JPH06176796A - Charge type battery discharger - Google Patents

Abstract

PURPOSE:To extend the life of a battery and realize a low cost by providing resistors and a variable shunt regulator to fix a base current in a discharge- control power transistor. CONSTITUTION:A discharge current mostly flows in a power transistor PT and a resistor r3. A light emitting diode, therefore, keeps emission during discharge. It is found that, when the light emitting diode puts out emission, discharge is completed. By properly setting the partial pressure ratio of a resistor r4 externally attached to a variable shunt regulator TL, the power transistor PT is switched off to stop discharge at the time when the terminal voltage of a battery BA equals to a preset voltage. As a result, overdischarge can be prevented. Since the variable shunt regulator TL is used, the battery BA when at a preset voltage stops discharge to prevent overdischarge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery discharger which can prolong the service life of a rechargeable battery by appropriately discharging the battery as compared with a conventional battery.

[0002]

2. Description of the Related Art Conventionally, the power source of portable equipment has been
A rechargeable nickel-cadmium (NiCd) battery is used. For example, a rechargeable battery such as a rechargeable electric razor, a camera-integrated VTR, or a rechargeable camera / flash is usually not used continuously for a long time until it reaches the minimum potential, and is charged halfway. Or
It charges even after a short period of use. A device using such a rechargeable battery always needs to be sufficiently charged, but in reality, it is overcharged because the device is used a little and is repeatedly charged. The battery life was shortened. That is, the broken line 10 in FIG.
As shown in FIG. 1, in the conventional rechargeable battery, after being used for a short time, it is charged without being sufficiently discharged, and this is repeated. Charging of NiCd batteries and the like is based on chemical changes, and if charging is repeated after insufficient discharge, the battery becomes accustomed to this, and as a result,
There is an apparent decrease in capacity such as 5AH being reduced to 3AH. Generally, in a sealed NiCd battery, when a deep charge is discharged after repeating a shallow charge / discharge cycle, a so-called “memory effect”, in which the voltage at the time of discharge drops by two steps, as indicated by a broken line 201 in FIG. The phenomenon called is happening.
In applications where the end-of-discharge voltage is set high, an apparent capacity decrease occurs with a decrease in the operating voltage, but this drop in discharge voltage is a temporary phenomenon that is resolved by one or two complete discharges. is there. Thus, in the conventional usage,
Since it is charged by the charger every day, it becomes overcharged and shortens the life. On the other hand, as another usage method, a rechargeable battery is incorporated into a device to be used, and the device is used and discharged until it becomes unusable, resulting in over-discharge and a reduction in life. Normally, the battery-manufacturing manufacturer's discharger was over-discharged.

[0003]

Therefore, in order to suppress such a decrease in life, the prior art has been disclosed in JP-A-49-1282.
39 (hereinafter referred to as "A"), JP-A-3-65027.
Japanese Patent Publication (hereinafter referred to as B), or Japanese Patent Laid-Open No. 4-168.
A rechargeable battery as described in Japanese Patent No. 926 (hereinafter referred to as C) has been proposed. In the charger with a built-in discharger of A above, a plurality of batteries connected in parallel are uniformly discharged in a predetermined manner prior to charging, and then charging is started to make the residual charge amount of each battery uniform. As a result, some of the batteries will not be overcharged, and some of the batteries will be discharged quickly and will not be reversely charged. However, the above-mentioned charger A is provided with a timer motor for setting the discharge time, and the rotation of the timer motor switches the switching contact at a constant time to start charging. Next, in the battery-charger with a discharger of the above B, a charge control circuit, a discharge control circuit for discharging to a predetermined value equal to or lower than the undercut voltage of the operating voltage of the device, and a battery-charge / discharge switching control circuit are provided. Provided, for the battery whose remaining capacity of the battery has not reached a predetermined capacity,
It is designed to be discharged before charging. However, in this case, it is necessary to provide a complicated circuit such as a battery-charge / discharge switching control circuit. Next, in the above-described C discharger, the battery is first discharged, the voltage of the connection terminal is monitored by the voltage monitoring circuit, and when the voltage becomes a predetermined value or less, the brightness of the lamp is changed. This is notified to the outside. However, in this case, it is necessary to incorporate an operational amplifier as a comparison circuit and a reference voltage as a voltage monitoring circuit. The purpose of the present invention is to
Such a conventional problem is solved, charging and discharging are repeated in an appropriate cycle to extend the life of the rechargeable battery, overdischarge can be prevented, and the number of parts can be reduced and the cost can be reduced. An object is to provide a rechargeable battery discharger.

[0004]

In order to achieve the above object, a discharger for a rechargeable battery of the present invention comprises: (a) a rechargeable battery (BA) which is a power transistor for turning on / off a discharge current. (PT) and the resistance that carries the discharge current (r ₃ )
Connected to a discharge circuit and a power transistor (P
The feature is that an over-discharge prevention circuit is connected which connects a resistor (r ₁ , r ₂ ) that determines the base current of T) and a variable shunt regulator (TL) that can arbitrarily set the discharge stop voltage. There is. (B) In addition, in parallel with the resistor (r ₃ ) through which the discharge current of the discharge circuit flows, the currents flowing through the light emitting diode (LED) and the light emitting diode (LED) for notifying the discharge completion and the discharge completion are provided. It is also characterized by connecting limiting means.

[0005]

In the present invention, a light emitting diode is connected to the discharge circuit of the battery to indicate the discharge in progress and the end of discharge, and the base of the power transistor for controlling the discharge.
Variable shunt regula-
Set up. The provision of this variable shunt regulator eliminates the need for a battery that provides a reference voltage and a comparator that compares the reference voltage with the voltage of the discharging battery. As a result, it is possible to inexpensively configure the discharger of the rechargeable battery with a small number of parts.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a circuit configuration diagram of a rechargeable battery discharger showing an embodiment of the present invention. In FIG. 1, BA
Is a rechargeable battery, PT is a power transistor, LE
D is emitting diode - _{de, r 1, r 2, r} 3, r 4 each resistor, TL is variable shunt regulating - a motor. The charge of the battery-BA is the power transistor PT and the resistance r.
₃ and light emitting diode LED connected in parallel
A current flows through the resistors r ₁ and r ₂ and the shunt regulator TL while being discharged. For example, r
_{1 = 10KΩ, r 2 = 20KΩ} , r 3 = 20Ω, r 4 = 30
By setting it to 0Ω, almost all the discharge current flows through the power transistor PT and the resistor r ₃ . Therefore, the light emitting diode emits light during discharge. When the light emitting diode is turned off, it can be seen that the discharge is completed. Now, if the voltage dividing ratio of the external resistor r ₄ of the shunt regulator TL is appropriately set to, for example, 4V, when the terminal voltage of the battery-BA becomes 4V, the power transistor PT is reached. Is switched off and the discharge is stopped. As a result, over-discharge can be prevented. As described above, in the circuit of FIG. 1, by using the variable shunt regulator TL, the discharge is stopped when the battery-BA reaches a predetermined voltage, so that the discharge is never over-discharged. The variable shunt regulator TL is capable of temperature-compensated high-precision operation, has an extremely fast response speed, and has an output voltage controlled within a range of 2.5V to 36.0V by two external resistors r _4. It is possible to set the voltage. It has high stability,
Since the output current is also large, it can be replaced with a Zener diode in a normal circuit.

FIG. 2 is a diagram showing an equivalent circuit of FIG.
FIG. 5 is a circuit diagram when an operation equivalent to that of the variable shunt regulator used in the present invention is performed by another circuit. Figure 2
As shown in, the variable shunt regulator TL has the functions of the switch TL-1 and the comparison unit TL-2, and the reference voltage Vref = 2.5V across the regulator TL.
When the resistance values when the resistance r ₄ is divided at an arbitrary ratio are R ₁ = 2V and R ₂ = 2V, the battery-terminal voltage that can be controlled by the regulator is V ₀ = Vref ×
(1 + R ₁ / R ₂ ) = 2.5 × 2 = 5 (V). Therefore, in the equivalent circuit of FIG. 2, the resistance r ₄ is changed to R ₁ ,
When divided into R ₂ , 2.5 V is compared with the voltage generated by the resistor R ₁ by the comparator TL-2, and if the voltage of the resistor R ₁ is high, the switch TL-1 is closed. When the switch TL-1 is closed, a current flows through the switch TL-1 and the resistors r ₁ and r ₂ , so that the switch of the power transistor PT is closed and the battery-BA continues discharging. As a result of the comparison, the resistance R ₁
When the voltage of V becomes low, the switch TL-1 of the variable shunt regulator is opened, so that no current flows through the resistors r ₁ and r ₂ and the switch of the power transistor PT is opened, so that the battery-BA is discharged. Be stopped.

Since the regulator TL is a variable type, the terminal voltage V which can be controlled by the regulator is set by dividing the resistance r ₄ into arbitrary values and setting the resistance values R ₁ and R _2.
The value of ₀ can be set freely. In the present invention, by using only one variable shunt regulator, it is possible to stop the discharge at the time when the discharge reaches the predetermined minimum voltage and prevent over-discharge of the battery.
In the present invention, since charging and discharging are appropriately repeated, sufficient discharging is performed as compared with the conventional case, as indicated by the solid line 102 in FIG.
Further, since the deep discharge and the charging are constantly repeated, the battery of the present invention has a long life as shown by the solid line 202 in FIG. 4, and at least a memory effect such as a two-stage drop of the discharge type voltage cannot be obtained. I can't see it. On the other hand, when other components are used, as shown in FIG. 5, the battery that supplies the reference potential Vref, the comparator CP, and the Zener.
A diode ZD is required. In FIG. 5, the reference voltage battery is connected to the-input terminal of the comparator CP, and the Zener diode ZD is connected to the + input terminal, and the + side of the discharged battery-is the A terminal and the-side is the K terminal. Connect to. When the potential of the battery being discharged through the Zener diode ZD becomes lower than the reference voltage Vref, the output of the comparator CP cannot be obtained and the discharge is stopped. However, since the circuit of FIG. 5 requires a large number of parts,
The cost is increased and the circuit is complicated.

[0009]

As described above, according to the present invention, by setting the undercut voltage to an arbitrary value, it is possible to prevent over-discharging below that voltage. By repeating charging, the life of the rechargeable battery can be extended as compared with the conventional one. Further, the discharger of the present invention has the advantages that the number of parts is small, the circuit is simple, and it can be realized at low cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a rechargeable battery discharger showing an embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of FIG.

FIG. 3 is a diagram showing a charge / discharge cycle of a rechargeable battery.

FIG. 4 is a diagram illustrating a memory effect.

FIG. 5 is a circuit diagram in the case where an overdischarge prevention circuit is configured using components other than the variable shunt regulator according to the present invention.

[Explanation of symbols]

PT power - transistor TL variable shunt regulating - data LED light emitting diode - de BA rechargeable battery _{- r 1, r 2, r} 3 resistor V ₀ variable shunt regulating - terminal voltage is controlled by a motor

Claims (2)

[Claims] 1. A discharge current is turned on / off to a rechargeable battery.
A discharge circuit in which a power transistor to be turned off and a resistor for flowing the discharge current were connected, and a resistor for determining a base current of the power transistor and a variable shunt regulator capable of arbitrarily setting a discharge stop voltage were connected. A rechargeable battery discharger, which is connected with an overdischarge prevention circuit. 2. A discharger for a rechargeable battery according to claim 1, wherein a light emitting diode for notifying discharge in progress and discharge end in parallel with a resistor for flowing a discharge current of the discharge circuit, and the light emission. A discharger for a rechargeable battery, characterized in that means for limiting the current flowing through the diode is connected.