JP2931927B2 - Battery charging method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention sets an incoming standby state in an electronic device having a secondary battery such as a nickel-cadmium battery, for example, a rechargeable portable wireless communication device. Therefore, a self-contained battery discharged in a practical state in which a receiver that is always energized is used as a first load, and a transmitter that is a second load during communication is further supplied with power from the battery by using the temperature change rate is used. The present invention relates to a charging method for fully charging a battery by floating charging with only a battery or a load connected thereto.

[Prior Art] In the conventional example shown in FIG. 5, a battery pack in which the battery 3 can be attached and detached by a connector and a CPU of a wireless device are used.
The load including the receiving unit including the first load R _L1 and the transmitter as the second load R _L2 is connected to the charging stand mainly including the charging device 1 via the first switch K ₁ for power supply. In the case of connecting and charging the charged battery, as shown in FIG. 6 showing the change of the battery voltage E with respect to the charging time H determined by the magnitude of the charging current of the battery, for example, in the case of a nickel-cadmium battery, As the current charging progresses, the terminal voltage of the battery gradually increases, and at the end of charging, the terminal voltage sharply increases, and a mountain-like peak value appears.

To match the variation pattern of a battery voltage with respect to the charging time in the charging characteristics of the battery, only the output voltage of the charging device according to the constant current characteristic as one input, the switch K ₀ t ₁ at Nyuse', t ₂ period opens release is provided a comparator 2 having a sampling hold circuit for accumulating charges in the capacitor C ₁ to the other input, detects a charging voltage, when it reaches the peak value into the falling region of the comparator There is known a charging method in which a constant current function of the charging device is released by a signal whose logic output changes from "H" to "L", and the function is switched to a mere DC power supply function.

The potentials at the input and output sides of the comparator are
As a voltage with respect to the charging time obtained by intermittently changing K ₀ at the sampling period, the voltage changes as shown in the graphs of FIG. 6, and the difference between the characteristic curve of the battery and the difference voltage ΔV between the ± input of the comparator is obtained. The potential is held at the potential at the point when the step pattern of the point falls from the peak value, that is, at the time of falling, and becomes higher than the potential at the point. Therefore, the logical output of the comparator changes from “H” to “H”. “L”
And that the battery has reached full charge.

However, according to the conventional charging method, the first load that always supplies a weak current via a battery and the second load that is supplied for transmission by a charging device under the practical use of such a wireless device are used by the charging device. If floating charged by the constant current through the battery in a discharged state, when the first switch K ₁ for power supply initially during feeding only battery disconnection state against entering the K _1, of the K ₁ While supplying power to the first load and the battery in the connected state,
When the second switch K ₂ is in contact input (In this embodiment, the operating state charged to the transmitter) when matches the peak hold period even people sampling hold circuit, the detection voltage or the point of the comparator , The comparator output, that is, the logical output of the point, is changed from “H” to “L”, and the constant current function of the charging device is released. In other words, the problem that the progress of the charging is stopped halfway even though the battery is being charged and not fully charged is included.

Also, when charging the battery alone by disconnecting the load,
The differential coefficient at the timing of applying the sample and hold along the charging characteristic curve gradually decreases, and the difference between the actual charging characteristic curve and the apparent curve (indicated by a dashed line) becomes smaller, and finally the difference voltage Has the drawback of being undetectable.

"Problems to be Solved by the Invention" It is an object of the present invention to eliminate shortcomings and shortcomings in the conventional charging method, thereby preventing insufficient charging or overcharging of a battery based on such obstacles.

"Means for Solving the Problem" The present invention detects a sudden rise in internal temperature near full charge in the charging characteristics of a battery to be charged, and detects a range of a certain difference voltage from a true charging characteristic curve. A battery that detects the change in charging voltage by repeating sampling at a fixed cycle while maintaining the current, and releases the constant current power supply method of the charging device at the falling point after the peak hold at the end of charging and switches to the normal DC power supply function It is intended to utilize the rate of change of the internal temperature.

Hereinafter, the present invention will be described in detail with reference to FIGS.

[Embodiment] FIG. 1 is a circuit configuration diagram for carrying out the charging system of the present invention, and the same symbols and notations are given to the same corresponding parts in FIG.

FIG. 2 is a graph showing a change in the temperature inside the battery and a change in the charging voltage with respect to the charging time of the battery. FIG. FIG. 4 is a graph showing the change in the terminal voltage of the battery with respect to the charging time in the charging method of the present invention, that is, the charging characteristic.

First, FIG. 1 shows an example of floating charging of a battery and a load. Reference numeral 1 denotes a charging device having a constant current function, which is constituted by, for example, a series transistor control type circuit, and has a constant voltage element and a switch arranged at the output terminal. By simply connecting and disconnecting this switch and short-circuiting both ends of the constant voltage element, the constant current function can be released and a normal DC converter can be obtained. Reference numeral 5 denotes a differential amplifier for detecting the internal temperature of the battery, for example, a terminal voltage of a temperature detecting element 4 such as a thermistor as one input and the other input for providing a reference potential, Vcc being the amplifier, the comparator 2
直流 V is the difference voltage generated by the resistors R7 and R8 between the ± input terminals of the comparator, and the comparator output which makes the constant level of the comparator “H” or “L” logic output ,
Current flowing one input point of the amplifier adding the detection voltage of the temperature detection element, DB is blocking diode, I ₁ is the current flowing into the first load R _L1, I ₂ is the second load R _L2, I _C is the inflow current to the battery 3, and I _D (= I _C + I ₁ + I ₂ ) is the total output current of the charging device, that is, the full load current. K ₁ and K ₂ are the first and second respectively
The battery 3 belongs to a battery pack that can be detachably connected to a charging device and a load at a terminal portion, and the charging device 1, the amplifier, and the comparator belong to a charging stand. It is put together in a lump.

According to the above configuration, the internal temperature of the battery is input from the temperature sensing element to the amplifier, and a voltage based on the resistance value of the temperature sensing element appears at the output point of the amplifier at V ₀ , and is connected to the input intermediate point of the comparator to have the same resistance. A difference voltage ΔV is created by the values R ₇ and R ₈ . This ΔV is determined by resistors R ₇ and R ₈ (= R), resistors R ₆ and
The resistance values of the resistors are arbitrarily selected so that the relationship between R ₉ (=) and the voltage of the common power supply Vcc is as follows: ΔV = / + R × Vcc = constant (1)

Here, the + side input of the comparator is V ₀ + (Vcc−V ₀ ) / + R (2) and the one side input is × V ₀ / + R (3). , (3) is given by equation (1).

When the constant current charging is continued to the first and second loads including the battery discharged from the charging device, the temperature inside the battery is detected every moment and introduced as an amplifier input. input contact with time point t _1, as shown in FIG, t ₂
The period opening of the sampling condition to check the differential coefficient along the charging characteristic curve by intermittent switch K _0, increase in the temperature detecting voltage due to a sudden rise of the battery temperature as shown in FIG. 2 when approaching the fully charged Appears, the potential of one input point of the comparator drops sharply, and becomes higher than the potential of the other input point, which has been peak-held with the charge signal, and the output point of the comparator becomes the H level. From the low level to the low level, the constant current function of the charging device is removed, and the battery eventually reaches full charge.

Even if an attempt is made to recharge immediately after the detection of the above full charge, the temperature of the battery is still rising, the temperature detection voltage does not drop, and the conditions for continuing charging are not satisfied. There is no fear of overcharging in the state of the state, and conversely, since sampling and holding is performed according to the true charging characteristics of the battery, insufficient charging may occur without being confused by the apparent battery voltage. Disappears.

In the present invention, a thermistor is used as a temperature detecting element for detecting the temperature inside the battery, and the amount of charge of the battery due to constant current charging of the battery corresponds to the change in the internal temperature, and eventually the terminal voltage of the battery is accurately adjusted. It has contributed enough to capture.

Further, the present invention can be applied not only to the charging of the battery alone but also to the floating charging with a load connected thereto to obtain good results.

[Effect] According to the charging method of the present invention, while detecting the internal temperature of the battery that changes with the progress of the charging of the battery, the differential coefficient for sampling and holding along the true charging characteristic curve of the battery is instantaneously calculated. Since the check is performed, the battery alone or the electronic device serving as a load is integrated with the battery and charged with a constant current, so that the charge is managed depending on the internal temperature of the battery regardless of the load fluctuation. The battery can be fully charged without excess or shortage, without suddenly running out of battery, the expected life of the battery can be kept sufficiently long, etc.
A practically simple and reliable high-reliability charging method can be achieved.

[Brief description of the drawings]

Circuit diagram for implementing the charging method of the first figure invention, the graph FIG. 2 which represents a change in the internal temperature T _C and the charging voltage E of the battery with respect to charging time H, Figure 3 is ambient temperature T _A
FIG. 4 is a graph showing a characteristic pattern sampled at a difference voltage ΔV along a battery voltage characteristic curve with respect to a charging time, and FIG. FIG. 6 is a circuit configuration diagram for implementing the charging method, and FIG. 6 is an explanatory graph of the battery charging method according to the configuration of FIG. 1: charging device, 2: comparator, 3: cell, 4: thermometric element, 5: amplifier, K _1: a first switch, K _2: second switch, R _L1: first
Load, R _L2 : second load.

Claims (1)

(57) [Claims] In a charging system for a secondary battery, wherein a charging device is controlled in accordance with a change in temperature inside the battery, a power supply for connecting and disconnecting the charging device between both terminals of the battery to be charged. A first load, which is always maintained in an energized state by connecting and disconnecting the first switch, and a second load, which is connected in series to the second switch, are provided in parallel with each other. A constant-current power is supplied to the battery and the first and second loads, a temperature detection voltage for detecting an internal temperature accompanying the progress of charging of the battery and a reference potential are input to amplifying means, and a DC power supply is divided. The voltage and the voltage obtained by intermittently detecting the change in the charging voltage accompanying the progress of the charging of the battery are input to the comparator and the momentary peak value is held.
The amplifying means and the comparator are connected in cascade, and the difference voltage at the input of the comparator is output in reverse at the time of reverse rotation, thereby releasing the constant current function of the charging device and switching to the normal DC power supply. A battery charging method characterized by using a battery.