JPH0888027A - Storage battery charging circuit and storage battery charger using this charging circuit - Google Patents

Abstract

PURPOSE: To suppress the influence of charging current variation by detecting current and voltage of a storage battery every specified time, finding internal resistance value from the variation of detected values, and making full charging when the internal resistance value obtained exceeds a threshold. CONSTITUTION: Current from a solar cell 4 to a storage battery 10 is detected with a current detecting part 20, voltage is detected with a voltage detecting part 20, and ambient temperature of the battery 10 is detected with a temperature detecting part 24, and detected data are sent to an operating part 26 every constant periods. The variation ratios of current and voltage every constant periods are found, and internal resistance value of the battery 10 is calculated from the variation ratios. Temperature correction is conducted with the output of the temperature detecting part 24, and internal resistance value R is obtained. This value and a reference value stored in a memory part 28 are compared with a comparator 30. When the resistance value R is larger than a threshold value, the battery 10 is considered as fully charged, a signal is outputted to a controller 32, a charging circuit is shut off with a switch 14, and a display 16 displays full charging. Thereby, full charging is accurately detected and overcharging is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a storage battery charging circuit and a storage battery charger using the same.

[0002]

2. Description of the Related Art Conventionally, there are various charging methods for charging a storage battery, such as constant current charging, constant voltage charging, pulse charging and -ΔV charging.

In particular, for those intended for nickel-cadmium storage batteries, the -ΔV charging system which enables quick charging in a short time is widely adopted.

A conventional storage battery charging circuit using such a −ΔV charging system will be described with reference to FIGS. 11 and 12.

This storage battery charging circuit comprises a constant current power supply a as a charging power supply, a switching circuit s, and a -ΔV detection circuit d. The −ΔV detection circuit d compares the peak value storage circuit p that stores the peak value of the charging voltage of the storage battery e with the peak value stored in the peak value storage circuit p and the charging voltage of the storage battery e. Comparison circuit c
Consists of

In this configuration, when the storage battery e is charged, when the storage battery e has not yet reached the fully charged state, the output state from the comparison circuit c turns on the switching circuit s.

As a result, the constant current power supply a is connected to the storage battery e, and the storage battery e is charged with a constant charging current supplied from the constant current power supply a via the switching circuit s.

Due to the characteristics of the storage battery e, as shown in FIG. 12, when the charging voltage reaches the end of charging, the charging voltage decreases from the previous rising tendency as the battery temperature rises due to the heat of oxidation reaction. Turn to a tendency.

Therefore, by utilizing this characteristic, the peak value when the charging voltage of the storage battery e reaches the peak value is stored in the memory circuit p, and in the comparison circuit c, the peak value and the peak value are stored. After that, by comparing with the charging voltage of the storage battery e, a minute amount change-ΔV of the voltage when the charging voltage drops from the peak value is detected, and when this minute amount change-ΔV is detected, the When the storage battery e has reached the end of charging, that is, when it has reached full charge, the switching circuit s is operated so as to disconnect the storage battery e from the constant current power supply a (see FIG. 1).
2 at time t ₀ ).

As a result, even after the storage battery e is fully charged, it is prevented from being overcharged by being charged with the charging current as it is.

[0011]

As described above, in the conventional storage battery charging circuit shown in FIG. 11, it is detected whether or not there is a slight drop -ΔV in the charging voltage of the storage battery e at the end of charging, and the charging current is changed. Although controlled, this circuit has the following problems.

(1) In the storage battery charging circuit shown in FIG. 11, the constant current power supply a is used to perform the constant current charging in order to detect the minute drop -ΔV of the charging voltage. Since a itself has a complicated circuit configuration and is expensive, it is not suitable for use in charging a storage battery at a simple and low price.

Moreover, in a power source such as a solar cell or a lead storage battery, its output current fluctuates, but in such a power source, the charging voltage also fluctuates according to the fluctuation of the output current.
The minute drop -ΔV in the charging voltage cannot be detected accurately, which makes it difficult to apply these power supplies.

In particular, a solar cell is extremely economical as a charging power source used for charging a storage battery because it can be used repeatedly as many times as there is sunlight.
Although there is an extremely high demand for charging a storage battery using a solar cell, the conventional charging circuit cannot sufficiently meet such a demand.

(2) Further, as a characteristic of the storage battery e, when the charging current supplied from the charging power source a to the storage battery e is small, the charging voltage has a peak value even when the storage battery e is at the end of its charging. A phenomenon occurs in which it hardly descends even after being shown. Similarly, even when the ambient temperature of the storage battery e is high, a phenomenon occurs in which even when the storage battery e reaches the end of charging, the charging voltage hardly drops even after it shows a peak value.

When such a phenomenon occurs, as shown in FIG.
In the conventional charging circuit shown in FIG. 3, the -ΔV detection circuit d is set even though the storage battery e is actually fully charged.
Therefore, the minute drop -ΔV of the charging voltage cannot be accurately detected.

Therefore, the switching circuit s cannot be turned off, or even if the minute drop −ΔV can be detected, the detection timing is delayed, resulting in a storage battery.
e is overcharged, which causes a problem such as shortening the life of the storage battery e.

According to the present invention, the full charge of the storage battery is always accurately detected and the overcharge is reliably prevented without being affected by the fluctuation of the output current of the charging power source, and the deterioration of the storage battery can be avoided. An object of the present invention is to provide a storage battery charging circuit to which an extremely economical power source for charging such as a solar battery can be applied, and a storage battery charger using the storage battery charging circuit.

[0019]

The present invention adopts the following constitution in order to solve the above problems.

That is, the storage battery charging circuit according to the first aspect of the present invention detects the time rate of change of each of the charging current supplied to the storage battery from the charging power source and the charging voltage of the storage battery, and detects the rate of change of the storage battery from both of them. The internal resistance value is obtained, and the charging operation of the storage battery is stopped when the internal resistance value becomes larger than a preset threshold value.

According to the second aspect of the present invention, there is provided a storage battery charging circuit, wherein switch means for setting a charging path between the charging power source and the storage battery to a connected state or a disconnected state in response to a control signal, and the charging path. Detecting means for respectively detecting the charging current and the charging voltage of the storage battery supplied from the charging power source to the storage battery, and based on the charging current and the charging voltage supplied from the detecting means, obtain respective time change rates. Calculating means for calculating an internal resistance value of the storage battery, and an internal resistance value calculated by the calculating means, and a predetermined threshold value set in advance corresponding to the internal resistance value when the storage battery is fully charged. And comparing means for outputting a predetermined comparison output when the calculated internal resistance value becomes larger than the threshold value, and the switch hand in response to the comparison output from the comparison means. And a control means for stopping the charging operation by applying a control signal to the charging path to the blocking state.

According to a third aspect of the present invention, in the storage battery charging circuit according to the second aspect, there is provided temperature detecting means for detecting an ambient temperature of the storage battery, and the arithmetic means is
It is characterized in that the calculation of the internal resistance value is corrected by the detection output from the temperature detecting means, and the corrected internal resistance value is given to the comparing means.

According to a fourth aspect of the present invention, there is provided a storage battery charging circuit according to the second or third aspect, further comprising timer means for outputting a timer output to the control means at predetermined intervals, Means for forcibly stopping the charging operation of the storage battery by giving a control signal to the switch means in response to a timer output from the timer means to cause the charging path to be in an interrupted state. .

A storage battery charging circuit according to a fifth aspect of the present invention is characterized in that, in the structure according to any one of the first to fourth aspects, the charging power source is a solar cell.

A storage battery charging circuit according to a sixth aspect of the present invention is characterized in that, in the configuration according to any one of the first to fifth aspects, the storage battery is for a mobile phone.

A storage battery charger according to a seventh aspect of the present invention has the storage battery charging circuit according to any one of the first to fifth aspects housed therein, and a solar cell is charged by the storage battery charging circuit. The storage battery is connected as a power source for charging the storage battery, and the storage battery housed inside is connected to the charging circuit in a predetermined state through the insertion port. Have a structure.

[0027]

In the invention according to claim 1 and claim 2,
Each of the charging current and the charging voltage to the storage battery is detected at regular intervals, and the internal resistance value is obtained from the time change rate,
When the internal resistance value exceeds the threshold value, it is determined that the battery is fully charged. Therefore, even if the charging current supplied from the charging power source to the storage battery fluctuates, it is not affected by the fluctuation. Moreover, even if the amount of change in the charging voltage at the end of charging is small, the internal resistance value appears as a large change due to the relationship with the charging current, so full charge can be accurately detected. Therefore, overcharging can be reliably prevented.

In the invention according to claim 3, since the ambient temperature of the storage battery is detected by the temperature detecting means and the internal resistance value obtained by the calculating means is corrected by this detection output, the ambient temperature of the storage battery is not affected. It is possible to detect the full charge without fail.

Further, in the invention according to claim 4, during the charging of the storage battery, the charging circuit is temporarily forcibly shut off by the output of the timer means, and the open circuit voltage when the storage battery is in the non-charged state, Since the internal resistance value is obtained based on the amount of change from the charging voltage of the storage battery when the charging current is flowing before the interruption, it is possible to detect the presence or absence of full charge according to the actual charging capacity of the storage battery.

In the invention according to claim 5, since the solar cell is applied as the charging power source, it is extremely economical and lightweight.

In the invention according to claim 6, since the storage battery is used for the mobile phone, even if the storage battery of the mobile phone is abruptly consumed, it can be immediately charged and reused, which is convenient.

According to the seventh aspect of the invention, when the storage battery is exhausted, the storage battery charger can be taken out to charge the battery as needed.

[0033]

1 and 2 are perspective views showing a schematic structure of a storage battery charger.

The storage battery charger 1 comprises a charger main body 2, to which a solar cell 4 is connected as a charging power source. The solar cell 4 may be provided so as to be foldable because it is convenient to carry.

A storage battery charging circuit 8 to be described later is accommodated in the case 6 of the charger main body 2, and an insertion port 12 for the storage battery 10 is provided on the front surface of the charger main body 2. The storage battery 10 mounted inside the case 6 through the opening 12 is connected to the storage battery charging circuit 8 in a predetermined state.

In this embodiment, the storage battery used in the storage battery charger 1 is a sealed nickel-cadmium battery, but other storage batteries may be used.

In particular, in the case where the storage battery 10 is used for a mobile phone such as a PHS (Personal Handy Phone System), when the storage battery 10 is abruptly consumed, the storage battery charger 1 can be installed outdoors if necessary. It is convenient because it can be easily charged by taking it out to expose the solar cell 4.

Reference numeral 14 is a switch portion including a relay switch for connecting / disconnecting the charging path in the storage battery charging circuit 8, and 16 is an LED provided on the top of the case 6 and turned on when fully charged. It is a display unit including light emitting elements such as.

FIG. 3 is a block diagram showing the storage battery charging circuit 8 described above, FIG. 4 is a block diagram showing the details of the inside of the controller in the circuit 8, and FIG. 5 is a block diagram of the circuit 8.

The storage battery charging circuit 8 of this embodiment is provided between the solar battery 4 as a charging power source and the storage battery 10, and includes a switch unit 14, a display unit 16, a backflow prevention diode 18, and a charging current detection unit. 20, controller 22,
And a temperature detector 24.

The switch section 14 electrically connects or disconnects the charging path between the solar cell 4 and the storage battery 10 in response to the input of a control signal, which will be described later. In the above, a relay switch is used, but other switching means such as a switching transistor can be applied.

The charging current detection unit 20 detects the charging current supplied from the solar cell 4 to the storage battery 10 through the charging path. In this example, a shunt resistor is used, but in addition, the charging current is changed to the charging path. It is also possible to have a configuration in which a container is provided.

The charging voltage detector 21 detects the charging voltage of the storage battery 10.

The temperature detector 24 detects the ambient temperature of the storage battery 10 being charged, and is composed of a temperature sensitive element such as a thermistor.

On the other hand, the controller 22 detects the time rate of change of each of the charging current and the charging voltage applied from the solar cell 4 to the storage battery 10, determines the internal resistance value of the storage battery 10 from both, and the internal resistance value is When the threshold voltage becomes larger than a preset threshold value, the switch unit 20 is shut off to stop the charging operation of the storage battery 10. In this example, the calculation unit 26 and the storage unit 28 are used. , A comparison unit 30, and a control unit 32. Each of these units 26, 28, 30 and 32 can also be configured by one CPU.

The calculation unit 26 is provided with the above-mentioned detection units 20 and 21.
The detection outputs of the charging current and the charging voltage detected respectively at are taken in, and the time change rates ΔI / Δt and ΔV / Δt of each charging current and charging voltage are calculated for each constant period Δt, and the charging current and charging voltage The internal resistance value R ′ (= ΔV / ΔI) of the storage battery 10 is calculated based on the time change rates ΔI / Δt and ΔV / Δt, and the calculated value R ′ is corrected by the temperature detection output from the temperature detection unit 24. The calculated internal resistance value R is output.

The storage unit 28 is composed of a memory or the like, and stores in advance an internal resistance value corresponding to the full charge of the storage battery 10 as a threshold value Rsh.

The comparison unit 30 compares the internal resistance value R calculated by the calculation unit 28 with a threshold value Rsh stored in advance in the storage unit 28, and the internal resistance value R is larger than the threshold value Rsh. When it becomes (R> Rsh), it is determined that the storage battery 10 is fully charged, and a signal indicating that it is fully charged is output.

When the signal output from the comparison unit 30 indicates that the charging unit is fully charged, the control unit 32 controls the switch unit 14 to disconnect the charging path in response to the signal output. In addition to giving a signal, a lighting signal for indicating a fully charged state is output to the display unit 16.

Next, the charging operation of the storage battery 10 using the storage battery charging circuit 8 having the above configuration will be described with reference to the flowchart shown in FIG.

When the storage battery 10 has not reached the fully charged state, the controller 32 of the controller 22
A control signal for connecting the charging path to the switch unit 14 is output. Therefore, since the solar cell 4 is connected to the storage battery 10 via the storage battery charging circuit 8, the storage battery 10 is gradually charged by the charging current supplied from the solar cell 4.

The charging current supplied from the solar cell 4 to the storage battery 10 is detected by the charging current detection unit 20, and the charging voltage of the storage battery 10 is detected by the charging voltage detection unit 21, and the detection output is calculated by the calculation unit 26. Given to.

Further, the ambient temperature of the storage battery 10 is detected by the temperature detecting section 24, and the detection output thereof is also given to the calculating section 26.

The computing section 26 takes in the detection outputs of the charging current detecting section 20, the charging voltage detecting section 21, and the temperature detecting section 24 at every constant cycle Δt (step 1), and at the same time, charges the charging current at each constant cycle Δt. The change rate ΔI / Δt and the change rate ΔV / Δt of the charging voltage are calculated by the following equations (step 2).

ΔI / Δt = (I ₀ −I ₁ ) / (t ₀ −t ₁ ) (1) ΔV / Δt = (V ₀ −V ₁ ) / (t ₀ −t ₁ ) (2) where I ₀ and I ₁ are charge currents at time t ₀ and time t ₁ ,
V ₀ and V ₁ are respective charging voltages at time t ₀ and time t ₁ .

Subsequently, the calculation unit 26 causes the above (1),
From the values ΔI / Δt and ΔV / Δt of the time change rates of the charging current and charging voltage obtained based on the equation (2),
The internal resistance value R'of the storage battery 10 is calculated (step 3).

R ′ = (ΔV / Δt) / (ΔI / Δt) = ΔV / ΔI (3) Further, the calculation unit 26 calculates the temperature with respect to the internal resistance value R ′ obtained based on the equation (3). Based on the detection output from the detection unit 24, temperature correction is performed based on the following equation to obtain the corrected internal resistance value R (step 4).

R = k _T · R ′ (4) Here, k _T is a temperature correction coefficient determined by the value of the ambient temperature of the storage battery 10, and this temperature correction coefficient k _T is to be charged in advance. By investigating the temperature characteristics of the storage battery 10, it is tabulated in advance as a function of temperature and registered in the computing unit 26.

As shown in FIG. 7 (a), when the charging current supplied from the solar cell 4 is small or the ambient temperature of the storage battery 10 is high, the charging voltage is not changed even when the storage battery 10 is at the end of its charging. Even if the voltage does not almost drop even after the peak value is shown, the internal resistance value R of the storage battery 10 determined by the above formula (4) shows a clear rising curve as shown in FIG. 7 (b). Show.

Therefore, the comparison section 30 sequentially compares the corrected internal resistance value R obtained by the calculation section 26 with a predetermined threshold value Rsh stored in advance in the storage section 28.

The internal resistance value R is a predetermined threshold value R
If it becomes larger than sh (R> Rsh), the storage battery 10
Is judged to be fully charged, and a signal indicating that it is fully charged is output.

When the signal output from the comparison section 30 indicates that the signal is fully charged, the control section 32 responds to this by
A control signal for turning off the charging path is given to the switch unit 14 and a lighting signal for indicating the fully charged state is output to the display unit 16 (step 6). As a result, the charging of the storage battery 10 is completed, and the completion of the charging is displayed on the display unit 16.

As described above, in the present invention, by utilizing the characteristic that the internal resistance value of the storage battery 10 increases at the end of charging, it is determined whether the storage battery 10 is fully charged or not by observing the change of the internal resistance value. Therefore, when the storage battery 10 is charged, full charge can be accurately detected even if the charging current of the solar cell 4 changes, and the internal resistance value R showing a clear rising curve is the threshold value. When Rsh is exceeded, charging is immediately terminated, so that there is no delay in detecting full charge, and as a result, overcharging of the storage battery 10 can be reliably prevented.

In the above embodiment, the charging voltage detector 21 detects only the charging voltage during charging of the storage battery 10, but the charging path is temporarily forcibly cut off during charging of the storage battery 10. If the internal resistance value is obtained based on the difference between the open-circuit voltage of the storage battery 10 in the non-charged state and the charging voltage V during charging, the charge state according to the actual charge capacity of the storage battery 10 can be known. In addition, the presence or absence of full charge can be detected more accurately.

A storage battery charging circuit therefor is shown in FIGS. 8 and 9.

FIG. 8 is a configuration diagram of the storage battery charging circuit 8, and FIG. 9 is a block diagram of the circuit 8. The portions corresponding to those in FIGS. 4 and 5 are designated by the same reference numerals.

Storage battery charging circuit 8 shown in FIGS. 8 and 9.
Is provided with a timer unit 34 that outputs a timer output to the control unit 32 at every specific cycle (for example, every few minutes, depending on the charge capacity of the storage battery 10).

Then, the control unit 32 uses the timer unit 34.
In response to the timer output from, the control signal is supplied to the switch section 14 to operate the charging path in the cutoff state. The timer unit 34 can also use an internal timer included in the CPU.

Since the other structure is the same as that shown in FIGS. 4 and 5, detailed description will be omitted.

Next, the operation of the storage battery charging circuit 8 shown in FIGS. 8 and 9 will be described with reference to the flowchart shown in FIG.

When the storage battery 10 has not reached the fully charged state, the controller 32 of the controller 22
A control signal for connecting the charging path to the switch unit 14 is output. Therefore, since the solar cell 4 is connected to the storage battery 10 via the storage battery charging circuit 8, the storage battery 10 is gradually charged by the charging current supplied from the solar cell 4 (step 11).

During the course of this charging, the arithmetic unit 26 fetches the detection outputs of the charging current detecting unit 20, the charging voltage detecting unit 21, and the temperature detecting unit 24.

On the other hand, from the timer section 34, the timer output is added to the control section 32 at every specific cycle.

In response to the timer output from the timer section 34, the control section 32 gives the control signal to the switch section 14 to bring the charging path into the cutoff state for a certain period. As a result, the charge from the solar cell 4 to the storage battery 10 is temporarily forcibly cut off (step 12).

At this time, the calculation unit 26 takes in the detection output of the charging voltage detection unit 21. The detection output at this time is the open circuit voltage Vopen of the storage battery 10, and indicates the charge state according to the actual charge capacity of the storage battery 10 (step 1
3). The charging current is 0 because the charging path is blocked by the switch unit 14.

Subsequently, the calculation unit 26 is based on the charging current I and the charging voltage V of the storage battery 10 obtained during charging and the charging voltage Vopen obtained when the timer 34 forcibly shuts off the charging path. Then, the internal resistance value R'of the storage battery 10 is calculated by the following equation (step 14).

R ′ = (V−Vopen) / (I−0) = ΔV / I (5) Further, the calculation unit 26 calculates the temperature with respect to the internal resistance value R ′ obtained based on the equation (5). Based on the detection output from the detection unit 24, temperature correction is performed based on the above equation (4) to obtain the corrected internal resistance value R (step 15).

The comparing section 30 successively compares the corrected internal resistance value R obtained by the calculating section 26 with a predetermined threshold value Rsh stored in advance in the storage section 28.

Then, the internal resistance value R is a predetermined threshold value R
If it becomes larger than sh (R> Rsh), the storage battery 10
Is judged to be fully charged, and a signal indicating that it is fully charged is output.

When the signal output from the comparison unit 30 indicates that the signal is fully charged, the control unit 32 responds to this by
A control signal for turning off the charging path is given to the switch unit 14, and a lighting signal for indicating the fully charged state is output to the display unit 16 (step 17). As a result, the charging of the storage battery 10 is completed, and the completion of the charging is displayed on the display unit 16.

In the above embodiment, the solar battery 4 is used as the charging power source, but the present invention is not limited to this, and another storage battery such as a lead storage battery may be used, or a constant current may be used as in the conventional case. It is also possible to use a power supply.

Further, the internal resistance value R'obtained by the calculation unit 26 is corrected based on the detection output from the temperature detection unit 24. However, based on the detection output from the temperature detection unit 24, the storage unit It is also possible to correct the threshold value R ₀ stored in 28.

Further, in this embodiment, it is premised that the output voltage of the charging power source 4 is higher than that of the storage battery 10, but when using the charging power source 4 lower than the full charge voltage of the storage battery 10, An insulating DC-DC converter may be interposed between the charging power source 4 and the storage battery charging circuit 8 to apply the boosted charging voltage to the storage battery 10.

[0084]

According to the present invention, the following effects can be obtained.

(1) In the invention according to claim 1 and claim 2, the charging current and the charging voltage to the storage battery are detected for each unit time, and the internal resistance value is obtained from the amount of change, and the internal resistance value is calculated. When the resistance value exceeds the threshold value, it is determined that the battery is fully charged. Therefore, even if the charging current supplied from the charging power source to the storage battery fluctuates, it is not affected by the fluctuation.

In addition, even if the amount of change in the charging voltage at the end of charging is small, the internal resistance value appears as a large change due to the relationship with the charging current, so full charge can be accurately detected. Therefore, overcharge can be reliably prevented, and deterioration of the storage battery can be prevented.

(2) In the invention according to claim 3, since the ambient temperature of the storage battery is detected by the temperature detecting means and the internal resistance value obtained by the calculating means is corrected by this detection output, the influence of the ambient temperature of the storage battery is reduced. The full charge can be detected accurately without receiving the charge.

(3) In the invention according to claim 4, during the charging of the storage battery, the charging path is temporarily forcibly shut off by the output of the timer means, and the open voltage when the storage battery is in the non-charged state, Since the internal resistance value is obtained based on the amount of change from the charging voltage of the storage battery when the charging current is flowing before the interruption, it is possible to detect the presence or absence of full charge according to the actual charging capacity of the storage battery.

(4) In the invention according to claim 5, since the solar battery is applied as the charging power source, it is extremely economical and lightweight.

(5) In the invention according to claim 6, since the storage battery is used for the mobile phone, it is convenient because the storage battery of the mobile phone can be immediately charged and reused even if the storage battery is abruptly consumed.

(6) In the invention according to claim 7, when the storage battery is exhausted, the storage battery charger can be taken out to charge the battery easily if necessary.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a storage battery charger according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a schematic configuration of a storage battery charger according to an embodiment of the present invention.

FIG. 3 is a configuration diagram showing a storage battery charging circuit according to an embodiment of the present invention.

FIG. 4 is a configuration diagram showing details of the inside of the controller in the storage battery charging circuit of FIG.

FIG. 5 is a block diagram of the storage battery charging circuit of FIG.

6 is a flowchart for explaining a charging operation of the storage battery charging circuit shown in FIGS. 4 and 5. FIG.

FIG. 7 is a characteristic diagram showing changes with time in charging current, charging voltage, and internal resistance value when a storage battery is charged using the storage battery charging circuit according to the embodiment of the present invention.

FIG. 8 is a configuration diagram showing a modified example of the storage battery charging circuit according to the present invention.

9 is a block diagram of the storage battery charging circuit of FIG.

10 is a flowchart for explaining a charging operation of the storage battery charging circuit shown in FIGS. 8 and 9. FIG.

FIG. 11 is a configuration diagram of a conventional storage battery charging circuit.

12 is a characteristic diagram showing changes with time of a charging current and a charging voltage when the storage battery is charged using the storage battery charging circuit of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Storage battery charger, 4 ... Charging power source (solar cell), 8 ... Storage battery charging circuit, 10 ... Storage battery, 12 ... Slot, 14 ... Switch part, 16 ... Display part, 20 ... Charging current detection part, 21
... Charge voltage detection unit, 22 ... Controller, 24 ... Temperature detection unit, 26 ... Calculation unit, 28 ... Storage unit, 30 ... Comparison unit, 3
2 ... control unit, 34 ... timer unit.

Claims (7)

[Claims] 1. An internal resistance value of the storage battery is obtained from both by detecting a time change rate of each of a charging current applied to the storage battery from a charging power source and a charging voltage of the storage battery, and the internal resistance value is preset. The storage battery charging circuit is configured to stop the charging operation of the storage battery when it becomes larger than the threshold value. 2. A switch means for switching a charging path between the charging power source and the storage battery to a connection state or a disconnection state in response to a control signal; and a switch means for supplying the charging battery from the charging power source to the storage battery. Detecting means for detecting the charging current and the charging voltage of the storage battery respectively, and calculation for calculating the internal resistance value of the storage battery by obtaining the respective time change rates based on the charging current and the charging voltage given from the detecting means. Means for comparing the internal resistance value calculated by the calculation means with a predetermined threshold value set in advance corresponding to the internal resistance value when the storage battery is fully charged, and the calculated internal resistance value is Comparison means for outputting a predetermined comparison output when the threshold value is exceeded, and a control means for causing the switching means to cut off the charging path in response to the comparison output from the comparison means. Battery charging circuit, characterized in that it and a control means for stopping the charging operation giving signals. 3. A temperature detecting means for detecting an ambient temperature of the storage battery, wherein the calculating means corrects the calculation of the internal resistance value with a detection output from the temperature detecting means, and the corrected internal resistance value is calculated. The storage battery charging circuit according to claim 2, wherein the storage battery charging circuit is provided to the comparison means. 4. A timer means for outputting a timer output to the control means at a predetermined cycle, the control means in response to the timer output from the timer means, connecting the charging path to the switch means. The storage battery charging circuit according to claim 2 or 3, wherein the charging operation of the storage battery is forcibly stopped by giving a control signal for turning off the storage battery. 5. The storage battery charging circuit according to claim 1, wherein the charging power source is a solar cell. 6. The storage battery charging circuit according to claim 1, wherein the storage battery charger is for a mobile phone. 7. The storage battery charging circuit according to any one of claims 1 to 6 is housed inside, and a solar cell is connected as a power source for charging the storage battery charged by the storage battery charging circuit. A storage battery charger having a storage battery insertion port, and having a structure in which the storage battery housed inside through the insertion port is connected to the storage battery charging circuit in a predetermined state. .