit fails. The fuse protection unit is connected in series in a charging circuit to cut off the charging circuit when the secondary protection is activated and fused.

[0034] The utility model discloses a primary protection unit is one -level protection IC (U2), and one -level protection IC (U2) is connected with the positive pole B+ of power supply, and the overcharge protection voltage of one -level protection IC (U2) is lower than the overcharge protection voltage of two -level protection IC (U1). In which, one -level protection IC (U2) connects the positive pole B+ of power supply through VDD pin, and is grounded (GND) through VSS pin, and connects the positive pole B+ of power supply through BAT pin, and connects current detection resistance R5, R7 respectively through SRP pin and SRN pin, and current detection resistance R5 and R7 are connected in series, and connect the positive pole B+ and negative pole B- of power supply, and form closed loop. Current detection resistance (R5, R7) is used in cooperation with SRP and SRN pin, can accurately monitor charging current, ensures timely reaction when current exceeds safe range, prevents excessive current from causing battery overheating or battery internal damage. Current protection circuit passes through careful current monitoring and voltage regulation resistance's configuration, ensures that the current in the battery charging process does not exceed the set range, avoids the overcurrent phenomenon when battery charges, reduces the security risk.

[0035] The utility model discloses a primary protection, two -level protection and fuse protection triple protection mechanism, ensure the safety of battery in charging process, and the primary protection unit (U2) provides the basic overcharge protection, ensures timely cut-off when battery voltage reaches the set overcharge voltage, prevents the damage of battery due to overcharge;Two -level protection unit (U1) as secondary protection, when primary protection unit fails or fails to respond in time, two -level protection will intervene, further protects the battery from overcharge damage;The fuse protection unit will fuse when two -level protection starts, completely cuts off the charging circuit, ensures that the battery will not continue to charge under extreme conditions, thereby effectively avoiding the risk of battery damage or even explosion.

[0036] In the embodiment, current limiting resistor R6 and current limiting resistor R9 are connected between the VDD and BAT pins of the primary protection IC (U2) for current limiting of capacitor C4; resistor R8 and capacitor C6 are connected between the TS pin and the VSS pin of the primary protection IC (U2). The SCL pin of the primary protection IC (U2) is connected with voltage dividing resistor R13 and voltage dividing resistor R14, and the SDA / HDQ pin of the primary protection IC (U2) is connected with voltage regulating resistor R15 and voltage regulating resistor R16; the SRP pin of the primary protection IC (U2) is connected with resistor R17, the SRN pin is connected with resistor R18, and capacitor C7 is connected between the SRP pin and the SRN pin of the primary protection IC (U2) to suppress differential mode signals.

[0037] In this embodiment, the VDD pin of the secondary protection IC (U1) is connected to the positive supply B+ through adjusting resistor R1 and adjusting resistor R2, the VSS pin of the secondary protection IC (U1) is grounded (GND), the CS pin of the secondary protection IC (U1) is grounded through capacitor C5, a resistor R4 is connected between the CS pin and the GND of the secondary protection IC (U1), and a resistor R11 is connected between the overcharge pin of the secondary protection IC (U1) and the base of the field effect transistor Q3.

[0038] The secondary protection IC (U1) controls the base of the field effect transistor Q3 through the overcharge pin, the collector of the field effect transistor Q3 is connected to the positive supply B+, and the emitter of the field effect transistor Q3 is grounded through resistor R12. The secondary protection IC (U1) is also connected to the collector of the field effect transistor Q3 through the gate of the field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging circuit.

[0039] In the normal working state, the secondary protection IC (U1) outputs a high level on the overcharge pin, so that the field effect transistor Q3 is turned off, the field effect transistor Q2 is turned off, the fuse F1 of the fuse protection unit is turned on, and the charging circuit remains normal.

[0040] In this embodiment, the collector of the field effect transistor Q3 is connected to the positive supply B+, the emitter is grounded through resistor R12, and the base is connected to the overcharge pin of the secondary protection IC (U1) through resistor R11. The gate of the field effect transistor Q2 is connected to the collector of the field effect transistor Q3, the source is grounded, and the drain is connected in series in the charging circuit.

[0041] The fuse F1 of the fuse protection unit is connected in series in the charging circuit between the drain of the field effect transistor Q2 and the charging device P+, and the fuse F1 provides additional protection. When the secondary protection is activated, F1 will automatically melt and cut off the charging circuit. This design effectively prevents the hazards caused by the continuous charging of the battery in extreme cases. The melting function has high reliability and can respond immediately when the protection circuit fails or the battery state is abnormal, thereby avoiding battery overcharging and other potential risks.

[0042] In the embodiment, the voltage protection circuit further comprises a temperature protection switch (PTC1) connected in series between the positive pole B+ of the power supply and the charging device P+, and connected through a detection point, for providing temperature detection and protection function, and cutting off the circuit at high temperature.

[0043] In the embodiment, the voltage protection circuit further comprises bus connections SCL, SDA, P+ and P-; the SCL and SDA are connected to the communication interface and the MCU of the secondary protection IC (U1) respectively, for data communication, and the P+ and P- are connected to the positive pole and the negative pole of the charging circuit respectively.

[0044] The voltage protection circuit further comprises protection diodes (D1, D2, D3 and D4), the protection diode D1 is connected to the positive pole of the charging circuit, for preventing voltage backflow, the protection diodes D2, D3 and D4 are connected to the SCL and SDA bus lines, for providing ESD protection, which can effectively prevent the occurrence of voltage backflow, protect the circuit from reverse voltage, and avoid damage to the device, wherein the D1 protects the positive pole of the charging circuit from reverse flow of overvoltage, and the D2, D3 and D4 mainly provide ESD protection for the data communication lines (SCL and SDA), and enhance the tolerance of the circuit to electrical interference.

[0045] Through the cooperation of the multiple protection mechanisms, the utility model can cope with different abnormal conditions, ensure the stability of the battery, the charging device and the circuit during the charging process, the hierarchical design of the multi-stage protection not only enhances the precision of protection, but also reduces the risk of single point failure, and improves the reliability of the whole system. The voltage protection circuit of the utility model greatly improves the safety and reliability of the charging system through the multiple protection mechanisms, accurate voltage and current monitoring, temperature protection, automatic fuse protection and auxiliary protection of the protection diode. These designs not only can effectively prevent the risks of overcharging, overcurrent and overheating of the battery, but also can cope with various safety hazards in extreme conditions, and ensure the long-term stable operation of the battery and the charging device.

[0046] The above is the exemplary embodiment disclosed by the utility model, but it should be noted that various changes and modifications can be made without departing from the scope of the utility model embodiment defined by the claims. The functions, steps and / or actions of the method claims described herein do not need to be performed in any particular order. Furthermore, although the elements of the utility model embodiment disclosed can be described or claimed in individual form, or in a hierarchical form, unless otherwise specified, each element can be fractionized into a plurality of elements.

[0047] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and not intended to suggest that the scope of the utility model embodiment disclosed (including the claims) is limited to these examples; the above embodiments or technical features among different embodiments can also be combined, and there are many other changes of the different aspects of the utility model embodiment as above. In order to be brief, they are not provided in details. Therefore, any omission, modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model embodiment should be included in the protection scope of the utility model embodiment.

Claims

1. A voltage protection circuit for lithium-ion single-cell positive-end secondary overcharge protection, characterized in that, The application relates to a protection unit for a charging device, which comprises a primary protection unit, a secondary protection unit and a fuse protection unit; the primary protection unit is connected with a positive pole of a power supply and connected with a current detection resistor, and provides primary overcharge protection; the secondary protection unit is connected with a field effect transistor, and starts overcharge protection when the primary protection unit fails; and the fuse protection unit is connected in series in a charging loop, and cuts off the charging loop when the secondary protection unit is activated.

2. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 1, wherein, The primary protection unit is a primary protection IC, the primary protection IC is connected with a positive pole B+ of the power supply; the secondary protection unit is a secondary protection IC, and the overcharge protection voltage of the primary protection IC is lower than that of the secondary protection IC.

3. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 2, wherein, The primary protection IC is connected with the positive pole B+ of the power supply through a VDD pin, grounded through a VSS pin, connected with the positive pole B+ of the power supply through a BAT pin, connected with current detection resistors R5 and R7 through SRP and SRN pins respectively, and the current detection resistors R5 and R7 are connected in series and connected with the positive pole B+ and the negative pole B- of the power supply, thereby forming a closed loop.

4. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 3, wherein, A current limiting resistor R6 and a current limiting resistor R9 are connected between the VDD and BAT pins of the primary protection IC, and are used for current limiting of a capacitor C4; a resistor R8 and a capacitor C6 are connected between a TS pin and a VSS pin of the primary protection IC, and are used for signal interference suppression. A voltage dividing resistor R13 and a voltage dividing resistor R14 are connected with an SCL pin of the primary protection IC, a voltage regulating resistor R15 and a voltage regulating resistor R16 are connected with an SDA / HDQ pin of the primary protection IC; a resistor R17 is connected with the SRP pin of the primary protection IC, a resistor R18 is connected with the SRN pin of the primary protection IC, and a capacitor C7 is connected between the SRP pin and the SRN pin of the primary protection IC, thereby suppressing differential mode signals.

5. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 1, wherein, A VDD pin of the secondary protection IC is connected with the positive pole B+ of the power supply through an adjusting resistor R1 and an adjusting resistor R2, a VSS pin of the secondary protection IC is grounded, a CS pin of the secondary protection IC is grounded through a capacitor C5, a resistor R4 is connected between the CS pin and the GND of the secondary protection IC, and a resistor R11 is connected between an overcharge pin of the secondary protection IC and a base of a field effect transistor Q3.

6. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 5, wherein, The secondary protection IC controls the base of the field effect transistor Q3 through the overcharge pin, the collector of the field effect transistor Q3 is connected with the positive pole B+ of the power supply, and the emitter of the field effect transistor Q3 is grounded through a resistor R12.

7. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 6, wherein, The secondary protection IC is also connected with the collector of the field effect transistor Q3 through the gate of a field effect transistor Q2, the source of the field effect transistor Q2 is grounded, and the drain of the field effect transistor Q2 is connected in series in the charging loop.

8. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 7, wherein, The collector of the field effect transistor Q3 is connected with the positive pole B+ of the power supply, the emitter is grounded through the resistor R12, the base is connected with the overcharge pin of the secondary protection IC through the resistor R11, the gate of the field effect transistor Q2 is connected with the collector of the field effect transistor Q3, the source is grounded, and the drain is connected in series in the charging loop.

9. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 8, wherein, A fuse F1 of the fuse protection unit is connected in series in the charging loop and connected between the drain of the field effect transistor Q2 and a charging device P+.

10. The voltage protection circuit for lithium-ion single-cell positive terminal secondary overcharge protection of claim 9, wherein, The voltage protection circuit further comprises a temperature protection switch connected in series between the positive pole B+ of the power supply and the charging device P+, and connected through a detection point, for providing temperature detection and protection functions, and cutting off the circuit when the temperature is high.

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