JPH03277134A - Charger circuit - Google Patents

Abstract

PURPOSE:To certainly prevent overcharging of a battery by calibrating a reference voltage depending on battery temperature with a temperature calibrating member, comparing the calibrated reference voltage with a battery voltage and stopping the charging of a converter when the battery voltage is equal to or higher than the reference voltage. CONSTITUTION:Since a battery 13 is in high temperature condition, the power supply is turned off and when the power supply is then turned on for recharging, the battery 13 keeps again the high temperature condition, the battery 13, even when it is in the adequately charged condition, provides a voltage, at the time of starting the charging, which is almost equal to a voltage when the charging is stopped. However, since the reference voltage is dropped through temperature calibration by a thermister 19, the voltage of battery 13 reaches the reference voltage after a little rise, a high level signal is outputted from a comparator 20 and the recharging is stopped immediately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a charging circuit that converts AC voltage of a power source into DC to charge a storage battery.

(Prior Art) Conventionally, as such a charging circuit, the one shown in FIG. 5 is known.

In FIG. 5, 1 is a rectifier circuit that converts the voltage of an AC power source into DC, and 2 is a DC-DC that converts the DC voltage converted by the rectifier circuit 1 into a predetermined DC voltage to charge the storage battery 3.
The converter 4 is a timer circuit that starts measuring time after charging is started and stops charging the DC-DC converter 2 when the timer reaches a predetermined time. 5 is the load,
6 is a switch.

Now, when the storage battery 3 is charged by the DC-DC converter 2 from a completely discharged state, the timer circuit 4 is activated from the start of charging, and when the timer circuit 4 measures a predetermined time, the charging of the DC-DC converter 2 is started. to stop. Thereby, the storage battery 3 is charged by a predetermined amount, and overcharging of the storage battery 3 is prevented.

(Problem to be Solved by the Invention) However, in the conventional charging circuit, when the storage battery 3 is charged from a completely discharged state, the timer circuit 4
For example, when storage battery 3 is
There is a problem that if the battery is charged from a state of 72 discharge, it will be overcharged.

Therefore, since the storage battery 3 has a property that the temperature increases as it is charged, a system has been proposed that detects the temperature of the storage battery 3 to prevent overcharging of the storage battery 3.

However, since the storage battery 3 has a large heat capacity, the temperature will rise after a while after the start of charging of the storage battery 3.
Therefore, when the temperature indicating the overcharged state of the storage battery 3 is detected, the storage battery 3 is already in the overcharged state, so there is a problem that overcharging of the storage battery cannot be reliably prevented.

This invention was made in view of the above-mentioned problems, and its purpose is to provide a charging circuit that can reliably prevent overcharging of a storage battery.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a DC converter that converts AC voltage of a power source into DC and charges a storage battery, and A charging circuit comprising a timer circuit that stops charging by the converter, a reference voltage generation circuit that generates a predetermined reference voltage, and a temperature correction member that corrects the reference voltage according to the temperature of the storage battery; The present invention is characterized by comprising a comparison circuit that compares the voltage during charging of the storage battery with the corrected reference voltage and stops charging of the converter when the voltage is equal to or higher than the reference voltage.

(Function) Since the present invention has the above configuration, the reference voltage generation circuit generates a predetermined reference voltage, the temperature correction member corrects the reference voltage according to the temperature of the storage battery, and the comparison circuit corrects the reference voltage. The reference voltage is compared with the voltage of the storage battery, and when the voltage is higher than the reference voltage, charging of the converter is stopped.

(Example) Hereinafter, an example of a charging circuit according to the present invention will be described based on the drawings.

FIG. 1 is a circuit diagram showing the configuration of charging circuit A.
In the figure, 11 is a rectifier circuit that converts the AC voltage of the AC power source E into DC, and 12 is a DC-DC that converts the DC voltage converted by the rectifier circuit 11 into a predetermined voltage to charge the storage battery 13.
The converter is configured to stop charging when it receives an H level signal output from the flip-flop 14. 15, when charging circuit A is connected to power supply E,
That is, it is a timer circuit that starts timing when the DC-DC converter 12 starts charging, and outputs an H level signal when the timing reaches a preset time.

Reference numeral 16 denotes a reference voltage generation circuit that outputs a reference voltage, and this includes resistors 17 and 18 connected in series. 19 is resistance 1
A thermistor (temperature correction member) connected in series with 7 is installed in the storage battery 13 and corrects the reference voltage according to the temperature of the storage battery 13.

20 compares the voltage of the storage battery 13 input via the resistor R with the reference voltage output from the reference voltage generation circuit 16;
This is a comparator (comparison circuit) that outputs an H level signal when the voltage of the storage battery 13 is equal to or higher than the reference voltage.

Reference numeral 21 denotes an OR circuit that operates the flip-flop 14 in response to an H level signal output from the timer circuit 15 or the comparator 20; the flip-flop 14 is the OR circuit 21;
When an H-level signal is output from , it continues to output an H-level signal.

23 is a power supply circuit that operates the timer circuit 15 and the comparator 20. Further, a capacitor C and a resistor R connected to the inverting terminal of the comparator 20 are a low-pass filter for removing noise. 25 is a load operated by the storage battery 13;
6 is a switch.

Incidentally, as the storage battery 13 is charged, it exhibits characteristics as shown in FIG. 2 (here, the charging characteristics of the Ni-Ca storage battery are shown, but other storage batteries also exhibit similar characteristics). That is, the voltage of the storage battery gradually increases depending on the charging time, and when overcharging occurs, the voltage reaches the maximum voltage Vp, and thereafter the voltage decreases.

Therefore, when the charging time is T1, that is, when the storage battery 13 is charged by an appropriate amount (80 to 90% of full charge), the voltage of the storage battery 13 is Vt (appropriate voltage), and the reference voltage V
Set f to be V p) V f ) V t, compare the voltage of the storage battery 13 during charging with the reference voltage Vf, and stop charging when the voltage V exceeds the reference voltage Vf. In addition to preventing overcharging,
This means that the battery can be charged to just the right amount.

However, the voltage (2) of the storage battery 13 changes depending on the temperature of the storage battery 13, as shown in FIG. That is, when the temperature of the storage battery 13 is high, the maximum voltage Vp and the appropriate voltage ■t
becomes lower, and the decline is exponential. Therefore, the reference voltage Vf also needs to be corrected exponentially according to the temperature of the storage battery as shown by the chain line in FIG.

In this embodiment, the correction is performed by the thermistor 19, but a diode may be used instead of the thermistor 19. Further, the reference voltage Vf is set by resistors 17.18 so that VP>Vf>Vt.

Next, the operation of the charging circuit of the above embodiment will be explained.

A case will be described in which the storage battery 13 is charged from a completely discharged state.

Now, as the storage battery 13 is being charged by the DC-DC converter 12, the voltage of the storage battery 13 gradually increases as shown in FIG. Since is equal to the atmospheric temperature, the reference voltage Vf is sufficiently higher than the storage battery voltage ■. Then, as the charging of the storage battery 13 progresses, the temperature of the storage battery 13 gradually increases. With this temperature rise, thermistor 19
As the resistance decreases, the reference voltage Vf decreases and at time t
1, the temperature of the storage battery 13 at this time is Vf, and Tb is the temperature of the storage battery 13 at this time.

On the other hand, when the storage battery 13 starts charging (time to), the timer circuit 15 operates and measures time. When this time reaches T1, the timer circuit 15 outputs an H level signal, and the OR circuit 21 and the flip-flop 14 via D
Charging by the C-DC converter 12 is stopped.

At this time, the voltage V of the storage battery 13 is as shown in FIG.
However, if the charging time is before TI elapses, the second
It is clear from the figure that the voltage ■ is lower than the reference voltage Vf, and the comparator 20 does not output an H level signal and stop charging before the timer circuit 15 reaches T1. That is, when the storage battery 13 is charged from a completely discharged state, charging is performed for a predetermined time T1 by the operation of the timer circuit 15, so that it is reliably charged by an appropriate amount and is not overcharged.

Further, at time t1 in FIG. 4, if the temperature of the storage battery 13 is higher or lower than Tb, the voltage 2 of the storage battery 13 will fluctuate from Vt according to the temperature, but the reference voltage Vf will also change from the thermistor. The temperature is corrected by 19 and varies from f. That is, if the voltage (2) of the storage battery 13 increases with temperature, the reference voltage Vf also increases with the temperature, and conversely, if the voltage (2) decreases with the temperature, the reference voltage Vf also decreases with the temperature.

Therefore, due to fluctuations in the temperature of the storage battery 13, the time t1
There is no case where the voltage V of the storage battery 13 reaches the reference voltage Vf and the comparator 20 stops charging.

At time t2 after a certain period of time T2 has elapsed from time t1, that is, when the temperature of the storage battery 13 remains high, when the power supply E is cut off and then turned on again to perform recharging, the storage battery 13 is Since the high temperature is maintained, the voltage (2) at the start of charging of the storage battery 13 is almost the same voltage as Vt, even though the storage battery 13 is charged to an appropriate amount. However, since the reference voltage Vf has been reduced by temperature correction by the thermistor 19,
The voltage of the storage battery 13 becomes the reference voltage Vf by increasing only a little.
At time t3), the comparator 20 outputs an H level signal, and recharging is immediately stopped.

That is, charging of the storage battery 13 is stopped only after a short period of time T3 has elapsed from the time of recharging t2, and overcharging can be reliably prevented. In this case, the timer circuit 15 is reset and starts timing at L2 during recharging, but T
Since 3<T I, the timer circuit 15 does not stop recharging before the H level signal is output from the comparator 20.

When the storage battery 13 is charged to an appropriate amount and the temperature of the storage battery 13 is at atmospheric temperature, that is, when the complete battery starts from time t4 shown in FIG. 4, the reference voltage Vf is Since the temperature of the storage battery 13 is the atmospheric temperature, the voltage v4 at the start of charging of the storage battery 13 is higher than the voltage v2, although it may or may not be low. Therefore, when the voltage (2) of the storage battery 13 increases slightly as it is being charged, at time t5) when it reaches the reference 1 voltage Vf, an H level signal is output from the comparator 20 and the charging is immediately stopped. Overcharging must be reliably prevented.

Next, a case will be described in which the storage battery 13 is recharged from a state that is not completely discharged, for example, a case where it is recharged from a 1/2 discharged state.

In the 1/2 discharge state, as shown at time t8 in FIG. 4, the voltage 5 at the start of charging of the storage battery 13 is lower than v4 because it is in the 1/2 discharge state.

Then, with charging, the voltage of the storage battery 13 changes from the voltage of ■6 to the voltage of the storage battery 13.
increases and reaches the reference voltage Vf at time t7.

In this case, the difference between the voltage v6 and the reference voltage Vf at time t6 is larger than the difference at time t21 ta, so the time T7 from time t6 to time t7 is equal to T3 or T4.
much longer than that. In other words, the charging time becomes sufficiently long, and the storage battery 13 is charged to a proper state of charge.

Further, the difference between the voltage v6 and the reference voltage Vf at time t6 is the difference between time 1. Since the difference is smaller than the difference in Tl)T7, charging is not stopped by the timer circuit 15.

At time t, the temperature is rising due to charging, so is it possible to store electricity? l! Voltage 13 (■) does not rise significantly even when it is near an overcharged state, but since the reference voltage Vf is temperature-corrected by the thermistor 19 and is decreasing, the storage battery 13 is near an overcharged state. If the voltage V becomes a little higher, the voltage V will reach the reference voltage Vf, and overcharging will be reliably prevented.

In the above example, the case where the storage battery 13 is charged from the same state as the atmospheric temperature has been explained, but even if the temperature is higher or lower than this, the reference voltage Vf is temperature-corrected by the thermistor 19, so the storage battery 13 is charged. Even if the voltage (2) changes depending on the temperature, overcharging is prevented as described above, and the battery is charged to a proper charging state.

In this way, even if the temperature of the storage battery 13 changes, the thermistor 19 temperature-corrects the reference voltage Vf according to the temperature, so overcharging of the storage battery 13 can be reliably prevented, and the storage battery 13 can be properly It can be charged so that it is in a charging state.

The timer circuit 15 is provided to ensure that the battery 13 is properly charged when it is charged from a completely discharged state.
This is only for charging. By the way, if the charging of the storage battery 13 is stopped using only the comparator 20, there will be considerable variation in the charging characteristics of the storage battery 13 shown in FIG. This is because the times vary, making it difficult to ensure that the appropriate amount of charging is performed.

(Effects) According to the present invention, since the reference voltage is temperature-corrected by the temperature correction member according to the temperature of the storage battery, overcharging can be reliably prevented even if the temperature of the storage battery changes, and The storage battery can be charged to a proper state of charge.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the configuration of a charging circuit according to the present invention, Fig. 2 is a graph showing charging characteristics of a storage battery, Fig. 3 is a graph showing the relationship between voltage and temperature of a storage battery, and Fig. 4 is a graph showing the relationship between voltage and temperature of the storage battery. The figure is a graph showing the relationship between the voltage of the storage battery and the reference voltage corrected according to the temperature, and the temperature change of the storage battery during charging. FIG. 5 is a circuit diagram showing the configuration of a conventional charging circuit. 11... Rectifier circuit 12... DC-DC converter (converter) 13.
...Storage battery l5...Timer circuit 16...Reference voltage generation circuit 19...Thermistor (a degree correction member) 20...Comparator Fig. 1 Fig. 0 0 3゜0 0 607゜

Claims (1)

[Scope of Claims] A charging circuit that includes a converter that converts AC voltage of a power source into DC to charge a storage battery, and a timer circuit that stops charging by the converter after a predetermined time has elapsed from the start of charging. , a reference voltage generation circuit that generates a predetermined reference voltage; a temperature correction member that corrects the reference voltage according to the temperature of the storage battery; and a comparison between the voltage during charging of the storage battery and the corrected reference voltage. and a comparison circuit that stops charging the converter when the voltage is equal to or higher than a reference voltage.