JPH10243564A - Unconnected terminal detecting circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an unconnected terminal detecting circuit for a battery charger for charging a battery pack which detects the unconnected state of a discrimination terminal which is attached to a battery pack for making the kind of the battery pack distinguishable. SOLUTION: This battery charger can be used commonly to a first kind of battery packs the discrimination terminal B' of which is connected to the positive pole of a battery through a resistor R0 and a second kind of battery packs the discrimination terminal B' of which is connected to a ground terminal and, when a battery charger-side discrimination terminal B is connected to the discrimination terminal B' of a battery pack, the charger discriminates the kind of the battery pack from the potential at the charger-side discrimination terminal B and charges the battery pack by using the charging system corresponding to the kind of the battery pack. In this case, an unconnected terminal detecting circuit impresses a reference voltage VRE upon the charger- side discrimination terminal B through a resistor R1 and judges whether the first kind of the second kind of battery packs is normally connected and whether or not the battery pack-side discrimination terminal B' is connected from the potential at the charger-side terminal B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charger for charging a battery pack, and more particularly to a terminal disconnection detection for detecting disconnection of a determination terminal for determining the type of a battery pack. It is related to the circuit.

Generally, as a power source for a cellular phone or the like, a battery pack is used in which a secondary battery composed of a lithium battery such as a lithium ion battery or a nickel battery such as a nickel cadmium battery is housed in a package having the same shape. At the same time, a method has been adopted in which two types of battery packs can be charged using the same charger.

[0003] Such a charger has a discriminating terminal for discriminating a type of a mounted battery.
Even if the determination terminal is unconnected for some reason, it is necessary to prevent the battery from being erroneously determined and charged by an inappropriate method.

[0004]

2. Description of the Related Art A secondary battery as a power source for a cellular phone or the like is
For the purpose of use, it is necessary that charging can be completed in as short a time as possible. Therefore, a quick charging method different from a normal case is employed.

FIG. 3 shows a method of charging a Li-based battery pack. Charging of the Li-based battery pack is performed by a combination of a constant current (CC) mode and a constant voltage (CV) mode. For example, from the complete discharge state, first, constant current charging is performed at a charging current of 800 mA, and when the battery voltage reaches 3.5 V, the charging current is switched to 580 mA, and further constant current charging is performed. ±
When the voltage reaches 50 mV, the charging is switched to the constant voltage charging and the charging is further continued. When the charging current reaches 100 mA, it is determined that the battery is fully charged, and the charging is completed. The same applies when charging a Li-based battery pack having a remaining charge.

FIG. 4 shows a method of charging a Ni-based battery pack. Ni-based batteries are charged at a constant current (CC)
It is performed only by the mode. For example, from a completely discharged state, first, a constant current charge is performed at a charge current of 800 mA.
When the battery voltage reaches 3.5 V, the charging current is 580 m
Switching to A and further performing constant-current charging, and when it is detected that the battery voltage has reached the maximum value and has dropped by a constant voltage ΔV, it is determined that the battery is fully charged and charging is completed. In this case, the voltage drop ΔV = −25 mV indicates a decrease in battery voltage based on a rise in battery temperature due to heat generated during charging.
The same applies when charging a Ni-based battery pack having a remaining charge.

As described above, the charging method differs depending on the type of the secondary battery. However, if the charging is performed by the different charging method, abnormal heat generation occurs. There is a possibility that a situation such as ignition may occur.

Therefore, the battery pack charger has a determination terminal for identifying the type of the mounted battery pack, and is mounted by detecting the voltage of the determination terminal on the charger side. The battery is charged by a charging method suitable for the battery pack.

FIGS. 5A and 5B show a battery pack discriminating method in a conventional charger. FIG. 5A shows a charger section, FIG. 5B shows a Li battery pack, and FIG. 5C shows a Ni battery. Each pack is shown. In the figure, reference numeral 1 denotes a rectified power supply unit, which rectifies an AC input to generate a required DC output. 2
Is a charge control unit that has a microcomputer and performs predetermined charge control according to a program stored therein. Reference numeral 3 denotes a charge output switching element for switching the charge output on and off, which is composed of, for example, a transistor. Reference numeral 4 denotes a battery pack having terminals A ', B', and D 'corresponding to terminals A, B, and D on the charger side. Terminals A and A 'are charging terminals, B and B' are determination terminals, and D and D 'are ground terminals.

In the battery pack 4, a secondary battery E is connected between a charging terminal A 'and a ground terminal D'. Li
In the case of a system battery pack, the battery E is connected to the determination terminal B ′ via the resistor R0 from the positive electrode side. In the case of a Ni-based battery pack, the determination terminal B 'is connected to the ground terminal D'.

In the charge control unit 2, reference numeral 5 denotes a charge voltage detection analog-to-digital converter (A / D) which converts the charge voltage between the charge terminal A and the ground terminal D into resistors R3 and R3.
The input voltage _VA divided by 4 is converted into a digital value and taken into the microcomputer. Reference numeral 6 denotes a discrimination voltage detection analog-to-digital converter (A / D) which converts the input voltage VB from the discrimination terminal _B into a digital value and takes it into the microcomputer. The input of A / D6 is connected to ground (GND) via resistor R2.

When the battery pack is mounted, terminals A ', B', D '
Are connected to terminals A, B, and D, respectively, whereby the battery voltage and the voltage of the discriminating terminal are taken into the charge control unit 2, thereby performing charge control in a charging method according to the type of the secondary battery. Is compared with a preset voltage value, and when the voltage is in the abnormal voltage range, the charging output switching element 3 is turned off to stop charging.

That is, when the voltage input through the determination terminal B is within a preset range, the battery is determined to be a Li-based battery, and the charging control unit 2 determines whether the charging method is as shown in FIG. Controls the rectifying power supply unit 1 so as to supply a charging current to the battery pack. On the other hand, when the voltage input via the determination terminal B is the ground potential, it is determined that the battery is a Ni-based battery, and the charging control unit 2 applies the charging current to the battery pack by the charging method shown in FIG. The rectifying power supply unit 1 is controlled so as to supply the power.

[0014]

In the conventional battery pack discriminating method shown in FIG. 5, terminals A, B, D, and A ',
In the state where B 'and D' are normally connected, the type of the secondary battery can be correctly determined as described above. However, the voltage V _B1 generated at the discrimination terminal B when the Ni-based battery pack is normally connected and the discrimination when the discrimination terminals B and B ′ are not connected when any type of battery pack is mounted. The voltage V _B2 generated at the terminal B is at the same level, and the two states cannot be distinguished.

That is, the voltage V _B1 is 0 V because the terminal B ′ is connected to the ground (excluding the influence of the pattern resistance and other impedances), and the voltage V _B2 is that the terminals B and B ′ are not connected. Voltage is not applied to terminal B,
Since the terminal B is connected to the ground via the resistor R2, the voltage is 0 V (excluding the influence of noise).

In the conventional system shown in FIG. 5, even when a Li-based battery pack is mounted, when the terminals B and B 'are not connected, it is determined that a Ni-based battery pack is mounted. As a result, there is a problem that the charger cannot perform an appropriate charging operation according to the battery type, and thus the charger and the battery pack cannot be properly protected.

An object of the present invention is to solve such problems of the prior art.
In the battery charger shared with the system battery pack, the disconnection of the determination terminal for determining the type of the battery can be detected, so that the determination of the type of the battery is not erroneously performed. It is an object of the present invention to provide a terminal non-connection detection circuit capable of preventing a charging operation by the device from being performed and properly protecting a charger and a battery pack.

[0018]

Means for Solving the Problems Normal operation of the Ni-based battery pack
At the time of mounting, the determination terminal B is connected by the connection on the battery pack side.
It becomes the ground potential. On the other hand, the charging terminal
When the discrimination terminal B 'on the pond pack side is not connected, the terminal
No voltage is applied to B, and terminal B is grounded via resistor R2.
To the ground potential. Therefore
In this state, the charging control unit 2 cannot distinguish between the two cases.
Is connected to a terminal B via a resistor R1 and a reference voltage V _REFGive
Terminal B is at a certain voltage higher than the ground potential.
So that it is possible to distinguish between the two cases.
You.

When the Li-based battery pack is normally mounted, the determination terminal B has a potential determined by the charging voltage of the Li-based battery pack. Then, a reference voltage _VREF is applied to the terminal B via the resistor R1, and this reference voltage is
A voltage higher than the voltage generated at the determination terminal B due to the maximum voltage of the Li-based battery pack at the time of normal connection of B '
By setting the voltage at the discriminating terminal B when B 'is not connected, when the discriminating terminal B on the charger side and the discriminating terminal B' on the battery pack are not connected, the terminal B becomes the terminal B,
Since the voltage becomes higher than that at the time of normal connection of B ', it is possible to determine both cases.

Hereinafter, specific means for solving the problems of the present invention and the operation thereof will be described.

In the terminal disconnection detecting circuit of the present invention, the determination terminal B 'is connected to the first battery R connected to the battery positive electrode via the first resistor R0.
And a second type of battery pack having the determination terminal B ′ connected to the ground terminal, and connected to the ground potential via the second resistor R2. When the discriminating terminal B on the charger side is connected to the discriminating terminal B 'on the battery side, the type of the battery pack is discriminated based on the potential of the discriminating terminal B on the charger side, and the charging method corresponding to the type of the battery pack is determined. In a charger that performs charging,
When the reference voltage _VREF is applied to the determination terminal B on the charger side via the third resistor R1 and this reference voltage is applied, when the determination terminal of the first type battery pack in the highest voltage state is normally connected. By setting the voltage higher than the voltage generated at the determination terminal B to a voltage generated at the determination terminal B on the charger side when the determination terminal B ′ on the battery pack is not connected, the determination terminal B on the charger side is determined. Depending on the potential, when the first type of battery pack is normally connected, when the second type of battery pack is normally connected, the discriminating terminal B on the charger side and the discriminating terminal B ′ on the battery pack side are not connected. It is configured to determine the case.

When the discriminating terminal B on the charger side is not connected to the discriminating terminal B 'on the battery pack side, the discriminating terminal B is connected to the first terminal when the terminals B and B' are normally connected by the reference voltage _VREF .
Is always higher than the voltage generated at the determination terminal B by the voltage of the battery pack of the first type, it is possible to reliably determine that the first type of battery pack is normally connected. In addition, the second terminal in which the determination terminal B is at the ground potential.
Can be reliably determined even when the battery pack of the type is normally connected.

[0023]

1 shows an embodiment of the present invention, in which (a) shows a charger section, and (b) shows Li.
And (b) shows a Ni-based battery pack. In the figure, the same components as those in FIG. 5 are indicated by the same numbers, R1 is a resistor, and V _REF is a reference voltage.

In the present invention, the conventional charger circuit shown in Figure 5, the reference voltage V _{RE F} via a resistor R1 and configured to apply to the determination terminal B, the voltage of the discrimination terminal B in this state by measuring V _B, the type of the implemented battery pack, discrimination terminal B, B 'is determined in the case of unconnected.

In the case of FIG. 1, the voltage V generated at the determination terminal B is
_{As B} , the following three cases can be considered. (A) When Li-based battery pack is normally connected… V _B1 (B) When Ni-based battery pack is normally connected… V _B2 (C) When B and B 'terminals are not connected… V _B3

FIG. 2 shows an equivalent circuit at the time of measuring the determination terminal voltage.
(A) shows the voltage V _B1Measurement state, (b) is
Voltage V_B2Measurement state, (c) is voltage V_B3It is in the measurement state.

In the measurement state of the voltage V _B2 , the potential of the terminal B ′ is 0 because the terminal B ′ is connected to the ground potential. V _B2 = 0 (1)

In the state of measuring the voltage V _B3 , the potential of the terminal B becomes a middle voltage when the reference voltage V _REF is _divided by the resistors R1 and R2. V _B3 = V _REF × R2 / (R1 + R2) (2)

Although the voltage V _B1 varies depending on the battery voltage V _BAT , the reference voltage V _REF and the values of the resistors R0, R1 and R2 are selected, and the determination terminal B ′ of the Li-based battery pack at the highest voltage is selected. By setting the voltage higher than the voltage generated at the determination terminal B when normally connected to the voltage at the determination terminal B on the charger side when the determination terminal B ′ on the battery pack is not connected, the Li-based Maximum value V of battery pack voltage
_Including the case of _BATMAX , the condition of V _B3 > V _B1 (2) can always be satisfied. In this case, a current flows in a direction in which the battery pack is charged by the reference voltage _VREF .

Therefore, the circuit shown in FIG. 1 can be configured such that V _B3 > V _B1 > V _B2 (3), so that the voltage range corresponding to each case is stored in advance in the charge control unit 2. The cases (A) to (C) described above can be determined by setting and comparing this.

When such a reference voltage V _REF is given,
The voltage V _B1 is obtained from the following relationship. That is, the resistance R
1, the battery voltage V _BAT from the voltage V _B1 via the resistor R0
The current i ₀ which flows in a current I ₂ flowing to the ground potential via the resistor R2 is superimposed. Therefore _{i o = (V B1 -V BAT} ) / R0 i 2 = V B1 / R2 V REF -V B1 = (i o + i 2) · R1 = _{[{(V B1 -V BAT) /} R0} + V B1 / R2] ・ R1

As an example, assuming that the minimum voltage of the Li-based battery pack is 0 V (complete discharge state) and the maximum voltage is 4.1 V, the resistance R0 = 10 kΩ, the resistance R1 = 10 kΩ, and the resistance R2 = 10
In the case of 0 kΩ, assuming that the reference voltage V _REF = 5.2 V, the voltages V _B1 , V _B2 , and V _B3 are as follows. V _B1 = 2.476V to 4.428V V _B2 = 0V V _B3 = 4.727V

[0033] By this arrangement, at the check, if the value of the setting range corresponding to the voltage V _B3 as the voltage V _B is input, even if the one of the Li-based battery pack and Ni-based battery pack is mounted Since it is possible to determine that the determination terminals B and B 'are not connected, charging can be stopped to prevent charging by an incorrect charging method.

[0034]

As described above, according to the present invention, L
In the battery charger shared by the i-based battery pack and the Ni-based battery pack, it is possible to correctly determine the type of the battery and to determine the state where the determination terminal for identifying the type of the battery is not connected. It is possible to prevent a charging operation using an incorrect charging method from being performed.

Therefore, according to the present invention, it is possible to prevent malfunction of the charging operation and properly protect the charger and the battery pack.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, in which (a) shows a charger section, (b) is a Li-based battery pack, and (b) is Ni.
Each shows a system battery pack.

FIG. 2 is a diagram showing an equivalent circuit at the time of measuring a discrimination terminal voltage, where (a) is a voltage V _B1 measurement state, (b) is a voltage V _B2 measurement state, and (c) is a voltage V _B3 measurement state. .

FIG. 3 is a diagram showing a method of charging a Li-based battery pack.

FIG. 4 is a diagram illustrating a method of charging a Ni-based battery pack.

5A and 5B are diagrams showing a battery pack discriminating method in a conventional charger, wherein FIG. 5A shows a charger section, FIG. 5B shows a Li-based battery pack, and FIG. 5C shows a Ni-based battery pack, respectively. .

[Explanation of symbols]

 B determination terminal B 'determination terminal R0 resistance R1 resistance R2 resistance

Claims (1)

[Claims] 1. A first type of battery pack having a determination terminal connected to a battery positive electrode via a first resistor, and a second type of battery pack having a determination terminal connected to a ground terminal. The battery pack is connected to the battery-side determination terminal when the charger-side determination terminal connected to the ground potential via the second resistor is connected to the battery-side determination terminal. In the charger that determines the type of the battery pack and performs charging by a charging method corresponding to the type of the battery pack, a reference voltage is applied to a determination terminal on the charger side through a third resistor, and the reference voltage is When the discrimination terminal of the first type of battery pack in the highest voltage state is normally connected, a voltage higher than the voltage generated at the discrimination terminal on the charger side is set, and the discrimination terminal on the battery pack side is not connected. Generated at the discriminating terminal on the charger side With such a voltage, the normal connection of the first type of battery pack, the normal connection of the second type of battery pack, A terminal disconnection detection circuit configured to determine whether the determination terminal of the battery pack is not connected to the determination terminal of the battery pack.