JP2894370B2 - Charger control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for a charger for floatingly charging a battery.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional example of a charger control circuit for floatingly charging a battery. In FIG. 3, the AC power from the AC power supply 1 is converted into smooth DC power by the rectifier 2 and the smoothing capacitor 3 and input to the charger 4. The DC power output from the charger 4 is filtered by a smoothing capacitor 5 to remove a ripple component, and then charges a battery 8 via a battery switch 7.
The battery is supplied to the inverter 6 as a load. When the charger 4 starts operating, the battery switch 7 is open and the battery 8 is disconnected from the charger 4.

[0003] The charger 4 is provided with a voltage regulator 10. The voltage regulator 10 receives an output voltage value output by the charger 4 and a voltage target value set by the output voltage setting device 11. Therefore, control for making the charger output voltage equal to the target value is performed in the voltage regulator 10. The charger output voltage is also input to the comparator 13. If the output voltage matches the predetermined value set by the predetermined voltage setting device 14, the signal from the comparator 13 closes the battery switch 7. The charging of the battery 8 is started, but at the same time, the charging switch 15 is closed, and the charging voltage setting device 1 reaches the target value set by the output voltage setting device 11.
2 is added, and the charger output voltage is
To a voltage suitable for charging.

[0004]

The battery terminal voltage at the start of charging of the battery 8 is the same as that of the battery 8.
Has different values depending on how much has been discharged. On the other hand, the charger output voltage is controlled by the output voltage setting device 11 so as to be a voltage target value assumed as the battery terminal voltage. Therefore, if the voltage target value set by the output voltage setting unit 11 is applied while the battery 8 is discharged in large quantities and the terminal voltage thereof is greatly reduced to about the discharge end voltage, an excessive current will flow. As a result, both the charger 4 and the battery 8 could be seriously damaged.

When the output voltage of the charger 4 is V _C and the battery 8
Is a terminal voltage of V _B and a total impedance of the charger 4 and the battery 8 is Z, a current I flowing into the battery 8 is expressed by the following equation 1.

[0006]

(Equation 1)

Here, since the impedance Z is an extremely small value, the current I becomes an excessively large value.

Accordingly, an object of the present invention is to prevent an excessive current from flowing when a charger is connected to charge the battery, regardless of the value of the battery terminal voltage. To avoid the risk of damage.

[0009]

In order to achieve the above object, a charger control circuit according to the present invention comprises a charger for outputting a direct current and a battery switch connected between the charger and a load. Battery, a voltage adjusting means for controlling the output voltage of the charger to match the voltage target value set by the voltage setting means, and a comparator for detecting that the output voltage of the charger matches a predetermined voltage set separately. And charging voltage setting means for setting the charging voltage of the battery, wherein when the comparator operates, the battery switch is closed, and the voltage target value input to the voltage adjusting means is set to a charging voltage setting value. A charger control circuit configured to switch, a voltage adjusting means for performing control for matching the charger output voltage to the battery terminal voltage, and the battery Battery approximation voltage generation means for setting a voltage slightly lower than the slave voltage, and a comparator for detecting a match between the output of the battery approximation voltage generation means and the charger output voltage, or Voltage adjustment means for performing control to match the battery terminal voltage; subtraction means for calculating a deviation between the charger output voltage and the battery terminal voltage; deviation range setting means for setting a deviation range; Or a comparator for detecting a match between the output of the deviation range setting means and a battery terminal voltage input to the voltage adjustment means while closing the battery switch if any of the comparators operates. Is switched to the charging voltage set value.

[0010]

According to the present invention, the battery terminal voltage is supplied to the voltage regulator as a voltage target value, and the charger output voltage is controlled so as to match this battery terminal voltage, which is the target value. The charger output voltage follows this value even if the value is too large.
Here, when the output voltage of the charger approaches the battery terminal voltage, it is detected by a battery approximate voltage generator or a deviation between the two voltages, and a closing command is given to the battery switch. Is negligible, so there is no danger of excessive current flowing.

[0011]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. The AC power supply 1, the rectifier 2, and the rectifier 2 shown in FIG.
The smoothing capacitor 3, the charger 4, the smoothing capacitor 5, the inverter 6, the battery switch 7, the battery 8, the voltage regulator 10, and the comparator 13 are described in FIG. Since the functions are the same, their description is omitted.

In the circuit of the first embodiment, the terminal voltage of the battery 8 is input to the voltage regulator 10 as a voltage target value,
Control is performed so that the charger output voltage matches the battery terminal voltage. Further, a battery approximate voltage generator 23 for inputting a battery terminal voltage and outputting a slightly lower voltage than the battery terminal voltage is provided.
Is input to the comparator 13 together with the charger output voltage. Therefore, when the charger output voltage rises to the output value of the battery approximate voltage generator, the comparator 13
Operates to close the battery switch 7 and connect the battery 8 to the charger 4, but the current at this time is small. The comparator 13 further gives a changeover command to the changeover switch 22, and the charging voltage set by the charging voltage setting unit 21 instead of the battery terminal voltage is input to the voltage regulator 10 as a target value. Therefore, the output voltage of the charger 4 rises accordingly and starts charging the battery 8.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention. The AC power source 1, rectifier 2, smoothing capacitor 3, charger 4, smoothing capacitor 5,
Inverter 6, battery switch 7, battery 8,
The voltage regulator 10 and the comparator 13 have the same names, applications, and functions as those described in the conventional circuit described above with reference to FIG. 3, and the charging voltage setter 21 and the changeover switch 22 are the same as those described in FIG. Since the names, uses, and functions of the circuit described in the first embodiment are the same as those described in the first embodiment, description thereof will be omitted.

In the circuit of the second embodiment, the terminal voltage of the battery 8 is input to the voltage regulator 10 and the charger output voltage is controlled so as to be equal to the battery terminal voltage. This is the same as the circuit of the embodiment, except that the deviation value between the charger output voltage and the battery terminal voltage calculated by the subtractor 31 and the deviation range set by the deviation range setting device 32 are input to the comparator 13. I have. Therefore, if this deviation range is set to a small value,
When the values of the charger output voltage and the battery terminal voltage decrease, the comparator 13 operates to close the battery switch 7 and connect the battery 8 to the charger 4.
At this time, only a small amount of current flows. Since the comparator 13 further gives a switching command to the changeover switch 22, the charging voltage set by the charging voltage setting unit 21 is input to the voltage regulator 10 instead of the battery terminal voltage as a command value. The voltage rises accordingly and starts charging the battery 8.

[0015]

According to the present invention, since the battery terminal voltage is given as the voltage target value to the voltage regulator for controlling the output voltage of the charger, the output voltage of the charger is made equal to the battery terminal voltage. You can do it. Also, a means is provided for detecting that the charger output voltage has risen to a value close to the battery terminal voltage, so that an excessive current flows when the battery switch is closed and the charger is connected to the battery. The effect that can be prevented is obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a conventional example of a charger control circuit for floatingly charging a battery.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 4 Charger 7 Battery switch 8 Battery 10 Voltage regulator 13 Comparator 21 Charge voltage setter 22 Changeover switch 23 Battery approximate voltage generator 31 Subtractor 32 Deviation range setter

Claims (2)

(57) [Claims] 1. A charger for outputting a direct current, a battery connected between the charger and a load via a battery switch, and a voltage target value for setting a charger output voltage by voltage setting means. Voltage adjusting means for performing control to match the voltage, a comparator for detecting that the charger output voltage matches a predetermined voltage separately set, and charging voltage setting means for setting the charging voltage of the battery, wherein the comparator When operated, the battery control circuit closes the battery switch and switches the voltage target value input to the voltage adjusting means to the charging voltage set value, wherein the charger output voltage matches the battery terminal voltage. Voltage adjusting means for performing control for causing the battery to operate, and battery approximate voltage generating means for setting a voltage slightly lower than the battery terminal voltage. A comparator for detecting a match between the output of the battery approximate voltage generation means and the output voltage of the charger; when the comparator operates, the battery switch is closed, and the battery terminal voltage input to the voltage adjustment means is provided. A charging voltage setting value. 2. A charger for outputting a direct current, a battery connected between the charger and a load via a battery switch, and a voltage target value for setting the charger output voltage by voltage setting means. Voltage adjusting means for performing control to match the voltage, a comparator for detecting that the charger output voltage matches a predetermined voltage separately set, and charging voltage setting means for setting the charging voltage of the battery, wherein the comparator When operated, the battery control circuit closes the battery switch and switches the voltage target value input to the voltage adjusting means to the charging voltage set value, wherein the charger output voltage matches the battery terminal voltage. Voltage adjusting means for performing control for causing the battery to operate, subtracting means for calculating the difference between the charger output voltage and the battery terminal voltage, and setting a deviation range. A deviation range setting means, and a comparator for detecting coincidence between the output of the subtraction means and the output of the deviation range setting means. When the comparator operates, the battery switch is closed and the voltage is input to the voltage adjustment means. A battery terminal voltage that is switched to a charging voltage set value.