Power supply circuit

Abstract

Reducing safety risks posed by lithium-ion batteries. [Solution] The device comprises a plurality of MOS semiconductors, each with its drain and source connected in parallel via a fuse resistor to the load side from a lithium ion battery; a photorelay, the output side of which is inserted between the battery and each gate terminal of the plurality of MOS semiconductors via a first resistor that applies a gate voltage to the plurality of MOS semiconductors and the input side of which is connected to the battery via a second resistor for turning on the photorelay; a set switch inserted in a first line consisting of the battery, the input side of the photorelay, and the second resistor; a second line connecting one of the drain or source of one of the plurality of MOS semiconductors to the output terminal on the input side of the photorelay; and a memory function unit having a third line connecting the other of the drain or source to the gate terminal of one of the MOS semiconductors via a third resistor for removing charge from the gate of the MOS semiconductor.

Description

[Technical Field]

[0001] The present invention relates to a power supply circuit that supplies power to a load from a lithium-ion battery, and to a power supply circuit that has fail-safe characteristics. [Background technology]

[0002] Lithium-ion batteries have various advantages, such as high energy density, long life, and low self-discharge rate. However, because the internal resistance of the battery is said to be low, at a few milliohms, it has been pointed out that there is a risk of fire if a short circuit occurs in the load (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Paragraph 0003 of Japanese Patent Application Laid-Open No. 2024-27068 [Patent Document 2] Paragraphs 0005-0009 of Japanese Utility Model Application No. 2024-001383 Summary of the Invention [Problem to be solved by the invention]

[0004] It is believed that the low internal resistance of lithium-ion batteries causes a large current to flow through the load, causing the fire.

[0005] The present invention focuses on this point and aims to provide a power supply circuit that can reduce safety risks caused by lithium-ion batteries by blowing a fuse provided in a fuse resistor when an abnormally large current occurs due to a short circuit in the load, etc. [Means for solving the problem]

[0006] The power supply circuit according to the present invention comprises a plurality of MOS semiconductors, each having a drain and source connected in parallel via a fuse resistor from a lithium ion battery to a load side; a photorelay, the output side of which is interposed between the lithium ion battery and each gate terminal of the plurality of MOS semiconductors via a first resistor that applies a gate voltage to the plurality of MOS semiconductors and the input side of which is connected between the + terminal and - terminal of the lithium ion battery via a second resistor for turning on the photorelay; a set switch interposed in a first line consisting of the lithium ion battery, the input side of the photorelay, and the second resistor; a second line connecting one of the drain or source of one of the plurality of MOS semiconductors connected in parallel to an output terminal on the input side of the photorelay; and a third line connecting the other of the drain or source to the gate terminal of the one MOS semiconductor via a third resistor for removing charge from the gates of the plurality of MOS semiconductors connected in parallel.

[0007] The power supply circuit according to the present invention further comprises a reset switch inserted in a fourth line formed by the lithium ion battery and the second resistor.

[0008] In the power supply circuit according to the present invention, the resistance value of the first resistor is greater than the resistance value of the third resistor, and the ratio of the resistance values ​​of the first resistor and the third resistor is configured to bring about conduction between the drain and source of the one MOS semiconductor when a voltage is applied to the gate of the one MOS semiconductor.

[0009] Commonly used power supply controllers pose a risk of lithium-ion battery fires due to electrical short circuits caused by component failure, which can cause mechanical switches to malfunction. Furthermore, when an overcurrent occurs, the electromagnetic relay contacts fuse, preventing the electrical circuit from being shut off, making it impossible to detect the risk. In contrast, the power supply circuit of the present invention uses a MOS semiconductor device, photorelay, and fuse resistor to shut off the power supply when an overcurrent occurs in the direct current of a lithium-ion battery. Furthermore, if the overcurrent condition persists due to a component failure, the fuse resistor will blow, shutting off the power circuit, providing a fail-safe function. This reduces safety risks associated with lithium-ion batteries.

[0010] A power supply circuit according to another aspect of the present invention comprises a photorelay, a set switch for supplying power from a power source via a resistor to the input side of a light emitting section of the photorelay, an output terminal on the output side of the photorelay, and a MOS semiconductor gate. By applying a voltage to the output terminal and the gate of the MOS semiconductor to make the MOS semiconductor conductive, the potential becomes the same as the ground voltage and the photorelay continues to emit light, thereby providing a memory function, and the voltage applied to the gate is the gate voltage having the memory function, which is distributed to other gates connected in parallel, so that all of the MOS semiconductors connected in parallel are conductive, and all of the drain voltages become the ground voltage, and this ground voltage is connected to the load terminal by a fuse resistor connected in parallel, and the negative voltage on the power supply side of the lithium ion battery is connected to the negative voltage A load is connected between the positive terminal on the lithium-ion battery's power supply side and the negative terminal on the negative side. If a current exceeding the lithium-ion battery's current limit value flows due to a short circuit in the load or a short circuit in the MOS semiconductor, the fuse in the fuse resistor will blow and the power supply will be stopped, ensuring fail-safe functionality that prevents the risk of a fire involving the lithium-ion battery.The negative terminal of the photorelay is at ground potential, so if necessary for inspection purposes, etc., turning on this reset switch will set it to ground voltage, turning off the output side of the photorelay and eliminating the applied voltage to all gate voltages connected in parallel, turning off all MOS semiconductors. [Effects of the Invention]

[0011] According to the present invention, safety risks caused by lithium-ion batteries can be reduced while providing fail-safe performance, and chattering can also be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a circuit diagram showing a configuration of a power supply circuit according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a circuit diagram showing the configuration of a power supply circuit according to one embodiment of the present invention, in which an input gate of a commercially available IGBT-type N-type semiconductor MOS transistor is connected to a resistor group via a memory function.

[0015] In Figure 1, reference numeral 1 denotes a lithium-ion battery, reference numeral 2 denotes a photorelay that is normally off (no driving voltage is applied), reference numeral 3 denotes a resistor that applies gate voltage, reference numeral 4 denotes a resistor that turns on the photorelay, reference numeral 5 denotes a resistor that removes the gate charge, reference numeral 6 denotes an on-switch (normally off) that resets the memory, reference numeral 7 denotes an on-switch (normally off) that sets the memory, reference numeral 8 denotes an N-type MOS semiconductor, reference numeral 9 denotes a fuse resistor, reference numeral 10 denotes a load supply terminal on the positive side, reference numeral 11 denotes a terminal that serves as the ground voltage on one side, reference numeral 12 denotes the current direction, reference numeral 13 denotes an LED that indicates a blown fuse or an open fault in the N-type MOS semiconductor, and reference numeral 14 denotes a current protection resistor for the LED.

[0016] Here, the N-type MOS semiconductors 8 are capable of handling large currents, and four of them are connected in parallel with fuse resistors 9. Of course, the present invention is not limited to the number of semiconductors connected in parallel. Here, if the maximum current per semiconductor is X amperes, then because four semiconductors are connected in parallel, a maximum of four times that current, or 4X amperes, can flow. Each fuse resistor 9 is assumed to be able to blow at X amperes.

[0017] The photorelay 2 is normally off, and the combination of this photorelay 2 and the N-type MOS semiconductor 8 at the bottom of the drawing provides a memory function.

[0018] When the onset switch 7 is turned on, a voltage is applied from the lithium ion battery 1 via the resistor 4 to the light emitting input side of the photorelay 2. This causes the output side of the photorelay 2 to become conductive, and a voltage is applied from the output terminal on the output side of the photorelay 2 to the gate of each N-type MOS semiconductor 8, causing conduction between the drain and source of each N-type MOS semiconductor 8.

[0019] Here, the resistance value of resistor 3 is set to be larger than the resistance value of resistor 5, and the ratio of the resistance values ​​of resistor 3 and resistor 5 is such that a voltage (referred to as an ON voltage) applied to the gate of the N-type MOS semiconductor 8 in the lowest row in the figure provides conduction between the drain and source of that N-type MOS semiconductor 8 and the remaining N-type MOS semiconductors 8. By providing conduction between the drain and source of the N-type MOS semiconductor 8 in the lowest row with this configuration, the input-side output terminal, which is the light-emitting portion of photorelay 2, becomes the same potential as the ground voltage (the negative side of the lithium-ion battery) via the drain and source of the N-type MOS semiconductor 8 in the lowest row (when conductive), and an ON voltage is applied to the gate of the N-type MOS semiconductor 8 in the lowest row, so that even if the set switch 7 is opened to turn it off, the photorelay 2 continues to emit light and the ON voltage continues to be applied to the gate of the N-type MOS semiconductor 8 in the lowest row, thereby demonstrating a memory function.

[0020] The set switch 7 must normally be kept off, as the purpose of the resistor 5 is to remove any charge remaining in the capacitor at the gate of each N-type MOS semiconductor 8. The values ​​of resistors 3 and 5 are determined by the characteristics of the N-type MOS semiconductor 8 under the above conditions.

[0021] When the drain-source (when conductive) of the bottom N-type MOS semiconductor 8 in the figure is at ground voltage, turning on the reset switch 6 turns off the secondary side (output side) of the photorelay 2. Since no voltage is applied to the gates of the four parallel-connected N-type MOS semiconductors 8, all four parallel-connected N-type MOS semiconductors 8 are turned off. This stops the power supply from the power supply circuit. However, the present invention is not limited to this method of turning off (resetting) the memory function. For example, there is a method described in Patent Document 2 for turning off (resetting) the memory function. When using this method, it is necessary to connect a fuse resistor according to a bias that blows at a maximum of 4 × X amperes.

[0022] The power supply circuit configured in this way controls and supplies current from the lithium ion battery 1 to the load between the positive load supply terminal 10 and the negative ground voltage terminal 11 while maintaining a constant voltage.

[0023] To cope with large current loads, the N-type MOS semiconductor 8 is configured in a parallel connection to provide redundancy for the load current due to the current limit of the MOS transistor, but since the lithium-ion battery 1 can handle large currents due to its low internal resistance, a current exceeding the current supply capacity of the lithium-ion battery 1 could cause a fire. Therefore, in the power supply circuit of this embodiment, based on the gate voltage of the circuit using the memory function of the N-type MOS semiconductor 8 and photorelay 2, a gate voltage is simultaneously applied to the N-type MOS semiconductors 8 connected in parallel, and connection is made via the N-type MOS semiconductor 8 connected in parallel and fuse resistor 9, and a large current is applied to the load.

[0024] The internal resistance of the lithium-ion battery 1 is said to be a low value of a few milliohms, but if it were to drop even further for some reason, or if the load or N-type MOS semiconductor 8 were to short-circuit and cause a large current to flow, which could lead to the lithium-ion battery 1 catching fire, connecting the lithium-ion battery 1 via a fuse resistor 9 prevents the fuse of the fuse resistor 9 from blowing and causing a risk of a large current to flow, thereby ensuring fail-safe safety against risks to the lithium-ion battery 1. Furthermore, blowing of the fuse resistor 9, which is connected in multiplexed parallel by the light-emitting diode 13 and the light-emitting diode current protection resistor 14, and an open fault in the N-type MOS semiconductor are indicated by the light-emitting diode going out.

[0025] Furthermore, in the power supply circuit according to this embodiment, the gate of the N-type MOS semiconductor 8 is controlled using the memory function of the photorelay 2, so that in the normal set and reset states, chattering does not occur even though the off switch has a mechanical structure.

[0026] The present invention is not limited to the above-described embodiment, and various modifications can be made, and the scope of such modifications also falls within the technical scope of the present invention.

[0027] For example, in the above embodiment, the N-type MOS semiconductor 8 is used as the MOS semiconductor, but a P-type MOS semiconductor can also be used. In this case, the source of the N-type MOS semiconductor 8 is connected to the negative side of the power supply, but in a similarly configured P-type MOS semiconductor, the source can be connected to the positive side of the power supply.

[0028] Furthermore, the power supply circuit according to the present invention may have a lithium ion battery 1, or may be inserted between the lithium ion battery 1 and a load. [Explanation of symbols]

[0029] 1. Power supply such as lithium-ion battery 2. A photorelay that is normally off (no driving voltage is applied) 3. Resistor that provides gate voltage 4 Resistor to turn on the photorelay 5. Resistor to remove gate charge 6 On switch for resetting memory, normally off 7 On switch for setting memory, normally off 8 N-type MOS semiconductor 9 Fuse Resistor 10 + side load supply terminal 11 -side ground voltage terminal 12 Current direction 13 Light-emitting diodes that indicate blown fuses or open circuit faults in N-type MOS semiconductors 14 Light-emitting diode current protection resistor

Claims

1. a plurality of MOS semiconductors each having a drain-source connected in parallel via a fuse resistor to a load side from the lithium ion battery; a photorelay, the output side of which is interposed between the lithium ion battery and each gate terminal of the plurality of MOS semiconductors via a first resistor that applies a gate voltage to the plurality of MOS semiconductors, and the input side of which is connected between the positive and negative terminals of the lithium ion battery via a second resistor that turns on the photorelay; a set switch inserted in a first line consisting of the lithium ion battery, the input side of the photorelay, and the second resistor; a memory function unit having a second line connecting one of the drain or source of one of the MOS semiconductors connected in parallel to an output terminal on the input side of the photorelay, and a third line connecting the other of the drain or source to a gate terminal of the one MOS semiconductor via a third resistor for removing charges from the gates of the MOS semiconductors connected in parallel; A power supply circuit comprising:

2. 2. The power supply circuit according to claim 1, a reset switch inserted in a fourth line formed by the lithium ion battery and the second resistor; A power supply circuit comprising:

3. 3. The power supply circuit according to claim 1, The resistance value of the first resistor is set to be larger than the resistance value of the third resistor, and the ratio of the resistance value of the first resistor to the resistance value of the third resistor is set to make the drain-source of the one MOS semiconductor conductive when a voltage is applied to the gate of the one MOS semiconductor. Power supply circuit.

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