JPH08205412A - Charger - Google Patents

Abstract

PURPOSE: To provide a charger which can detect the abnormality of a metal contact with a secondary cell. CONSTITUTION: When a battery 80 is placed on the charging base of a charger 10, a metal contact 81 is brought into contact with a metal contact 22, and a charging circuit is closed. A charging current ICHG is generated by a power source 21 and a first resistor 23 or a second resistor 24, applied to a secondary cell 83 through the reverse preventing diode 82 of the battery 80, and the cell 83 is gradually charged. When the conducting state between the contacts 22 and 81 is deteriorated and a contact resistance Rg is increased, the value of the current ICHG is decreased. The ratio of the resistance value of the resistor 23 or 24 is relatively decreased, and the voltage difference between the voltage Vp of the position (p) and the voltage Vq of the position (q) is reduced. Accordingly, the effect that the voltage drop value of the second comparator 36 of the abnormality detector 30 is smaller than the second threshold value THL2 is detected, and the second LED 42 of the unit 40 is lit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging a secondary battery, and more particularly to closing / closing a circuit via a metal contact.
The present invention relates to a charging device that can detect an abnormality of a metal contact portion of a charging device that charges by opening.

[0002]

2. Description of the Related Art For example, in a cordless telephone,
In order to use the cordless handset separately from the base unit, it is necessary to fully charge the secondary battery built in the cordless handset from the base unit while the handset is placed in the predetermined position of the base unit. is there. An example of a charging circuit for that purpose is shown in FIG. In FIG. 4, when the battery device 80 is placed on the charging stand of the charging device 90, the metal contact 81 of the battery device 80 and the metal contact 22 of the charging device 90.
Contact each other and the charging circuit is closed. And power supply 2
1, and the charging current I _CHG by the first resistor 23 or the second resistor 24 is generated, the charging current I _CHG is passed through the diode 82 for reverse current prevention in the battery device 80, the secondary battery 83 Applied to. As a result, the secondary battery 83 is gradually charged. Therefore, in the charging detection unit 91, by detecting the voltage V _p at the position _p and the voltage V _q at the position q in the charging detection circuit as illustrated,
It is possible to detect the charging current I _CHG and turn on the LED 92 to make it possible to confirm the charging state.

[0003]

However, in such a charging device, the contact resistance increases when dust or an oxide film adheres to the metal contact portion. As a result, the charging current supplied to the battery may decrease due to the influence of the voltage drop across the contact resistance, and the desired charging may not be performed regardless of the charged state. That is, the capacity charged within a certain period of time decreases. If such a phenomenon occurs, for example, in a cordless telephone, etc., even though the cordless handset is set in the parent device for a sufficient time, it is not sufficiently charged and a failure occurs during use of the cordless handset. Then, it cannot be used satisfactorily.

Therefore, an object of the present invention is to provide a charging device capable of detecting an abnormality in a metal contact portion with a secondary battery.

[0005]

Means for Solving the Problems When dust or the like adheres to a metal contact portion to cause poor contact, the contact resistance increases and the charging current decreases abnormally. This abnormally small charging current is detected.

Therefore, the charging device of the present invention is a charging device for charging a secondary battery, comprising two metal contacts electrically connected to the secondary battery charging circuit to be charged and the two metal contacts. A current source composed of a power source and a resistor connected in series with the contacts at both ends, a voltage drop detecting means for detecting a voltage drop in the resistor of the current source, a voltage drop value detected by the voltage drop detecting means and the A charging current calculating unit that calculates a charging current based on a resistance value, an abnormality detecting unit that determines whether the charging current calculated by the charging current calculating unit is proper and detects an abnormality, and an abnormality detecting unit that detects the abnormality. Display means for displaying an abnormality of the charging current.

[0007]

According to the present invention, the voltage drop across the resistor forming the current source is detected, and the charging current is detected based on the voltage drop value and the resistance value. This charging current is compared with a predetermined appropriate charging current, an abnormality in the charging state is detected, and if it is abnormal, it is displayed on the display means.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the charging device of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of the charging device of the present invention, showing a state in which the charging device 10 of the present invention is connected to a battery device 80 to be charged. The charging device 10 of the present embodiment is built in a master device of a cordless telephone, and the battery device 80 to be charged is built in a slave device. The charging system shown in FIG. 1 is a system in which charging is started by placing the slave unit on a predetermined charging base of the master unit so that metal contacts of both the master unit and the slave unit come into contact with each other.

First, the structure of the charging device 10 will be described. The charging device 10 includes a charging unit 20, an abnormality detection unit 30, and a display unit 40.

The charging section 20 includes a power source 21, metal contacts 22,
The first resistor 23, the second resistor 24, and the switch 2
5, and constitutes a charging circuit for applying a charging current to the metal contact 22. The charging unit 20 has two metal contacts 22.
When the circuit is closed, the metal contact 22 composed of a and 22b is applied so that a predetermined voltage is applied to the metal contact 22.
A power supply 21 is connected in series between a and 22b. Furthermore, in the series circuit, a first resistor 23 and a second resistor 24, which are two resistors arranged in parallel and having different resistance values, are provided.
Is connected. Then, one of these resistors is selected by the switch 25, and the charging current I _CHG flowing through the metal contact 22 is switched. Further, the voltage V _p at the position p at the output end of the power source 21 of this charging circuit, and the voltage at the position q of the metal contact 22a sandwiching this position p and the switch 25, the first resistor 23 and the second resistor 24. Each is connected to the abnormality detection unit 30 so that V _q can be measured.

The abnormality detecting section 30 includes the first A / D converter 3
1, second A / D converter 32, subtractor 33, memory 3
4, the first comparator 35, and the second comparator 36, and configures a circuit for detecting an abnormality in the charging current of the charging unit 20. As described above, in the abnormality detector 30, the voltage V _p of the position p of the charging unit 20, and can be measured voltage V _q position q. Then, the voltage V _{p at} the position p of the charging unit 20 is transferred to the first A / D converter 31 and to the charging unit 20.
The voltage V _{q at} the position q is input to the second A / D converter 32. First A / D converter 31 and second A / D
Each voltage signal input to the converter 32 is quantized, converted into a digital signal, and output to the subtractor 33. The subtractor 33 subtracts the digitized voltage value V _p from the voltage value V _q to obtain the voltage drop between the position p and the position q of the charging unit 20.

The memory 34 in the abnormality detecting section 30 is a memory for storing two reference values for checking the state of the charging section 20. Specifically, the memory 34 has a first threshold value THL1 for detecting that the charging device 10 is in a charging state when the battery device 80 is connected to the charging device 10 via a metal contact, and the standard. Second threshold value THL2 for detecting that the normal charging current is flowing
The two reference values of and are stored. The first threshold value THL1 is determined by the first comparator 35 and the second comparator 3
6, and the second threshold value THL2 is connected so that it can be read by the second comparator 36.

In the abnormality detector 30, the voltage drop value from the position p to the position q obtained by the subtracter 33 is stored in the memory 34 in the first comparator 35 and the second comparator 36. The state of the charging unit 20 is detected by comparison with the reference value that is set. First, the first comparator 35
, The voltage drop value and the first threshold value THL
1 is compared, and when the voltage drop value is larger than the first threshold value THL1, it is determined that the slave unit is being charged, and a predetermined LED in the display unit 40 described later is turned on. Therefore, the output of the first comparator 35 is set to the low level. In addition, the second comparator 36 uses the first threshold value THL1 to perform the same comparison as the first comparator 35, and further determines the voltage drop value and the second threshold value THL2. Compare. That is, the first threshold TH
It is determined that charging is being performed in comparison with L1,
Further, when the voltage drop value is smaller than the second threshold value THL2, it is determined that charging is not normally performed, and a predetermined LED in the display unit 40 described later is turned on,
The output of the second comparator 36 is set to low level.

As described above, when the voltage drop value is used as it is for comparison, it is stored in the memory 34 when the first resistor 23 and the second resistor 24 are switched in the charging section 20. The reference value that is present can also be switched appropriately.

The display section 40 has a first LED 41 and a second LED 42, and displays the charging state of the charging section 20. One terminal of the first LED 41 is connected to a predetermined high-level voltage source 43, and the other terminal is connected to the output of the first comparator 35 of the abnormality detection unit 30.
With this configuration, when the output of the first comparator 35 becomes low level, that is, when the charging unit 20 enters the charging state, the first LED 41 lights up. Second LED 42
Has one terminal connected to a predetermined high-level voltage source 44 and the other terminal connected to the output of the second comparator 36 of the abnormality detection unit 30. With this configuration, the second
When the output of the comparator 36 becomes low level, that is, when the charging current of the charging unit 20 is small and it is detected that the charging state is abnormal, the second LED 42 is turned on.

Next, the operation of the charging device 10 having such a configuration will be described with reference to FIG. FIG. 2 shows the value of the charging current I _CHG of the charging system shown in FIG.
It is a figure which shows the relationship of the lighting state of the 1st LED41 and 2nd LED42 of this.

When the battery device 80 is placed on the charging stand of the charging device 10, the metal contact 81 of the battery device 80 and the metal contact 22 of the charging device 10 come into contact with each other, and the charging circuit is closed. Then, the charging current I _CHG is generated by the power source 21 and the first resistor 23 or the second resistor 24, passes through the backflow prevention diode 82 in the battery device 80, and is applied to the secondary battery 83. . As a result, the secondary battery 83 is gradually charged. Normally, when the contact resistance Rg between the metal contact 22 and the metal contact 81 is sufficiently small, the first resistance 23 or the second resistance 23 is provided between the voltage V _p at the position _p and the voltage V _{q at the} position q. 24, a sufficient voltage difference is generated, and the charging current I _CHG satisfying the standard is supplied to the battery device 80.
Is applied to In the abnormality detection unit 30, the first comparator 35 detects that the battery is in the charged state, and the display unit 4
The first LED 41 of 0 is turned on. This state is shown in FIG.
In the case where the charging current I _CHG is equal to or more than the current value i4, the first LE indicating that the charging is appropriately performed is displayed.
D41 lights up.

However, when the conductive state between the metal contacts 22 and 81 deteriorates and the contact resistance Rg increases, the value of the charging current I _CHG decreases. In terms of voltage, the ratio of the resistance values of the first resistor 23 and the second resistor 24 becomes relatively small, and the voltage V _p at the position _p and the voltage V at the position q are relatively small.
The voltage difference of _q becomes small. Therefore, the abnormality detection unit 30
The second comparator 36 detects that the voltage drop value is smaller than the second threshold value THL2, and the second LED 42 of the display section 40 is turned on. In FIG. 2, the charging current I _CHG is in the state between the current values i2 and i4, and the first
The second LED 42 also lights up together with the LED 41. Note that, in FIG. 2, when the charging current I _CHG is i2 or less, the child device is not set and the charging state is not established.

As described above, in the charging device 10 of the present embodiment, normal charging is performed due to the voltage drop caused by the increase of the contact resistance Rg due to the adhesion of dust or oxide film on the metal contact portion. When it is not possible, the user can be notified of the abnormal state by lighting the LED. Therefore, the user can perform a procedure such as cleaning the metal contact portion to enable normal charging.

The charging current I _CHG becomes smaller as the charging is completed, but it does not become smaller than a predetermined value larger than i4 in FIG. Therefore, in this charging device 10, an abnormality in the charging state is not erroneously detected due to the decrease in the current.

The charging device of the present invention is not limited to this embodiment, and various modifications can be made. For example, although the charging device 10 of the present embodiment is a device that is built in the base unit of the cordless telephone and is used to charge the battery device 80 of the cordless telephone, it is not limited to the cordless telephone, and various other devices. It can be applied to products, etc. without any problem.

The circuit for detecting an abnormality in the charging current in the abnormality detecting section 30 is not limited to the circuit shown in FIG. 1, and may be realized by any suitable circuit. For example, in the present embodiment, the voltages at the positions p and q of the charging section 20 are converted into digital signals through the A / D converters, and the conversion result is used to detect an abnormality by the digital circuit. Alternatively, the detected analog signal may be used as it is in an analog circuit.

Further, in this embodiment, the abnormality detecting section 30
In the above, the difference between the detected voltage values at the position p and the position q is compared with a predetermined reference value as it is.
However, based on the voltage drop value, the first resistor 23
Alternatively, the current value of the charging current may be calculated with reference to the resistance value of the second resistor 24, and the current value may be compared with the reference value. The current value can be easily calculated by using the subtractor 33 of the abnormality detection unit 30 as an arithmetic unit capable of division not limited to subtraction.

Further, the abnormality detecting section 30 can be constructed by using a general-purpose arithmetic unit having an A / D conversion input without forming a dedicated circuit. FIG. 3 is a block diagram showing the configuration of the charging device 10 in that case. If the two input signals from the charging unit 20 are connected to the A / D conversion input of the arithmetic unit 50, the subsequent processing can be easily realized by the arithmetic circuit inside the arithmetic unit 50. With this configuration, the structure is simplified, and thus the charging device 10 having a small volume and a low cost can be realized. Further, it becomes possible to use the arithmetic unit 50 also as a general-purpose arithmetic unit for other uses of the cordless telephone. With such a configuration, a device having a more efficient configuration can be realized.

Further, the display method of the display section 40 is not limited to the LED display as in the present embodiment, and any display means may be used. Further, it may be displayed on a liquid crystal display device or the like already provided in the cordless telephone.

[0026]

According to the charging device of the present invention, the abnormality of the metal contact portion with the secondary battery can be easily detected by turning on the LED or the like. Therefore, the user can take measures such as cleaning the metal contacts, and normal use of such various devices becomes possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a charging device of the present invention, showing a state in which the charging device of the present invention is connected to a battery device to be charged.

2 is a value of a charging current of the charging system shown in FIG.
It is a figure which shows the relationship of the lighting state of the 1st LED and 2nd LED of a display part.

FIG. 3 is a block diagram showing a configuration when the charging device shown in FIG. 1 is realized by using a general-purpose arithmetic unit.

FIG. 4 is a block diagram showing a configuration of a conventional charging device.

[Explanation of symbols]

10 ... Charging device 20 ... Charging part 21 ... Power source 22 ... Metal contact 23 ... First resistance 24 ... Second resistance 25 ... Switch 30 ... Abnormality detection part 31 ... First A / D converter 32 ... Second A / D converter 33 ... Subtractor 34 ... Memory 35 ... First comparator 36 ... Second comparator 40 ... Display unit 41 ... First LED 42 ... Second LED 43, 44 ... Voltage source 50 ... Computing device 80 ... Battery device 81 ... Metal contact 82 ... Diode 83 ... Secondary battery 90 ... Conventional charging device 91 ... Charge detection unit

Claims (1)

[Claims] 1. A charging device for charging a secondary battery, comprising: two metal contacts electrically connected to a secondary battery charging circuit to be charged; and the two metal contacts connected in series at both ends. Current source consisting of a power source and a resistor, a voltage drop detecting means for detecting a voltage drop in the resistor of the current source, and a charging current based on the voltage drop value and the resistance value detected by the voltage drop detecting means. A charging current calculating means for calculating, an abnormality detecting means for determining whether the charging current calculated by the charging current calculating means is proper or not, and an abnormality of the charging current detected by the abnormality detecting means are displayed. And a charging device having a display means for operating.