JPH03276579A - Battery circuit - Google Patents

Abstract

PURPOSE:To efficiently extract the energy in a battery by opening a switch section not to feed a current to a resistor train and a load from the battery when the signal with a preset value is outputted from a comparator. CONSTITUTION:The voltage at the connection point of resistors R1, R2 is applied to the upper input terminal of a comparator 5, and the reference voltage Vref is applied to the lower input terminal of the comparator 5. When the voltage of the upper input terminal of the comparator 5 becomes smaller than the voltage of the lower input terminal, the output level signal is inverted. When the inverted output level signal is outputted from the comparator 5, a switch section 2 is turned off, and no current flows out from a battery 1. The capability of the battery 1 can be extracted to the maximum regardless of a load by merely adding one resistor.

Description

[Detailed Description of the Invention] [Summary] Regarding the improvement of battery circuits, the purpose of the present invention is to provide a battery circuit that can efficiently extract energy from the battery and does not have a negative effect on the life of the battery. a resistor array consisting of resistors R1, R2, and R, a load having one end connected to the upper end of resistor R1 and the other end connected to the junction of resistors R2 and R3, a reference voltage source, and a switch section. , a comparator in which the voltage of a reference voltage source is applied to one input terminal and the midpoint voltage of resistors R1 and R2 is applied to the other input terminal, and when the switch section is closed, the resistor A string is connected to both ends of the battery, current is supplied from the battery to the resistor string and the load, and when a signal of a predetermined value is output from the comparator, the switch section is opened and the resistor string is disconnected from the battery. , the structure is such that no current is supplied from the battery to the resistor string and load.

[Industrial Application Field] The present invention relates to an improvement in a battery circuit that prevents overdischarge of a secondary battery (battery).

[Conventional technology]

Generally, secondary batteries are designed to recover their capacity when they are charged, and are guaranteed to recover several hundred times over their lifetime. This is only a case where the load is disconnected in order to prevent over-discharging and to stop discharging at the discharge end voltage (discharging until the voltage across the battery falls below this value will shorten the battery life).

FIG. 2 shows a conventionally used general circuit.

In the figure, 1 is the battery, 2 is the switch section, 3 is the load, 4 is the voltage detection section, 5 is the comparator, R and R2 are resistances, v3 is the constant voltage source, and r is the internal resistance of the battery. show.

The conventional battery circuit is composed of a voltage detection section 4 during discharging and a switch section 2 that disconnects the load 3 from the battery 1, and detects the voltage at one terminal of the battery for 7 days during discharging.
When discharged to the discharge end voltage, the switch section 2 is operated to disconnect the battery 1 and the load 3 to prevent overdischarge.

[Problem to be solved by the invention]

FIG. 3 shows the relationship between the battery's output current and the end-of-discharge voltage. According to this, the discharge end voltage of the battery needs to be set in accordance with the discharge current. Therefore, for devices whose load fluctuates, in the conventional example, it was necessary to set the discharge end voltage high according to the time when the discharge current was low.If a heavy load is connected at that time, the battery capacity will decrease. There was a drawback that the discharge time was shortened because the load was disconnected before the discharge was sufficiently discharged.Also, in the opposite case, the set voltage is low (set for heavy loads) If a light load is connected under these conditions, over-discharge will occur as shown in FIG. 3, resulting in a shortened lifespan.

The present invention was created in view of this point, and in a battery circuit that operates a load using a battery as an energy source, the energy in the battery is efficiently extracted by changing the discharge end voltage according to the load. ,
The purpose of the present invention is to provide a battery circuit that does not adversely affect the life of the battery.

[Means to solve the problem]

Therefore, the battery circuit of the present invention includes a battery, a resistor string consisting of series-connected resistors R, , R, , R, one end of which is connected to the upper end of resistor R, and a junction of resistors R2 and R1. The voltage of the reference voltage source is applied to one input terminal, and the midpoint voltage of resistors R1 and R2 is applied to the other input terminal. and when the switch section is closed, the resistor string is connected to both ends of the battery, current is supplied from the battery to the resistor string and the load, and a predetermined value is output from the comparator. When a signal is output, the switch section is opened to disconnect the resistor string from the battery, so that no current is supplied from the battery to the resistor string and the load.

[Example] FIG. 1 shows an example of the present invention. In the figure, 6 indicates a correction type voltage detection section, and R3 indicates a resistor.

Note that the same reference numerals as in FIG. 2 indicate the same parts.

The corrected voltage detection section 6 includes a comparator 5. Reference voltage source V,. ,
and resistors R and -R. Resistors R1 and R2
The voltage at the junction of is applied to the upper input terminal of comparator 5,
A reference voltage V r*f is applied to the lower input terminal of the comparator 5 . Comparator 5 inverts the output level signal when the voltage at the upper input terminal becomes smaller than the voltage at the lower input terminal. When the inverted output level signal is output from the comparator 5, the switch unit 2 is turned off and no current flows from the battery 1.

In the present invention, the load current is passed through the resistor R1, and the resistor R
The end-of-discharge voltage is corrected by utilizing the fact that the voltage drop in No. 3 is proportional to the discharge current of the battery. The principle of the present invention will be explained below.

Generally, the internal resistance of a battery increases at the end of discharge. Assuming that this internal resistance is r, the battery at the end of discharge can be represented by a constant voltage 3 and an internal resistance rl connected in series, as shown in FIGS. 1 and 2. This can also be inferred from the fact that the discharge end voltage specified value shown in FIG. 3 has a linear region. Therefore, the terminal voltage of the battery in this linear region can be expressed by the following equation.

Vg = v@I wr −r vl・”・=
(2) Also, the discharge current II+ is divided into Io, Io, and merges when flowing through R1. Furthermore, the comparator compares the reference voltage with the voltage at the midpoint of the resistors R, , R, and detects when the midpoint voltage has fallen below the reference voltage. The midpoint voltage at this time is expressed by the following equation.

V, r = I+ ・Rz + (1+ + Io)
R3=1.・R2+I, ・R3・Old... From the 00 formula, the detected voltage of the correction type voltage detection section 6 can be expressed by the following formula.

Vg =I+ (Ri +Rz)+ (It +1
゜) R3-I r (Ri + Rz) 10 I m
・R1...Substituting ■■ into ■ gives the following result.

...■ Therefore, In order for ■=■ to hold, 2 All you have to do is set the constants so that

Furthermore, ■. −The battery voltage at 〇 is ■.

Then, The following formula holds true.

As described above, it has been confirmed that the conventional drawbacks can be overcome by simply adding one resistor so as to satisfy the above equations (1), (2), and (3) as shown in FIG.

[Effects of the Invention] Since the shortcoming of the battery life is more problematic than the shortening of the discharge time, conventionally the end-of-discharge voltage has been set high when the discharge current is low. When such a conventional method is adopted, the discharge time is shortened, so conventionally, it has been customary to use a battery with one rank larger capacity. In contrast, with the present invention, it is possible to maximize the battery's performance regardless of the load by simply adding one resistor, so it is expected to have a significant effect on downsizing and cost reduction of battery circuits. I can do it.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of a conventional battery circuit, and FIG. 3 is a diagram showing the relationship between discharge current and discharge end voltage. l... Battery, 2... Switch section, 3... Load, 4... Voltage detection section, 5... Comparator, 6... Correction type voltage detection section, R1-R1... Resistance, vIl...
Constant voltage source, rll... internal resistance of the battery.

Claims (1)

[Claims] A battery, a resistor string consisting of resistors R_1, R_2, and R_3 connected in series, one end of which is connected to the upper end of resistor R_1, and resistors R_2 and R_3.
The voltage of the reference voltage source is applied to one input terminal, and the midpoint voltage of resistors R_1 and R_2 is applied to the other input terminal. and a comparator applied to the input terminal, and when the switch section is closed, the resistor string is connected to both ends of the battery, current is supplied from the battery to the resistor string and the load, and the comparison is performed. When a signal of a predetermined value is output from the device, the switch section is opened to disconnect the resistor string from the battery, so that no current is supplied from the battery to the resistor string and the load.