JPH07123605A - Charged quantity detecting method for rechargeable cell - Google Patents

Abstract

PURPOSE:To make it possible to raise a charged capacity approximately up to 100% by detecting a charged quantity, by comparing the terminal voltage of a rechargeable cell in a power-supplied state from a charging power source with that at the time of no power supply. CONSTITUTION:When the charging of a rechargeable cell 6 is started, an H-level signal is outputted to a control signal outputting terminal 12 during the charge operation, but an L-level signal is outputted every specified time, and during that time an electronic switch 9 is in the off-state. And a terminal voltage of the rechargeable cell 6 at on-time is converted into a digital signal by an A/D converter 11, and is inputted to a charge control circuit 8. Along with it, a terminal voltage at off-time is inputted to the charge control circuit 8 to compare the terminal voltages. Incidentally, the detection and comparison of the terminal voltages is performed every specified time repeatedly. And if the difference of the terminal voltages becomes a specified value, the control operation of a charge current supply circuit 7 is performed, and the supply of the charging current is stopped. Consequently, it becomes possible to raise the charged capacity of the chargeable cell approximately up to 100%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the charge amount of a rechargeable battery.

[0002]

2. Description of the Related Art Audio equipment such as disk players and tape recorders, which are used by being carried around, is in widespread use. However, since such audio equipment is used outdoors, a battery is used as a power source. In recent years, the number of devices using rechargeable batteries such as NiCd batteries as such batteries is increasing.

The relationship between the charging current and the charging time of a rechargeable battery is such that a large current flows at the start of charging and the charging current decreases as the charging operation is performed and the charging amount increases. A charging circuit configured to control the charging operation of a rechargeable battery by detecting such a change in charging current is generally used, and such a technique is disclosed in, for example, Japanese Utility Model Laid-Open No. 64-16143. There was something that was done.

[0004]

The detection operation of the charging current in the technique described in the above publication is performed by detecting the potential difference between both ends of the detection resistor inserted in the charging current supply path. Be seen.

Since the charging method when the rechargeable battery is a nickel-cadmium battery is carried out at a constant current, the resistance value of the detection resistor can be set in accordance with this current value, but lithium is being used recently. The rechargeable battery called an ion battery has the following problems.

That is, the charging characteristics of the lithium ion battery are
As shown in FIG. 2, the value of the charging current changes greatly. Therefore, if the resistance value of the detection resistor inserted in the charging current supply path for detecting the charging current is set in accordance with the point where the current is large, it cannot be detected at the point where the current is small. On the contrary, if the resistance value is set according to the point where the current is small, there is a problem that the voltage loss increases.

There is also a charging circuit configured to detect the amount of charge by detecting the battery voltage, but the lithium ion battery is a battery which is being charged, as is apparent from the charging characteristic diagram shown in FIG. Since the voltage does not change, it is not possible to detect the charge amount by detecting the battery voltage.

The present invention intends to provide a method for detecting the amount of charge that has improved such points.

[0009]

The present invention charges the rechargeable battery by comparing the terminal voltage of the rechargeable battery in the state where the charging current is supplied with the terminal voltage of the rechargeable battery when the supply of the charging current is cut off. It is designed to detect the quantity.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The circuit shown in FIG. 1 is an embodiment of a charging circuit according to the charge amount detecting method of the present invention. In the figure, 1
Is a power supply terminal connected to a commercial AC power supply, 2 is a power supply transformer for stepping down the AC voltage to a predetermined voltage, 3 is a diode bridge circuit for rectifying the AC stepped down by the power supply transformer 2 into direct current, 4 is the diode bridge A smoothing capacitor for smoothing the signal rectified by the circuit 3, and a direct current power supply circuit 5 together with the diode bridge circuit 3.
Are configured.

6 is a rechargeable battery such as a lithium ion battery,
A charging current supply circuit 7 is supplied with DC power from the DC power supply circuit 5 , and has a function of supplying a charging current to the rechargeable battery 6 based on the control operation of the charging control circuit 8.

Reference numeral 9 denotes an electronic switch that is inserted and connected in the charging current supply path between the charging current supply circuit 7 and the rechargeable battery 6, and an H (high) level signal is applied to the control terminal 10. It is configured to be in the closed state when in the closed state.

Reference numeral 11 denotes an A / D converter which is connected to detect the terminal voltage of the rechargeable battery 6 and converts the detected DC voltage into a digital signal, which digital signal is input to the charge control circuit 8. It is configured to be.

In such a circuit configuration, the control terminal 10 of the electronic switch 9 is connected to the control signal output terminal 12 provided in the charging control circuit 8. Also,
The control signal output terminal 12 provided in the charge control circuit 8 is configured to alternately output an H level signal and an L (low) level signal at predetermined time intervals. Then, the charging control circuit 8 uses the electronic switch 9
Is switched from the closed state to the open state, the change in the terminal voltage of the rechargeable battery 6 is detected from the digital signal output from the A / D converter 11. In this way, a change in the terminal voltage of the rechargeable battery 6 is detected, and when the changed voltage becomes smaller than a predetermined value, the charging current supply circuit 7 supplies the charging current to the rechargeable battery 6 by the control operation of the charging control circuit 8. It is configured to stop the operation.

The charging circuit according to the present invention is constructed as described above. Next, the operation of such a circuit will be described.
The commercial AC power input from the power supply terminal 1 is stepped down by the power supply transformer 2 and supplied to the DC power supply circuit 5 to be rectified and smoothed. When a DC voltage is output from the DC power supply circuit 5 , the charging control circuit 8 controls the charging current supply circuit 7 and the electronic switch 9, and the charging current supply circuit 7 passes the electronic switch 9 to the rechargeable battery 6. Charging current is supplied.

As a result of the charging current being supplied to the rechargeable battery 6 in this way, the charging operation of the rechargeable battery 6 is started, but the charging current supply circuit accompanying the control operation of the charging control circuit 8 is started. The charging operation by 7 is performed based on the characteristics shown in FIG.

When such charging operation is being performed,
Although an H level signal is output to the control signal output terminal 12, an L level signal is output at every predetermined time. When an L level signal is output to the control signal output terminal 12, the electronic switch 9 is opened while the L level signal is being output.

The terminal voltage of the rechargeable battery 6 when the electronic switch 9 is in the closed state is converted into a digital signal by the A / D converter 11 and input to the charging control circuit 8 and the electronic switch 9 is turned on. The terminal voltage of the rechargeable battery 6 in the open state is converted into a digital signal by the A / D converter 11, and the charging control circuit 8
Entered in.

When a digital signal based on the terminal voltage of the rechargeable battery 6 in such a different state is input to the charging control circuit 8, the charging control circuit 8 performs a terminal voltage comparison operation.

The terminal voltage when the electronic switch 9 is closed, that is, when the charging current supply circuit 7 supplies the charging current to the rechargeable battery 6, changes as shown by the solid line in FIG. On the other hand, the terminal voltage detected each time the electronic switch 9 is opened changes as shown by the broken line in FIG.

Comparing the battery voltage shown by the solid line and the battery voltage shown by the broken line in FIG. 2, the voltage difference becomes smaller as the charging operation of the rechargeable battery 6 is performed. Then, the above-described detection / comparison operation of the terminal voltage of the rechargeable battery 6 is repeatedly performed every predetermined time. Although the charging operation of the rechargeable battery 6 is performed while performing the detection / comparison operation, when the difference between the terminal voltages reaches a predetermined value, the charge control circuit 8 sets the capacity charged in the rechargeable battery 6 to a predetermined value. When it is determined that the charging current has been reached, the charging current supply circuit 7 is controlled to stop the charging current supply operation to the rechargeable battery 6.

Thus, by comparing the terminal voltage when the charging current is being supplied to the rechargeable battery 6 and the terminal voltage when the supply of the charging current is cut off, the charge amount of the rechargeable battery 6 is determined. Since the detection is performed, the charge capacity of the rechargeable battery 6 can be made close to 100%.

In this embodiment, the detection / comparison operation of the terminal voltage of the rechargeable battery 6 is performed every predetermined time when the charging operation is started. However, the detection / comparison operation is performed when the charging operation is performed for a predetermined time. Can be set to start. That is, the operation of detecting the charge amount of the rechargeable battery 6 is an operation performed to detect the time to end the charging operation, and is an operation that is unnecessary for a predetermined time after the start of charging. According to this method, since the wasteful detection and comparison operation is not performed, the charging operation of the rechargeable battery 6 can be efficiently performed.

The case where the detection / comparison operation of the terminal voltage of the rechargeable battery 6 is performed when the charging operation is performed for a predetermined time has been described, but it is performed when the value of the charging current decreases to a predetermined value. You can also do it. That is, as is clear from the characteristic diagram of the charging current shown in FIG. 2, the charging current continues to be a large current for a predetermined time at the start of the charging operation, but thereafter changes to a small current value. If such a detection / comparison operation of the terminal voltage is performed when such a decrease in the charging current is detected, an unnecessary detection / comparison operation is not performed, so that the charging operation of the rechargeable battery 6 is efficiently performed. be able to.

[0025]

According to the present invention, the rechargeable battery is compared by comparing the terminal voltage of the rechargeable battery in the state where the charging current is supplied with the terminal voltage of the rechargeable battery when the supply of the charging current is cut off. Since the charging amount of the rechargeable battery is detected, the charge control operation of the rechargeable battery can be easily performed and the charge capacity of the rechargeable battery can be close to 100%.

Further, since the detection / comparison operation of the terminal voltage of the rechargeable battery is performed when the charging operation is performed for a predetermined time or when the charging current is reduced to a predetermined value, the charging operation of the rechargeable battery is efficiently performed. You can do it well.

[Brief description of drawings]

FIG. 1 is an example of a charging circuit according to a charge amount detection method of the present invention.

FIG. 2 is a charging characteristic diagram of a rechargeable battery.

[Explanation of symbols]

 6 Rechargeable battery 7 Charging current supply circuit 8 Charging control circuit 9 Electronic switch 11 A / D converter

Claims (3)

[Claims] 1. Comparing the terminal voltage of the rechargeable battery when the charging current is being supplied from the charging current supply circuit with the terminal voltage of the rechargeable battery when the supply of the charging current is cut off. The method for detecting the charge amount of a rechargeable battery is characterized in that the charge amount of the rechargeable battery is detected by. 2. The charge amount detecting method according to claim 1, wherein the charge amount detecting operation is performed by a comparison operation of terminal voltages of the rechargeable battery when the charge operation is performed for a predetermined time. 3. The charge amount detecting method according to claim 1, wherein the charge amount detecting operation is performed by a comparison operation of terminal voltages of the rechargeable battery when the charge current drops to a predetermined value.