CN101521390A - Battery pack charge balancing circuit - Google Patents

Abstract

The invention discloses a battery pack charge balancing circuit which is used for being connected between two charge and discharge ends of a charge and discharge circuit so as to charge a battery pack consisting of a plurality of battery units connected in series. The battery pack charge balance circuit comprises a first balance control circuit, a second balance control circuit and a protection circuit. The first balance control circuit and the second balance control circuit are connected in series between two charging and discharging ends of the charging and discharging circuit. The first balancing control circuit has a plurality of control units connected in parallel with the respective battery cells. The second balance control circuit is provided with a first branch and a second branch which are connected in parallel. The protection circuit is connected with the control unit, the first branch and the second branch. The battery pack charge balancing circuit can control the magnitude of the charging current by controlling the connection or disconnection of the first branch circuit or the second branch circuit, thereby effectively enabling each battery unit of the battery pack to achieve charge balancing.

Description

Battery Pack Charge Balance Circuit

technical field

The invention relates to a charging circuit, in particular to a charging balancing circuit capable of charging each battery unit of a lithium battery pack equally.

Background technique

Most of today's portable digital products are powered by rechargeable batteries. However, in practical applications, since the voltage provided by a single battery is limited, multiple battery cells are usually connected in series to form a battery pack to provide power to digital products. After the power of the battery pack is exhausted, the battery pack needs to be charged through the charging circuit.

However, when charging the battery packs connected in series, the phenomenon of "unbalanced battery cells" often occurs, which affects the normal charging of the battery packs. This phenomenon is caused by the unequal residual power in each battery cell in the series battery pack. Therefore, when charging the battery pack, the battery cells with more residual power will reach the charging saturation state faster than the battery cells with less residual power. When a battery cell reaches the state of full charge, the protection IC of the battery pack will activate the overvoltage protection (Over Voltage Protection) function to prevent the charging circuit from continuing to charge the battery pack, while other battery cells that have not yet reached the state of charge saturation cannot continue to charge reaches saturation. When discharging, the battery unit that has not reached full charge reaches a preset residual power in advance, and the undervoltage protection function of the protection IC is activated to stop the battery pack from providing power to the outside. Therefore, the phenomenon of "unbalanced battery cells" will lead to frequent charging of the battery pack, thereby affecting the normal use of digital products and affecting the service life of the battery.

In order to overcome the influence of the above-mentioned "battery cell unbalanced" phenomenon, a series battery pack charging circuit is used in the industry, as shown in Figure 1. The charging circuit for a battery pack connected in series connects a first resistor R1' and a first switch SW1' connected in parallel at both ends of the first battery B1' of a battery pack B', and at the same time connects a first battery B1' connected in series with the first battery B1'. Two terminals of the second battery B2' are connected in parallel with a second resistor R2' and a second switch SW2' in series.

When charging, if the first battery B1' reaches charging balance first, the first switch SW1' is turned on. At this time, part of the charging current originally flowing through the first battery B1' flows into the second battery B2' through the first resistor R1' and the first switch SW1', thereby preventing charging from being stopped due to the overcharge protection function of the battery pack B' being activated , and then continue to charge the second battery B2' that has not yet reached a saturated state.

However, since the charging current in the actual charging circuit is very large, after starting the first switch SW1', there will still be a relatively large current flowing through the first battery B1', thus causing the charging effect of the balancing circuit to be poor and ineffective. To realize the charging balance of the battery pack B'.

Contents of the invention

The object of the present invention is to provide a charging balance circuit for a battery pack that can effectively charge a battery pack in order to address the defects in the above-mentioned background technology.

In order to achieve the above object, the present invention provides a charging balance circuit for a battery pack, which is used to connect between two charging and discharging terminals of a charging and discharging circuit, so as to perform a battery pack consisting of a plurality of battery cells connected in series. Charge. The charging balance circuit of the battery pack includes a first balance control circuit, a second balance control circuit and a protection circuit. The first balance control circuit is connected with a charging and discharging terminal of the charging and discharging circuit. The first balance control circuit has a plurality of control units connected in series and connected in parallel with corresponding battery units, each control unit includes a switch element and a resistance element connected in series. The second balance control circuit is connected between the other charge and discharge end of the charge and discharge circuit and the first balance control circuit, and has a first branch and a second branch connected in parallel, the first branch includes a switching element, and the second branch The circuit includes a switching element and a resistive element connected in series. The protection circuit has multiple control terminals, and the multiple control terminals are respectively connected to the above-mentioned switching elements. When the switch element of the first balance control circuit is turned off, the protection circuit controls the switch element of the first branch to be turned on and controls the switch element of the second branch to be turned off; at least one switch element of the first balance control circuit is turned on When , the protection circuit controls the switch elements of the second branch to be turned on and controls the switch elements of the first branch to be turned off.

As mentioned above, the charging balance circuit of the battery pack of the present invention controls the conduction of the first branch or the second branch of the second balance control circuit through the protection circuit, thereby controlling the magnitude of the charging current in the charging and discharging circuit. The control unit connected in parallel shunts the battery cells in the battery pack that reach a preset starting voltage point for unbalance protection, thus preventing the protection circuit from prematurely activating the overcharge protection function, so that the battery cells of the battery pack can continue to be charged. Charging, in order to effectively achieve the charging balance of each battery unit.

Description of drawings

In the accompanying drawings

FIG. 1 is a circuit diagram of a battery pack balancing circuit disclosed in the prior art.

FIG. 2 is a circuit diagram of an embodiment of the battery pack balancing circuit of the present invention.

The reference numerals of each element in the figure are explained as follows:

[Background technique]

Battery Pack B’ First Battery B1’

Second battery B2’ First resistor R1’

The first switch SW1' The second resistor R2'

The second switch SW2'

[this invention]

Battery charge balance circuit E

The first balance control circuit C1

The second balance control circuit C2

Charging and discharging terminal 11, 12 The first branch A1

The second branch A2 The first switch SW1

The second switch SW2 The third switch SW3

Fourth switch SW4 Fifth switch SW5

The sixth switch SW6 The first resistor R1

The second resistor R2 The third resistor R3

Battery Pack B First Battery Unit B1

The second battery unit B2 charging and discharging circuit 10

Protection Circuit P P Control Terminal P1-P6

Detailed ways

In order to describe the technical content, structural features, goals and effects of the present invention in detail, the following examples are given and described in detail with accompanying drawings.

FIG. 2 discloses an embodiment of the charging balance circuit E of the battery pack of the present invention. The charging balance circuit E of the battery pack of the present invention is connected with a charging and discharging circuit 10 to charge a battery pack B. The charging and discharging circuit 10 has two charging and discharging terminals 11 , 12 . The battery pack B is composed of a plurality of battery cells connected in series. In this embodiment, the battery pack B is composed of a first battery unit B1 and a second battery unit B2 connected in series.

The charging balance circuit E of the battery pack includes: a first balance control circuit C1 , a second balance control circuit C2 and a protection circuit P. The protection circuit P is connected to the charging and discharging terminal 11 of the charging and discharging circuit 10 so as to provide an operating voltage from the charging and discharging circuit 10 or the battery pack B, and has multiple control terminals. In this embodiment, the protection circuit P has six control terminals, and the six control terminals are labeled P1-P6 respectively.

The first balance control circuit C1 has two control units connected in series. Wherein, each control unit is connected in parallel with a corresponding battery unit in the battery pack B, and each control unit includes a switch element and a resistance element connected in series. In this embodiment, the first balance control circuit C1 has two control units, wherein the first control unit includes a first switch SW1 and a first resistor R1. The first switch SW1 is preferably a field effect triode, its grid (Gate Electrode) is connected to the control terminal P1 of the protection circuit P, and its drain (Drain Electrode) is connected to the charging and discharging terminal 11 of the charging and discharging circuit 10 and the first battery The positive pole of the unit B1 is connected, and the first resistor R1 is connected between the source electrode (Source Electrode) of the first switch SW1 and the negative pole of the first battery unit B1; the second control unit includes a second switch SW2 and a second resistor R2 , the second switch SW2 is preferably a field effect transistor, its gate is connected to the control terminal P2 of the protection circuit P, its drain is connected to the positive electrode of the second battery unit B2, and the second resistor R2 is connected to the source of the second switch SW2 pole and the negative pole of the second battery cell B2.

The second balance control circuit C2 includes a first branch A1 and a second branch A2 connected in parallel. The first branch A1 includes a third switch SW3 and a fourth switch SW4 connected in series. The third switch SW3 and the fourth switch SW4 are field effect transistors, the source of the third switch SW3 is connected to the second resistor R2 of the first balance control circuit C1 and the negative electrode of the second battery unit B2, and the drain of the third switch SW3 It is connected to the drain of the fourth switch SW4, the gate of the third switch SW3 is connected to the control terminal P3 of the protection circuit P; the source of the fourth switch SW4 is connected to the charging and discharging terminal 12 of the charging and discharging circuit 10, and the fourth switch SW4 The gate of the gate is connected to the control terminal P4 of the protection circuit P.

The second branch A2 includes a fifth switch SW5 , a sixth switch SW6 and a third resistor R3 connected in series. The fifth switch SW5 and the sixth switch SW6 are field effect transistors, the source of the fifth switch SW5 is connected to the second resistor R2 of the first balance control circuit C1 and the negative electrode of the second battery unit B2, and the drain of the fifth switch SW5 It is connected to the drain of the sixth switch SW6, the gate of the fifth switch SW5 is connected to the control terminal P5 of the protection circuit P; the gate of the sixth switch SW6 is connected to the control terminal P6 of the protection circuit P; the third resistor R3 is connected to between the source of the sixth switch SW6 and the charging and discharging terminal 12 of the charging and discharging circuit 10 .

The process of charging the battery pack B by the battery pack charge balancing circuit E disclosed in the present invention is described as follows:

Before the first battery unit B1 and a second battery unit B2 reach a preset starting voltage point of unbalance protection (the voltage point is generally lower than the voltage point of charging saturation), the first switch SW1, the second switch SW2, the fifth The switch SW5 and the sixth switch SW6 are in the off state, and the third switch SW3 and the fourth switch SW4 are in the on state, so the charging current output by the charging and discharging terminal 11 of the charging and discharging circuit 10 passes through the first battery unit of the battery pack B B1 , the second battery unit B2 , the third switch SW3 and the fourth switch SW4 flow into the other charging and discharging terminal 12 of the charging and discharging circuit 10 .

When a battery unit in the battery pack B first reaches the preset starting voltage point for unbalance protection, the protection circuit P triggers the third switch SW3 and the fourth switch SW4 to be turned off, and the fifth switch SW5 and the sixth switch SW6 are turned on , so that the third resistor R3 is connected in series to reduce the charging current of the battery pack B; at the same time, the control unit connected in parallel with the battery unit that reaches the starting voltage point of unbalance protection is turned on to shunt the charging current of the battery unit , so as to prevent it from being damaged due to overcharging; at this time, the control unit connected in parallel with other battery cells remains disconnected, so as to continue to charge other battery cells to charge balance with a larger current.

Now take the example that the first battery unit B1 first reaches the unbalance protection starting voltage point for illustration.

At this time, the protection circuit P turns off the second switch SW2, the third switch SW3 and the fourth switch SW4, turns on the first switch SW1, the fifth switch SW5 and the sixth switch SW6, thereby reducing the The charging current of the battery pack charging balancing circuit E. Since the first switch SW1 is turned on to shunt the charging current to the first resistor R1, the current flowing through the first battery cell B1 is reduced, which prolongs the time for the first battery cell B1 to reach charging saturation, thereby preventing the protection circuit from P activates the overvoltage protection function prematurely to continue charging the other battery cells of battery pack B.

When the battery pack B is discharging, the third switch SW3 and the fourth switch SW4 of the first branch circuit A1 in the battery pack charge balancing circuit E remain on, and the first switch SW1, the second switch SW2, the fifth switch SW5, the The six-switch SW6 is in an off state, so as to provide electric energy to an electronic device (not shown) through the charge-discharge circuit 10 .

In summary, the charging balance circuit E of the battery pack of the present invention controls the conduction of the first branch circuit A1 or the second branch circuit A2 through the protection circuit P, thereby controlling the charging current of the battery pack B; The battery cells that reach the starting voltage point of the unbalanced protection are shunted, thus preventing the protection circuit P from starting the overcharge protection function prematurely, so that the other battery cells of the battery pack B can continue to be charged, so as to effectively achieve each battery cell. charge balance.

The above disclosure is only a preferred embodiment of the present invention and should not limit the scope of the present invention. As for other equivalent modifications or changes of the present invention, they should all be covered within the scope of the claims of the present invention.

Claims (3)

1. A charging balance circuit for a battery pack, used to be connected between two charging and discharging terminals of a charging and discharging circuit to charge a battery pack made up of a plurality of battery cells connected in series, characterized in that the battery The bank charge balancing circuit consists of: A first balance control circuit, connected to one end of the charging and discharging circuit, the first balance control circuit has a plurality of control units connected in series and connected in parallel with corresponding battery cells, each control unit includes a switch element connected in series and a resistance element; A second balance control circuit, connected between the other end of the charging and discharging circuit and the first balance control circuit, it has a first branch and a second branch connected in parallel, the first branch includes a switching element, and the second branch comprising a switching element and a resistive element connected in series; and A protection circuit, which has a plurality of control terminals, the plurality of control terminals are respectively connected to the above-mentioned switching elements, when all the switching elements of the first balance control circuit are turned off, the protection circuit controls the switching elements of the first branch to conduct And control the switching element of the second branch to turn off, when at least one switching element of the first balance control circuit is turned on, the protection circuit controls the switching element of the second branch to turn on and controls the switching element of the first branch to turn off . 2. The battery charge balancing circuit according to patent claim 1, characterized in that: the first branch is composed of two switching elements connected in series. 3. The charging balance circuit of battery pack according to patent claim 1, characterized in that: the second branch is composed of two switching elements and one resistance element.

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