JP2000014034A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid stoppage charging, even if the contact resistance of a charger output terminal and a battery varies and to obviate a constant-current control portion for charging current by detecting the battery voltage, when a switching element is turned off according to a signal from a charge control portion. SOLUTION: A connection of the positive terminal a' and negative terminal b' of a battery with the output positive terminal (a) and output negative terminal b of a charger is detected by a charge control portion 4, which in turn outputs a charge starting signal to turn on a switching element 3. Then a charging current flows from a direct-current power supply 2 for charging to a battery 7 via the switching element 3, and charging is started. When a certain time has passed after the start of charging, the charge control portion 4 generates a charging current off signal to interrupt the charging current. Although the charge control portion 4 reads the battery voltage during the charging current interrupt period, the detected voltage is equal to a voltage Vb' obtained by adding to the actual battery voltage a voltage drop, which is produced when the charging current is passed through a contact resistance between the charger output positive terminal (a) and the battery positive terminal a' and the contact resistance between the charger output negative terminal b and the battery negative terminal b'.

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 rechargeable battery such as a nickel cadmium storage battery or a nickel hydride storage battery.

[0002]

2. Description of the Related Art Conventionally, as a charging method for charging a rechargeable battery such as a nickel cadmium storage battery or a nickel hydride storage battery, a charging current controlled at a constant current is continuously supplied to a battery to be charged, and the battery voltage peaks. A charge control method for detecting completion of charging and detecting completion of charging after that, that is, a so-called -ΔV control method, has been widely used. FIG. 5 shows a circuit block diagram, and FIG. 6 shows a charging current and a battery voltage according to a conventional method.

[0005] In FIG. 5, reference numeral 1 denotes a charging device, which includes a DC power supply 2, a switch element 3, a charge control unit 4, and a constant current control unit 5. Reference numeral 7 denotes a secondary battery to be charged. The DC power supply 2 is connected to an external AC power supply, supplies a charging current, and outputs a constant current in a constant current control unit.
Then, the charging current is turned on and off by the switch element 3, and the charging current is supplied or stopped for a predetermined period. The charge control unit 4 detects the battery voltage and detects the completion of charging.

A charging operation in this configuration will be described with reference to FIG. In FIG. 6, I is a constant current controlled charging current, which flows to the battery continuously from the start of charging to the completion of charging. Vb is the battery voltage, and the voltage rises as the charging proceeds with the charging current I. When the charging is completed, the battery voltage Vb peaks due to self-heating inside the battery,
Then start descent. The battery voltage drop after this voltage peak is detected to detect the completion of charging of the battery.

[0005]

However, in the above-mentioned conventional method, since the battery voltage is always detected while the charging current is flowing, the charging is performed based on the contact resistance between the output terminal of the charging device and the battery terminal. A voltage drop occurs due to the current, and the charging control unit of the charging device detects the voltage obtained by adding the voltage drop at the contact resistance of the terminal to the actual battery voltage as the battery voltage. When the contact resistance changes, the voltage drop at the contact resistance also changes, and the charge control unit considers that the battery voltage has changed. In the charging control method that detects that the battery voltage has peaked and dropped, if the voltage drop in the contact resistance increases, it is determined that the battery voltage has risen and there is no problem, but if the voltage drop in the contact resistance decreases. Is detected as a drop in battery voltage, it is determined that charging is completed, and charging ends. Specifically, when the user touches the battery during charging, or when the charging device is being charged by placing the charging device in a constantly vibrating place, there is a possibility that the charging may be terminated halfway due to the above operation. Was. In addition, it is necessary to provide a constant current control unit for the charging current so that the charging current decreases when the input voltage decreases and the battery voltage does not drop due to the reduction in the charging current, and the cost is reduced. There was also a problem that this was the case.

The present invention solves the above-mentioned conventional problems. Even if the contact resistance between the output terminal of the charging device and the battery changes, the charging does not end halfway, and the constant current control unit for the charging current. It is an object of the present invention to provide a charging device that does not require a charging device.

[0007]

In order to achieve the above object, a charging apparatus according to the present invention comprises: a DC power supply for converting a commercial power supply to DC and supplying a charging current; and a charging apparatus for detecting charging completion by detecting a battery voltage. And a switch element for receiving a signal from the charge control unit and performing ON-OFF control of a charging current, wherein when the switch element is turned off by a signal from the charge control unit, the charge control unit Is used to detect the battery voltage.

As a result, the measurement error of the battery voltage due to the change in the contact resistance can be reduced.

Further, the charging device of the present invention detects the completion of the charging by detecting that the battery voltage reaches a peak and then drops. In the charging device employing the-△ V control method, a signal from the charging control unit is used. By detecting the battery voltage by the charge control unit when the switch element is turned off, it is possible to prevent the battery from being erroneously recognized as being charged due to a measurement error of the battery voltage and from being terminated.

The charging apparatus according to the present invention includes a DC power supply for converting a commercial power supply into DC power and supplying a charging current, a charging control unit for detecting a battery voltage to detect completion of charging, and a signal from the charging control unit. And a switch element that performs ON-OFF control of the charging current in response to the charging, and charges the secondary battery by directly using the charging current obtained from the DC power supply. In other words, the conventional charging device does not include the constant current control unit. As a result, costs can be reduced.

Further, the charging device of the present invention includes a DC power supply for converting a commercial power supply to DC and supplying a charging current, a charging control unit for detecting a battery voltage and detecting completion of charging, and a signal from the charging control unit. And a switch element for performing ON-OFF control of a charging current. The secondary battery is charged by directly using the charging current obtained from the DC power supply, and the switching element is switched by a signal from the charging control unit. When the is turned off, the battery voltage is detected by the charge control unit.

Thus, even if a constant current control unit is not provided, even if the charging current is reduced due to a change in the input voltage, an inexpensive and excellent charging device that does not erroneously recognize as -ΔV detection can be provided.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to detecting a contact voltage between a battery output terminal and a battery terminal in order to detect a battery voltage during a charging current suspension period, that is, to detect a battery voltage when a charging current is not flowing. The charging does not end prematurely even if changes.

An embodiment of the present invention will be described below with reference to a charging current and a battery voltage shown in FIG. 1 and a circuit block diagram shown in FIG.

In FIG. 1, Vb is a battery voltage when charged by the charging device according to the present embodiment, and I is a charging current. In addition, in the circuit block diagram of FIG. 2, reference numeral 1 denotes the entire charging device, 2 denotes a DC power supply for supplying a charging current, and 3 denotes on / off of the charging current to supply or stop the charging current for a predetermined period. Switch element. 4
Is a charge control unit for detecting the battery voltage and detecting the completion of charging. Reference numeral 7 denotes a battery to be charged. In the present embodiment, no constant current control unit is provided.

A is an output + terminal of the charging device, b
Is an output-terminal of the charging device. a 'is the + terminal of the battery, and b' is the-terminal of the battery.

The operation of the charging device configured as described above will be described below. First, the + terminal a 'and the-terminal b' of the battery are the output + terminal a and the output-of the charging device.
The connection to the terminal b is detected by the charge control unit 4 and a charge start signal is output, the switch element 3 is turned on, and the charging current is supplied from the charging DC power supply 2 to the battery 7 via the switch element 3. Flows, and charging is started. After a lapse of time T1 from the start of charging, the charging control unit 4 issues a charging current OFF signal for a period of time T2, and the charging current is stopped.

In the charging current suspension period T2, the charging control unit 4 reads the battery voltage. The detected voltage is the actual battery voltage VB between the charging device output + terminal a and the battery + terminal a ', and the charging voltage. A voltage Vb 'is obtained by adding a voltage drop generated by the flow of the charging current to the contact resistance between the device output-terminal b and the battery-terminal b'.

FIG. 3 shows the battery voltage and the charging current during the charging current suspension period T2. When the charging current is stopped at the time Ta, the battery voltage starts to drop. However, since the gradient of the battery voltage drop immediately after the stopping of the charging current is steep, the charging control unit 4 starts the time Tb after about T2 / 2 has elapsed. Start reading the battery voltage. After that, the time Tc, T
The battery voltage is read at d, Te,..., Tx points, the average value of all the read values of Tb-Tx is calculated, and this average value is stored as the battery voltage in the main T2 period. Thereafter, when the charging current suspension period T2 elapses, the charging control unit 4 issues a charging current ON signal, and the charging current starts flowing again. Thereafter, when the charging current energizing period T1 elapses, the charging current stopping period T2 comes again, and thereafter, the charging of the battery proceeds by repeating this operation.

The charge control unit 4 supplies Vb 'in each T2 period.
Is read and compared with the Vb 'value in the previous T2 period, and if it has risen from the previous value, it is updated and stored as a new peak value. If it is lower than the previous value, it will not be updated as the peak value, and will be read next time, one after another,
Vb 'lower than the stored peak value by a predetermined voltage or more
Is continued for a predetermined number of times or more, it is determined that charging is completed, a charging current OFF signal is issued, and charging ends.

Here, the case where the contact resistance between the charging device output + terminal a and the battery + terminal a 'has changed will be described with reference to FIG. Vb in FIG. 4 is the actual battery voltage, and Vb ′ indicated by a dotted line is a value obtained by adding the voltage drop in the contact resistance R of the + terminal and the − terminal to the battery voltage Vb, and this voltage Vb ′ is the charge control unit. 4 is the voltage to be detected. The detection voltage Vb ′ of the charging control unit 4 during the charging current conduction period T1 increases with the progress of charging as shown by the dotted line in FIG. Here, it is assumed that the normal contact resistance R at the + terminal and the − terminal is 10 mΩ, and the value of the charging current I is 1 A. In the charging current suspension period T2, the charging current does not flow and only the minute voltage detection current Is is provided. Here, the voltage detection current Is is set to 1 mA. Also, it is assumed that the completion of charging of the battery is set to be detected when the battery voltage drops by 10 mV from the peak value.

At this time, the normal charging current conduction period T1
, The voltage drop at the contact resistance R between the + terminal and the − terminal is I × R = 1A × 10 mΩ = 10 mV, and the detection voltage Vb ′ is higher than the battery voltage Vb by 10 mV. Further, the voltage drop of the contact resistance R during the charging current suspension period T2 is Is × R = 1 mA × 10 mΩ = 0.01 mV, and the detection voltage Vb ′ is higher than the battery voltage Vb by 0.01 mV. The normal detection voltage Vb 'is shown by a dotted line in FIG.

In this state, when the contact resistance R at the + terminal and the-terminal increases from 10 mΩ to 30 mΩ, the voltage drop at the contact resistance R becomes I × R = 1A × 30 mΩ = 30 mV during the charging current conduction period T1. Vb
30 mV higher than the normal time, and increased by 20 mV compared to the normal state. The voltage drop of the contact resistance R during the charging current stop period T2 is Is × R = 1 mA × 30 mΩ =
0.03 mV, which is 0.03 mV higher than the battery voltage Vb, and 0.02 mV higher than normal. As a result, the charging control unit 4 sets the actual battery voltage Vb
Although the contact resistance has not changed, it is recognized that the battery voltage has increased by 20 mV during the charging current conduction period T1 due to the increase in the contact resistance R between the + terminal and the − terminal, and during the charging current suspension period T2, Battery voltage is 0.0
It is recognized that the voltage has risen by 2 mV.

When the contact resistance R increases, the detected battery voltage only increases, so that no problem arises. However, after that, the contact resistance R at the + terminal and the-terminal becomes the normal value. Returning to, the charging control unit 4 recognizes that the battery voltage has dropped by 20 mV during the charging current energizing period T1, and 0.02 mV during the charging current suspension period T2.
Recognize that it has dropped.

Therefore, if the battery voltage detection is performed during the charging current conduction period T1 as in the prior art, the detection voltage Vb 'of the charging control unit 4 is set to the charging completion detection set voltage of 10 mV.
Since the battery has descended as described above, it is determined that the charging is completed, and the charging ends even though the charging is actually being performed. However, the charging device according to the present invention performs the battery voltage detection during the charging current conduction period T1, so that the charging completion detection voltage drops only by 0.02 mV from the setting voltage of 10 mV, and the charging is continued without being terminated halfway. Is what is done.

When the charging current is reduced due to a decrease in the input voltage, the battery voltage drops greatly in the charging current energizing period T1 and erroneous detection of -ΔV occurs, but in the charging current suspension period T2, the battery voltage decreases. Since the drop is extremely small, no false detection of -ΔV occurs. That is, according to the method of the present invention,-
Erroneous detection of ΔV is eliminated, and the constant current control unit for the charging current, which has been indispensable in the conventional charging device of the −ΔV control system, is no longer indispensable.

[0027]

As described above, according to the present invention, the charging current is stopped for a predetermined period, and the battery voltage is detected during the charging current stop period, whereby the contact resistance between the output terminal of the charging device and the battery terminal is reduced. Even if it changes, the advantageous effect that the charging does not end halfway can be obtained.

[Brief description of the drawings]

FIG. 1 is a correlation diagram between a battery voltage and a charging current according to an embodiment of the present invention.

FIG. 2 is a circuit block diagram according to one embodiment of the present invention.

FIG. 3 is a correlation diagram between a battery voltage and a charging current according to another embodiment of the present invention.

FIG. 4 is a correlation diagram between a battery voltage and a charging current according to still another embodiment of the present invention.

FIG. 5 is a conventional circuit block diagram.

FIG. 6 is a conventional correlation diagram between battery voltage and charging current.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging device 2 DC power supply 3 Switching element 4 Charge control part 5 Constant current control part 7 Secondary battery

Claims (5)

[Claims] 1. A DC power supply for converting a commercial power supply into a direct current and supplying a charging current, a charging control unit for detecting a battery voltage to detect completion of charging, and receiving a signal from the charging control unit to turn on / off the charging current. A switch element for performing OFF control, wherein the switch element is turned on by a signal from the charge control unit.
A charging device, wherein the battery voltage is detected by the charging control unit when the charging becomes FF. 2. A charging device that detects the completion of charging by detecting that the battery voltage has reached a peak and then drops. In a charging device employing a △ V control system, the switch element is turned off by a signal from a charging control unit. The battery voltage is detected by the charging control unit when the battery voltage becomes low.
The charging device as described. 3. A DC power supply for converting a commercial power supply into a direct current to supply a charging current, a charging control unit for detecting a battery voltage to detect completion of charging, and receiving a signal from the charging control unit to turn on / off the charging current. A charging device comprising: a switch element for performing OFF control; and charging a secondary battery by directly using a charging current obtained from the DC power supply. 4. A DC power supply for converting a commercial power supply into a direct current and supplying a charging current, a charging control unit for detecting a battery voltage to detect completion of charging, and receiving a signal from the charging control unit to turn on / off the charging current. A switch element for performing OFF control, the secondary battery is charged by directly using the charging current obtained from the DC power supply, and when the switch element is turned off by a signal from the charge control unit, A charging device, wherein a battery voltage is detected by a charging control unit. 5. A charging device employing a △ V control system for detecting charging completion by detecting that a battery voltage has reached a peak and then decreasing. A DC power supply for converting a commercial power supply to DC and supplying a charging current. When,
A charge control unit that detects a battery voltage and performs charge completion detection,
ON-OF of charging current in response to a signal from the charging control unit
And a switch element for performing F control. The secondary battery is charged by directly using the charging current obtained from the DC power supply, and when the switch element is turned off by a signal from the charge control unit, A charging device, wherein a battery voltage is detected by a charging control unit.