KR20070064399A - Protecting method for lithium battery and device thereof - Google Patents

Abstract

A protecting method of a lithium battery and a protecting apparatus thereof are provided to finely control balance of each serially connected lithium battery by performing a discharge process after a parallel connected circuit board checks the over-charging of the lithium battery. A protecting apparatus for a lithium battery controls an external circuit charging and discharging a chargeable battery to prevent over-charging and over-discharging of the chargeable battery, and includes a fault detecting circuit(2) and a photo coupling circuit(3). The fault detecting circuit(2) checks voltage of the chargeable battery, and outputs a measurement signal. The photo coupling circuit(3) is electrically connected to the fault detecting circuit(2), and adjusts impedance according to a state of the measurement signal in order to block connection between the chargeable battery and the external circuit or to continuously charge or discharge the chargeable battery.

Description

PROTECTING METHOD FOR LITHIUM BATTERY AND DEVICE THEREOF

1 is a circuit diagram of a protective device of a lithium battery according to the prior arts.

2 is a circuit diagram of one parallel connection module of the protective device for a lithium battery according to the present invention.

3 is a circuit diagram showing one parallel connection module of the protection device for a lithium battery according to the present invention connected in parallel to a rechargeable battery.

4 is a circuit diagram showing a protection device for a plurality of serially connected lithium batteries according to the present invention.

5 is a circuit diagram showing another protection device for a plurality of series connected lithium batteries according to the present invention.

6 is a circuit diagram illustrating a protection device for a plurality of series-connected lithium batteries according to the present invention including an external circuit.

7 is a view showing another embodiment of a protective device for a lithium battery according to the present invention.

8 is a view showing another embodiment of a protective device for a lithium battery according to the present invention.

9 is a flow chart of a protection method for charging and discharging a lithium battery according to the present invention.

TECHNICAL FIELD The present invention relates to a control circuit connected in parallel to a battery connected in series to another battery, and more particularly, to a method for protecting a lithium battery and a device thereof.

The rechargeable batteries are classified into nickel-cadmium (Ni-Cd) batteries and nickel-hydrogen (Ni-MH) batteries. Ni-Cd batteries are the last generation of products and are rarely found on the market today. The fatal drawback of Ni-Cd cells is that they have a memory effect and a short service life. In addition, cadmium is a kind of heavy metal that easily causes environmental pollution. Ni-MH cells have been developed to overcome the disadvantages of such Ni-Cd cells. Advantages of Ni-MH batteries include reduced memory effects, improved charge capacity, durability against overcharging or overdischarging, extended life of regeneration, short charging times, and especially no use of hazardous metals, resulting in no environmental contamination. Can be mentioned. Of course, Ni-MH cells are not 100% perfect. For example, the environmental adaptability of Ni-MH cells is insufficient. Ni-MH cells are of little use in certain environments where temperatures are above 45 ° C or below 0 ° C. Therefore, in very hot or very cold places, Ni-MH cells cannot power electronic equipment. Also, when charged and idle for a period of time, the power of the Ni-MH battery is greatly attenuated unless recharged.

When the lithium battery is charged, if the charging voltage is too high, there is a risk of the battery exploding. On the other hand, when the lithium battery is being discharged, if the discharge voltage is too low, the service life of the lithium battery is affected because the voltage of the lithium battery is lower than the basic voltage. Therefore, during charging and discharging, the protection device shown in FIG. 1 is attached.

1, four series connected lithium batteries are illustrated. The protection device 100 includes a protection IC 101 of four series-connected batteries; And a circuit switch 103. During the actual design, an appropriate protection IC 101 is selected depending on the number of lithium batteries 102 connected in series. When a voltage abnormality of the lithium battery 102 is detected, the protection IC 101 transmits a signal to the circuit switch 103, whereby the circuit switch 103 is jumped off to block the charge or discharge current. off). Therefore, when there are not four lithium batteries 102 connected in series, a new set of protection devices 100 must be reproduced. At present, manufacturers can only provide protection IC 101 of four series-connected lithium battery elements. The more lithium battery elements connected in series, the more complicated the circuit design of the protection IC 101 is. Due to the complexity and unbalance of circuit design caused by uneven aging and attenuation for each series connected cell, it is very difficult to produce a protection circuit of five or more series connected lithium cell elements.

The main object of the present invention is to solve the disadvantages mentioned in the prior art. In order to avoid the existing disadvantages, the present invention redesigns the entire protection device of the rechargeable battery, and is characterized by the following: First, there is no need to consider the number of lithium batteries connected in series; Second, each series-connected lithium battery is also connected in parallel to a separate circuit board having an interface for interconnection with another circuit board; Third, if any lithium battery is abnormal, the corresponding circuit board generates a signal to notify the system of the location of the abnormal battery, and then turns off the circuit switch to cut off the charge or discharge current.

Another main object of the present invention is to determine if a series connected lithium battery is abnormal, the parallel connected circuit board first determines whether the lithium battery is overcharged, and then processes the discharge procedure for the battery, if necessary, so that each series connected It is to provide a protective device that allows fine adjustment of the balance of the used lithium battery at the same time.

Another main object of the present invention is that when the number of series-connected lithium batteries increases or decreases, it is possible to change the circuit board through external wiring so that a plurality of series-connected lithium batteries do not need to be reproduced. It is to provide a protective device.

In order to achieve the above objects, the protection device of a lithium battery according to the present invention is to prevent overcharge or overdischarge of the rechargeable battery by control of an external circuit for charging or discharging the battery. The protection device is composed of an abnormality detection circuit, a photo coupling circuit, a balance circuit, and an identity circuit. The abnormality detection circuit checks the voltage value of the charged battery and outputs a measurement signal. If the signal is normal, the charging or discharging operation continues, and if abnormal, it is cut off. Next, the balance circuit determines that the charged battery should be discharged if the measurement signal is an overcharge signal. On the other hand, depending on the state of the measurement signal, the photo coupling circuit adjusts its impedance to cut off the connection between the charged battery and the external circuit, and the identification circuit provides the system with the position of the battery sending the abnormal signal. .

In order to achieve the above objects, the present invention provides a method for protecting a lithium battery for preventing overcharging or overdischarging of a charged battery by control of an external circuit that charges or discharges a lithium battery. The protection method of the lithium battery includes the following steps:

First, it is checked whether the battery is being charged or discharged. When the checked cell is charging, it is checked whether the average voltage is greater than the maximum charge voltage of a single cell. If the answer is yes, then the charging loop is opened to stop the charging procedure. If the answer is no, check whether the output signal of the protective device is normal or abnormal. If the output signal is abnormal, the battery is charged to a lower current, and if normal the normal charging procedure continues.

If the checked cell is discharging, it is checked whether the average voltage is lower than the minimum discharge voltage of the single cell. If the answer is yes, the discharge loop is opened to stop the discharging procedure. If the answer is no, it is discharged for a few more seconds and then checks whether the output signal of the protection device is normal. If the determined signal is normal, the discharge continues, and if abnormal, the discharge operation is stopped.

The technical contents of the present invention will be described in detail with the accompanying drawings.

Reference is made to FIGS. 2 and 3, which are circuit diagrams of one parallel connection module of a protection device of a lithium battery according to the present invention and one parallel connection module of a protection device of a lithium battery connected in parallel to a rechargeable battery. In this embodiment according to the present invention, the protection device is composed of an abnormality detection circuit 2 and a photo coupling circuit 3.

First, the abnormality detection circuit 2 checks the voltage of the charged battery 4 and outputs a measurement signal to the photocoupling circuit 3. The photocoupling circuit 3 is a protective device 11 and an external circuit. In order to cut off the connection between them or to continuously charge / discharge the rechargeable battery 4, its impedance is adjusted according to the state of the signal.

The photo coupling circuit 3 includes a light emitting diode (LED) 31 and a transistor 32. The LED 31 is electrically connected to the abnormality detection circuit 2 in such a manner as to determine whether to emit light according to the voltage value of the rechargeable battery 4. On the other hand, the transistor 32 is electrically connected to an external circuit which is connected or disconnected depending on the light emitting state of the LED 31 which determines the impedance value of the transistor 32.

In this embodiment, when the battery 4 is in a steady state, the abnormality detection circuit 2 sends a measurement signal of the voltage of the battery 4 to the LED 31 of the photo coupling circuit 3. After receiving the measurement signal, the LED 31 starts to emit light, and the emitted light is incident on the other side of the transistor 32, so that the impedance between both sides of the transistor 32 is lowered.

When the battery 4 is in an abnormal state, the abnormality detection circuit 2 does not send any signal to the LED 31 so that the LED 31 does not emit light, so that the impedance between both sides of the transistor 32 increases, The photo coupling circuit 3 becomes a (blocking) open circuit because no light is incident on the other side of the transistor 32.

By light incidence, both sides of the photo coupling circuit 3 are conducted without any electrical contact, and there is a very high degree of insulation between these two sides. Thereby, as shown in FIG. 4, many series-connected lithium batteries 4 can be connected in parallel with this kind of protection module. Since both sides of the transistors 32 of each module are connected to each other by a series connection method, there is no electrical contact between the rows of transistors 32 and the rows of lithium batteries 4.

In FIG. 4, as described above, when an abnormal situation occurs in the series-connected lithium battery 4, the abnormality detection circuit 2 sends a measurement signal to stop light emission of the corresponding LED 32. Since there is no light incident on the other side of the transistor 32, the impedance between both sides of the transistor 32 becomes large, and the transistor 32 becomes an almost open circuit. In addition, since all the transistors 32 are connected to each other in series, the impedance of all the columns of the transistors 32 increases, and there is no current passing between the two sides.

On the other hand, if all lithium batteries are in a steady state, the impedance between both sides (ie, A and B) of the entire transistor 32 rows is very small. As soon as an abnormality occurs in the series-connected lithium batteries 4, the impedance between the A side and the B side immediately rises to almost an open circuit.

Further, based on this impedance variation between the A side and the B side of the transistor 32 column, another embodiment of a protection device for a plurality of series-connected lithium batteries according to the present invention may be provided as shown in the circuit diagram of FIG. Can be. In this embodiment, the circuit switch 5 and the switch control circuit 6 are also designed in the protection device. Here, the switch control circuit 6 is electrically connected to the last level of the photo coupling circuit 3. According to the impedance of the entire column of the transistor 32, a control signal can be output from this switch control circuit 6 to which the circuit switch 5 is electrically connected. By judging from the state of this control signal, the charge or discharge current is interrupted or continued. Therefore, when the impedance between the A side and the B side is low, the circuit switch 5 is turned on, but when the impedance between the A side and the B side is high, the circuit switch 5 is turned off to cut off the charge or discharge current.

Reference is now made to FIG. 6, which is a circuit diagram of an embodiment of a protection device for a plurality of series-connected lithium batteries with external circuits in accordance with the present invention. Here, the A side and the B side are electrically connected to an external circuit 7, which may for example be a system or a charger, but are not included here only.

In FIG. 6, the abnormality detection circuit 2 notifies the external circuit 7 via the impedance variation between the A side and the B side. Therefore, the external circuit 7 functions as usual when notified that the impedance between the A side and the B side is low, but when the impedance is high, the normal operation is interrupted and the charge or discharge current is interrupted.

Reference is made to FIG. 7, which shows another embodiment of a protective device for a lithium battery according to the present invention. Here, the identification circuit 8 is electrically connected to the photocoupling circuit 3 of the protection device 1. The identification circuit 8 is a resistor with an Rx value. When the photocoupling circuit 3 adjusts its impedance according to the state of the measurement signal to interrupt the electrical connection between the rechargeable battery 4 and the external circuit, the identification circuit 8 simultaneously generates a signal (resistance value). The output to the external circuit notifies the external circuit that the battery 4 is abnormal. In the example of FIG. 4, the photocoupling circuits 3 of each protection device 1 are all electrically connected to the identification circuit 8, which identifies resistance values such as resistance values 5K, 10K, 15K, 20K, and the like. This is specifically assigned. When the photocoupling circuit 3 of the second detection device 1 is in an open circuit state, the external circuit is informed of an abnormal state occurring in the second battery by receiving a resistance value of 10K.

Next, referring to FIG. 8, which shows another embodiment of the protective device for a lithium battery according to the present invention. In this embodiment, besides the identification circuit 8 is electrically connected to the photocoupling circuit 3 of the protection device 1, the balance circuit 9 is also electrically connected to the abnormality detection circuit 2. When the battery 4 is overcharged, the abnormality detection circuit 2 outputs a measurement signal to the balance circuit 9, and the balance circuit controls the battery 4 to take a discharge operation, thereby causing battery damage caused by overcharge. This can be avoided.

Reference is made to FIG. 9, which shows a flowchart of a protection method for charging and discharging a lithium battery according to the present invention. In the charging procedure of the battery 4, as shown in step 10, the charge or discharge state of the battery 4 is first determined. When the state of charge of the battery 4 is confirmed, the process proceeds to step 10a to check whether the average voltage of the battery 4 is greater than V _high (maximum charge voltage of a single battery, for example, 4.2V). If the answer is yes, the process proceeds to step 10b to open the charging loop. That is, the charging procedure is stopped. On the other hand, if the average voltage of the battery 4 is not greater than V _high , the process switches to step 10c to check the output signal of the protective device of the lithium battery. If the signal is abnormal, the process proceeds to step 10d to charge the battery 4 to low current i _low . If the signal is normal, the process proceeds to step 10e to continue the normal charging procedure.

If the determined battery 4 is in the discharged state, the process proceeds to step 10f to check the average voltage of the battery 4. If the value checked is less than V _low (minimum discharge voltage of a single cell), the process proceeds to step 10g to open the discharge loop and stop the discharge process. On the other hand, if the checked voltage is greater than V _low , the process proceeds to step 10h, and after discharge for several seconds, the process proceeds to step 10i to check whether the output signal of the protection device of the lithium battery is OK, and the signal If is normal, the process proceeds to step 10j to continue the discharge procedure. If not normal, the procedure goes to step 10k to stop the discharge operation.

Although the present invention has been described above, it is only preferred embodiments and does not limit the scope of execution. Equivalent changes and minor modifications made in accordance with the claims by one of ordinary skill in the art are included in the claims claimed by the present invention.

When the series-connected lithium battery is abnormal, the parallel-connected circuit board first determines whether the lithium battery is overcharged, and then processes the discharge procedure for the battery if necessary, so that the balance of each series-connected lithium battery is simultaneously Provide a protective device that allows for fine tuning.

In addition, when the number of series-connected lithium batteries increases or decreases, it is possible to change the circuit board through external wiring, thereby providing a protection device for a plurality of series-connected lithium batteries that do not need to reproduce a new circuit board.

Claims (11)

A protective device for a lithium battery provided to control an external circuit for charging or discharging the rechargeable battery so that overcharge or overdischarge of the rechargeable battery can be prevented. An abnormality detection circuit for checking a voltage of the rechargeable battery and outputting a measurement signal; And Electrically connected to the abnormality detection circuit to adjust its impedance according to the state of the measurement signal to interrupt the connection between the rechargeable battery and the external circuit or to discharge or charge the rechargeable battery continuously; A protective device for a lithium battery including a photo coupling circuit. The method of claim 1, The photo coupling circuit, A light emitting diode (LED) electrically connected to the abnormality detecting circuit and emitting light according to the state of the voltage signal measured by the abnormality detecting circuit; And And a transistor electrically connected to the external circuit for determining the impedance of the transistor according to the light emitting condition of the LED and for connecting or disconnecting the external circuit. The method of claim 2, The protection device for a lithium battery in which the LED emits light when the rechargeable battery is in a normal state. The method of claim 2, And when the LED emits light, the impedance of the transistor is in a low value state, whereby the connection between the LED and the external circuit is maintained in a normal state. The method of claim 2, And the LED stops emitting light when the rechargeable battery is in an abnormal state. The method of claim 5, And when the LED stops emitting light, the impedance of the transistor has a high impedance and the connection to the external circuit is cut off. The method of claim 1, A switch control circuit electrically connected to the photo coupling circuit for outputting a control signal according to the impedance state of the photo coupling circuit; And And a switch electrically connected to the switch control circuit in order to determine blocking of charge or discharge current according to the state of the control signal. The method of claim 1, An identification circuit electrically connected to the photo coupling circuit, And said identification circuit notifies the position of a battery in an abnormal state outputting a signal for notifying the position of the battery in an abnormal state to said external circuit when said photo coupling circuit is in an off state. The method of claim 8, And said output signal of said identification circuit is a resistance value. The method of claim 1, A balance circuit electrically connected to the abnormality detection circuit and the rechargeable battery; When the battery is overcharged, the abnormality detection circuit outputs a measurement signal to the balance circuit, and the balance circuit processes a discharge operation on the battery. A method of protecting a lithium battery provided to control an external circuit for charging or discharging a rechargeable battery so that overcharging or overdischarging of the rechargeable battery can be prevented. a) During the charging or discharging process of the battery, it is first determined whether the battery is in a charged state or a discharged state, and when the battery is in the charged state, it is checked whether the average voltage of the charged battery is larger or smaller than the maximum charging voltage of a single battery. And if the average voltage is greater than the maximum charging voltage, opening the charging loop to stop the charging process; b) In step a), if the average voltage is less than the maximum charging voltage of a single battery, it is checked whether the output signal of the protection device of the lithium battery is normal or abnormal, and if the signal is abnormal, Charging with current and continuing the normal charging operation if the signal is normal; c) In step a), if the determined battery is in the discharged state, the average voltage of the discharged battery is checked, and if the checked average voltage is less than the minimum discharge voltage of a single battery, opening the discharge loop to stop the discharge procedure. step; And d) In step c), if the checked average voltage is greater than the minimum discharge voltage of a single cell, the discharge process is continued for several seconds, after which it is checked whether the output signal from the protection device of the lithium battery is normal or abnormal. And if the checked signal is normal, continuing the discharge process, and if the checked signal is abnormal, stopping the discharge operation.

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