JPH03103038A - Charger - Google Patents

Abstract

PURPOSE:To detect completion of charging operation accurately and to prevent overcharge by continuing the charging operation with a large current for a predetermined time after droppage of the terminal voltage of a battery to a predetermined level, which is considerably lower than the voltage level upon finish of charging operation, thereafter carrying the charging operation with a small current. CONSTITUTION:Upon droppage of the terminal voltage Vc of a battery 4 below a predetermined level, a detection signal Q is provided from a voltage detecting section 6 to a counter section 7 while a current increasing signal C1 is provided to a current control section 2 thus bringing the charging current Ic for the battery 4 to a large current level. When the terminal voltage Vc of the battery 4 reaches a predetermined level upon finish of charging operation, no detection signal Qv is provided from the voltage detecting section 6 to the counter section 7, which then starts counting operation. The counting operation finishes when the terminal voltage Vc of the battery 4 approximately reaches the peak level, whereby no current increase signal C1 is provided from the counter section 7 to the current control section 2 and the charging current Ic having small current level is fed to the battery 4.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a charging device that prevents overcharging. [Prior art and its problems J] Conventionally, in order to prevent the storage battery from deteriorating due to overcharging, such charging devices have been designed to reduce the terminal voltage of the storage battery by a small amount when the storage battery is fully charged and becomes overcharged. There is a known device that detects a relative drop in the battery and shuts off the rechargeable battery to prevent overcharging. However, with such devices, when the device is used while charging, a voltage drop occurs, and this voltage drop is mistakenly recognized as a voltage drop that occurs after charging is complete, resulting in charging being aborted even though the device is not fully charged. There was a problem. In addition, the voltage drop that occurs after charging is very small, so
In order to detect this voltage drop, a highly accurate voltage detector is required, which poses the problem of complicating the circuit and making it expensive.

It should be noted that if no overcharging prevention circuit is provided, the cost will be lower, but it will be very inconvenient as you will have to constantly check whether charging has finished or not. [Object of the Invention] This invention was made in view of the above-mentioned circumstances, and its purpose is to provide a charging device that can accurately detect the completion of charging and prevent overcharging with a simple circuit configuration. The goal is to provide the following. [Summary of the Invention] In order to achieve the above-mentioned object, the present invention detects the terminal voltage of a storage battery at a fixed constant voltage that is one step lower than the voltage at the completion of charging, which is easy to detect, and then The key point is that charging is continued with a large current until a certain period of time has elapsed, and after this period of time, charging is performed with a small current. Therefore, the detection of the terminal voltage of a storage battery does not involve constantly tracking changes in the voltage value in order to detect the point where the voltage value rises and then falls, as when detecting the maximum peak value of the voltage value. Since this is done based on whether a fixed voltage has been reached, the circuit structure is simple and a temporary voltage drop due to equipment use will not be misinterpreted as reaching the maximum peak value. Also, the reason why we did not directly detect the maximum peak value is that if the detection value set in the circuit changes slightly due to temperature changes and exceeds the maximum peak value even slightly, charging will not be terminated. This is because the battery will become overcharged. [Example 1] An example of the present invention will be described in detail below with reference to the drawings. Figure 1 shows the overall circuit of the charging device. In the figure, 1 is a power supply circuit, and this circuit 1 rectifies the current from an alternating current (AC) power source, and also adjusts the voltage of the alternating current. This is to keep the output voltage constant even if the voltage fluctuates. The output current from the power supply circuit 1 is supplied to the storage battery 4 via the current control section 2 and the current detection section 3 as a charging TL current flow c. This storage battery 4 can be used repeatedly by repeatedly charging it. Electric power from this storage battery 4 can be supplied to and discharged from a load 5 via a switch S. The terminal voltage vc of the storage battery 4 is given to the voltage detection unit 6, and is a constant voltage V d e t determined in advance by charging or discharging the storage battery 4.
Detection is made as to whether or not this has been reached. This constant voltage V d
e t is the maximum peak voltage V when charging of the storage battery 4 is completed
The voltage value is set one step lower than IJK. When the terminal voltage ■, of the storage battery 4 is less than the constant voltage V de t, the voltage detection section 6 outputs a detection signal Qv, which is given to the counter section 7 as a reset} (R) signal, and the constant voltage V d When e t is exceeded, the test t11 signal QV is no longer output. As this voltage detection section 6, for example, a comparator circuit consisting of an OF amplifier, a Zener diode, etc. can be used. The counter section 7 receives an enable signal at the E terminal,
It counts for a predetermined period of time when a reset signal is not given to the R terminal.
The configuration also includes a flip-flop type flip-flop, and the detection signal Qv is applied to the set (S) terminal of the 7 flip-flops and the counter set (R) terminal, and the carry signal of the counter is applied to the set (S) terminal of the 7 flip-flops. } (R)
The Q output of this flip-flop is supplied to the current control section 2 as a current increase signal CI, and is also supplied to the E terminal of the counter as an enable signal. Therefore, the terminal voltage VC of the storage battery 4 is a constant voltage V de
When time t is reached and the detection signal Qv is no longer given to the counter section 7, the counter section 7 starts counting, and the carry signal after counting is input to the R terminal of the flip-flip, and its Q output, that is, the current The increased signal CI is no longer output. Since this Q output is also an enable signal for the counter section 7, the counter section 7 is placed in a non-enabled state and the counting is terminated. The current control unit 2 supplies the charging current Ic from the power supply circuit l to the storage battery 4 as is while the current increase signal CI from the counter unit 7 is applied, but the current Cr is no longer applied. and charging current I from power supply circuit l
A small current dropped from cz to Icl level is supplied to the storage battery 4. As this current control section 2, for example, a DC chopper circuit or the like can be used. Charging current Ic
Low current IC! The level of is set to a level that prevents potential drop due to natural discharge of the storage battery 4. The constant voltage V d e t of the voltage detection section 6 and the count time of the counter section 7 are determined by the charging characteristics of the storage battery 4, but the constant voltage V d e t is determined by the maximum peak voltage at the completion of charging. A stable point with a large slope of the charging characteristic curve is best, close to Vla
It is preferable to set the time to reach ax, but it is not necessarily limited to this. The charging current Ie from the current control section 2 is transmitted to the current detection section 3.
When the current Ic2 is large, the current detection section 3 applies a driving current to the charging state display section 8, and when the current Icl is small, this driving current is not applied. It consists of a light emitting diode (light emitting diode), etc., and lights up when a driving current is applied to indicate that it is being charged.
If no drive current is applied, the light will turn off, indicating that charging is complete. Operation> Next, the operation of this embodiment will be described. FIG. 2 shows a time chart of the output levels of each part in FIG. 1. When the first charging device is connected to an AC source (charger), a charging voltage is applied to the storage battery 4. As shown in FIG. 2 TI, the terminal voltage VC of the storage battery 4 falls below the constant voltage V d e t.
Therefore, the detection signal Qv from the voltage detection section 6 is sent to the counter section 7.
Therefore, the current increase signal CI is given to the current control unit 2, and the charging current Ic to the storage battery 4 becomes the large current Ic2.
The level of As charging progresses and the terminal voltage vc of the storage battery 4 reaches a constant voltage V de t as shown in FIG. The counter section 7 starts counting.
When the terminal voltage VC of the storage battery 4 almost reaches the maximum peak voltage V*ax, the counter section 7 finishes counting as shown in FIG. 2 T3, and the current increase signal C from the counter section 7 is
I is no longer applied to the current control 882, and the charging current Ic to the storage battery 4 becomes the level of the small current Icl. thus,
The storage battery 4 can be charged accurately until the maximum peak voltage v wax is reached, and after charging is completed, a small current Icl that is sufficient to compensate for the natural discharge of the storage battery 4 is supplied to the storage battery 4. In addition to preventing potential drop, storage battery 4
It can also prevent overcharging. T4 to T7 in Figure 2 operate exactly the same as TI''T3 above, so their explanation will be omitted. Then, while the charging device is connected to the AC power source (charger), switch S is turned on to load the load. When power is supplied and discharged from the storage battery 4 to the storage battery 4, the terminal voltage VC of the storage battery 4 decreases and becomes a constant voltage V.
When the voltage drops below d e t, as shown in T8 in FIG.
I is applied, and charging by the large current Ic2 is restarted. When the constant voltage V det is recovered by this charging, counting is performed in the counter section 7 in the same way as T2 to T3 described above, and charging is performed to the maximum peak voltage v wax (T9 to Too in FIG. 2). ．． Thereafter, trickle charging is performed to compensate for the natural discharge due to the small current Icl (second
In this way, after charging is completed, even if power is supplied to the load 5 while the charging device is connected to the AC power source (charger), charging is automatically restarted without error by supplementing the power supplied to the load 5. It should be noted that the present invention is not limited to the above embodiments.
Various modifications can be made without departing from the spirit of the invention. [Effects of the Invention] As explained in detail above, the present invention detects the terminal voltage of the storage battery at a fixed constant voltage that is one step lower than the voltage at the completion of charging, which is easy to detect, and detects the terminal voltage of the storage battery after reaching this constant voltage. Since charging is continued with a large current until a certain period of time has elapsed, and after this period of time has elapsed, charging with a small current is performed, so detecting the terminal voltage of the storage battery is similar to detecting the maximum peak value of the voltage value. In order to detect the point at which the voltage value once rises and falls, the circuit structure is simplified and the equipment is This eliminates the possibility of misinterpreting a temporary voltage drop due to use as reaching the maximum peak value, making it possible to accurately detect charging completion. In addition, voltage detection is performed at a voltage one step lower than the maximum peak voltage.
The detection value set in the circuit changes slightly due to temperature changes and exceeds the maximum peak value even slightly, which prevents charging from being terminated.This has the effect of preventing overcharging. Play.

[Brief explanation of drawings]

Fig. 1 is an overall circuit diagram of the charging device, and Fig. 2 is a time chart showing the state of the output level of each part in Fig. 1.

Claims (1)

[Claims] A storage battery that can be used repeatedly by being repeatedly charged, and a voltage that detects whether the terminal voltage of this storage battery has reached a constant voltage lower than a predetermined voltage at the completion of charging due to charging or discharging. a detection means, a counting means for counting a predetermined fixed time from the time when the constant voltage is reached based on the detection result of the voltage detecting means, and a relatively long period of time until the counting means finishes the counting operation. A charging device comprising current control means for supplying current to the storage battery and supplying a relatively small current to the storage battery after the count operation ends.