JPS6352644A - Battery charger - 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] Industrial Application Field The present invention detects a peak point that appears in the charging voltage characteristics of a battery, and after detecting this peak point, the charging voltage of the battery remains lower than the peak point voltage for an arbitrarily set period of time. This invention relates to a battery charging control device that stops rapid charging using a large current and switches to trickle charging using a small current, or completely prevents the charging current from flowing, when the charging current continues.

Conventional technology In recent years, when the voltage drops by a predetermined voltage (hereinafter referred to as -ΔV lightning voltage) from the peak point that appears in the charging voltage characteristics of a battery, rapid charging using a large current is stopped and switching to trickle charging using a trickle current, or A charging device equipped with a method (hereinafter referred to as a -ΔV control method) that prevents the charging current from flowing completely is widely used as a charging system for portable electronic devices.

Hereinafter, with reference to the drawings, the conventional −Δ
Description of the charging device using the V control method Figure 3 shows the circuit configuration of a conventional charging device using the -ΔV control method. In FIG. 3, 1 is a Zener diode ZD1. ZD2, a voltage dividing circuit consisting of a resistor R1, 2 a filter circuit consisting of a resistor R2 and a capacitor C1, 3
is a ΔV detection control circuit consisting of a resistor R5, a capacitor C2, a diode D+, an operational amplifier OP1, and switches S+ and S2; 4 is a DC power supply; and 5 is a battery to be charged.

The operation of the conventional -ΔV control system charging device configured as described above will be explained with reference to FIGS. 3 and 4.

First, before charging starts, switch S1 is open, switch S
2 is in a conductive state and capacitor C2 is discharged. Next, when charging starts, the switch S1 becomes conductive, the switch S2 becomes open, and the terminal voltage vB of the battery 6 to be charged is determined by a voltage divider circuit consisting of a Zener diode ZD<, a resistor R+, and a Zener diode ZD2 connected in series. The pressure is divided by 1.

The divided voltage VPj at the connection point P1 between the Zener diode ZD+ and the resistor R1 is the voltage obtained by subtracting the Zener voltage "ZDj of the Zener diode ZD" from the terminal voltage VBATT of the battery, and the voltage between the Zener diode ZD2 and the resistor R
The voltage vP4 at the connection point P4 of 1 is the Zener diode Z
The Zener voltage of D2 becomes 'l'ZD2 and is constant. From the start of charging until the terminal voltage of the battery reaches the peak point color, the divided voltage "Pl" increases corresponding to the terminal voltage of the battery, but the voltage at the connection point P between the resistor R3 and the capacitor C2 increases.
2 voltage Vp2H rises with a delay determined by the time constant of the filter circuit 2 consisting of the resistor R2, the capacitor C1, the resistor Rs, and the time constant of the capacitor C2. In this way, the divided voltage "l" at the voltage dividing point P1 increases as shown in FIG. The connection point P2
When the voltage VP2 is greater than the voltage VP2, the capacitor C2 is charged and a one-vertical voltage drop occurs across the diode D1.

When the forward voltage '/D1 of the diode D1 is positive, the operational amplifier P1 which receives these voltages as input outputs a voltage that satisfies the input condition (CVps>Vpa). This voltage causes the switch S1 to remain conductive, allowing rapid charging to continue.

When the terminal voltage of the battery passes the peak point a, the voltage 'l'PI at the voltage dividing point P1 drops in accordance with the terminal voltage of the battery, but the voltage VP2 at the connection point P2 decreases below the voltage dividing point P1. The voltage increases until there is no voltage difference with the voltage Vl at point P1. When the voltage VP2 at the connection point P2 is rising, the capacitor C2 is charged and the forward voltage vD1 is generated in the diode D1, so that rapid charging continues as described above. The voltage VPt at the voltage dividing point P1 and the connection point P2
When the voltage ``P2'' becomes equal, capacitor C2 is no longer charged, and the terminal voltage VC2 of p1 capacitor C2 becomes the maximum value V.
C2MAI and υ, forward voltage VD1 of diode D1
becomes zero. Further, when the rapid charging continues and the terminal voltage of the battery drops, the voltage "P2" at the connection point P2 has a delay determined by the time constant of the filter circuit 2 with respect to the drop in the voltage Vl+ at the voltage dividing point P1. However, the capacitor C2 is prevented from discharging by the diode D19, and the terminal voltage VO2 of the capacitor C2 continues to hold the maximum value VC2MAI, and the voltage VP3 at the connection point P3 is equal to the voltage VP2 at the connection point P2. As a result, the voltage Vp5 at the connection point P3 becomes smaller than the voltage VP4 at the connection point P4, and the operational amplifier OP+, which receives these voltages as input, meets the input condition (Vp s
<Vp 4) A voltage satisfying 4) is output to the switch S1. This causes the switch S1 to be in an open state, and rapid charging is stopped.

Problems to be Solved by the Invention Recently, there has been an increasing demand for a charging device with a small -ΔV voltage due to a decrease in the number of batteries connected in series due to a decrease in the power supply voltage of electronic devices. However, in the above configuration, the time constant determined by resistor R2, capacitor C+, resistor R3, and capacitor C2 is set large in order to prevent malfunctions when the terminal voltage of the charged battery is flat. Since the voltage drop in the forward direction of the diode D1 is relatively large, the -ΔV voltage is large, and there is a problem that it cannot be set arbitrarily.

In view of the above problems, the present invention provides a battery charging device that can arbitrarily set the -ΔY voltage.

Means for Solving the Problems To achieve this objective, the battery charging device of the present invention comprises:
a first voltage divider circuit provided between both terminals of the battery to be charged;
a peak point detection circuit that stores a divided voltage corresponding to the charging voltage of the battery and detects a peak point appearing in the charging voltage characteristic of the battery by comparing the stored voltage with the divided voltage; and the peak inspection circuit. and a control circuit that stops rapid charging when the charging voltage of the battery continues to be lower than the peak point voltage for an arbitrary period of time after charging.

Effect Since there is a positive correlation between the time from the peak point detection to the charge control operation and -ΔV electric pressure, the time from the peak point detection to the charge control operation in the above configuration can be set arbitrarily. By setting -ΔV electric pressure, it is possible to arbitrarily set the voltage to 0.Example Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit configuration of a battery charging device according to an embodiment of the present invention.

In Figure 1, 1 is a Zener diode π1, a resistor R
1 is a first voltage dividing circuit, and 2 is a first operational amplifier OP.
+, diode D+, capacitor C (resistance R2, R3,
A peak point detection circuit consisting of a switch S2, 3 a transistor Q1, and resistors Ra and Rs.

A control circuit consisting of R6, capacitor C2, second operational amplifier OP2, and switch S1, 4 is a DC power supply, and 5 is a battery to be charged.0 Regarding the operation of the battery charging device configured as above, FIG. This will be explained using FIG. First, before charging starts, the switch S1 is in an open state, the switch S2 is in a conductive state, and the capacitor C1 is discharged. Next, when charging is started, the switch S1 becomes conductive, the switch S2 becomes open, the terminal voltage of the battery 5 to be charged is divided by the first voltage dividing circuit 1, and the voltage dividing point P1 is connected to the terminal voltage of the battery 5. Terminal voltage vB
Zener voltage v of Zener diode ZIh from mu τ
A divided voltage Vl obtained by subtracting ZDj is applied. This divided voltage VPj is applied to the non-inverting input terminal of the first operational amplifier OPt, and the capacitor C1, which has been in a discharged state, remains at the output point P of the operational amplifier OP+ until it becomes equal to the divided voltage VP+.
5. Instantly charged via diode D1. Terminal voltage of capacitor C1 (inverting input voltage of operational amplifier OF+)
A voltage vps, which is the sum of the divided voltage VPi and the forward voltage VDI of the diode D1, is applied to the output point P5 of the operational amplifier OP+ so that Vp2 and the divided voltage Vl are equal.

This voltage P3 biases the base of the transistor Q1 connected to the voltage dividing point of the second voltage dividing circuit 6 consisting of resistors R2 and R3, and this transistor Q1 becomes conductive. The capacitor C2 of the timer circuit 7 consisting of R4 and the capacitor C2 is in a discharged state, and the terminal voltage VP4 at the voltage dividing point P4 becomes almost zero potential.

At this time, the voltage VPS at the voltage dividing point P5 of the third voltage dividing circuit 8 consisting of resistors R5 and R6 is the terminal voltage vp of the capacitor C2.
4, second operational amplifier OP2:l:Vps
A voltage satisfying the relationship >Vpa is output to the switch S1, and the switch S1 maintains a conductive state to continue rapid charging. This state is maintained until the terminal voltage of the battery reaches the peak point a. When the terminal voltage of the battery passes the peak point a, the first divided voltage "Pl" becomes smaller than the terminal voltage VP2 of the capacitor C1, and the first operational amplifier OP+
The output voltage VPS becomes almost zero potential.

As a result, the base voltage of the transistor Q1 also becomes approximately zero potential, and the transistor Q1 becomes an open state. Therefore, the terminal voltage vP4 of the capacitor C2 of the timer circuit 7 consisting of the resistor R4 and the capacitor C2 is gradually charged with a time constant determined by the resistor R4 and the capacitor C2, and the resistor R5,
When the voltage becomes larger than the divided voltage VP5 of the third voltage dividing circuit made up of R6, the output of the second operational amplifier OP2 is inverted, the switch S1 becomes open, and rapid charging is stopped.

As described above, according to this embodiment, by arbitrarily setting the constant of the timer circuit 7 consisting of the resistor R4 and the capacitor C2 and the constant of the third voltage dividing circuit 8 consisting of the resistors Rs and Rg, the battery to be charged can be charged. It becomes possible to arbitrarily set the time t from when the peak point appearing in the terminal voltage of .

In this embodiment, the third voltage dividing circuit 8 of the control circuit 3 and the timer circuit are connected between the terminals of the battery to be charged, but they may be connected between other reference voltage terminals.

Effects of the Invention As described above, the present invention includes a first voltage dividing circuit provided between both terminals of a battery to be charged, a divided voltage corresponding to the charging voltage of the battery, and a divided voltage corresponding to the charging voltage of the battery. a peak point detection circuit that detects a peak point that appears on the charging characteristics of the battery by comparing the peak points; and after detecting the peak point, the charging voltage of the battery continues to be lower than the peak voltage for an arbitrary period of time. The device is equipped with a control circuit that controls quick charging by controlling the rapid charging, and by arbitrarily setting the time from the detection of the peak point until the quick charging is controlled, the -ΔV voltage that has a positive correlation with the above-mentioned time can be set. Since it can be set arbitrarily, -ΔV voltage is lower than before.
A charging device using the ΔV control method can be realized, and the practical effects are significant.

[Brief explanation of the drawing]

Fig. 1 shows the circuit of the battery charging device according to the present invention, Fig. 2 shows the charging characteristics of the battery by the same charging device, Fig. 3 shows the circuit diagram of the conventional charging device, and Fig. 4 corresponds to Fig. 2. This is a diagram of the conventional charging characteristics. 1...First voltage dividing circuit, 2...Peak point detection circuit, 3...Control circuit, 6...-
Second voltage dividing circuit, 7... Timer circuit, 8...
...Third voltage divider circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure/-Pe supination 2-Fi 2 leg-Danro 3--△V Io 1B and town bo tein detour] N each - 4-1 Chang's door 3 6- View 45 3 Figure No. Figure 4

Claims (3)

[Claims] (1) A first voltage dividing circuit provided between both terminals of the battery to be charged and a divided voltage corresponding to the battery voltage are memorized, and the stored voltage and the divided voltage are compared to A peak point detection circuit that detects a peak point appearing in charging voltage characteristics; and a control circuit that stops rapid charging when the battery voltage continues to be lower than the peak point voltage for an arbitrary period of time after detecting the peak point. battery charging device. (2) The peak point detection circuit connects the voltage dividing point of the first voltage dividing circuit and the non-inverting input terminal of the operational amplifier, and connects a diode between the output terminal and the inverting input terminal of the operational amplifier so that its anode side is The inverting input terminal of the operational amplifier is connected to the output terminal side of the operational amplifier, the inverting input terminal of the operational amplifier is grounded via a capacitor, and the output terminal of the operational amplifier is grounded via a second voltage dividing circuit. 2. The battery charging device according to claim 1, wherein a peak point appearing in charging voltage characteristics of the battery is detected based on the output voltage of the operational amplifier. (3) The control circuit connects the voltage dividing point of the voltage dividing circuit in the peak point detection circuit to the base of the transistor, grounds the emitter of the transistor, and connects a timer circuit consisting of a resistor and a capacitor between both terminals of the battery. the collector of the transistor is connected to the connection point of the resistor and the capacitor, the connection point of the resistor and the capacitor is connected to one input terminal of the operational amplifier, and the collector of the transistor is connected between both terminals of the battery. The voltage dividing point of the third voltage dividing circuit is connected to the other input terminal of the operational amplifier, and the output terminal of the operational amplifier is connected to a switch that controls the charging current, the timer circuit and the 2. The battery charging device according to claim 1, wherein the time from detection of the peak point until rapid charging is stopped can be arbitrarily set by selecting a constant of the third voltage dividing circuit.