JP2010041797A - Battery charger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the reduction in a charge amount more than required by preventing battery overcharging. <P>SOLUTION: A battery is charged by tuning on a switching element FET connected between a DC power supply 2a and the battery BT only during a battery voltage is reduced to be lower than the maximum value of a pulsating voltage, in comparison between the battery voltage Vb and the pulsating voltage. Since the charge amount changes, according to the difference when the battery voltage is reduced with respect to a full charge voltage, charge current supply time is shortened, as the battery reaches closer to full charge, and thereby there is no occurrence of battery overcharging. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a battery charger suitable for charging an in-vehicle battery.

  2. Description of the Related Art Conventionally, for example, an onboard battery for a motorcycle is small and has a small charge capacity. Therefore, the amount of charge may be reduced due to spontaneous discharge during the winter season when the battery tends to be left unused. Moreover, since the amount of charge decreases even in a short period when the battery capacity decreases, there is a battery charger for performing such charging when left unattended.

As a charge control in the battery charger, there is one that stops charging when a predetermined overcharge voltage is exceeded to protect the battery. For example, a first threshold value and a lower second threshold value are set, an overcharge voltage is set as the first threshold value as an initial state, and if the battery voltage exceeds the first threshold value, it is regarded as overcharge. There is one in which the overcharge voltage is switched to a second threshold value and control is performed so as to return to the initial state when the battery is discharged (see, for example, Patent Document 1).
JP 2005-80347 A

  However, in Patent Document 1, since charging is stopped after overcharging is detected, there is a problem that the battery may be overcharged, which may cause deterioration.

  On the other hand, in order to prevent overcharging as much as possible in charging the battery, there is charging to a specified voltage by a constant voltage power source. Alternatively, it is desirable that charging is performed to a specified voltage by a constant current power source, for example, charging to near full charge with a current of about 1/10 of the capacity, and then charging is terminated.

  However, when full charge is reached and charging is stopped, the battery is discharged again after being left for a long period of time. Therefore, discharging and charging are repeated, and frequent discharging may also have an adverse effect on battery life. . There is a charger that continues the charging current even after full charge is reached, but in that case, overcharging occurs, causing damage or deterioration of the battery.

  In order to solve such a problem, to prevent overcharge of the battery, and to prevent a decrease in the amount of charge more than necessary, in the present invention, the charging device body, and the charging device body and the power source are connected. A battery charging device having a power connection cable and a battery connection cable for connecting the charging device main body and the battery, wherein the charging device main body is turned on when charging the battery with electric power from the power source. Pulsating voltage generating means for outputting a pulsating voltage that rises and falls in a predetermined cycle between a first voltage lower than the full charge voltage of the battery and a second voltage corresponding to the full charge voltage, and the voltage of the battery Comparing with the pulsation voltage, the battery control device includes a charge control unit that turns on the switching unit only while the voltage of the battery is lower than the pulsation voltage.

  In particular, a constant current circuit for making a charging current constant is connected to the negative terminal of the battery, and the voltage of the battery is preferably calculated by subtracting the voltage of the negative terminal from the voltage of the positive terminal of the battery. . In addition, it is preferable that dark current supply means for supplying dark current to the battery when the switching means is off is provided.

  As described above, according to the present invention, when charging the battery, the battery voltage is compared with the pulsation voltage that rises and falls between the first voltage and the second voltage, and the battery voltage is reduced with respect to the full charge voltage. Since the amount of charge is changed according to the difference, the charging current supply time is shortened as the battery approaches full charge, so that battery charging without overcharging can be performed.

  Further, according to claim 2, by connecting a constant current circuit to the negative terminal of the battery and charging with a constant current, a voltage difference between the positive terminal and the negative terminal of the battery can be reduced. Stable charging can be performed without changing as in the case of use. According to the third aspect of the present invention, even when the switching means is turned off due to full charge, natural discharge can be prevented by flowing dark current through the battery.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an overall explanatory view showing a usage state of a battery charging device for charging an in-vehicle battery BT of a motorcycle M to which the present invention is applied. As shown in FIG. 1, the battery charging device 1 includes a charging device body 2, a power connection cable 3, and a battery connection cable 4. The in-vehicle battery BT is, for example, a general 12V lead battery for a motorcycle, and includes a positive terminal and a negative terminal.

  One end of the power connection cable 3 is connected to the charging device main body 2, and the other end is connected to an outlet PW as a power source, for example, a 100 V commercial AC power source for a single family by a known plug 3 b. One end of the battery connection cable 4 is connected to the charging device body 2 and the other end is connected to the in-vehicle battery BT.

  The charging device main body 2 has a box shape as shown in FIG. A power supply terminal hole 5a for detachably connecting a terminal 3a provided at one end of the power connection cable 3 and a terminal 4a provided at one end of the battery connection cable 4 are detachable on the side surface of the charging device main body 2. And a battery terminal hole 5b for connection to the battery. The other end of the battery connection cable 4 is provided with a terminal 4b made of, for example, two alligator clips that can be connected to the positive and negative terminals of the in-vehicle battery BT.

  On the surface of the charging device main body 2, a monitor 23 for displaying the battery voltage of the in-vehicle battery BT, an indicator lamp 24 for indicating that the in-vehicle battery BT is being charged, and charging of the in-vehicle battery BT has been completed. May be provided. The indicator lamps 24 and 25 may be LEDs, for example. Note that these controls can be easily configured from a circuit to be described later, and are omitted because they are not directly related to the present invention.

  Next, a circuit configuration of the battery charging device 1 will be described with reference to FIG. FIG. 3 shows a state in which the power source PW and the in-vehicle battery BT are connected. As shown in FIG. 3, in the battery charger 1, switching means for appropriately connecting the DC power source 2 a to which the power connection cable 3 is connected, and the DC power source 2 a and the positive terminal (+) of the battery BT. As a switching element FET, a charge control circuit 2b for controlling the gate of the switching element FET, a smoothing circuit CR and a constant circuit connected to a line connecting the negative terminal (−) of the battery BT and the charge control circuit 2b. A current circuit Ri is provided. Further, a dark current energizing resistor Rd as dark current supply means is provided in parallel with the switching element FET. The constant current circuit Ri is for making a charging current constant when charging the battery BT, and is made of, for example, a semiconductor element. The smoothing circuit CR is a known circuit in which a capacitor and a resistor are combined.

  The charge control circuit 2b includes a gate control terminal O1 for controlling the gate of the switching element FET, a battery voltage detection terminal I1 connected to the positive terminal (+) of the battery BT, and a negative terminal ( And a zero-point detection terminal I2 connected to-. For example, as shown in FIG. 4, the charge control circuit 2b includes a differential amplifier AP1 that outputs a battery voltage Vb obtained by subtracting the zero point voltage Vi of the zero point detection terminal I2 from the battery applied voltage Vo of the battery voltage detection terminal I1. The ramp circuit LP1 that outputs, for example, a sawtooth voltage Vr in the form of a sawtooth wave as a pulsation voltage, compares the output Vb of the differential amplifier AP1 with the sawtooth voltage Vr, and compares the comparison result with a pulse that controls the gate of the switching element FET. And a comparator CP1 that outputs the gate voltage Vg. Note that this configuration may be realized by a one-chip microcomputer.

  The zero point voltage Vi is a voltage by the constant current circuit Ri. When the resistance of the constant current circuit Ri is represented by Ri, the charging current Ib flowing to the battery at the time of charging is Vi / Ri and is constant. The zero point voltage Vi is smoothed by the CR circuit and input to the zero point detection terminal I2. The relationship between the voltages described above is Vb = Vo-Vi as shown in FIG.

  Further, as shown in the upper part of FIG. 5, the sawtooth voltage Vr gradually increases from the second voltage VL to the first voltage VH and switches to the second voltage VL when reaching the first voltage VH. A sawtooth waveform that is sequentially repeated at a predetermined cycle is output.

  Further, the comparator CP1 compares the sawtooth voltage Vr with the battery voltage Vb (two-dot chain line), and the comparator CP1 outputs a high level voltage only while the battery voltage Vb is equal to or lower than the sawtooth voltage Vr. The gate control terminal Vg outputs the gate voltage Vg. As a result, the switching element FET is turned on only for the time during which the gate voltage Vg is output.

  A charging control procedure by the battery charging device 1 configured as described above will be described with reference to FIG. FIG. 6 shows the charge control procedure in the present invention in an easily understandable manner. When the battery voltage Vb gradually decreases due to natural discharge or the like as indicated by a two-dot chain line in FIG. 5, the time (pulse width) during which the gate voltage Vg is output increases in accordance with the voltage decrease. As shown in FIG. 6, when the battery voltage Vb falls below the first voltage VH corresponding to the full charge voltage, the time during which the charging current Ib flows increases as the on-time of the switching element FET increases. In addition, the battery voltage Vb sets a second voltage VL to start charging. The second voltage VL corresponds to the minimum voltage of the sawtooth voltage Vr. Therefore, while the battery voltage Vb is equal to or lower than the second voltage VL, the high-level voltage output as the comparison result of the comparator CP1 is always constant. Since it is in the output state (pulse width 100% state), the charging current Ib always flows, and the battery charger 1 is in the 100% charged state.

  When the battery BT is charged and the battery voltage Vb rises and becomes equal to or higher than the second voltage VL, the switching element FET is turned on / off again according to the comparison result between the battery voltage Vb and the sawtooth voltage Vr. As the battery voltage Vb approaches the first voltage VH, the time during which the charging current Ib flows is shortened. When the battery voltage Vb reaches the first voltage VH, the charging current Ib is not supplied and the charging is stopped. In this control, the pulse width of the charging current Ib increases in accordance with the decrease in the battery voltage Vb. Therefore, in the charging control in a state where the battery BT is not deteriorated, the battery voltage Vb decreases to the second voltage VL or less. There is no such thing, and the state is always maintained close to the first voltage VH.

  As described above, in charging the battery BT, the supply time of the charging current Ib is shortened as it approaches full charge (VH), and as a result, a battery charger that does not cause overcharging is achieved. Can do. In the case of a one-chip microcomputer, the PWM control used in a brushless motor or the like can be applied, the control can be easily configured, and the control device can be configured at low cost.

  Even when the charging is stopped, the switching element FET is turned off at that time, but the dark current Id flows through the dark current energizing resistor Rd. The dark current Id is preferably set to a value corresponding to the natural discharge of the target battery BT. As a result, it is possible to prevent the battery from being discharged again due to natural discharge after full charge, and to prevent a decrease in battery life due to repeated discharge and charge.

  Further, the pulsating voltage waveform generated in the ramp circuit LP1 of the above embodiment is not limited to the sawtooth waveform, and may be another waveform such as a triangular wave.

It is whole explanatory drawing which shows the use condition of the battery charging device to which this invention was applied. It is a perspective view which shows a battery charging device. It is a block diagram which shows schematic structure of a battery charging device. It is a figure which shows a charge control circuit. It is a wave form diagram which shows the switching control point. It is a wave form diagram which shows the charge control point.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery charging device 2 Charging apparatus main body 2a DC power supply 2b Charging control circuit 3 Power supply connection cable 4 Battery connection cable BT Car battery CP1 Comparator FET Switching element LP1 Lamp circuit PW Power supply Rd Dark current energization resistance Ri Constant current circuit

Claims (3)

A battery charging device having a charging device body, a power connection cable for connecting the charging device body and a power source, and a battery connection cable for connecting the charging device body and a battery,
The charging device main body is a switching means that is turned on when the battery is charged with power from the power source;
Pulsating voltage generating means for outputting a pulsating voltage that rises and falls in a predetermined cycle between a first voltage lower than the full charge voltage of the battery and a second voltage corresponding to the full charge voltage;
A battery charging device comprising charge control means for comparing the battery voltage with the pulsating voltage and turning on the switching means only while the battery voltage is lower than the pulsating voltage. A constant current circuit for making the charging current constant is connected to the negative terminal of the battery,
The battery charging device according to claim 1, wherein the voltage of the battery is calculated by subtracting the voltage of the negative terminal from the voltage of the positive terminal of the battery.   3. The battery charging device according to claim 1, wherein dark current supply means is provided for supplying dark current to the battery when the switching means is off. 4.

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