JP7338986B2 - power supply - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having a battery, and more particularly to a power supply device that prohibits charging of a deeply discharged battery to improve safety.

In a secondary battery such as a lithium ion battery, which is a non-aqueous electrolyte secondary battery, when it is discharged further than the minimum voltage and enters a deep discharge region, the copper of the negative electrode material becomes copper ions, and when charged in this state, Copper ions are deposited as copper, causing an internal short circuit in the battery, which may result in fire, explosion, or the like. This problem can be eliminated by prohibiting charging of a battery that has been discharged to the deep discharge region.

Devices have been developed to inhibit charging of deeply discharged batteries. (See Patent Document 1)

JP 2013-211975 A

FIG. 4 shows the power supply device of Patent Document 1. As shown in FIG. This power supply device has a charging switching element 92 connected in series with a battery 91 . The charging switching element 92 has a switching circuit 93 connected to its input side. The switching circuit 93 switches the charging switching element 92 to the OFF state in response to an OFF signal from an arithmetic circuit 95 that detects deep discharge of the battery 91 and outputs an OFF signal. The switching circuit 93 connects an arithmetic circuit 95 containing a CPU 96 that digitally processes the battery voltage to determine deep discharge, and a deep discharge detection circuit 94 that detects deep discharge from the battery voltage. Deep discharge detection circuit 94 compares the voltage of battery 91 with a reference voltage to detect deep discharge, and outputs an off signal to switching circuit 93 when deep discharge is detected. An arithmetic circuit 95 containing a CPU 96 detects the voltage of the battery 91, converts the detected voltage into a digital signal, performs arithmetic processing, determines whether the battery 91 is deeply discharged, and switches the off signal to a switching circuit 93 when the battery 91 is determined to be deeply discharged. output to Switching circuit 93 receives OFF signals from both arithmetic circuit 95 and deep discharge detection circuit 94, and switches charge switching element 92 to the OFF state. 92 to the off state. Therefore, even when the arithmetic circuit 95 does not operate normally, the deep discharge detection circuit 94 detects the deep discharge of the battery 91 and switches the charge switching element 92 to the OFF state. Therefore, charging of the battery 91 can be inhibited more reliably when the battery 91 is deeply discharged than in a power supply device in which the CPU 96 performs arithmetic processing to detect the deep discharge of the battery 91 and switch the charge switching element 92 to the OFF state.

In the power supply device of FIG. 4, even if the arithmetic circuit 95 of the CPU 96 fails, the deep discharge detection circuit 94 can switch the charge switching element 92 to the off state. Since the input OFF signal is switched to switch the charge switching element 92 to the OFF state, even if the arithmetic circuit 95 and the deep discharge detection circuit 94 are in a state of normal operation, if the switching circuit 93 and the FET control circuit fail. , charging cannot be prohibited when the battery 91 is deeply discharged.

The present invention was developed for the purpose of preventing the above-mentioned harmful effects, and one of the objects of the present invention is to surely prohibit charging when the battery is deeply discharged, thereby achieving higher safety. The object is to provide a power supply device that realizes the above.

A power supply device according to an embodiment of the present invention includes a battery 1, a charging switching element 2 connected in series with the battery 1 and formed of a semiconductor element for controlling charging of the battery 1, and a battery voltage turning off the charging switching element 2. It comprises a first OFF circuit 3 for switching, and a second OFF circuit 4 for switching the charging switching element 2 to an OFF state by the battery voltage. The first OFF circuit 3 includes an arithmetic circuit 5 that detects the battery voltage, digitally processes the detected voltage, determines whether the battery 1 is deeply discharged, and switches the charge switching element 2 to the OFF state. The second off circuit 4 inputs an off signal to the input side of the charging switching element 2 and divides the battery voltage into the FET of the forced off switch 6 that switches the charging switching element 2 to the off state, and the gate of the FET. It has a voltage dividing resistor 7 for input. The FET has a cut-off characteristic that cuts off the current between the drain and the source when the battery voltage input to the gate through the voltage dividing resistor 7 drops to the deep discharge voltage, and the first off circuit 3 outputs an off signal. The terminal is connected to the source of the FET and is connected to the input side of the charge switching element 2 via the drain and source of the FET, and the off signal output from the first off circuit 3 via the FET is used for the charge switching. The FET of the forced off switch 6 is an off signal that is input to the source from the output terminal of the first off circuit 3 when the voltage of the battery 1 is a charging inhibition voltage lower than the deep discharge voltage. Then, a signal input to the gate from the voltage dividing resistor 7 turns off, and an off signal is input to the input side of the charging switching element 2 to switch the charging switching element 2 to the off state.

The above power supply ensures a high degree of safety by prohibiting charging of the battery when the battery is deeply discharged.

1 is a block circuit diagram of a power supply device according to an embodiment of the present invention; FIG. FIG. 4 is a block circuit diagram of a power supply device according to another embodiment of the present invention; FIG. 4 is a block circuit diagram of a power supply device according to another embodiment of the present invention; 1 is a block diagram of a conventional power supply; FIG.

The present invention will now be described in detail with reference to the drawings. In the following description, terms indicating specific directions and positions (e.g., "upper", "lower", and other terms including those terms) are used as necessary, but the use of these terms is These terms are used to facilitate understanding of the invention with reference to the drawings, and the technical scope of the invention is not limited by the meaning of these terms. Also, parts with the same reference numerals appearing in a plurality of drawings indicate the same or equivalent parts or members.
Furthermore, the embodiments shown below show specific examples of the technical idea of the present invention, and the present invention is not limited to the following. In addition, unless there is a specific description, the dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention, but are intended to be examples. It is intended. In addition, the contents described in one embodiment and example can also be applied to other embodiments and examples. Also, the sizes and positional relationships of members shown in the drawings may be exaggerated for clarity of explanation.

A power supply device according to a first aspect of the present invention comprises a battery, a charging switching element comprising a semiconductor element connected in series with the battery to control charging of the battery, and a first charging switching element for switching the charging switching element to an off state by a battery voltage. and a second OFF circuit for switching the charging switching element to an OFF state according to the battery voltage. The first OFF circuit detects the battery voltage, digitally processes the detected voltage, and deeply discharges the battery. The second off circuit is connected in series between the first off circuit and the input side of the charge switching element, and the battery voltage is input and a forced off switch for switching the charging switching element to an off state when the input battery voltage is lower than the deep discharge voltage, and the second off circuit is turned off when the battery voltage is lower than the deep discharge voltage and the charging inhibition voltage is lower than the deep discharge voltage. The forced off switch is turned off to switch the charge switching element off.

The above power supply device has an extremely simple circuit configuration, and while reducing both the parts cost and the assembly cost, it surely prohibits charging of the battery even if the arithmetic circuit fails in a state where the battery is deeply discharged. It has the advantage of ensuring a high level of safety. The above power supply device connects a second off circuit for forcibly switching off the charging switching element to the input side of the charging switching element, and this second off circuit is configured to allow the battery voltage to be deeply discharged. This is because a forced off switch that switches to the off state when the voltage is below the voltage is provided, and the forced off switch forcibly switches the charging switching element to the off state without going through a switching circuit.

Furthermore, the above power supply device has a simple circuit configuration that omits the switching circuit that switches between the off signal from the first off circuit and the off signal from the second off circuit, and controls the charging switching element to turn on and off. However, when the battery is in a deeply discharged state, it has the characteristic that recharging of the battery can be prohibited.

In the power supply device of the second aspect of the present invention, the forced off switch is an FET whose gate is input with the battery voltage, and the cut-off characteristic of this FET cuts off the current when the battery voltage drops to the deep discharge voltage. Characteristically, the source and drain of the FET are connected in series between the first off-circuit and the input side of the charging switching element.

The above-described power supply device has the characteristic that charging of the battery can be reliably prohibited when the battery voltage drops to the charging prohibition voltage while the second OFF circuit has an extremely simple circuit configuration. The second off circuit has a simple circuit configuration consisting only of FETs with cut-off characteristics that cut off the current when the battery voltage drops to the deep discharge voltage, and the battery voltage is compared with a reference voltage to determine deep discharge. This is because there is no need for a complicated circuit such as a comparator, the number of parts is reduced, the operation is reliable, and the charging switching element is reliably switched to the OFF state at the charging inhibition voltage of the battery. Therefore, in the above power supply device, when the battery is discharged to the deep discharge voltage, the charging switching element is turned off not only by the arithmetic circuit, but also by the forced off switch consisting of only the FETs with a very simple circuit configuration. Therefore, it is possible to reliably prohibit recharging of a battery with a charging prohibition voltage, and to reliably prevent adverse effects due to recharging of a deeply discharged battery.

In the power supply device of the third aspect of the present invention, the second off circuit has a voltage dividing resistor connected to the gate of the FET which is the forced off switch, and the voltage dividing resistor divides the battery voltage to Entering the gate.

The power supply device described above can forcibly switch the FET of the forced off switch to the off state by adjusting the electrical resistance of the voltage dividing resistors and in a state in which the battery is lowered to the charging prohibition voltage. Also, the number of batteries connected in series can be adjusted by the electrical resistance of the voltage dividing resistors, so that the FET of the forced off switch can be reliably switched to the off state at the charging prohibition voltage of the batteries.

In a power supply device according to a fourth aspect of the present invention, the arithmetic circuit of the first off circuit includes an A/D converter that converts the battery voltage into a digital signal and detects the battery voltage.

In the power supply device according to the fifth aspect of the present invention, the arithmetic circuit of the first OFF circuit has a CPU, and the CPU digitally processes the battery voltage to determine whether the battery is deeply discharged.

According to a sixth aspect of the present invention, the power supply device provides the second deep discharge voltage at which the second OFF circuit switches the charge switching element to the OFF state, and the first OFF circuit switches the charge switching element to the OFF state. is set lower than the deep discharge voltage of

In the above power supply device, the second deep discharge voltage at which the second off circuit inhibits recharging of the battery is set lower than the first deep discharge voltage at which the first off circuit inhibits recharging of the battery. Therefore, when the battery is discharged and the voltage gradually drops to the first deep discharge voltage, the first OFF circuit switches the charge switching element to the OFF state to stop recharging the battery. When the battery is further discharged and the voltage drops to a second deep discharge voltage, a second off circuit inhibits recharging of the battery. Therefore, even in a state in which the battery voltage drops to the first deep discharge voltage and recharging is not prohibited, the power supply device is further turned off when the battery voltage drops to the second deep discharge voltage. Since the circuit inhibits recharging of the battery, it is possible to more reliably prevent recharging of the battery that has dropped to the charge inhibition voltage.

The charging inhibition voltage can be set low to widen the range of battery usage, but it becomes difficult to ensure sufficient safety. Conversely, although the charging prohibition voltage can be set high to increase safety, the state in which the user can use the device is restricted, and the device cannot be used effectively. The first off circuit and the second off circuit cannot eliminate the error in the charge inhibit voltage that inhibits recharging of the battery. Charge inhibit voltage error reduces safety and limits the range that can be used by the user. This is because if the charge prohibition voltage becomes lower due to an error, the safety deteriorates, and if the charge prohibition voltage becomes higher, the usage range of the user becomes narrower. The first OFF circuit can set the charge inhibition voltage with higher accuracy than the second OFF circuit. Prohibiting charging and creating a state in which the user's range of use is not limited. If the first off-circuit does not operate normally, safety cannot be ensured. Therefore, in this state, the second off-circuit, which is set to a charging inhibition voltage lower than that of the first off-circuit, operates to turn off the battery. prohibit recharging. The second off-circuit, in which the charge inhibition voltage is set low, cannot ensure safety comparable to that of the first off-circuit. In the event of an emergency where the battery fails, a second off-circuit inhibits recharging of the battery to ensure safety.

(Embodiment 1)
The power supply device shown in the circuit diagram of FIG. It comprises a first OFF circuit 3 for switching the element 2 to the OFF state and a second OFF circuit 4 for switching the charging switching element 2 to the OFF state by the battery voltage.

The first OFF circuit 3 includes an arithmetic circuit 5 that detects the battery voltage, digitally processes the detected voltage, determines whether the battery 1 is deeply discharged, and switches the charge switching element 2 to the OFF state. The arithmetic circuit 5 includes an A/D converter 11 that converts the battery voltage into a digital signal, a CPU 12 that performs arithmetic processing on the battery voltage of the digital signal output from the A/D converter 11, and a memory that stores the deep discharge voltage. 13. This arithmetic circuit 5 converts the battery voltage into a digital signal by the A/D converter 11, compares the battery voltage converted into the digital signal with the deep discharge voltage stored in the memory 13 by the CPU 12, and determines the battery voltage. drops below the deep discharge voltage, it outputs an off signal to switch the charge switching element 2 to the off state.

The off signal output from the arithmetic circuit 5 is input to the gate of the charge switching element 2 via the FET, which is the forced off switch 6 of the second off circuit 4 . When the FET of the second OFF circuit 4 is in the ON state, the OFF signal output from the arithmetic circuit 5 via the FET switches the charge switching element 2 to the OFF state. When the FET of the second OFF circuit 4 is in the OFF state, the OFF signal from the arithmetic circuit 5 is blocked by the FET and is not input to the gate of the charging switching element 2, but the FET of the second OFF circuit 4 is in the OFF state. As a result, the charging switching element 2 is turned off.

The charge switching element 2 has a gate voltage that is turned off to cut off the current of the battery 1 and a gate voltage that is turned on to allow charging and discharging of the battery 1 . In the charge switching element 2, the FET of the second off circuit 4 is turned off and the gate voltage is set to the off voltage, or the FET of the second off circuit 4 is turned on and the first off circuit 3 is turned off. When the OFF signal to be output is input to the gate through the FET, the current of the battery 1 is cut off. That is, one of the first off-circuit 3 and the second off-circuit 4 is turned off, and the charging switching element 2 cuts off the current of the battery 1, so that the first off-circuit 3 operates normally. Even in the non-discharging state, the second OFF circuit 4 operates to prohibit recharging of the battery 1 by turning off the charging switching element 2 when the battery voltage drops to the deep discharge voltage.

The second OFF circuit 4 forcibly switches the charging switching element 2 to the OFF state regardless of the output signal of the first OFF circuit 3 when the battery voltage becomes equal to or lower than the deep discharge voltage. To achieve this, the second off-circuit 4 is connected in series between the first off-circuit 3 and the input side of the charging switching element 2 . The second off circuit 4 has a forced off switch 6 that turns off when the battery voltage drops below the deep discharge voltage. The forced off switch 6 is connected between the charge switching element 2 and the first off circuit 3, and is turned off when the voltage of the battery 1 reaches the charge inhibition voltage below the deep discharge voltage. 2 to the off state.

The forced off switch 6 is an FET whose gate receives the battery voltage. This FET has a cut-off characteristic that cuts off the current when the battery voltage input to the gate drops below the deep discharge voltage. In the OFF state, in order to forcibly switch the charging switching element 2 to the OFF state regardless of the output signal of the first OFF circuit 3, the FET has a source and a drain connected to the first OFF circuit 3 and the charging switching element. 2 is connected in series with the input side of That is, the circuit configuration is such that the off signal of the first off circuit 3 is input to the gate of the charging switching element 2 via the FET of the forced off transistor. When the FET of the forced off switch 6 is in the on state, the off signal output from the first off circuit 3 is input to the gate of the charge switching element 2. Therefore, when the first off circuit 3 outputs the off signal The charging switching element 2 is turned off to prohibit charging of the battery 1 . When the first off-circuit 3 does not operate normally, the FET of the second off-circuit 4 is turned off to forcibly switch the charge switching element 2 off.

The FET of the forced off switch 6 divides the battery voltage with the voltage dividing resistor 7 and inputs it to the gate. The voltage dividing resistor 7 divides the battery voltage at a predetermined ratio and inputs it to the gate of the FET. The ratio at which the voltage dividing resistor 7 divides the battery voltage is set so that when the battery voltage drops below the deep discharge voltage, the gate voltage of the FET drops below the off voltage at which current is interrupted. The second off circuit 4 divides the voltage of one battery 1 and inputs it to the gate of the FET as shown in FIG. 1, or multiple batteries 1 connected in series as shown in FIG. is divided and input to the gate of the FET. The FET turns off when the input voltage is lower than the set voltage with a constant cutoff characteristic. The resistance value of the voltage dividing resistor 7 is set so that when the voltage of the battery 1 reaches the deep discharge voltage, the FET is cut off and turned off.

In the power supply device, the first OFF circuit 3 and the second OFF circuit 4 set the deep discharge voltage at which the charge switching element 2 is switched to the OFF state to the same voltage value. This power supply device uses a lithium ion secondary battery as the battery 1, and sets the deep discharge voltage, that is, the charge inhibition voltage, to 2.00 V/cell, for example. However, in the power supply device, the first OFF circuit 3 and the second OFF circuit 4 may set the deep discharge voltages at which the charging switching element 2 is switched to the OFF state to different voltage values. In the power supply device that switches the charge switching element 2 to the off state at different deep discharge voltages, the second off circuit 4 preferably switches the charge switching element 2 to the off state by switching the second deep discharge voltage to the first off circuit. 3 is set lower than the first deep discharge voltage that switches the charge switching element 2 to the OFF state. This power supply device uses a lithium ion secondary battery as the battery 1, and sets the first deep discharge voltage to 2.10V and the second deep discharge voltage to 2.00V, for example.

In the power supply device described above, the first off-circuit 3 sets the first deep discharge voltage that prohibits recharging of the battery 1, and the second off-circuit 4 sets the second deep discharge voltage that prohibits recharging of the battery 1. , the voltage gradually drops as the battery 1 is discharged, and when the voltage drops to the first deep discharge voltage, the first OFF circuit 3 first outputs an OFF signal, It operates to switch the charge switching element 2 to the OFF state to stop the recharging of the battery 1 . When the battery 1 is further discharged and the voltage drops to the second deep discharge voltage, the FET of the second off circuit 4 is turned off to prohibit recharging of the battery 1 . In this power supply device, the charge switching element 2 is switched to the OFF state even though the first OFF circuit 3 does not operate normally and the voltage of the battery 1 drops to the first deep discharge voltage. When the voltage of the battery 1 further drops to the second deep discharge voltage in the non-discharged state, the FET of the second off circuit 4 is turned off, and the gate voltage of the charge switching element 2 is set below the cut-off voltage. Inhibit recharging of battery 1. Therefore, even when the first off-circuit 3 does not operate normally, the second off-circuit 4 prohibits recharging of the battery 1 when the battery voltage drops to the charge prohibition voltage.

By the way, although the power supply device can set the deep discharge voltage that prohibits recharging of the battery 1 to be low to widen the usage range of the battery 1, it becomes difficult to ensure sufficient safety. Conversely, although the charging prohibition voltage can be set high to improve safety, the actual chargeable/dischargeable capacity is limited and the actual capacity becomes small. Since the real capacity and safety of the battery 1 at the deep discharge voltage that prohibits recharging of the battery 1 are contradictory characteristics, it is necessary to prohibit recharging of the battery 1 accurately at a preset deep discharge voltage. is important. The first OFF circuit 3 digitally processes the detected voltage of the battery 1 in the arithmetic circuit 5 to determine the deep discharge of the battery 1 and switches the charge switching element 2 to the OFF state. The charging inhibition voltage can be set with high accuracy. When the first off-circuit 3 operates normally, the first off-circuit 3 prohibits recharging of the battery 1, thus safely prohibiting recharging without limiting the actual capacity of the battery 1. can.

In a power supply device in which the charging inhibition voltage of the second off-circuit 4 is set lower than that of the first off-circuit 3, the first off-circuit 3 that prohibits recharging of the battery 1 with high precision does not operate normally. In this state, the second off-circuit 4 operates to prohibit recharging of the battery 1, so safety can be ensured.

1 and 2 connect the charging switching element 2 to the negative side of the battery 1, but the power supply device connects the charging switching element 2 to the positive side of the battery 1 as shown in FIG. You can also

INDUSTRIAL APPLICABILITY The present invention is a power supply device having a chargeable/dischargeable battery, and is particularly suitable for use as a power supply device capable of improving safety by prohibiting charging of a deeply discharged battery.

Reference Signs List 1 Battery 2 Charging switching element 3 First OFF circuit 4 Second OFF circuit 5 Arithmetic circuit 6 Forced OFF switch 7 Voltage dividing resistor 11 A/D converter 12 CPU
DESCRIPTION OF SYMBOLS 13... Memory 91... Battery 92... Charge switching element 93... Switching circuit 94... Deep discharge detection circuit 95... Operation circuit 96... CPU

Claims (4)

a battery;
a charging switching element comprising a semiconductor element connected in series with the battery to control charging of the battery;
a first off circuit that switches the charging switching element to an off state by battery voltage;
a second off circuit for switching the charging switching element to an off state with battery voltage;
The first off circuit is
an arithmetic circuit that detects battery voltage, digitally processes the detected voltage, determines whether the battery is deeply discharged, and switches the charging switching element to an off state;
The second off circuit is
a forced off switch FET for inputting an off signal to the input side of the charging switching element to switch the charging switching element to an off state;
Equipped with a voltage dividing resistor that divides and inputs the battery voltage to the gate of the FET,
The FET is
A cut-off characteristic that cuts off the current between the drain and the source when the battery voltage input to the gate through the voltage dividing resistor drops to the deep discharge voltage,
The first off circuit is
the output terminal of the off signal is connected to the source of the FET and is connected to the input side of the charging switching element through the drain-source of the FET,
inputting an off signal output from the first off circuit via the FET to the input side of the charging switching element;
The FET of the forced off switch is
At a charge inhibition voltage in which the voltage of the battery is equal to or lower than the deep discharge voltage,
an off signal input to a source from an output terminal of the first off circuit;
A signal input to the gate from the voltage dividing resistor turns off,
inputting an off signal to the input side of the charging switching element,
A power supply device, wherein the charging switching element can be switched to an off state. The power supply device according to claim 1,
The power supply device, wherein the arithmetic circuit of the first OFF circuit includes an A/D converter that converts the battery voltage into a digital signal and detects the battery voltage. The power supply device according to claim 1 or 2,
the arithmetic circuit of the first off circuit comprises a CPU;
A power supply device, wherein the CPU digitally processes the battery voltage to determine whether the battery is deeply discharged. The power supply device according to any one of claims 1 to 3,
a second deep discharge voltage at which the second off circuit switches the charge switching element to an off state,
A power supply device, wherein said first OFF circuit is set lower than a first deep discharge voltage for switching said charge switching element to OFF state.

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