JPS6359736A - Charging control circuit - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a charging control circuit for rechargeable vacuum cleaners and the like used in general households.

2. Description of the Related Art Conventionally, this type of charging control circuit has generally had the configuration shown in FIG. The conventional technology will be explained below based on the drawings.

FIG. 3 shows an embodiment of a conventional charging control circuit. In the figure, it is assumed that a charging adapter is connected to the child terminal and one terminal, and a pulsating current obtained by full-wave rectification of the AC power source is added to the child terminal and one terminal. Here, a main thyristor 1 and an N pond 2 are connected in series between the +2 and terminals. diode 3
is an element for preventing reverse discharge of the battery 2, and is inserted between the anode of the battery 2 and the cathode of the main thyristor 1.

The diode 4 and capacitor 5 are used to smooth the full-wave rectified pulsating current and maintain the on state when the second thyristor 6 is turned on. A gate resistor 7 is connected to the gate terminal of the main thyristor 1, and a gate sensitivity adjustment resistor 8 is connected between the gate and the cathode.

A Zener diode and a resistor 10 are connected in series between the cathode terminal (point P) of the main thyristor 1 and the GND terminal, and one end of the resistor 11 is connected to the connection point between the anode terminal of the Zener diode 9 and the resistor 10. The other end is connected to the gate terminal of the second thyristor 6.

Further, a resistor 12, 13 and a light emitting diode 14 are connected in series between both ends of the capacitor 5. Resistance 12.
The anode terminal of the diode 15 is connected to the connection point with the diode 13, and the cathode terminal at the other end is connected to the second thyristor 6.
connected to the anode terminal of the

Furthermore, between the anode and cathode of the main thyristor 1,
A resistor 16 is connected.

In the above circuit configuration, the main thyristor 1 is turned on because a gate current flows into the gate terminal from the DC power supply through the gate resistor 7. When the battery is uncharged, a charging current flows into the battery 2 via the main thyristor 1 and the diode 3 to maintain charging. At this time, the light emitting diode 14 lights up because a current flows through the resistor 12.13. Diode 15 is in a reverse biased state in this case and is therefore cut off.

Here, as battery 2 continues to be charged, the voltage between the terminals of battery 2 gradually increases, reaching a certain set potential (charging completion potential).
, the Zener diode 9 enters the saturation current region, a Zener current flows through the Zener diode 9, and the resistor 10
The voltage between the terminals of increases. When this inter-terminal voltage reaches the gate trigger voltage of the second thyristor 6, a gate current flows through the resistor 11, and the second thyristor 6 is turned on.

When the second thyristor 6 is turned on, the gate potential of the main thyristor 1 is pulled lower than the cathode potential, so the main thyristor 1 is turned off and charging is stopped. Further, the light emitting diode 14 also goes out because the diode 15 becomes conductive when the second thyristor 6 is turned on. Even if main thyristor 1 turns off, resistor 1
6, a weak current flows through the battery to perform supplementary charging.

FIG. 4 shows the charging characteristics of the circuit of FIG. 3.

From FIG. 4(A), it can be seen that the terminal voltage of the battery 2 increases over time, and when it reaches the set potential of the Zener diode 9, the main thyristor 1 is turned off. FIG. 4(B) shows the relationship between the charging current of the battery 2 and the time T, and it can be seen that the current is cut off when charging is completed.

However, since the supplementary charging of the resistor 16 is continued, the voltage across the terminals of the battery 2 rises again.

However, if the battery is left connected to a load (such as an electric blower) for a long time during use, the internal resistance of the battery will increase, and if the battery is left unused for one to three months, the internal resistance will increase to several hundred ohms. It also reaches.

If an attempt is made to charge such an over-discharged battery using the conventional charging circuit described above, inconveniences will occur. This situation is shown in FIG.

FIG. 5(A) shows a case where the internal resistance 17 of the battery 2 increases. When this battery 2 is connected to the charging circuit, since the resistance value R of the internal resistor 17 is large, when the charging current ■ flows, the apparent voltage between the terminals of the battery 2 increases, and as shown in FIG.
, C), charging is stopped immediately after charging starts. This is because the charging circuit shown in FIG. 3 detects the potential at point P. As described above, over-discharged batteries cannot be charged using conventional charging circuits, which has caused great dissatisfaction for users. Furthermore, in the market, although the overdischarge phenomenon of batteries is not a problem that occurs easily, if it occurs, the battery must be replaced, which is also problematic from an economical point of view.

Problems to be Solved by the Invention As described above, the conventional charging control circuit has the problem that it is not possible to charge an over-discharged battery. The present invention aims to overcome these conventional drawbacks and improve the charging control circuit so that even over-discharged batteries can be charged.

Means for Solving the Problem In order to solve this problem, the present invention maintains a main current control element and a rechargeable battery in series between the terminals of a DC power supply, and a detection circuit between both terminals of the battery. This detection circuit is provided with a first memory circuit and a second memory circuit that memorize the voltage of the battery, and a time difference is provided between the operations of these two memory circuits. Input the output to the comparator and
The main current control element is drive-controlled by the output of this comparator.

Effect With this configuration, for a battery in an over-discharged state, the voltage before the current is applied is input to the first memory circuit, the voltage after the current is applied to the second memory circuit, and the second memory circuit is inputted to the second memory circuit. An over-discharge state can be detected from the difference between the two voltages, and forced charging can be performed.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 and 2. In the figure, 21 is a voltage drop transformer, 22 is a rectifier circuit for converting the secondary current of the transformer 21 into direct current, 23 is a main current control transistor for charging, and 24 is a rechargeable battery such as a small sealed lead-acid battery. It is.

When the main current control transistor 23 is turned on, the current that has been stepped down by the transformer 21 and converted to direct current by the rectifier circuit 22 passes through the main current control transistor 23 to the battery 24.
Then, the battery 24 is charged. The magnitude of the current at this time is determined by the voltage and internal resistance of the battery 24 and the impedance of the transformer 21.

Further, 25 is a detection circuit, 26 is a drive transistor, and 21 is a light emitting diode. The voltage of the child terminal of the battery 24 is input to the a terminal of the detection circuit 25, the + side output of the rectifier circuit 22 is connected to the b terminal, and the base terminal of the drive transistor 26 is connected to the C terminal. , d terminals are connected to one terminal of the rectifier circuit 22 via a common ground line.

When the drive transistor 26 is turned on, a base current flows to the main current control transistor 23 through the current limiting resistor 28 and the light emitting diode 21, and the main current control transistor 23 is also turned on. light emitting diode 27
This indicates that the main current control transistor 23 is in the on state and the battery 24 is being charged, and also raises the level of the emitter of the drive transistor 26 to stabilize the off state.

Further, 28 is a resistor for stabilizing the off state of the main current control transistor 23, and a resistor 29 is a resistor for supplying the base current of the drive transistor 26.
This resistor 29 and capacitor 30 form a delay circuit,
A time lag is provided between when the power is turned on and when the drive transistor 26 is turned on.

FIG. 2 is a circuit diagram showing in detail the contents of the detection circuit 25, and the terminals a to d correspond to the terminals a to d in FIG. 1. 51 is a first memory circuit, and 52 is a second memory circuit, which stores the voltage between the terminals of the battery 24.

The first storage circuit 51 works first and stores the voltage across the terminals of the battery 24. 1st. Both values stored in the second storage circuits 51 and 52 are compared by a comparator 53 and outputted from the cli element through a latch circuit 54.

On the other hand, a time constant circuit is formed by the resistor 55 and the capacitor 56, and a delay time is provided for the operation of the third transistor 57. When this third transistor 57 is turned on, a current determined by the constant current control device 58 flows into the battery 24 via the a terminal.

The operation of this embodiment having the above configuration will be explained.

First, when the power is turned on, drive transistor 2
9 and the third transistor 57 are not turned on immediately, so no current flows through the battery 24 yet.

At this time, the first memory circuit 51 stores the battery 24 in the open state.
voltage is stored.

Next, the third transistor 57 is turned on, a current determined by the low current control device 58 flows through the battery 24, and the voltage of the battery 24 at that time is input to the second storage circuit 52.

When the battery 24 is in an over-discharged state, its internal resistance has increased, so there is a large difference between the voltage when it is open and the voltage when current is flowing. Therefore, when the difference is detected by the comparator 53, it is determined that the battery 24 is in an over-discharged state, and the latch circuit 54 operates to maintain the C terminal in the oven state. Therefore, a base current flows through the drive transistor 26 due to the resistor 29, the main current control transistor 23 is turned on, and a current flows through the battery 24 regardless of its voltage. By continuing to supply current in this manner, the internal resistance of the battery 24 gradually decreases and returns to its normal state.

Electric i'l! ! 24 is in a normal state, the voltage of the aQ terminal increases during charging, and when the battery is fully charged, the latch circuit 54 lowers the C terminal to a low level through the comparator 53. Then, drive transistor 2
6 is turned off, the main current suppressing transistor 23 is also turned off, and charging is completed.

In this way, even if the battery has been over-discharged due to user carelessness or due to the battery being left in a discharged state for a long time, it will take a little more time to recover, but it will not last long after use. It becomes possible to restore the battery to a fully charged state without requiring the user to perform any special operations. Also, during this time, the light emitting diode remains lit to indicate that charging is in progress.

Although this embodiment shows an example in which a transistor is used as the main current control element, it goes without saying that similar effects can be obtained with other switching elements such as thyristors and relays.

Effects of the Invention As is clear from the above explanation, according to the present invention, two circuits are provided for detecting and storing the battery voltage, one of which receives the voltage when it is open, and the other which receives the voltage when the current is applied. Inputs the voltage and compares both to determine whether or not it is over-discharged.If it is over-discharged, by performing forced charging, even an over-discharged battery can be returned to its normal state and then fully charged. be able to. As a result, the usability of the device is improved and the reliability is also improved.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a charging control circuit according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing main parts of the circuit in detail,
Figure 3 is a circuit diagram showing an example of a conventional charging control circuit.
Figures (A, B) and Fig. 5 (A, B, C) are graphs showing the state of charging according to the conventional example. 21... Transformer 22... Rectifier circuit 23...
Main current control transistor 24...Battery 25...
Detection circuit 16 Drive transistor 51... First memory circuit 52... Second memory circuit 53...
Comparator 54...Latch circuit 2]--Transformer Fig. 1 Fig. 2 Fig. 3 Fig. 4

Claims (2)

[Claims] (1) A main current control element and a rechargeable battery are connected in series between the terminals of a DC power supply, a detection circuit is connected between both terminals of the battery, and the voltage of the battery is stored in this detection circuit. A first memory circuit and a second memory circuit are provided, a time difference is provided between the operations of these two memory circuits, and the outputs of these two memory circuits are input to a comparator. A charging control circuit characterized by being configured to control a main current control element. (2) One memory circuit of the detection circuit memorizes the voltage across the terminals of the battery before charging current flows through the battery, and the other memory circuit memorizes the voltage across the battery terminals when charging current flows. Claim (1) wherein the comparison circuit is configured to compare these two storage voltages and maintain the main current control element in the drive state when a difference of more than a predetermined value is found.
The charging control circuit described in section.