JP3643711B2 - Charger - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a charger that can charge a plurality of secondary batteries while preventing overcurrent.
[0002]
[Prior art]
Chargers that charge a plurality of batteries include a type in which batteries are connected in series and a type in which batteries are connected in series, and a type in which batteries are connected in parallel and charged. A battery charger connected in series charges all batteries with the same current. For this reason, when batteries with different charge states are charged together, one of the batteries is overcharged or cannot be fully charged.
[0003]
The method of charging by connecting a plurality of batteries in parallel can make the charging voltage of all the batteries constant. For this reason, a battery with a high voltage close to full charge has a small charge amount, and a battery that is completely discharged and has a low voltage has a large charge current and a large charge amount. For this reason, there is a feature that a plurality of batteries having different charge states can be charged together while being balanced.
[0004]
[Problems to be solved by the invention]
However, in a charger that charges a battery by connecting a plurality of secondary batteries in parallel, the charging current of each battery is different, so that one of the batteries may be charged with an overcurrent. At this time, it is necessary to interrupt the charging of the battery charged with the overcurrent. However, the circuit for realizing this is complicated. This is because it is necessary to detect the charging currents of all the batteries because the charging currents of the respective secondary batteries are not the same. In a charger that charges a plurality of secondary batteries connected in series, the charging currents of all the secondary batteries are the same, so that the charging current can be detected by a single charging current detection circuit. However, the charger that connects and charges multiple secondary batteries in parallel changes the charging current depending on the electrical characteristics of each battery, so charging stops when any battery is charged with an overcurrent. In order to achieve this, it is necessary to separately detect charging currents of all the batteries and stop charging.
[0005]
A technique for preventing charging with an overcurrent by connecting a current adjustment resistor in series with a battery being charged is described in, for example, Japanese Patent Laid-Open No. 1-270740. The charger described in this publication detects the overcurrent by detecting the temperature of the current adjustment resistor. However, if the charging circuit that detects the temperature of the current adjustment resistor and detects the overcurrent of each battery is designed to charge, for example, four batteries, four current adjustment resistors and each current adjustment resistor And an overcurrent detection circuit for detecting the temperature of the battery, which makes the charging circuit complicated and increases the manufacturing cost.
[0006]
This problem can be solved, for example, by connecting a fuse in series with all the secondary batteries. However, since the fuse does not return when it is blown, for example, if a secondary battery with an internal short circuit is set and charging is stopped due to overcurrent, this battery will be replaced even if it is replaced with a normal secondary battery. Can not be charged. This makes it extremely difficult to use a charger that removes and charges the secondary battery. Furthermore, the fuse that protects the secondary battery from overcurrent needs to have a very low fusing current. This type of fuse has a smaller fusing current than a commercially available fuse and is a special fuse. For this reason, it is difficult to supply as a replacement part, and there is a disadvantage that the cost is increased.
[0007]
The present invention was developed with the object of solving these drawbacks, and an important object of the present invention is that it is an extremely simple circuit, and any secondary battery that is connected in parallel and charged is excessive. The object is to provide a charger capable of interrupting charging when charged with current.
[0008]
[Means for Solving the Problems]
The charger of the present invention charges a plurality of secondary batteries 1 connected in parallel. The charger includes a current adjustment resistor 12 connected in series with each secondary battery 1. The current adjustment resistors 12 are arranged close to each other. Further, one thermistor 13 is disposed close to the plurality of current adjustment resistors 12. The thermistor 13 is connected to the charge interruption circuit 9. When the signal for detecting the temperature of each current adjustment resistor 12 is input from the thermistor 13 to the charge cut-off circuit 9 and the temperature of any current adjustment resistor 12 becomes higher than the set temperature, all of the secondary batteries 1 are connected. Suspend charging.
[0009]
In the present specification, the current adjustment resistor 12 "closes" to each other and the current adjustment resistor 12 and the thermistor 13 "close" to each other include not only the state of being in direct contact and being adjacent to each other, It shall mean a state where they are arranged so as to be close to each other where heat transfer is performed. Therefore, it is used in a broad sense including a state where the printed circuit board 3 is disposed on the front and back sides of the printed circuit board 3 so as to be close to the extent of heat transfer through the printed circuit board 3.
[0010]
In the charger according to claim 2 of the present invention, a plurality of current adjusting resistors 12 are arranged close to each other on the surface of the printed circuit board 3. The thermistor 13 is located on the back surface of the printed circuit board 3 and is disposed close to the current adjustment resistor 12. That is, the plurality of current adjusting resistors 12 and the thermistor 13 are arranged so as to face the front and back of the printed circuit board 3.
[0011]
The charger according to claim 3 of the present invention is attached to the case 2 so that the plurality of secondary batteries 1 can be detached.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a charger for embodying the technical idea of the present invention, and the present invention does not specify the charger as follows.
[0013]
Further, in this specification, in order to facilitate understanding of the scope of claims, the numbers corresponding to the members shown in the examples are referred to as “the scope of claims” and “the means for solving the problems”. It is added to the member shown by. However, the members shown in the claims are not limited to the members in the embodiments.
[0014]
The charger shown in the perspective view of FIG. 1 and the cross-sectional view of FIG. 2 includes a printed circuit board 3 in a case 2. The printed circuit board 3 is built in the bottom of the case 2 and fixes an electronic part 18 that realizes a charging circuit.
[0015]
The case 2 incorporates a printed circuit board 3 and is molded separately into a plastic upper case 2A and a lower case 2B so that the case 2 can be easily assembled. The upper case 2A is provided with a mounting portion 4 on the upper surface so that the secondary battery 1 can be attached and detached.
[0016]
The battery mounting portion 4 provided in the case 2 is formed into a groove shape having an opening at the top, and the central portions of the side walls 5 on both sides are lowered so that the secondary battery 1 can be easily removed. In the case 2 shown in the figure, a partition wall 6 is provided vertically in the center of the mounting portion 4 so that four cylindrical batteries can be mounted side by side on the mounting portion 4.
[0017]
In FIG. 2, the upper case 2 </ b> A is provided with a mounting portion 4 on the left, and the right portion is formed high so as to incorporate the electronic part 18. A charging circuit component to be mounted on the printed circuit board 3 is built in a portion of the upper case 2A that is to be formed high. The lower case 2B is provided with an outlet 7 by forming almost the entire bottom surface into a flat shape. The outlet 7 is connected to the printed circuit board 3.
[0018]
The mounting part 4 of the upper case 2A is provided with charging contacts 8 at both ends thereof. The charging contact 8 is electrically connected to the secondary battery 1 set in the mounting portion 4 and charges the secondary battery 1. The charging contact 8 is fixed by soldering to the printed circuit board 3 or connected to the printed circuit board 3 via a lead wire (not shown) or the like and connected to a charging circuit provided on the printed circuit board 3. Yes.
[0019]
A charging circuit mounted on the printed circuit board 3 is shown in FIG. The charging circuit in this figure connects and charges a plurality of secondary batteries 1 in parallel. The charging circuit includes a switching power source 10 that converts an input commercial power source into a charging voltage for the secondary battery 1, and a current adjustment resistor 12 that is connected between the negative side charging contact 8 of the secondary battery 1 and the ground. And a thermistor 13 for detecting the temperature of the current adjustment resistor 12 and a charge interruption circuit 9 for interrupting the charging of all the secondary batteries 1 by a signal from the thermistor 13.
[0020]
The charge cut-off circuit 9 is a control that switches the switching element 11 on and off by the signal of the switching element 11 connected between the output of the switching power supply 10 and the + side charging contact 8 of the secondary battery 1 and the thermistor 13. Circuit 14.
[0021]
The switching element 11 is an FET and is connected to the positive charging contacts 8 of the four secondary batteries 1 connected in parallel to each other. Therefore, when the switching element 11 is turned off, charging of all the secondary batteries 1 is stopped. The switching element 11 may be a transistor or a relay instead of the FET.
[0022]
The current adjusting resistors 12 are four resistors, and the four negative charging contacts 8 are connected to the ground via the current adjusting resistors 12. Therefore, each current adjustment resistor 12 flows a current flowing through each secondary battery 1. Each current adjustment resistor 12 is heated by Joule heat generated by a current for charging the secondary battery 1. Therefore, the temperature of the current adjustment resistor 12 increases as the current for charging the secondary battery 1 increases. The four current adjustment resistors 12 are arranged close to each other as shown in the perspective view of FIG. 4 and the plan view of FIG. In the current adjustment resistors 12 shown in these drawings, four current adjustment resistors 12 are fixed to the upper surface of the printed circuit board 3 so as to approach two vertical rows.
[0023]
The thermistor 13 detects the temperature of all the current adjustment resistors 12 as one. For this reason, the thermistor 13 is disposed close to all the current adjustment resistors 12. The printed circuit board 3 shown in FIGS. 4 and 5 has all the current adjusting resistors 12 disposed close to the upper surface. A thermistor 13 is disposed on the lower surface of the printed circuit board 3 so as to be close to the current adjustment resistor 12. In order to bring the current adjustment resistor 12 and the thermistor 13 close to each other through the printed circuit board 3, the thermistor 13 is disposed directly below the current adjustment resistor 12. The printed circuit board 3 shown in the figure has a current adjustment resistor 12 on the upper surface and a thermistor 13 on the lower surface. On the contrary, a current adjustment resistor is disposed on the lower surface of the printed circuit board and a thermistor is disposed on the upper surface. You can also. As described above, in the structure in which the current adjustment resistor 12 and the thermistor 13 are arranged on the front and back of the printed circuit board 3, a plurality of the current adjustment resistors 12 are made almost equal to one thermistor 13 and the thermal conductivity is made substantially equal. There is a feature that can be installed. However, although not shown, for example, a thermistor may be provided at the center and a plurality of current adjusting resistors may be provided around the thermistor.
[0024]
The thermistor 13 is connected to the control circuit 14. The control circuit 14 switches the switching element 11 on and off with the electric resistance of the thermistor 13. The control circuit 14 switches the switching element 11 off when any of the current adjustment resistors 12 becomes higher than the set temperature and the electrical resistance of the thermistor 13 decreases. The control circuit 14 shown in the figure includes a differential amplifier 15 and a driver input transistor 16.
[0025]
The differential amplifier 15 inputs a reference voltage to the + input terminal. The input terminal is connected to ground via the thermistor 13 and to the power supply via the current supply resistor 17. The input terminal receives a voltage that is approximately proportional to the electrical resistance of the thermistor 13. Therefore, when the temperature of the current adjustment resistor 12 increases and the electrical resistance of the thermistor 13 decreases, the input voltage at the −input terminal decreases. -When the input voltage at the input terminal becomes low, the output voltage of the differential amplifier 15 becomes "H". The output of the differential amplifier 15 is connected to the base of the input transistor 16. Therefore, when the output of the differential amplifier 15 becomes “H”, the input transistor 16 is turned on due to the base current flowing. When the input transistor 16 is turned on, the bias voltage is not input to the FET as the switching element 11 and is turned off.
[0026]
Therefore, in this control circuit 14, when an overcurrent flows through the current adjustment resistor 12 and is heated, and the electrical resistance of the thermistor 13 decreases, the switching element 11 is switched off and the charging of the secondary battery 1 is stopped. Is done.
[0027]
On the other hand, when the current of the current adjustment resistor 12 becomes normal and this temperature becomes lower than the set temperature, the electrical resistance of the thermistor 13 increases and the output of the differential amplifier 15 becomes “L”. The transistor 16 is turned off, and a bias voltage is input to the switching element 11 to be turned on.
[0028]
Accordingly, when the secondary battery 1 is set in the mounting portion 4 and an overcurrent flows to any of the secondary batteries 1 due to an internal short circuit or the like, the temperature of the current adjustment resistor 12 connected to this battery rises, and the The mr 13 detects this, and the control circuit 14 switches the switching element 11 off. When the switching element 11 is switched off, the charging of the secondary battery 1 is stopped and no current flows through the current adjustment resistor 12. Therefore, the temperature of the current adjustment resistor 12 gradually decreases. When the temperature of the current adjustment resistor 12 becomes lower than the set temperature, the thermistor 13 detects this and switches the switching element 11 on. At this time, a timer may be incorporated in the control circuit 14 to delay the time during which the switching element 11 turned off is switched on.
[0029]
When the internal short-circuited battery is replaced with a normal battery, the temperature of the current adjustment resistor 12 decreases, or when the set time of the timer elapses, the switching element 11 is turned on to charge the battery.
[0030]
【The invention's effect】
The charger of the present invention is a very simple circuit, and can stop charging when any secondary battery connected in parallel and charged is charged with an overcurrent. The charger of the present invention connects a current adjustment resistor in series with each battery connected in parallel, arranges a plurality of current adjustment resistors close to each other, and approaches all the current adjustment resistors. This is because when a single thermistor is disposed and the temperature of the thermistor rises to a set temperature, the charge cut-off circuit for controlling the charging of the battery is operated to stop the charging of all the batteries.
[0031]
Further, in the charger according to claim 2 of the present invention, the plurality of current adjustment resistors are disposed on the front surface of the printed circuit board and the thermistor is disposed on the back surface of the printed circuit board so that the plurality of current adjustment resistors and the thermistor are brought close to each other. Therefore, a plurality of current adjustment resistors can be disposed closer to each other, and the thermistor can be disposed closer to each current adjustment resistor. For this reason, the current adjusting resistors and the thermistors can be gathered and arranged in a narrow region, and the unevenness of the heat conduction state between all the current adjusting resistors and the thermistors can be reduced.
[Brief description of the drawings]
1 is a perspective view of a charger according to an embodiment of the present invention. FIG. 2 is a sectional view of the charger shown in FIG. 1. FIG. 3 is a circuit diagram of a charging circuit of the charger according to an embodiment of the present invention. FIG. 5 is a bottom perspective view showing a thermistor of a charger according to an embodiment of the present invention. FIG. 5 is a plan view showing a current adjusting resistor of the charger according to the embodiment of the present invention.
DESCRIPTION OF SYMBOLS 1 ... Secondary battery 2 ... Case 2A ... Upper case 2B ... Lower case 3 ... Printed circuit board 4 ... Mounting part 5 ... Side wall 6 ... Bulkhead 7 ... Outlet 8 ... Charge contact 9 ... Charge interruption circuit 10 ... Switching power supply 11 ... Switching element 12 ... Current adjustment resistor 13 ... Thermistor 14 ... Control circuit 15 ... Differential amplifier 16 ... Input transistor 17 ... Current supply resistor 18 ... Electronic parts

Claims (3)

In a charger that connects and charges a plurality of secondary batteries (1) in parallel, and is connected in series with each secondary battery (1), a plurality of current adjustment resistors ( 12), one thermistor (13) arranged close to the plurality of current adjustment resistors (12), and this thermistor (13) detects the temperature of the current adjustment resistor (12). And a charge cutoff circuit (9) for interrupting charging of all the secondary batteries (1) when the temperature of the current adjustment resistor (12) of the battery becomes higher than a set temperature. A plurality of current adjustment resistors (12) are arranged close to each other on the surface of the printed circuit board (3), and the thermistor (13) is close to the current adjustment resistors (12) on the back surface of the printed circuit board (3). The charger according to claim 1, wherein the charger is disposed. The charger according to claim 1, wherein the plurality of secondary batteries (1) are mounted so as to be removable.

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