CN108683219B

CN108683219B - Lithium battery protection circuit

Info

Publication number: CN108683219B
Application number: CN201810378757.2A
Authority: CN
Inventors: 不公告发明人
Original assignee: Shenzhen Zhendi Information Technology Co ltd
Current assignee: Shenzhen Zhendi Information Technology Co ltd
Priority date: 2018-04-25
Filing date: 2018-04-25
Publication date: 2021-03-26
Anticipated expiration: 2038-04-25
Also published as: CN108683219A

Abstract

The invention relates to a lithium battery protection circuit which comprises a lithium battery access port, a discharge port, a charge port and a charge circuit, wherein the lithium battery access port is used for connecting the positive electrode and the negative electrode of a lithium battery, the discharge port is used for discharging the lithium battery, the charge port is used for charging the lithium battery, and the charge circuit charges the lithium battery. Wherein charge the mouth separately with the discharge port, the discharge port can continue to adopt specific design in order to satisfy requirements such as performance, and the interface that the commonality is strong can be selected to the mouth that charges like this. An enabling port is added in the battery protection circuit, and after the battery protection circuit is placed in equipment, the MOS can be opened to discharge after the enabling port is pulled down. Meanwhile, a design circuit is added, so that an enable port can be automatically pulled down when charging is carried out, an MOS is opened, and normal charging is guaranteed. Under other conditions, the MOS of the battery is disconnected, and no output of the battery is ensured. The charging loop is additionally provided with a one-way conduction loop, so that no output is generated at a charging port during discharging.

Description

Lithium battery protection circuit

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium battery protection circuit.

Background

A "lithium battery" is a type of battery using a nonaqueous electrolyte solution with lithium metal or a lithium alloy as a negative electrode material. Lithium metal batteries were first proposed and studied by Gilbert n.lewis in 1912. In the 70 s of the 20 th century, m.s.whitetingham proposed and began to study lithium ion batteries. Because the chemical characteristics of lithium metal are very active, the requirements on the environment for processing, storing and using the lithium metal are very high. Therefore, lithium batteries have not been used for a long time. In recent years, more and more products such as PDAs, digital cameras, mobile phones, portable audio devices, bluetooth devices, and the like, adopt lithium batteries as main power sources, and now, lithium batteries have become the mainstream.

The lithium battery has the following advantages:

1. the energy ratio is relatively high, and the high storage energy density reaches 460-600Wh/kg, which is about 6-7 times that of the lead-acid battery;

2. the service life is long and can reach more than 6 years, and the battery 1C (100% DOD) taking lithium iron phosphate as the anode is charged and discharged and can be used for 10,000 times;

3. the rated voltage is high (the single working voltage is 3.7V or 3.2V), and is approximately equal to the series voltage of 3 nickel-cadmium or nickel-hydrogen rechargeable batteries, so that a battery power pack is convenient to form; the lithium battery can adjust the voltage to 3.0V by a novel technology of the lithium battery voltage regulator so as to be suitable for small electric appliances.

4. The lithium ion battery has high power bearing capacity, wherein the lithium ion battery of ferrous phosphate for the electric automobile can achieve the charge and discharge capacity of 15-30C, and the high-strength starting acceleration is facilitated;

5. the self-discharge rate is very low, which is one of the most outstanding advantages of the battery, and can be generally less than 1%/month, which is less than 1/20 of a nickel-hydrogen battery;

6. the weight is light, and the weight of the lead-acid product is 1/6-1/5 under the same volume;

7. the high-low temperature adaptability is strong, the material can be used in the environment of-20 ℃ to-60 ℃, and can be used in the environment of-45 ℃ after being processed in the process;

8. the environment-friendly paint is green and environment-friendly, and does not contain or generate any toxic and harmful heavy metal elements and substances such as lead, mercury, cadmium and the like no matter produced, used and discarded.

9. The production basically does not consume water, and is very beneficial to China with water shortage.

However, lithium batteries also have the following disadvantages:

1. the lithium primary batteries have poor safety and risk of explosion.

2. Lithium cobaltate lithium ion batteries cannot discharge large current, are expensive and have poor safety.

3. Lithium ion batteries all need protection circuits to prevent the batteries from being overcharged and overdischarged.

Therefore, unlike nickel-cadmium or nickel-hydrogen batteries, lithium ion batteries have a high energy density and must be safe in charge and discharge to prevent deterioration of characteristics. In order to improve the charging and discharging safety of the lithium battery, the following protection is generally adopted:

1. voltage protection: overcharge and overdischarge protection, which varies depending on the material of the battery.

And in the overcharge protection, the protection voltage of a single battery is 50-150 mV higher than the full charging voltage of the battery, and the full charging voltage of the power battery is even lower than the full charging voltage. For example, a manganese lithium battery, 4.18V-4.2V can be selected. Because the battery pack is provided with a plurality of strings, the service life capacity of the whole battery pack is mainly based on the battery with the lowest capacity, and the battery with the low capacity always works under high current and high voltage, so that the attenuation is accelerated. The large capacity is slightly charged and discharged each time, and the natural decay is much slower. In order to make the small-capacity battery also be lightly charged and lightly discharged, the overcharge protection voltage point is not selected to be too high.

Over-discharge protection is also related to the material of the battery, such as a manganese lithium battery which is generally selected to be 2.8V-3.0V. The voltage is slightly higher than the over-discharge voltage of a single battery. Because the discharge characteristics of the batteries produced in China are completely different after the battery voltage is lower than 3.3V, the batteries are protected in advance, and the service life of the batteries is well protected. The overall point is to make every battery work under light charge and light discharge, which is certainly helpful to the service life of the battery.

The over-discharge protection delay time varies with the load, for example, in the power tool type, the starting current is generally over 10C, so that the voltage of the battery is pulled to the over-discharge voltage point in a short time to protect the battery.

2. Current protection: the protection circuit is mainly characterized in that the MOS switch is disconnected by working current and overcurrent so as to protect a battery pack or a load.

The damage of the MOS tube is mainly caused by the rapid temperature rise, the heat generation of the MOS tube is determined by the current magnitude and the internal resistance of the MOS tube, certainly, the MOS tube is not influenced by the small current, and the MOS tube can be directly driven by the voltage under the small current of 10A. However, the large current must be applied to drive the MOS with a large enough driving current. At design time, no more than 0.3W of power can exist on the MOS transistor. If the power exceeds, the MOS will generate temperature rise of more than 25 degrees, and because they are sealed, even if the heat sink is arranged, the temperature will rise when the battery works for a long time, and the generated heat will affect the battery. Therefore, overcurrent protection (maximum current), which is an essential protection parameter for protection boards, is a very critical protection parameter. The magnitude of the protection current is closely related to the power of the MOS, so that the margin of the MOS capability is given as much as possible in the design.

3. Short-circuit protection: generally, the protection is of a voltage comparison type, namely, the protection is directly switched off or driven by voltage comparison, and meanwhile, the setting of short circuit delay is also very critical, because in a general product, input filter capacitors are very large, the capacitors are charged at the first time when in contact, and at the moment, the short circuit of a battery is equivalent to the short circuit of the battery to charge the capacitors.

4. Temperature protection: the battery pack is generally used for intelligent batteries and is also indispensable. The temperature of the battery is mainly detected to open the main switch to protect the battery or a load.

MOS protection: mainly the voltage, current and temperature of the MOS. The withstand voltage of the MOS generally exceeds the voltage of the battery pack. The current is the temperature rise across the MOS body at the nominal current through which it passes, typically not exceeding 25 degrees. The common overcurrent and short circuit driving can not be directly driven by a chip but is added externally. When a large current (more than 50A) works, the same current can be normally turned on and off at the same time of the MOS by multi-stage multi-path driving generally. Especially, when the current exceeds 50A, the current design needs to be more refined, and multi-level and multi-path driving control is necessarily achieved. Thus, the normal overcurrent and short-circuit protection of the MOS can be ensured. Meanwhile, attention is paid to MOS current balance, that is, when a plurality of MOS transistors are used together, the current passing through each MOS transistor is consistent in opening and closing time.

6. The power consumption is as small as possible, and the optimal state is zero, and the power consumption is divided into integral power consumption and power consumption of each string. The power consumption of each string is the most critical, and if the power consumption of each string is not the same, the capacity of the battery must be changed after a long time.

7. And (3) equalization: at present, the most common balancing modes are divided into two types, namely an energy consumption type and a energy conversion type.

A energy consumption type balance mainly consumes redundant electric energy by using a resistor when the electric quantity or voltage of a certain battery in a plurality of strings of batteries is high. It is also classified into the following three types.

The method is mainly applied to intelligent software schemes no matter what range the voltage of the battery is in. Of course how the definition can be arbitrarily adjusted by software. The advantage of this scheme is that it has more time to make the voltage equalization of the battery.

Secondly, the voltage is balanced at a fixed point, namely the balance start is fixed at a voltage point, such as a manganese lithium battery, and the balance is started by fixing at 4.2V. This is done only at the end of the battery charge, so the equalization time is short and useful.

And thirdly, static automatic equalization can be carried out in the charging process or the discharging process, and the method is further characterized in that when the battery is statically placed, if the voltage is inconsistent, the battery is equalized until the voltage of the battery is consistent.

The above three ways are all realized by using reference voltage to realize equalization. The battery has the advantages of low cost and simple design, can play a certain role when the voltage of the battery is inconsistent, and mainly reflects the inconsistent voltage caused by long-time shelf and self-consumption of the battery. Theoretically, there is little feasibility. The defects of complex circuit, more elements, high temperature, poor static electricity prevention and high failure rate.

And B, energy transfer type equalization, which is to transfer a large-capacity battery to a small-capacity battery in an energy storage manner. It also balances capacity by capacity from time to time and capacity by point. It is balanced by detecting the capacity of the battery, but does not seem to take into account the voltage of the battery. Taking a 10AH battery as an example, if there is a capacity of 10.1AH, a small point of the capacity of 9.8AH, the charging current is 2A, and the energy balance current is 0.5A. In this case, 10.1AH is charged for small capacity 9.8AH, and 9.8AH is charged with 2A +0.5A to 2.5A, and 9.8AH is charged with a capacity of 9.8AH, but what is the voltage of 9.8 AH? Obviously, the charging rate will rise faster than that of other batteries, if the charging end is reached, the 9.8AH battery will be protected by over-charging greatly, and the small-capacity battery is in a deep-charging and deep-discharging state all the time in each charging and discharging cycle. And if other batteries are fully charged, the uncertain factor is too much.

Due to the rapid development of power lithium batteries in recent years, the rapid development of power lithium batteries has a great breakthrough in both production process and material technology improvement or price advantage, and therefore, the rapid development of power lithium batteries lays a solid foundation for multiple series and multiple strings. The era of replacing lead-acid batteries is more and more recent. The market occupation rate of electric bicycles and backup power supplies is naturally also beginning to be greatly expanded, which is a non-repudiatable fact. The effective protection of lithium batteries is naturally scarce for the safety and life of the batteries, and the protection plate is one of the most central components in the battery pack.

The design scheme of the lithium battery protection circuit in the prior art has the following problems:

1. the problem that the charger DC head cannot be used universally;

2. the problems of short circuit, spark and the like caused by mistaken touch due to electrification before the battery is placed into equipment;

3. when discharging, the charging port also has voltage, causing the problem of water corrosion.

Disclosure of Invention

In order to solve the technical problem, the invention provides a lithium battery protection circuit which comprises a lithium battery access port, a discharge port, a charge port and a charge circuit;

the lithium battery access port comprises a first access end and a second access end and is used for connecting the positive electrode and the negative electrode of the lithium battery;

the discharge port comprises a first discharge electrode and a second discharge electrode, is respectively connected with the first access end and the second access end, and is used for discharging the lithium battery;

the charging port comprises a first charging electrode and a second charging electrode and is used for charging the lithium battery;

the charging circuit is connected between the charging port and the lithium battery access port and charges the lithium battery; wherein the content of the first and second substances,

the discharge port and the charging port are separated from each other.

Preferably, the charging port is a lotus head or a concentric circle.

Preferably, the charging circuit comprises a first resistor R8, a first capacitor C6, a first MOS transistor Q6 and a first MOS transistor controller.

Preferably, the first MOS transistor Q6 is AON6236, and the first MOS transistor controller is LM 5050-1.

Preferably, the first ends of pins 1-3 of AON6236, pin 4 of LM5050-1 and a first resistor (R8) are connected with the first charging electrode, the first ends of

pins

2 and 3 of LM5050-1 and a first capacitor (C6) are connected with the second charging electrode, the second ends of pin 1 of LM5050-1, a resistor R8 and a first capacitor C6 are connected, pin 5 of AON6236 and pin 6 of LM5050-1 are connected with the first access end, the second access end is connected with the second charging electrode, and the second access end is grounded with the second charging electrode.

Preferably, the lithium battery comprises a battery MOS tube, the lithium battery discharge circuit comprises an enabling circuit, the enabling circuit comprises an enabling port, and the enabling port is connected with the battery MOS tube.

Preferably, when the lithium battery is charged, the enabling port is automatically pulled down, and the MOS tube of the battery is opened, so that normal charging is ensured.

Preferably, the enabling circuit comprises a second resistor R13, a third resistor R17 and a second MOS transistor Q7.

Preferably, the enabling circuit is connected to the charging circuit through the second resistor R13 and the third resistor R17 connected in series.

Preferably, the second MOS transistor Q7 is 2N 7002K.

Preferably, pin 3 of 2N7002K is connected with the enable port, pin 2 of 2N7002K and a first end of a third resistor (R17) are grounded, a first end of a second resistor (R13) is connected with the first charging electrode, and pin 1 of 2N7002, a second end of the third resistor (R17) and a second end of a second resistor (13) are connected.

Preferably, the enabling circuit is designed to enable the MOS tube to be opened for discharging by pulling down the enabling port.

Preferably, the charging circuit further comprises a one-way conduction circuit, and the one-way conduction circuit ensures that no output exists at the charging port when discharging.

Preferably, the unidirectional conduction circuit comprises a diode.

Compared with the prior art, the scheme of the embodiment of the invention at least has the following beneficial effects:

1. the charging port and the discharging port are separated, so that the discharging port can be continuously designed in order to meet the requirements of performance and the like, the charging port generally only has a positive electrode and a negative electrode, and the current is relatively low, so that interfaces with strong universality, such as concentric circles and lotus heads, can be selected.

2. An enabling port is added in the battery protection circuit, and after the battery protection circuit is placed in equipment, the MOS can be opened to discharge after the enabling port is pulled down. Meanwhile, a design circuit is added, so that an enable port can be automatically pulled down when charging is carried out, an MOS is opened, and normal charging is guaranteed. Under other conditions, the MOS of the battery is disconnected, and no output of the battery is ensured.

3. The charging loop is additionally provided with a one-way conduction loop, so that no output is generated at a charging port during discharging.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

Fig. 1 is a schematic circuit diagram of a lithium battery protection circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of an enable circuit according to an embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.

It should be understood that although the terms first, second, third, etc. may be used to describe XXX in the embodiments of the present application, these XXX should not be limited to these terms. These terms are used only to distinguish XXX. For example, a first resistor may also be referred to as a second resistor, and similarly, a second resistor may also be referred to as a first resistor without departing from the scope of embodiments of the present application.

The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.

It is also noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a good or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such good or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a commodity or system that includes the element.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Example 1:

the embodiment provides a lithium battery protection circuit, which comprises a lithium battery access port, a discharge port, a charge port and a charge circuit; as shown in fig. 1, the lithium battery access port includes a first access end and a second access end, and is used for connecting the positive electrode and the negative electrode of the lithium battery; the discharge port comprises a first discharge electrode and a second discharge electrode, is respectively connected with the first access end and the second access end, and is used for discharging the lithium battery; the charging port comprises a first charging electrode and a second charging electrode and is used for charging the lithium battery; the charging circuit is connected between the charging port and the lithium battery access port and charges the lithium battery; wherein the discharge port and the charge port are separated from each other. Therefore, the discharging port can be continuously designed in order to meet the requirements of performance and the like, the charging port generally only has a positive electrode and a negative electrode, and the current is relatively low, so that interfaces with strong universality, such as concentric circles and lotus heads, can be selected.

The charging circuit comprises a first resistor R8, a first capacitor C6, a first MOS transistor Q6 and a first MOS transistor controller. Preferably, the first MOS transistor Q6 is AON6236, the first MOS transistor controller is LM5050-1, and the specific circuit connection manner thereof is as shown in fig. 1, wherein, pins 1-3 and LM5050-1, pin 4 of AON6236, the first end of a first resistor (R8) are connected to the first charging electrode, pins 2 and 3 of LM5050-1, the first end of a first capacitor (C6) are connected to the second charging electrode, pin 1 of LM5050-1, the second end of a resistor R8, the second end of a first capacitor C6 are connected, pin 5 and pin 6 of LM5050-1 of AON6236 are connected to the first access terminal, the second access terminal is connected to the second charging electrode, and the second access terminal, the second discharging electrode and the second charging electrode share a ground voltage.

Example 2:

the embodiment provides a lithium battery protection circuit, which comprises a lithium battery access port, a discharge port, a charge port and a charge circuit; the lithium battery access port comprises a first access end and a second access end and is used for connecting the positive electrode and the negative electrode of the lithium battery; the discharge port comprises a first discharge electrode and a second discharge electrode, is respectively connected with the first access end and the second access end, and is used for discharging the lithium battery; the charging port comprises a first charging electrode and a second charging electrode and is used for charging the lithium battery; the charging circuit is connected between the charging port and the lithium battery access port and charges the lithium battery; wherein the discharge port and the charge port are separated from each other.

The lithium battery comprises a battery MOS tube, the lithium battery discharging circuit comprises an enabling circuit, the enabling circuit comprises an enabling port, and the enabling port is connected with the battery MOS tube.

The enabling circuit comprises a second resistor R13, a third resistor R17 and a second MOS transistor Q7.

The enabling circuit is connected to the charging circuit through the second resistor R13 and the third resistor R17 which are connected in series.

The second MOS transistor Q7 is preferably 2N 7002K.

The specific circuit connection mode of the enabling circuit is shown in fig. 2, a pin 3 of 2N7002K is connected with the enabling port, first ends of a pin 2 of 2N7002K and a third resistor (R17) are grounded, a first end of a second resistor (R13) is connected with the first charging electrode, and a pin 1 of 2N7002, a second end of the third resistor (R17) and a second end of a second resistor (13) are connected.

Further preferably, the enable circuit is designed such that the enable port is pulled low to open the MOS transistor for discharging.

Under the other conditions of non-charging and non-discharging, the MOS of the battery is disconnected, and the battery is ensured not to output outwards. The problem of the battery have the electricity before putting into equipment, cause the mistake to touch short circuit, spark etc is solved.

Example 3:

The charging circuit further comprises a one-way conduction circuit, and the charging port is ensured to have no output when discharging. The problem of during discharging, the mouth that charges also has voltage, causes to meet water corrosion is solved. Preferably, under the condition that the charging current is small, the unidirectional conducting circuit can be realized by a diode, and the cost is lower.

Through the technical scheme of the embodiment, compared with the prior art, the technical scheme solves the corresponding technical problem and has the following beneficial technical effects:

1. the charging port and the discharging port are separated, so that the discharging port can be continuously designed in order to meet the requirements of performance and the like, the charging port generally only has a positive electrode and a negative electrode, and the current is relatively low, so that interfaces with strong universality, such as concentric circles and lotus heads, can be selected. The problem that the charger DC head cannot be used universally is solved.

2. An enabling port is added in the battery protection circuit, and after the battery protection circuit is placed in equipment, the MOS can be opened to discharge after the enabling port is pulled down. Meanwhile, a design circuit is added, so that an enable port can be automatically pulled down when charging is carried out, an MOS is opened, and normal charging is guaranteed. Under other conditions, the MOS of the battery is disconnected, and no output of the battery is ensured. The problem of the battery have the electricity before putting into equipment, cause the mistake to touch short circuit, spark etc is solved.

3. The charging loop is additionally provided with a one-way conduction loop, so that no output is generated at a charging port during discharging. The problem of during discharging, the mouth that charges also has voltage, causes to meet water corrosion is solved.

The above-described circuit embodiments are merely illustrative, and the units illustrated by the separate devices may or may not be physically separate, and the components as the circuits may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims

1. A lithium battery protection circuit is characterized by comprising a lithium battery access port, a discharge port, a charge port, a discharge circuit and a charge circuit;

the discharging port and the charging port are separated from each other;

the lithium battery comprises a battery MOS tube, the discharge circuit comprises an enabling circuit, the enabling circuit comprises an enabling port, and the enabling port is connected with the battery MOS tube;

when the lithium battery is charged, the enabling port is automatically pulled down, and the MOS tube of the battery is opened, so that normal charging is ensured;

the enabling circuit comprises a second resistor (R13), a third resistor (R17) and a second MOS transistor (Q7); the second MOS tube (Q7) is 2N 7002K; the pin 3 of the 2N7002K is connected with the enable port, the first ends of the pin 2 of the 2N7002K and the third resistor (R17) are grounded, the first end of the second resistor (R13) is connected with the first charging electrode, and the second ends of the pin 1 of the 2N7002, the third resistor (R17) and the second resistor (13) are connected;

the enabling circuit is designed in such a way that the enabling port is pulled down to open the MOS tube of the battery for discharging.

2. The lithium battery protection circuit of claim 1, wherein the charging port is a lotus head or concentric circles.

3. The lithium battery protection circuit according to claim 1, wherein the charging circuit comprises a first resistor (R8), a first capacitor (C6), a first MOS transistor (Q6), and a first MOS transistor controller; the first MOS tube (Q6) is AON6236, and the first MOS tube controller is LM 5050-1;

the first ends of AON6236 pins 1-3, LM5050-1 pin 4 and a first resistor (R8) are connected with the first charging electrode, LM5050-1 pins 2 and 3 and a first capacitor (C6) are connected with the second charging electrode, LM5050-1 pin 1, a second end of the first resistor (R8) and a second end of the first capacitor (C6) are connected, AON6236 pin 5 and LM5050-1 pin 6 are connected with the first access end, the second access end is connected with the second charging electrode, and the second access end, the second discharging electrode and the second charging electrode share the ground voltage.

4. The lithium battery protection circuit as claimed in any one of claims 1 to 3, wherein the charging circuit further comprises a unidirectional conduction circuit, and the unidirectional conduction circuit ensures that no output is generated at the charging port when discharging.