Charging protection circuit

Abstract

The utility model discloses a charging protection circuit, which relates to the technical field of circuits and comprises a battery cell, a charging end, a discharging end, a main control chip, a protection module, a battery cell and a peripheral circuit. The main control chip is used for detecting and controlling charging and discharging voltage and current to prevent the battery from being over-charged or over-discharged; the protection module switches on and off the charging and discharging circuit according to the detection of the main control chip; and the peripheral circuit is used for limiting charging and discharging voltage and current and simultaneously filtering. The charging protection circuit and the battery protection board have accurate overcharge detection voltage, so that safe and sufficient charging is ensured; the low backup current drains little current from the battery during storage. The method can be used for protecting the battery of a digital mobile phone, is also suitable for any other information equipment which needs long-term battery life and is driven by a lithium ion battery and a lithium polymer battery, and is applied to a charge-discharge battery module of electronic equipment.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, and particularly to a battery charging protection circuit. Background Art

[0002] A battery is a battery with lithium metal or lithium alloy as the positive / negative electrode material and using a non-aqueous electrolyte solution. With the development of technology, lithium batteries have become the mainstream. Existing lithium batteries such as lithium sulfur ion / polymer batteries all have a safe voltage range for use. The highest and lowest voltages are generally called charge and discharge termination voltages or cut-off voltages. When the actual working voltage of the battery is lower than the discharge termination voltage for a long time or higher than the charge termination voltage for a long time, irreversible damage will occur inside the battery, seriously damaging the battery and causing performance degradation, commonly known as battery attenuation. The manifestations of battery attenuation are increased internal resistance and decreased capacity of the battery, etc.

[0003] In existing battery protection schemes, MOS transistors and protection chips are generally used to protect the charging of lithium batteries. Usually, a single MOS transistor on-off switch is used to protect lithium batteries, which reduces the reliability of protecting lithium batteries. The battery charge and discharge voltage and current detection units are insufficient and cannot protect the battery protection chip and MOS transistor simultaneously. Summary of the Invention

[0004] This utility model aims to solve at least one of the technical problems existing in the prior art. For this reason, the embodiments of this utility model application propose a charging protection circuit, which realizes battery charge and discharge protection through the detection of overcharging, over-discharging, over-current, and load short-circuit protection.

[0005] A charging protection circuit according to an embodiment of the present utility model application includes a battery cell, a charging terminal, and a discharging terminal. It is characterized in that the charging protection circuit further includes a main control chip, a protection module, a battery cell, and a peripheral circuit. The main control chip is used to detect and control the charging and discharging voltage and current to prevent overcharging or over-discharging of the battery. The protection module switches the charging and discharging circuit according to the detection of the main control chip. The peripheral circuit is used to limit the charging and discharging voltage and current and at the same time perform filtering processing. The VDD terminal of the main control chip is connected in parallel with the first end of the first resistor and one end of the first capacitor. The second end of the first resistor is connected in parallel with the positive pole of the battery and the positive pole P+ of the charging and discharging terminal. The VSS terminal of the main control chip is connected in parallel with the second end of the first capacitor, the negative pole of the battery, and the source electrode of the first MOSFET. The DO terminal of the main control chip is connected to the gate of the first MOSFET. The CO terminal of the main control chip is connected to the gate of the second MOSFET. The drain of the first MOSFET is connected to the drain of the second MOSFET. The source of the second MOSFET is connected in parallel with the negative pole P- of the charging and discharging terminal and the second end of the second resistor. The V- terminal of the main control chip is connected to the first end of the second resistor. The source of the first MOSFET is connected to the positive pole of the first diode, and the negative pole of the first diode is connected to the drain of the first MOSFET. The source of the second MOSFET is connected to the positive pole of the second diode, and the negative pole of the second diode is connected to the drain of the second MOSFET.

[0006] The charging and discharging circuit, charging and discharging protection board, and charging and discharging protection device designed according to the above solution have all the protection functions required in battery applications, including overcharging, over-discharging, over-current, and load short-circuit protection, etc. Its accurate overcharging detection voltage ensures safe and sufficient charging. The low standby current discharges very little current from the battery during storage. This solution can be used not only for the protection of digital mobile phone batteries but also for any other information device driven by lithium-ion and lithium-polymer batteries that require long battery life. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The above and / or additional aspects and advantages of the present utility model will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0008] Figure 1 is a schematic diagram of the principle of a charging protection circuit according to an embodiment of the present utility model;

[0009] Figure 2 is a partial structural schematic diagram of a charging protection circuit according to an embodiment of the present utility model;

[0010] Figure 3 is a structural schematic diagram of the main control chip of a charging protection circuit according to an embodiment of the present utility model.

[0011] Among them, the meanings represented by the reference numerals of each drawing are as follows:

[0012] U1: Main control chip;

[0013] Q1: First MOSFET;

[0014] Q2: Second MOSFET;

[0015] B+: Positive electrode of the battery cell;

[0016] B-: Negative electrode of the battery cell;

[0017] P+: Positive electrode of the charge and discharge terminal;

[0018] P-: Negative electrode of the charge and discharge. Detailed implementation manners

[0019] The embodiments of the present utility model will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present utility model and should not be construed as a limitation to the present utility model.

[0020] The terms "first", "second", etc. in the specification, claims and above-mentioned drawings of the present application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include steps or units not listed, or may optionally further include other steps or units inherent to these processes, methods, products or devices.

[0021] A lithium battery is a battery using a lithium metal or lithium alloy as the positive / negative electrode material and a non-aqueous electrolyte solution. With the development of technology, lithium batteries have become the mainstream. Existing lithium batteries such as lithium sulfur ion / polymer batteries all have a safe voltage range for use. The highest and lowest voltages are generally referred to as the charge and discharge termination voltages or cut-off voltages. When the actual working voltage of the battery is lower than the discharge termination voltage for a long time or higher than the charge termination voltage for a long time, irreversible damage will occur inside the battery, seriously damaging the battery and resulting in performance degradation, commonly known as battery attenuation. The manifestations of battery attenuation are increased internal resistance and decreased capacity of the battery, etc.

[0022] In the existing charge and discharge battery protection solutions, MOS transistors and protection chips are generally used to protect the charging and discharging of rechargeable batteries. Usually, a single MOS transistor on-off switch is used to protect lithium batteries, reducing the reliability of protecting lithium batteries during charging and discharging; the battery charge and discharge voltage and current detection units are insufficient, and it is impossible to protect the battery protection chip and the MOS transistor at the same time.

[0023] To solve the above problems, the present application uses a protection module composed of two MOSFETs and two diodes; the protection module and the main control chip together form a protection circuit, which realizes overcharge, over-discharge, over-current and load short-circuit protection by detecting the charging and discharging voltage and current of the battery in real time. The circuit structure of the present application is simple, and the protection circuit can be placed in an ESOP-8 package, and only one external component makes it an ideal solution in the limited battery pack space; the protection circuit of the present application ensures safe and sufficient charging through accurate overcharge detection voltage, and at the same time uses MOSFET tubes, whose low standby current discharges very little current from the battery during storage, improving the battery usage efficiency.

[0024] Referring to Figures 1 to 3 , the present utility model discloses a charging protection circuit and a battery protection board, and the circuit or principle symbol explanations are as follows:

[0025] VDD: Power input terminal of the main control chip, voltage sampling point of the lithium battery;

[0026] VSS: Reference point of the measurement circuit of the main control chip, connection point of the negative pole of the lithium battery and the main control chip;

[0027] DO: Output control terminal of the main control chip for the discharge MOS tube;

[0028] CO: Output control terminal of the main control chip for the charging MOS tube;

[0029] VM: Sampling input terminal of the main control chip for the working current of the lithium battery;

[0030] U1 main control chip.

[0031] Referring to Figure 1 , a charging protection circuit of this embodiment is described as follows:

[0032] The battery protection circuit of this embodiment includes: a main control chip, a protection module, a battery cell, a peripheral circuit, and a battery cell, a charging terminal, and a discharging terminal. In this embodiment, the peripheral circuit includes two resistors and one capacitor, and the peripheral circuit is used to limit the charging and discharging voltage and current, and at the same time perform filtering processing; the protection module includes two diodes and two MOSFET tubes; the main control chip detects and controls the charging and discharging voltage and current to prevent overcharging or over-discharging of the battery; the protection module switches the charging and discharging circuits according to the detection of the main control chip.

[0033] The connection modes of each part of the battery protection circuit in this embodiment are as follows:

[0034] The VDD terminal of the main control chip U1 is connected in parallel with the first end of the first resistor R1 and one end of the first capacitor C1; the second end of the first resistor R1 is connected in parallel with the positive pole B+ of the battery and the positive pole P+ of the charging terminal; the VSS terminal of the main control chip U1 is connected in parallel with the second end of the first capacitor C1, the negative pole B- of the battery, and the source S terminal of the first MOSFET Q1; the DO terminal of the main control chip U1 is connected to the gate G terminal of the first MOSFET Q1; the CO terminal of the main control chip U1 is connected to the gate G terminal of the second MOSFET Q2; the drain D terminal of the first MOSFET Q1 is connected to the drain D of the second MOSFET Q2; the source S terminal of the second MOSFET is connected in parallel with the negative pole P- of the charging terminal and the second end of the second resistor R2; the V- terminal of the main control chip U1 is connected to the first end of the second resistor R2; the source S of the first MOSFET Q1 is connected to the positive pole of the first diode, and the negative pole of the first diode is connected to the drain D terminal of the first MOSFET Q1; the source S terminal of the second MOSFET Q2 is connected to the positive pole of the second diode, and the negative pole of the second diode is connected to the drain D terminal of the second MOSFET Q2.

[0035] In this embodiment, for the main control chip U1, the pin descriptions are as follows:

[0036] VDD: Power input terminal of the main control chip, voltage sampling point of the lithium battery;

[0037] VSS: Reference point of the measurement circuit of the main control chip, connection point between the negative pole of the lithium battery and the main control chip;

[0038] DO: Output control terminal of the main control chip for the discharge MOS transistor;

[0039] CO: Output control terminal of the main control chip for the charging MOS transistor;

[0040] VM: Sampling input terminal of the main control chip for the working current of the lithium battery.

[0041] The working principle of the battery protection circuit in this embodiment is as follows:

[0042] When the protection circuit is normal, VDD is at a high level, VSS and VM are at a low level; DO and CO are at a high level. When any one of the parameters of VDD, VSS, and VM changes, the level of the DO or CO terminal will change. Specifically, when the battery is charging, the current flows into from the positive pole B+ end of the battery cell through the positive pole P+ of the charge and discharge, and then flows out from the negative pole B- of the battery cell. Both MOS transistors are in a conducting state.

[0043] When charging the cell or battery, the main control chip will always monitor the voltage between the VDD and VSS terminals. When this voltage is greater than or equal to the overcharge cut-off voltage and the delay time of the overcharge voltage is met, the main control chip will turn off the MOS tube Q2 by controlling the CO terminal. After Q2 is turned off, the charging circuit is cut off. At the same time, the diode D2 between the source and drain of the MOS tube Q2 is also reversely cut off. At this time, the battery can only discharge.

[0044] The overcharge protection release condition can be satisfied by satisfying one of the following conditions:

[0045] 1. The voltage across the battery cell drops to the overcharge recovery voltage that protects the main control chip;

[0046] 2. Add a load to the output end of the battery cell and discharge it until the voltage is lower than the overcharge protection voltage.

[0047] When the battery cell is discharged, the protection circuit works as follows:

[0048] When a load is added to the P+ and P- ends of the battery cell for discharge, the direction of the discharge current is opposite to the charging current. When the battery is discharging, the main control chip U1 will also monitor the voltage between the VDD terminal and VSS at all times. When this voltage is less than or equal to the over-discharge cut-off voltage and reaches the delay time of the over-discharge voltage, the main control chip will turn off Q1 through the DO terminal. After Q1 is turned off, the discharge circuit is cut off, and the diode D1 between the source and drain of the MOS tube Q1 is reverse cutoff. At this time, the battery can only be charged.

[0049] Conditions for releasing over-discharge protection: remove the load and charge the battery cell. When the voltage between VM and VDD reaches the over-discharge recovery voltage value, the main control chip will reopen the MOS tube Q1.

[0050] Overcurrent protection and short-circuit protection: Overcurrent protection refers to protection against over-discharge current. The general main control chip has two types of protection: overcurrent protection and short-circuit protection. The main control chip always monitors the voltage value between VSS and VM. When the voltage value reaches the threshold of overcurrent protection or short-circuit protection and meets the delay time, the main control chip will turn off the MOS tube Q1 and cut off the discharge circuit.

[0051] The condition for releasing the over-current protection is: remove the output load, and the main control chip will automatically turn Q1 back on.

[0052] The voltage value of overcurrent protection is generally 0.1~0.2V, and the voltage value of short-circuit protection detection is generally 0.9V~2V. These two values are related to the main control chip. Different main control chips have different values.

[0053] The short - circuit protection voltage value refers to the conduction voltage drop when current flows through Q1 and Q2. That is, it can be concluded that the greater the on - resistance of the MOS transistor, the smaller the protection current value. For example, for a MOS transistor with an on - resistance of 20mΩ and a main control chip with an over - current value of 0.15V selected, the over - current protection current should be: 0.15V / (0.02 * 2)=3.75A.

[0054] In the technical solution of this embodiment, compared with the existing solution that protects the battery pack through a single switch circuit, the battery pack can be protected by the main control chip and the protection module, improving the reliability of protecting the battery pack.

[0055] Refer to Figure 3 , in the embodiment of the present application, the main control chip includes an over - current comparator, a short - circuit comparator, a charger / load detector, a short - circuit detection reference, an over - current detection reference, an over - charge & over - discharge reference, an over - charge detector, an over - discharge detector, an over - charge comparator, an over - discharge comparator, a logic processor, a delay circuit, and input / output terminals: VSS, DO, CO, Vm, Vcc; the short - circuit detection reference is connected to the inverting input terminal of the short - circuit comparator; the over - current detection reference is connected to the inverting input terminal of the over - current comparator; the non - inverting input terminal of the over - current comparator is connected in parallel with the non - inverting input terminal of the short - circuit comparator, the first terminal of the charger / load detector, and the VM terminal; the output terminals of the over - current comparator, the short - circuit comparator, the over - charge comparator, the over - current comparator, and the delay circuit are connected to the logic processor; the logic processing result is output to the DO and CO terminals; the over - charge detection terminal is connected to the non - inverting input terminal of the over - charge comparator; the over - discharge detection is connected to the inverting input terminal of the over - discharge comparator; the over - charge & over - discharge reference is connected to the inverting input terminal of the over - charge comparator and the non - inverting input terminal of the over - discharge comparator; the VCC terminal, the VSS terminal, and the VM terminal are connected; the VSS terminal is connected to the DO terminal; the DO terminal is connected to the CO terminal; the CO terminal is connected to the VM terminal; the VCC terminal is connected to the over - charge detection; the VSS terminal is connected to the over - discharge detection.

[0056] Through chip packaging, the above - mentioned parts are packaged into an SOT8 package for easy application.

[0057] Refer to Figure 2 , the embodiment of the present application also provides a battery protection module. The protection circuit is packaged in an SOT8 package, and at the same time, a metal heat sink, that is, the EPAD part, is provided at the bottom of the SOT8 package. The protection module dissipates heat during operation, further expanding the working range of the protection circuit.

[0058] The embodiment of the present application also provides a battery protection board, including the battery protection circuit in any of the above - mentioned embodiments. Here, the battery protection board can be a module that packages the above - mentioned battery protection circuit. That is to say, the battery protection board can include a packaging structure and the battery protection circuit encapsulated by the packaging structure.

[0059] The embodiments of the present utility model have been described in detail above in conjunction with the accompanying drawings. However, the present utility model is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the relevant technical field, various changes can be made without departing from the gist of the present utility model.

[0060] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0061] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0062] Although the embodiments of the present utility model have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and gist of the present utility model. The scope of the present utility model is defined by the claims and their equivalents.

Claims

1. A charging protection circuit, comprising a battery cell, a charging terminal, and a discharging terminal, characterized in that, The charging protection circuit further includes a main control chip, a protection module, a battery cell, and a peripheral circuit; the main control chip is used to detect and control the charging and discharging voltage and current to prevent overcharging or over-discharging of the battery; the protection module switches the charging and discharging circuit according to the detection of the main control chip; the peripheral circuit is used to limit the charging and discharging voltage and current and perform filtering processing at the same time; the VDD terminal of the main control chip is connected in parallel with the first end of the first resistor and one end of the first capacitor; the second end of the first resistor is connected in parallel with the positive electrode of the battery and the positive electrode P+ of the charging and discharging terminal; the VSS terminal of the main control chip is connected in parallel with the second end of the first capacitor, the negative electrode of the battery, and the source electrode of the first MOSFET; the DO terminal of the main control chip is connected to the gate of the first MOSFET; the CO terminal of the main control chip is connected to the gate of the second MOSFET; the drain of the first MOSFET is connected to the drain of the second MOSFET; the source of the second MOSFET is connected in parallel with the negative electrode P- of the charging and discharging terminal and the second end of the second resistor; the V- terminal of the main control chip is connected to the first end of the second resistor; the source of the first MOSFET is connected to the positive electrode of the first diode, and the negative electrode of the first diode is connected to the drain of the first MOSFET; the source of the second MOSFET is connected to the positive electrode of the second diode, and the negative electrode of the second diode is connected to the drain of the second MOSFET.

2. The charging protection circuit according to claim 1, characterized in that, The peripheral circuit includes two resistors and one capacitor.

3. The charging protection circuit according to claim 1, wherein The protection module includes two diodes and two MOSFETs.

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