TWI528683B - End of discharge point automatic adjusting circuit for battery management chip - Google Patents

Description

Battery management chip off-discharge voltage point automatic modulation circuit

The invention relates to a battery management integrated circuit (IC) discharge cutoff voltage point automatic adjustment circuit, in particular to a battery management IC which can automatically change the cutoff discharge voltage point when the battery outputs a large current instantaneously.

In general, one of the main sources of electrical power for portable computers, including mobile phones, tablets, and laptops, is a rechargeable lithium battery that can be recharged and discharged. The user may connect an AC to DC charger (adaptor) during the use of the notebook. When the external power supply is not used, the main power source for mobile phones and tablets will only be lithium batteries that can be recharged and discharged. The lithium battery that can be repeatedly charged and discharged has no memory effect of charge and discharge. However, the chemicals in lithium batteries are afraid of damage due to overcharging or overdischarging. Therefore, the battery of the above portable computer has a battery management IC to protect and manage the charging and discharging of the battery.

The discharge curve of the lithium battery after charging full is shown in Figure 1. The voltage of the lithium battery is fully charged (full charge), as shown in the figure is about 4.3V, and then, as the battery is discharged to the load, the lithium battery The terminal voltage of the pool is quickly dropped. For example, when the remaining power is still 90%, the voltage has dropped to 3.3V. Thereafter, the discharge curve of the battery is gentle. As the remaining power decreases, the battery terminal voltage is slowly reduced to 3V, the remaining power is about 10%. Smart battery management ICs, at this time, usually alert the user to connect the charger, otherwise, please store the work that has not been completed, in order to enter the sleep mode or shut down.

At this point, the terminal voltage of the battery has dropped to near the discharge cut-off voltage OD. The discharge cut-off voltage OD is generally set at a voltage of 8% of the remaining power, that is, a dotted line voltage as shown, which is about 2.9V. At this time, if the user does not perform any action, the operating system in the computer will also force the portable computer to go to sleep or shut down. In order to avoid a more rapid drop in the terminal voltage of the battery, the chemical in the battery is damaged and becomes unrecoverable.

As the central processing unit of the portable computer becomes more and more advanced, such as dual-core, quad-core or even eight-core, and the network transmission is developed, the transmission speed is obviously increased, the computer is no longer the turtle speed, and the user has the courage to let the portable computer Processing a large amount of audio and video data, therefore, the amount of data processed by the computer is significantly different from the past, when the battery has a large current output to the load.

Fig. 2A shows a discharge curve showing the relationship between the time when the battery has a large current output and the general current output and the battery terminal voltage. As shown in FIG. 2A, curve 10 and curve 20 are respectively shown. At high current output, the battery terminal voltage drops faster. That is, when the large current is output, the discharge curve is caused to hit the discharge cutoff voltage OD more quickly. This is of course. However, in fact, when measuring the remaining power of the battery, it is found that it is not 8% left, but higher. In other words, when the battery outputs a large current, the battery discharge curve (battery terminal voltage - residual power relationship curve) is not true. For example, when the remaining battery power is still 20%, the battery terminal voltage hits the discharge cutoff voltage OD because a large current is output briefly. At this point, the smart battery management IC showed a warning, after which the user stopped processing a large amount of audio and video data, and the above warning was resolved when the general current output was restored. This means that when the battery has a large current output, the battery management IC is not sure about the remaining battery power. There is a false overdischarge problem. This makes the portable computer work too early (shortening the available time).

2B is a schematic diagram of pins of a typical battery management IC application, including pins VDD, VSS, CS (current detection signal pin, detecting independent sense resistor voltage drop to know loop current), DOUT , COUT, V-.

2C is a schematic diagram of each of the pins of another typical battery management IC, It includes pins VDD, VSS, DOUT, COUT, V- (current detection signal pin, detecting external MOS voltage drop to know the loop current).

Among them, DOUT (discharge control signal), COUT (charge control signal), and each control MOS transistor (stop discharge, stop charging). The bold current I represents a large current output and the thin body current I represents a general current output. Please also match the bold curve 10 and the thin curve 20 of FIG. 2A.

In the case of this problem, it seems that the discharge cut-off voltage OD should be adjusted lower to overcome the problem that the pseudo-terminal voltage of the large current output is pulled down when the battery is discharged, as shown in Fig. 2D, that is, another OD. L is in response to a situation when a large current is output. However, this will cause the actual output to actually hit the discharge cut-off voltage OD but it is too late warning (too late to receive work) and damage the battery.

In view of the above, it is an object of the present invention to provide a technique to overcome the above problems.

One object of the present invention is to provide a large current detecting circuit, a switching circuit, and a discharge cutoff signal output circuit, which can be automatically cut off when a large current output is detected to exceed a predetermined delay time. A circuit that modulates the discharge voltage to overcome the problem of premature off-discharge of the prior art. And does not affect the performance of the general current output.

The invention discloses an off-discharge voltage point automatic modulation circuit for a battery management chip, which is exemplified by a typical battery management IC application for detecting an independent sense resistor voltage drop, which comprises: a large current detection function block for outputting A first signal, the signal indicates that the load has a large current output, and the high current detection function block detects whether there is a large current output by the current detecting pin CS of a battery management chip, and thereafter, switches over the discharge cutoff. Voltage function block, According to the output result of the large current detecting function block, the first overdischarge cutoff voltage or the second overdischarge cutoff voltage is automatically switched; finally, an overdischarge cutoff signal output function block is connected to the switched overdischarge cutoff voltage function. The output of the block outputs a discharge cutoff signal to the pin DOUT.

The high current detecting function block includes a first comparator output connected to a delay circuit, and the first comparator includes an input pin 1 and an input pin 2, and the input pin 2 is connected to a first reference voltage. The input pin 1 is connected to the pin CS.

The switching over-discharge cut-off voltage function block includes a voltage dividing circuit, and the voltage across the divided voltage is a voltage from a voltage across the battery, and the divided voltage has a second node and a lower score of a higher divided output. a first node of the voltage output, the first node is connected to a first output switch, and the second node is connected to a second output switch, wherein when the large current detection function block output signal indicates that there is a large current, switching the overdischarge cutoff The voltage output by the voltage function block is the voltage from the second node. Otherwise, the voltage output from the switching over-discharge cut-off voltage function block is the voltage from the first node.

The overdischarge cutoff signal output function block includes a second comparator, the negative input terminal of the second comparator is connected to a second reference voltage, and the positive input terminal of the second comparator is connected to the switched overdischarge cutoff voltage function block output. Voltage.

100‧‧‧High current detection function block

110‧‧‧First comparator

200‧‧‧Switch over discharge cutoff voltage function block

130‧‧‧First delay circuit

210‧‧‧voltage circuit

S1, S2‧‧‧ switch

INV1, INV2‧‧‧ inverter

10‧‧‧High current discharge curve

300‧‧‧Over discharge cutoff signal output function block

330‧‧‧second delay circuit

310‧‧‧Second comparator

20‧‧‧General current discharge curve

OD‧‧‧ cutoff discharge voltage point

OD.L‧‧‧lower cut-off discharge voltage point

VOD1 IC‧‧‧first cut-off discharge voltage point

VOD2 IC‧‧‧second cut-off discharge voltage point

CS, DOUT, COUT, VDD, VSS, V-‧‧‧ Battery Management IC Pins

R1, R2, R3, RS‧‧‧ resistance

C1‧‧‧ capacitor

VBatt‧‧‧ battery terminal voltage

EB+, EB2‧‧‧ battery pack terminal voltage

1 shows a conventional battery discharge curve; FIG. 2A shows a battery discharge curve (time-battery terminal voltage) when a battery discharge curve encounters a large current output and a general current output; 2B and 2C are schematic views showing the pins of the battery management IC.

Figure 2D shows that the discharge cut-off voltage should be set to OD when the battery discharge curve encounters a large current output. Schematic diagram of L.

3 is a schematic diagram showing the functional blocks of the circuit for automatically adjusting the discharge voltage point according to the first embodiment of the present invention.

As mentioned earlier, it is necessary to turn off the off-discharge voltage point when the battery has a large current output. However, this situation is compensated back when implemented in the circuit. That is, the terminal voltage of the battery at that time is regarded as a higher voltage. The original general current output does not change the off-discharge voltage. The detailed description is as follows: FIG. 3 is a schematic diagram showing the functional blocks of the circuit for automatically adjusting the discharge voltage point according to the first embodiment of the present invention. The high current detection function block 100, the switch over discharge cutoff voltage function block 200, and the overdischarge cutoff signal output function block 300 are included. The conventional battery management IC has only the over-discharge cutoff signal output function block shown in FIG. There is only one over discharge cutoff voltage. The discharge cutoff voltage point of the present invention can have more than two discharge cutoff voltage point outputs.

As shown in FIG. 3, the large current detecting function block 100 is provided with a first comparator 110 and a first delay circuit 130. Pin 2 of the voltage comparator is the first reference voltage Vref1, see Figure 3. The pin 1 of the comparator 110 outputs a voltage across the resistor at the CS terminal. At high current output, the voltage across the resistor RS from the CS terminal is naturally higher. It is compared with the first reference voltage Vref1.

The output signal of the high current detection function block 100 is input to the input terminal of the switching over discharge cutoff voltage function block 200. The switching discharge cutoff voltage function block 200 includes a voltage dividing circuit 210, two switches S1 and S2, and two inverters INV1 and INV2. In one embodiment, the voltage divider circuit 210 connects the positive and negative terminals of the battery to the VBatt+ and ground terminals to the ends of the three series connected resistors R1, R2, R3. The output of the resistor R1 is the first off-discharge voltage point VOD1, and the output of the resistor R2 is the second off-discharge voltage VOD2. When the positive current detecting function block 100 outputs a positive voltage, the switch S2 can be turned ON (ON) via the inverters INV1 and INV2. That is, the output is the second off-discharge voltage point VOD2. Switch S1 remains off (OFF).

Conversely, when the output current of the large current detecting function block 100 is negative, the switch S1 can be turned on (ON), that is, the first off-discharge voltage point VOD1 is output. However, the switch S2 remains OFF. In other words, after a simple high current detection function block 100 and a series connection of the switching over discharge cutoff voltage function block 200, the purpose of automatically switching to a higher second off discharge voltage point VOD2 when the battery has a large current output can be achieved. When the battery normally outputs a small current normally, it maintains a lower first off-discharge voltage point VOD1.

In addition, the positive terminal of the voltage dividing circuit (the positive terminal voltage of the resistor R3) is connected to the positive voltage VBatt output terminal of the battery, and therefore, the second off-discharge voltage point VOD2 outputted by the voltage dividing circuit 210 and the first off-discharge The voltage point VOD1 will vary. Therefore, pay attention to this when selecting R1, R2, and R3. The first off-discharge voltage point VOD1 is the off-discharge voltage at the normal current, and the second off-discharge voltage point VOD2 is the battery terminal voltage is pulled down when the battery has a large current output to the load terminal, and therefore, the current point is Pressing high (ie the aforementioned supplement Reimbursement). The second off-discharge voltage point VOD2 is higher than the first off-discharge voltage point VOD1 depending on how much the pseudo-battery terminal voltage is lowered. If the compensation value is too large, the actual battery remaining capacity will be low, but the discharge MOS transistor is not turned off, resulting in damage to chemicals such as lithium ions or lithium polymer in the battery.

The output voltage of the switching over-discharge cut-off voltage function block 200 is then input to the input pin 1 of the over-discharge cut-off signal output function block 300. The overdischarge cutoff signal output function block 300 includes a second voltage comparator 310 and a second delay circuit 330. Its output is the output discharge control signal DOUT. The pins 3 and 4 of the second voltage comparator 310 are the positive and negative ends of the battery, respectively. The pin 2 of the second voltage comparator is connected to a second reference voltage. The second reference voltage is a voltage taken from the battery management IC, and is set according to the voltage of the first off-discharge voltage point VOD1 (the off-discharge voltage during normal discharge).

The invention has the following advantages:

(a). The battery management IC automatically adjusts the cut-off discharge voltage point through a simple circuit (three function blocks). That is, if the battery has a large current output and the battery terminal voltage drops rapidly, the problem that the battery management IC pin DOUT is turned off prematurely is solved. It does not have any effect on the normal current output under undefined conditions.

(b). The voltage dividing circuit is simple, and the predetermined first node partial pressure can be adjusted according to different battery characteristics of different factories. This can be obtained by changing the resistance value. If you need multiple sections of switching, you can also do more VOD point design.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the present invention should be included. Within the scope of the patent application. For example, the above inverter INV1 can also be in the high current detection function block 100. Also, the positive and negative terminals of the comparator can be interchanged as described above, and an inverter can be reduced. The high current detecting function block of the present invention can distinguish a large current or a general current, and the switching over-discharge cut-off voltage function block can be detected according to a large current. The function block output results the appropriate node voltage to be compared to the second reference voltage.

100‧‧‧High current detection function block

110‧‧‧First comparator

200‧‧‧Switch over discharge cutoff voltage function block

130‧‧‧First delay circuit

210‧‧‧voltage circuit

S1, S2‧‧‧ switch

INV1, INV2‧‧‧ inverter

300‧‧‧Over discharge cutoff signal output function block

330‧‧‧second delay circuit

310‧‧‧Second comparator

VOD1 IC‧‧‧first cut-off discharge voltage point

VOD2 IC‧‧‧second cut-off discharge voltage point

VBatt‧‧‧ battery terminal voltage

R1, R2, R3, RS‧‧‧ resistance

C1‧‧‧ capacitor

Claims (8)

A battery management chip and an off-discharge voltage point automatic modulation circuit thereof, comprising at least: a battery management chip, comprising at least a discharge cutoff signal pin and a current detecting pin; a large current detecting function block, the current detecting The measuring pin is an input signal of the large current detecting function block, and is used for outputting a first signal, the first signal indicating whether the load has a large current output; and a switching over-discharge cut-off voltage function block, according to the large current detecting The output result of the function block is automatically switched to the first over-discharge cut-off voltage or the second over-discharge cut-off voltage; an over-discharge cutoff signal output function block is connected to the output end of the switched over-discharge cutoff voltage function block to output the discharge The cutoff control signal is at the discharge cutoff signal pin. The battery management chip and the off-discharge voltage point automatic modulation circuit according to claim 1, wherein the large current detecting function block comprises a first comparator, and the output of the first comparator is connected. A delay circuit, the first comparator includes two input pins, one of the two input pins is connected to a first reference voltage, and the other of the two input pins is connected to the current detecting pin. The battery management chip and the off-discharge voltage point automatic modulation circuit according to claim 1, wherein the value of the first reference voltage is set according to the large current definition value. The battery management chip and the off-discharge voltage point automatic modulation circuit according to the first aspect of the invention, wherein the switching over-discharge cut-off voltage function block comprises a voltage dividing circuit, and the two ends of the voltage dividing circuit The voltage is the voltage from the two ends of the battery, the voltage dividing circuit has a second node with a higher voltage dividing output and a first node of a lower voltage dividing output, and the first node is connected to a first input The output switch and the second node are connected to a second output switch, wherein when the first signal outputted by the large current detecting function block indicates a large current, the voltage outputted by the switching over-discharge cut-off voltage function block is from the second node The voltage, otherwise, the voltage output from the over-discharge cut-off voltage function block is the voltage from the first node. The battery management chip and the off-discharge voltage point automatic modulation circuit according to claim 1, wherein the partial voltage output of the second node is based on a false battery terminal voltage when the current is output. The battery terminal voltage is pulled high to avoid prematurely turning off the overdischarge cutoff discharge transistor. The battery management chip of claim 1, wherein the overdischarge cutoff signal output function block comprises a second comparator, the negative input of the second comparator The terminal is connected to a second reference voltage, and the positive input terminal of the second comparator is connected to the voltage output by the switching over-discharge cut-off voltage function block. A battery management chip and an off-discharge voltage point automatic modulation circuit thereof, comprising at least: a battery management chip, comprising at least a discharge cutoff signal pin and a current detecting pin; and a large current detecting function block comprises a comparator. Comparing the input signal of the current detecting pin with the first reference signal for outputting a first signal, the first signal indicating whether the load has a large current output; and switching the over-discharge cut-off voltage function block according to the high current The output result of the detection function block is automatically switched to the first over-discharge cutoff voltage or the second over-discharge cut-off voltage, wherein when the output result of the large current detection function block shows a large current output, the voltage value is switched to a high second over-discharge cut-off voltage, otherwise, a first over-discharge cut-off voltage having a lower output voltage value; an over-discharge cut-off signal output function block including a comparator for comparing the cuts to the cut The output voltage of the discharge cutoff voltage function block is replaced with a predetermined second reference voltage to output a discharge cutoff signal to the discharge cutoff signal pin. The battery management chip and the off-discharge voltage point automatic modulation circuit according to claim 7, wherein the second reference voltage is a discharge cutoff voltage determined by the battery management chip.