JPH01270742A - Charging circuit for storage battery - Google Patents

Abstract

PURPOSE:To obtain a suitable charging amount without excessive or insufficient charge by controlling the charge of a storage battery on the basis of the detected value of the output voltage of a differentiator for obtaining a differentiated value for the timing change of the terminal voltage of the battery. CONSTITUTION:When a start pulse generated at the time of turning ON a power source of a charging circuit is applied to the set terminal S of an FF 11, an output terminal Q becomes a high level, and a charge controller 2 becomes a quickly charging state. The output voltage Vout of a differentiator 4 for differentiating the terminal voltage VB of a storage battery 1 is input to a detector 9, and compared with a reference voltage Vth1 by a voltage comparator 10. When it becomes the Vout < the Vth1 at the end of charging (point P1), the output of the detector 9 becomes a low level. Accordingly, the FF 11 becomes a reset state. Since the output terminal Q of the FF 11 becomes a low level in the reset state, the controller 2 becomes a charge control state to stop charging of the battery 1 or to reduce charging current.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a charging circuit for a storage battery, and particularly to a charging circuit that controls charging by detecting a terminal voltage of a storage battery or a differential value with respect to a time change in a voltage proportional to this. Regarding circuits.

(Prior art) Various methods are known for charging storage batteries, but one method used in particular for rapid charging is to control charging by detecting the differential value of the terminal voltage of the storage battery with respect to time changes during charging. There is a way to stop charging or reduce charging current. A specific example of this method is described in, for example, Japanese Patent Publication No. 61-5339. In this conventional technology, a differentiating circuit consisting of a series circuit of a capacitor and a resistor is connected across the battery, and the output voltage of this differentiating circuit (the voltage at the connection point between the resistor and the capacitor) is higher than the trough voltage that occurs before the peak. Charging is stopped when the voltage drops to a low predetermined value.

(Problem to be Solved by the Invention) In the prior art, the output voltage v out of a differentiator circuit consisting of a series circuit of a resistor and a capacitor is as follows: where R is the resistance value, C is the capacitance value of the capacitor, and VB is the terminal voltage of the storage battery. It is expressed by the following formula (1).

Vout -R-C (dVB/clt -dVout/
dt) - (1) The exact differential value of the terminal voltage VB is given by the formula (1
), and the second term is the error. The influence of this error increases as the RCO value increases.

Here, since the time change of the terminal voltage VB of the storage battery is generally small, in order to detect its differential value with a differentiator circuit, R
It is necessary to significantly increase the value of C (time constant) to several tens of seconds. As a result, the above error increases,
Accurate differential output of VB cannot be obtained.

Therefore, it is not only difficult to appropriately control the amount of charge of the storage battery, but also the output voltage of the differentiator circuit V ou
There have been cases where t has reached a predetermined value, resulting in a significant charging shortage.

(Means for Solving the Problems) A storage battery charging circuit according to the present invention includes a differential circuit for obtaining a differential value with respect to a time change of a terminal voltage of a storage battery or a voltage proportional to the terminal voltage, an operational amplifier, and an inverting input of the operational amplifier. It mainly consists of a capacitor connected between the terminal and the input terminal of the differentiating circuit, and a resistor connected between the inverting input terminal and the output terminal of the operational amplifier, and detects the output voltage of this differentiating circuit. The charging of the storage battery is controlled based on the output of the detection circuit.

(Function) In the present invention, the output voltage of the differentiating circuit is determined by setting the resistance value to R,
If the capacitance value of the capacitor is C1 and the terminal voltage of the storage battery is VB, it becomes C-R (dV B/dt), that is, a value proportional to the exact differential value of VB, which was included in the output of the differential circuit in the conventional technology. An error term corresponding to the differential value of the output of the differentiating circuit itself is not included.

Therefore, the output voltage V out of this differentiating circuit decreases to a predetermined value lower than the trough voltage that occurs before the peak, or v out reaches a predetermined value, or v
If the detection circuit detects that out has decreased by a predetermined value or a predetermined rate from the maximum value and controls charging, an appropriate amount of charge can be obtained.

(Embodiment) FIG. 1 shows a charging circuit for a storage battery according to an embodiment of the present invention.

In FIG. 1, a storage battery 1 is connected to a charging power source 3 via a charging control circuit 2. As shown in FIG. The charging control circuit 2 is composed of, for example, a switching circuit. As the charging power source 2, a DC power source that rectifies an AC power source to obtain a direct current, or another relatively large capacity battery is used.

A differentiation circuit 4 is further connected to the storage battery 1 . This differentiating circuit 4 is not just a CR differentiating circuit as in the prior art, but is composed of a differential calculation circuit 5 and an inverting amplifier circuit 6.

The differential calculation circuit 5 includes an operational amplifier 7 whose non-inverting input terminal is grounded, and an inverting input terminal of the operational amplifier 7 and the differential circuit 4.
A series circuit of a resistor R1 and a capacitor C1 is connected between the input terminal a (one end of the storage battery 1), and a resistor R2 is connected between the inverting input terminal and the output terminal of the operational amplifier 7.
It consists of a parallel circuit of a capacitor C2, and an operational amplifier 7.
The output terminal of the differential calculation circuit 5 is the output terminal of the differential calculation circuit 5. Note that the resistor R1 and capacitor C2 are provided to stabilize the operation of the differential calculation circuit 5, and are not necessarily necessary.

On the other hand, the inverting amplifier circuit 6 includes an operational amplifier 8 whose non-inverting input terminal is grounded, a resistor R3 connected between the inverting input terminal of the operational amplifier 8 and the input terminal C of the inverting amplifier circuit 6;
and a resistor R4 connected between the inverting input terminal and the output terminal of the operational amplifier 8, and the output terminal of the operational amplifier 8 serves as the output terminal d of the inverting amplifier circuit 6.

Here, if the terminal voltage of the storage battery 1 is VB, the output voltage Vl of the differential calculation circuit 5 is Vl - - C1 - R2 (dVB/dt), and the amplification factor A of the inverting amplifier circuit 6 is A - - Since R4/R3, the output voltage v out of the differentiating circuit 4 is expressed by the following equation (3).

Vout-A-C1・R2(dVB/dt)=
13) This is the same as Equation (2) (C-C1, R-R2), and v out does not include an error term and is a value exactly proportional to the differential value of VB with respect to time change.

Output terminal of the differentiating circuit 4 (output terminal d of the inverting amplifier circuit 6)
is connected to the input terminal e of the detection circuit 9. In this example, the detection circuit 9 is constituted by a voltage comparator 10, and the non-inverting input terminal of the voltage comparator 10 is connected to the input terminal e of the detection circuit 9.
In addition, the output terminal is connected to the output terminal f of the detection circuit 9. Further, a reference voltage v thi is applied to the inverting input terminal of the voltage comparator 10.

The output terminal f of the detection circuit 9 is connected to the flip-flop circuit 11.
is connected to the reset terminal R of. A start pulse is applied to the set terminal S of the flip-flop circuit 11, which is generated when the power is turned on or in conjunction with the operation of a switch or the like. An output terminal Q of the flip-flora circuit 11 is connected to a control input terminal of the charging control circuit 2.

The charging control circuit 2 enters a rapid charging state when the output terminal Q of the flip-flop circuit 11 is at a high level, and enters a charging control state when the output terminal Q is at a low level. In the charging control state, charging of the storage battery 1 is completely stopped or the charging current is reduced.

Next, the operation of the charging circuit shown in FIG. 1 will be explained with reference to the voltage waveform shown in FIG. 2.

When a start pulse generated when the charging circuit is powered on or in conjunction with the operation of a switch, etc. is applied to the set terminal S of the flip-flop circuit 11, the output terminal Q of the flip-flop 11 goes to a high level, and the charging control circuit 2 quickly It will be in a charging state. In this state, a large current is supplied from the charging power source 3 to the storage battery 1, and rapid charging is started. At this time, the terminal voltage VB of the storage battery 1 gradually increases as the charging time passes, as shown in FIG. 2(a). As charging progresses to the end of charging, VB rises rapidly, eventually reaches a peak, and then gradually decreases.

In accordance with such changes in the terminal voltage VB of the storage battery 1, the output voltage v out of the differentiating circuit 4 changes as shown in FIG. 2(b). The output voltage V out of the differentiating circuit 4 is input to the detection circuit 9 and compared with the reference voltage V thl by the voltage comparator 1o. The reference voltage v tht is set to a value lower than the trough voltage VL that occurs before the output voltage V out of the differentiating circuit 4 reaches its peak (point P). At the end of charging, when V out < V thl (point P1), the output of the detection circuit 9 becomes low level, so the flip-flop circuit 11 enters the reset state. Since the output terminal Q of the flip-flop circuit 11 is at a low level in the reset state, the charging control circuit 2 enters the charging control state and stops charging the storage battery 1 or reduces the charging current.

In this way, 1, in the present invention, the terminal voltage VB of the storage battery 1
Since an accurate differential value with respect to the time change of is obtained by the differentiating circuit 4, when the output voltage v out of the differentiating circuit 4 falls below the set value given by the reference voltage V thl, charging control is performed to charge the storage battery 1. It is possible to charge an appropriate amount without causing insufficient charging or the like.

The present invention is not limited to the embodiments described above. For example, in FIG.
A reference voltage V thl that is lower than the valley point voltage VL that occurs before reaching the point Vout is applied, and charging control is performed when Vout < Vthl.
It may be configured as shown in FIGS.

In FIG. 3, the voltage comparator 1 constituting the detection circuit 9
The output terminal of the differentiating circuit 4 is connected to the inverting input terminal of 0, and the reference voltage V th2 is applied to the non-inverting input terminal. As shown in FIG. 2(b), this reference voltage V th2 is higher than the trough voltage VL that occurs before the output voltage V out of the differentiator circuit 4 reaches the peak value VP (and lower than the peak value vP). It is set.

In this case, charging progresses to the final stage of charging, and v ou
Charging control may be performed at 22 points in FIG. 2(b) where t > v thz. In this way, it is possible to prevent overcharging between points P and PL, which is a problem when charging in a shorter time (less than 1 hour) by increasing the charging current, and the battery life is not impaired.

FIG. 4 shows the output voltage v out of the differentiating circuit 4 and this v
Output voltage Vh of the peak holding circuit 12 that holds the maximum value of the voltage obtained by shifting out in the lower direction by a minute voltage ΔV
1 is compared with the voltage comparator 10, and based on the comparison result of the voltage comparator 10, it is determined that Vout<vht as shown in FIG.
Charging control is performed at 23 points in b).

In addition, FIG. 5 shows the output voltage V out of the differentiating circuit 4 and the voltage V out obtained by dividing this v out by resistors R5 and R6.
The output voltage V of the peak holding circuit 13 that holds the maximum value of d
th2 with the voltage comparator 10, and based on the comparison result of the voltage comparator 10, Volt<Vh2, that is, the 24 points in FIG. 2(b) where the output voltage Vout of the differentiating circuit 4 decreases by a predetermined rate. Charging control is performed using

Note that the charging control point P3. when using the detection circuits 9 of FIGS. 4 and 5 respectively. P4 is close to point P, which is the peak point, and close to each other.

Therefore, according to these embodiments, it is possible to prevent overcharging between points P and PL, which is a problem when charging is performed in a shorter time (for example, less than one hour) by increasing the charging current. This not only prevents the battery life from being degraded, but also detects the point in time when the output voltage v out of the differentiator circuit 4 passes the peak value vP and begins to fall, so charging Km can be done appropriately and more reliably. This makes it possible to perform charging control.

In the above embodiment, the differentiator circuit 4 is constituted by the differential arithmetic circuit 5 and the inverting amplifier circuit 6, but the inverting amplifying circuit 6 may not be used and the output of the differential arithmetic circuit 5 may be input directly to the detection circuit. In that case, the polarity of the reference voltage may be changed in the detection circuit.

Further, the charging control based on the present invention can also be implemented in combination with various conventional charging control methods such as timer control, voltage control, and temperature control.

In addition, the present invention can be implemented with various modifications without departing from the scope.

(Effects of the Invention) According to the present invention, by configuring a differential circuit that obtains a differential value with respect to a time change in terminal voltage of a storage battery or a voltage proportional to the terminal voltage of a storage battery using a differential operation circuit consisting of an operational amplifier, a capacitor, and a resistor, It is possible to obtain a value proportional to the accurate differential value of the terminal voltage of the differential circuit, so by controlling the charging of the storage battery based on the output of the detection circuit that detects the output voltage of this differentiating circuit, it is possible to prevent over- or under-charging. There is no charge, and the appropriate amount of charge is always obtained.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a storage battery charging circuit according to an embodiment of the present invention, Fig. 2 is a voltage waveform diagram for explaining the operation of the embodiment, and Figs. It is a figure showing an example of composition. DESCRIPTION OF SYMBOLS 1... Storage battery, 2... Charging control circuit, 3... Charging power supply, 4... Differential circuit, 5... Differential calculation circuit, 6
... Inverting amplifier circuit, 7.8... Operational amplifier, 9...
・Detection circuit. Applicant's agent Patent attorney Takehiko Suzue Figure 2

Claims (1)

[Scope of Claims] A differentiation circuit that obtains a differential value with respect to a time change in a terminal voltage of a storage battery or a voltage proportional to the voltage, a detection means for detecting the output voltage of the differentiation circuit, and a detection means for detecting the output voltage of the storage battery based on the output of the detection means. A storage battery charging circuit comprising: a charging control means for controlling charging of a storage battery, wherein the differentiating circuit includes an operational amplifier; a capacitor connected between an inverting input terminal of the operational amplifier and an input terminal of the differentiating circuit; A storage battery charging circuit comprising a resistor connected between an inverting input terminal and an output terminal of the operational amplifier.