JPH08195224A - Battery charge completion determination method - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a method for determining the completion of charging of a battery, which determines completion of charging based on the decay rate of the output current of the battery charger. In a method of determining the completion of charging of a battery in a battery charger having a determination unit that monitors the charging current of the battery and determines whether charging is completed, in the determination unit, the charging current of the battery, which is the output current of the battery charger, The sum of load currents is measured at an appropriate cycle, the required number of measured values are always stored in sequence, and the measured values when the load changes are excluded from them to obtain the output current attenuation rate (= charging current attenuation rate). When the attenuation rate is below the set value, it is determined that charging is complete and charging is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery charge completion determination method which can reliably determine battery charge completion without being affected by load fluctuations.

[0002]

2. Description of the Related Art Recently, a rechargeable low-voltage battery such as a lithium-ion battery has been widely used as a power source for a mobile phone or the like. Usually, a battery charger for charging the battery is prepared, and the mobile phone is charged by being inserted into the battery charger while the battery is loaded. Further, the mobile phone normally exchanges information with the base station through the control channel even during charging, and is normally in a standby state where a call can be made at any time when an incoming call is received.

FIG. 5 is a diagram showing an example of charging characteristics of a lithium-ion battery. As shown in the figure, the charging current shows a characteristic of decaying with time, the battery charger constantly monitors the charging current, and when the charging current becomes a constant current value i ₀ or less, it is determined that charging is completed (full charge). It is common to stop charging.

[0004]

However, as described above, when the portable telephone is in the standby state during charging, the battery charger not only supplies the charging current of the battery to the receiving portion and the base portion of the portable telephone. In addition, the current and the load current such as the current to the transmitter are superposed and supplied at the time of transmission. Moreover,
The load usually fluctuates during charging. In the conventional charging completion determination method, the output current of the battery charger is regarded as the charging current, and it is determined that the charging is completed (full charge) when the current becomes equal to or less than the constant current value i ₀ (set value). , In some cases, it was not possible to accurately determine the completion of charging.

In addition to this, there is also a method of extracting only the charging current of the battery and judging whether or not the charging is completed in order to make a more accurate judgment. However, this method increases the number of parts, and further, the battery charger and the portable device. There has been a problem that the connection part of the telephone becomes complicated and the cost increases.

The present invention has been made in view of the above-mentioned problems, and in order to eliminate the above-mentioned problems, it is determined whether or not the charging is completed by the decay rate of the output current of the battery charger, so that the influence of the load fluctuation is exerted. It is an object of the present invention to provide a battery charge completion determination method capable of reliably determining battery charge completion.

[0007]

In order to solve the above-mentioned problems, the present invention provides a method for judging the completion of charging of a battery in a battery charger having a judgment section for monitoring the charging current of the battery and judging the completion of charging. As shown in Fig. 5, the judgment unit measures the sum of the battery charging current, which is the output current of the battery charger, and the load current at an appropriate cycle, and always stores the required number of measured values in sequence. It is characterized in that the decay rate of the output current is obtained by excluding the measured value at the time, and when the decay rate becomes equal to or less than the set value, the charging is judged to be completed and the charging is stopped.

[0008]

The charging completion judging method of the present invention measures the sum of the charging current of the battery 21, which is the output current of the battery charger 1, and the load current as shown in the block configuration of FIG. Output current decay rate (= charging current decay rate, see Fig. 4 for details)
When the battery 21 is used in a mobile phone or the like, it is possible to accurately determine the charging completion even when the load changes in the standby state. Since the measurement and the charge completion determination process can be performed by software, the number of parts does not increase, and the connection portion between the battery charger 1 and the mobile phone 2 can be simplified by using two terminals.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 3 is a block diagram showing the configuration of a battery charger using the battery charging completion determining method of the present invention. As shown in the figure, the battery charger 1 includes a power supply unit 11, a charge control unit 12, a resistor 13, and a thermistor 14.

The power source unit 11 converts a AC power source (AC100V) into a direct current and controls a voltage and a current, and a charging circuit 111.
The output switch 112 turns on / off the output current. The charge controller 12 includes a current detector 122, a voltage detector 123, and a current value detected by the current detector 122.
The determination unit 121 is configured to read the voltage value detected by the voltage detector 123 and output a control signal. Determination unit 121
Although not shown in the figure, it has a memory and a CPU for storing data, programs, etc., and performs a determination process. The resistor 13 is a low resistance resistor for detecting a current.

The mobile phone 2 includes a battery 21 and a switch 2.
2, a base unit (including a receiving unit) 23, a switch 24, and a transmitting unit 25. The battery charger 1 charges the battery 21 via the charging terminal 3. The switch 22 is a power switch of the mobile phone 2 and is normally turned on during charging and is in a standby state. Since the transmitter 25 consumes a large amount of current, the switch 24 is manually or automatically turned on only during transmission to save power consumption.

The output current supplied by the battery charger 1 has three states. That is, the switch 22 is turned off to supply only the charging current i ₃ of the battery 21, the switch 22 is turned on and the switch 24 is turned off, and the charging current i ₃ and the base portion (including the receiving portion) are supplied. There are _three states: a state B in which the sum of the currents i ₁ is supplied, and a state C in which the switch 24 is also turned on and the sum of the charging current i ₃ , the base part current i ₁ and the transmitter part current i ₂ is supplied. is there.

FIG. 4 is a diagram showing changes in the output current when the loads are different. In the state A, the charging control unit 12 sets the voltage V _A so that the charging current i ₃ maintains a constant current i _B in the initial stage of charging.
As shown in, the charging voltage V is increased (constant current period).
After reaching ₀ (rated voltage), the voltage is controlled to be constant (constant voltage period). During that time, the charging current i ₃ exhibits an attenuation characteristic as shown in FIG.

In the constant current period of state B, the output current, that is,
Since the sum of the charging current of the battery 21 and the base portion current i ₁ is controlled to be constant and the charging current of the battery 21 is reduced to i _B −i ₁ , the progress of charging is delayed and the charging current showing the attenuation characteristic is also i.
_It becomes _3'and charging is delayed. Similarly, in state C, there is a further delay.

Assuming that charging is completed at time t ₁ in state A and the completion current (output current at completion of charging) is i ₀ (for example, 50 mA), in state B, base portion current i ₁ (for example, 60 m) is obtained.
A) is superimposed and charging is completed at time t ₂ , and the completion current is i ₀ + i
_In the state C, i ₂ (eg, 340 mA) is further superimposed in the state C to complete charging at time t ₃ and the completion current is i ₀ + i ₁ + i ₂ , but the decay rate (slope) of the completion current in each state is constant. Is. The method of the present invention detects the decay rate of the output current and determines that the charging is completed when the output current is below the set value.

FIG. 2 is a diagram showing an example of the attenuation characteristic of the output current. As shown in the figure, the charging control unit 12 measures the output current at an appropriate measurement cycle and stores the measured values in order in time series. After the output current decays below the current i _B during the constant current period minus the decay current Δi _S (setting value) at the completion current,
The charge control unit 12 uses the switch 22 based on the stored measured values.
Or attenuation rate (gradient) of output current under the same condition (state) except the measured value when load changes due to ON / OFF of switch 24
Is obtained and it is determined that the charging is completed when the value is equal to or less than the set value. The process will be described below.

FIG. 1 is a flowchart for carrying out the battery charge completion determination processing of the present invention. A program for executing this flow chart is stored in the memory (not shown) of the determination unit 121 and executed by the CPU. It will be described with reference to FIG. Attenuation current Δ at the completion current to determine the completion of charging
The setting value of i _S (for example, current change for 5 minutes) is set as an initial setting. At the measurement time (for example, one minute cycle) in the determination unit 121 (step ST11), the current output current is measured (step ST12) and sequentially stored, and the temperature is measured by the thermistor 14 for temperature correction (step S12). ST13). Note that the temperature measurement may be performed by using a temperature detecting means (not shown) such as a thermistor of the mobile phone 2 in FIG. 3 and separately providing data input / output terminals on both the battery charger 1 and the mobile phone 2. Good.

If the output current falls below the current i _B -Δi _S during the constant current period and the change in the output current becomes smaller than the change due to the load change due to the ON / OFF of the switch 22 or the switch 24 (step ST14). , The set value Δi _S based on the temperature measured in step ST13
The temperature is corrected by the correction value set in advance, and Δi _S is corrected when the temperature is high and decreased when the temperature is low (step ST15).

If the difference Δi between the output current before the determination period Δt (for example, 5 minutes) and the current output current becomes smaller than the set value Δi _S (corrected value) (step ST16), it is determined that the charging is completed and the output switch 112 is determined. An off signal is output (step ST18), and charging is completed. If it is larger than the set value Δi _S , the measurement data is updated (step ST17) and the process is repeated from step ST11.

In step ST14, the change in the load current due to ON / OFF of the switch 22 or the switch 24 is known in advance, so that it can be distinguished from the change in the current due to the attenuation characteristic of the charging current and the influence due to the load change can be eliminated.

As described above, the method of determining the completion of charging according to the present invention uses the battery 21 which is the output current of the battery charger 1.
The sum of the charging current and the load current of is measured at an appropriate cycle, and the decay rate of the output current (=
Since the completion rate of charging of the battery 21 is determined by determining the charge current decay rate), the completion of charging can be accurately determined when used in a mobile phone or the like even when the load changes in the standby state.

[0022]

As described in detail above, according to the present invention, the following excellent effects are expected. (1) The charge completion determination method of the present invention measures the sum of the battery charge current, which is the output current of the battery charger, and the load current at an appropriate cycle, and determines the output current from the measured value excluding the fluctuation of the load current. Since the decay rate (= the decay rate of the charging current) is obtained and the completion of charging the battery is determined, if used in a mobile phone or the like, the completion of charging can be accurately determined even when the load changes in the standby state.

(2) Since the output current measurement and the charge completion determination process can be performed by software, the number of parts does not increase, and the connecting portion between the battery charger and the mobile phone has only two terminals, which is the simplest and cheapest.

[Brief description of drawings]

FIG. 1 is a flowchart for performing a battery charging completion determination process of the present invention.

FIG. 2 is a diagram showing an example of attenuation characteristics of an output current of a battery charger.

FIG. 3 is a block diagram showing a configuration of a battery charger using the battery charging completion determination method of the present invention.

FIG. 4 is a diagram showing changes in output current when loads are different.

FIG. 5 is a diagram showing an example of charging characteristics of a lithium-ion battery.

[Explanation of symbols]

 1 Battery Charger 11 Power Supply Unit 111 Charging Circuit 112 Output Switch 12 Charging Control Unit 121 Judgment Unit 122 Current Detector 123 Voltage Detector 13 Resistor 14 Thermistor 2 Mobile Phone 21 Battery 22 Switch 23 Receiver 23 and Receiver 24 Switch 25 Transmitter 3 Charging terminal

Claims (1)

[Claims] 1. A method of determining the completion of charging of a battery in a battery charger having a determination unit that determines the completion of charging by monitoring the charging current of the battery, wherein the determination unit charges the battery that is the output current of the battery charger. The sum of the current and load current is measured at an appropriate cycle, and the required number of measured values are always stored in sequence, and the measured value when the load changes are excluded from them to obtain the output current attenuation rate, and the attenuation rate is below the set value. When it becomes, it is judged that the charging is completed and the charging is stopped.