JPH09331637A - Charger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable always adequate charging by preserving charging history when the output voltage of a solar battery or the like is completely cut off, by backing up the charging history data which has been stored with a secondary battery, when the output of a power source is cut off or becomes unstable. SOLUTION: When a charger 2 is loaded with a solar battery 1, power is supplied to the charger 2. A voltage compactor 3 compares the input voltage Vin of the charger 2 with specific reference voltage V1, V2 and delivers a signal showing the comparison results to a charge control part 5. On the basis of the signal from the voltage compactor 3, a microcomputer of the charge control part 5 detects a range where the input voltage Vin exists. When solar condition is changed worse (night or the like), and the input voltage becomes lower than or equal to the specific reference voltage V2, charging is interrupted, and charging history is preserved by a backup route 11 of the charging control part 5. Thereby, charging can be hesvmed when the input voltage Vin is recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device that uses a power source such as a solar cell whose output fluctuates and that can perform optimum full-charge detection of a secondary battery. .

[0002]

2. Description of the Related Art In a charging device using a power source such as a solar cell whose output is unstable including interruption, in the case of a secondary battery which performs constant voltage / current limiter charging (Ni-cd Batteries, lithium-ion batteries, lead batteries, etc.),
As in the “charger using a solar cell” previously filed by the present inventors as a Japanese patent application, the initial charging state of the secondary battery to be charged is detected to determine the total charge integration amount, and the charging current is determined. The full charge was detected by comparing with the integral value of.

[0003]

However, in the device according to the above-mentioned application, when the input voltage is completely cut off at night or the like, the accumulated charge amount calculated and updated until then is reset. When the input condition was recovered, it was necessary to detect the initial charging state again and to determine the total integrated charge amount. For this reason, when the sunshine gradually increases like the Asahi, it is difficult to detect the initial state of charging, and charging cannot be performed properly.

It is an object of the present invention to store the charging history up to that point so that even if the input voltage (output voltage of a solar cell or the like) is completely cut off, proper charging is always performed.

[0005]

In order to achieve the above object, in the present invention, a route for receiving power supply from a secondary battery for charging is provided in the control unit of a charging device to back up the charge control unit. .

[0006]

With this configuration, when the input condition of the charging device is recovered, it is not necessary to detect the initial state of charge of the secondary battery again and to determine the total integrated charge amount, and even under the input condition where this determination cannot be performed. Appropriate charging can be performed.

[0007]

1 is a block diagram of a charging system according to an embodiment of the present invention. In the figure, 1
Is a solar cell as an input, and 2 is a charging device characterized by the present invention. Further, 3 indicates that the input voltage Vin is a predetermined threshold value V2.
(Refer to FIG. 3) A voltage comparison unit that generates a signal to stop charging when the voltage drops below 4 is a stabilized power supply unit that stabilizes the charging voltage Vout required for charging and controls the current, and 5 is a start of charging. And a charging control unit for controlling termination, 6 is a resistor for limiting the charging current, 7 is a switch for turning on / off the charging current, 8 is a resistor for measuring the charging current Iout, 9 is a secondary battery To prevent backflow from the battery, 10 is a secondary battery charged with a constant voltage, and 11 is a diode as a power supply means for backing up the charging history when the input, which is a feature of the present invention, is cut off. Is.

When the solar cell 1 is mounted on the charging device 2, electric power is supplied to the charging device 2. When the input voltage Vin is applied to the charging device 2 in the state where the secondary battery 10 is connected, it is stabilized by the stabilized power supply unit 4, passes through the current limiting resistor 6, the switch 7, and the backflow prevention diode 9, and has a constant voltage. The secondary battery 10 to be charged is charged.

The voltage comparison unit 3 receives the input voltage V of the charging device 2.
comparing in with predetermined reference voltages V1, V2 (FIG. 3),
A signal indicating the comparison result is sent to the charging control unit 5. The charge control unit 5 receives this signal and turns on / off the switch 7.
Perform

The microcomputer in the charge controller 5 detects the range of the input voltage Vin based on the signal from the voltage comparator 3. Further, the charging voltage Vout supplied to the secondary battery 10 is detected, and the charging current Iout is detected by the potential difference generated across the resistor 8. Further, the integrated amount of the charging current is calculated by integrating the variation of the output current Iout with time. When the calculated integrated amount reaches the charging capacity (total integrated charging amount) required for the secondary battery 10, it is determined that charging is completed.

Further, the total integrated charge amount is changed according to the state of charge of the secondary battery at the start of charging. As a method, the relationship between the input voltage Vin at the start of charging, the output voltage Vout, and the charging current Iout is comprehensively determined, and the initial state of the secondary battery is determined. The judgment is the output voltage Vo
This is performed when the input voltage Vin is sufficiently higher than ut (Vin> V1 in FIG. 3). Secondary batteries that perform constant voltage charging include lithium ion batteries and lead batteries.

As a charging system, a constant voltage / current limiter system is adopted as represented by a lithium ion battery. As shown in FIG. 4, when the charging curve starts, constant current charging by the current limiter method is performed first, and the charging voltage 22 gradually increases to reach a constant voltage value Vmax. Due to the characteristic (2), the current is no longer accepted, and the charging current 23 stably decreases according to the charging state. Therefore, using the above characteristics, in the charging device, when the output voltage Vout does not reach the upper limit value Vmax, the charging start state is determined by the output voltage value Vout, and the output voltage Vout is the upper limit value Vmax.
When it has reached max, the charging start state is judged by the output current value Iout after the charging current starts to decrease.

Next, the specific control means for detecting and integrating the charging current performed by the microcomputer in the charging control section 5 will be described.

When the battery pack 10 is connected and the charging current Iout flows, a potential difference proportional to the charging current is generated at both ends of the charging current detection resistor 8, and this potential difference is input to the microcomputer of the charging control unit 5. Since constant voltage charging is performed, the charging current decreases or shuts off in response to a decrease in input power due to deterioration of the sunshine state (see FIG. 6). The value obtained by integrating the change of the charging current with time is the charging current amount.

A general method of obtaining the integrated value of the output current will be shown below with reference to FIG. In FIG. 4, the elapsed charging time is on the X-axis, and the charging output voltage and the charging output current are on the Y-axis. Charging start time is T1, charging end time is T2,
If the output current value draws a curve of Y = f (X) with respect to the charging time, the charging current integrated value S is

[0016]

[Equation 1] Is represented by

Assuming that the total charge integration amount determined by the detection of the initial charging state is Sa, the charging is terminated when T2 when Sa = S is reached.

Next, the charging control method by the charging control unit 5 of FIG. 1 will be described with reference to FIG. When the secondary battery is connected in step 13, charging is started in step 14 and the initial charging state of the secondary battery is detected in step 15. Depending on the detected state, the total charge integration amount is determined in step 16.

In step 17, the charging current is detected. Based on the detected charging current data, the charging current amount is integrated in step 18, and the total charging integrated amount and the integrated value of the charging current are compared in step 19.
The charging is continued until the integrated value of the charging current becomes equal to the total integrated charge amount, and when the total integrated charge amount = the integrated charge current value, the charging is ended in step 20.

In the present embodiment, the charging is stopped and the backup of the charging control unit 5 is performed when the input voltage drops to V2 or less due to the deterioration of the sunshine conditions (nighttime etc.) between Step 17 and Step 19. By storing the charging history through the path 11, it is possible to continue the charging when the input voltage is restored.

[0021]

EXAMPLE FIGS. 4 and 6 show the state of the charging output in the charging device of FIG. 1 when the solar cell output during charging fluctuates as the solar radiation changes as shown in FIGS. 3 and 5, respectively. next,
The relationship between the input voltage and the charging output will be described with reference to FIGS. 3 to 6. In FIG. 3, reference numeral 21 indicates a fluctuation of the input voltage that does not affect the charging. As shown in FIG. 4, the output voltage (charging voltage) 22 uniformly rises with respect to the charging time, and the output current (charging current) 23 is stable with respect to the fluctuation of the input voltage of 21.

In FIG. 5, reference numeral 24 shows the fluctuation of the input voltage which affects the charging. The output voltage (charging voltage) 25 increases or decreases according to the state of the output current (charging current) 26 as shown in FIG.

When the input voltage Vin is not lower than the reference voltage V2 and not higher than V1 (lower than the output voltage Vmax), the stabilized power supply unit 4 stabilizes only the charging voltage Vout and the charging current Io.
ut operates so as to freely flow with a small current.

When the input voltage Vin is higher than the reference voltage V1, the stabilized power supply unit 4 causes the charging voltage Vout and the charging current Io.
ut is operated to be stabilized (charging voltage Vo
It is controlled so that ut becomes Vmax and the charging current Iout does not exceed a predetermined maximum current). Input voltage Vi
When n is V2 or less, the charging control unit 5 opens the switch 7 and stops charging.

In the present embodiment, the input voltage Vin is reached during charging.
Is V2 or less and the switch 7 is opened, a path (diode 11) for supplying power to the charging control unit 5 using a secondary battery as a power source to back up the microcomputer in the charging control unit 5. Is provided.

As a result, the accumulated charge history data for performing full charge detection is not reset during charging, and it is possible to continue charging even when the input voltage Vin is restored again. Become.

The backup diode 11 provided in this embodiment does not perform charging through the path from the charge control section 5, and may be a transistor or other component as long as it does not backflow. In addition, the resistor 6 that limits the current
Is used as needed.

[0028]

As described above, according to the present invention,
Even if charging is performed using a power source whose output is not stable, such as a solar cell, or when no input is supplied at night, efficiency is obtained by backing up the charging history data using the secondary battery that is charging as the power source. It becomes possible to charge the battery. The present invention is particularly suitable for a secondary battery, such as a Ni-cd battery, in which the terminal voltage, that is, the output voltage of the charging device becomes substantially constant after the charging progresses to a certain extent and the charging start state is unknown at the terminal voltage. It is valid.

[Brief description of drawings]

FIG. 1 is a block diagram of a charging device according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining the operation of the apparatus of FIG.

FIG. 3 is a graph showing an example of variation in input voltage that does not affect charging.

FIG. 4 is a graph showing changes in charging output with respect to the input voltage of FIG.

FIG. 5 is a graph showing an example of fluctuations in input voltage that affect charging.

FIG. 6 is a graph showing a change in charging output with respect to the input voltage of FIG.

[Explanation of symbols]

1: solar cell, 2: charging device, 3: voltage comparison unit, 4: stabilized power supply unit, 5: charging control unit, 6: charging current limiting resistor,
7: Switch for charging ON / OFF, 8: Charging current detecting resistor, 9: Charge backflow prevention diode, 10: Secondary battery for constant voltage charging, 11: Backup diode.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H02N 6/00 H02N 6/00

Claims (1)

[Claims] 1. A charging device for charging a secondary battery using an unstable power source as a power source, detecting an initial state of charging of the secondary battery to determine a total charge integrated amount, and comparing it with an integrated value of a charging current. A full charge detection by doing so, storage means for storing data detected or calculated for the control, means for supplying backup power from the secondary battery to the storage means, A charging device, wherein when the output of the power source is cut off or becomes unstable, backup of charging history data accumulated up to that point is performed by the secondary battery.