Power supply device and electronic apparatus

Abstract

The purpose of the present invention is to make it possible, even if individual secondary batteries connected in parallel have suddenly short-circuited, to immediately disconnect the secondary batteries individually from a main circuit. The present invention relates to the sustainable development goal "9. Build foundations for industry and technical innovation." This power supply device is provided with a voltage detector that detects the voltage of a secondary battery and a control unit that is controlled by the voltage detector. The secondary battery and the control unit are connected in series to form a battery module, and a plurality of the battery modules are connected in parallel to a charging circuit that charges the secondary batteries.

Description

Power supplies and electronic devices

[0001] The present invention relates to a device that uses a secondary battery to form a backup power supply.

[0002] Electronic devices with semiconductor memory typically incorporate a backup circuit for the semiconductor memory, using a power source other than the main power source, such as a secondary battery, to retain information stored in the semiconductor memory even if the main power source is lost. When using a secondary battery, the secondary battery is charged by an external power source during normal use, and the secondary battery backs up the semiconductor memory when the power source is turned off. Furthermore, for long-term backup, multiple battery cells constituting the secondary battery must be connected in parallel, or multiple battery cells must be connected in series if the required voltage of the device to be backed up is higher than the voltage of the battery cells. However, if the battery cells deteriorate or develop an abnormality such as a short circuit during use, the backup power output cannot be obtained. One possible solution to this problem is to disconnect the abnormal battery cell from the circuit. For example, a technology for using multiple secondary batteries to disconnect battery cells that have become abnormal is described in the following Patent Document 1, which describes a method for identifying secondary batteries that have become abnormal by providing an auxiliary charging / discharging device and a voltage measuring device, charging each secondary battery using the auxiliary charging / discharging device, measuring the voltage of the secondary battery with the voltage measuring device, and using a switch connected in series to each secondary battery that opens when there is an abnormality and makes contact when there is a normal state.

[0003] JP 2012-90436 A

[0004] However, the disclosure of Patent Document 1 discloses a method for identifying abnormal secondary batteries, which includes providing an auxiliary charging / discharging device and a voltage measuring device, charging each secondary battery using the auxiliary charging / discharging device, measuring the voltage of each secondary battery with the voltage measuring device, and disposing of a switch connected in series with each secondary battery in a manner that turns OFF (open) when an abnormality occurs and turns ON (connected) when the secondary battery is normal. This method requires that each secondary battery be disconnected from the main circuit to identify the individual secondary batteries. The existence of a separate circuit for distinguishing between normal and abnormal batteries not only increases the overall system cost, but also complicates control, resulting in a first problem: the secondary batteries cannot be quickly disconnected from the main circuit if they suddenly short-circuit. Furthermore, while Patent Document 1 does not specifically disclose a method for individually controlling the switches connected in series with each secondary battery, it requires wiring control lines to control the switches and a memory device to control or retain the switch status, resulting in a complex system configuration and a second problem: reduced long-term reliability due to an increased number of components.

[0005] In order to achieve the first and second objects, in one embodiment of the present invention, for example, a power supply device includes a voltage detector that detects the voltage of a secondary battery and a control unit controlled by the voltage detector. The secondary battery and the control unit are connected in series to form a battery module, and a charging circuit that charges the secondary battery includes multiple battery modules connected in parallel.

[0006] According to the present invention, even in applications where a large number of secondary batteries are used in parallel to obtain sufficient battery capacity, even if there is a secondary battery that has been manufactured with a manufacturing defect (or that has become defective due to deterioration over time), it is possible to obtain an extremely reliable backup power supply system without suffering fatal damage during charging and discharging operations.

[0007] FIG. 1 is a configuration diagram of a first embodiment of a power supply device according to an embodiment of the present invention. FIG. 2 is a diagram showing a specific configuration of a first embodiment of a power supply device according to an embodiment of the present invention. FIG. 3 is a diagram showing a specific configuration of a first embodiment of a power supply device according to an embodiment of the present invention. FIG. 4 is a configuration diagram of a second embodiment of a power supply device according to an embodiment of the present invention. FIG. 5 is a configuration diagram of a third embodiment of a power supply device according to an embodiment of the present invention.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the description of the embodiments, and various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the present invention, components having the same functions are given the same reference numerals, and repeated explanations thereof may be omitted.

[0009] FIG. 1 shows the overall configuration of a power supply device according to one embodiment of the present invention. Power supply device 1 includes a charging circuit 28, a charging switch 2, an output switch 3, a battery module power input terminal 24, an output terminal 26, and ground terminals 25 and 27. Power supply device 1 also includes a pre-charging circuit 7, diodes 8 and 10, and resistors 9 and 11. This embodiment includes multiple battery modules, and in this example, a first battery module 4 and a second battery module 5 are used. First battery module 4 includes a secondary battery 12, a voltage detector 13, a control unit (control switch) 14, a positive terminal 18, a negative terminal 19, and a charge / discharge line terminal 20. Second battery module 5 includes a secondary battery 15, a voltage detector 16, a control unit (control switch) 17, a positive terminal 21, a negative terminal 22, and a charge / discharge line terminal 23. Secondary battery 15 may be an all-solid-state battery using a sulfide-based solid electrolyte or an oxide-based solid electrolyte.

[0010] Voltage detector 13 detects the voltage of secondary battery 12, and voltage detector 16 detects the voltage of secondary battery 15. The control unit performs control using voltage detectors 13 and 16. In this embodiment, the control unit is a control switch, but is not limited to this. Secondary battery 12 and control switch 14 are connected in series, and secondary battery 15 and control switch 17 are connected in series. Battery module 4 and battery module 5 are connected in parallel to a charging circuit 28 that charges the secondary batteries. Battery module 4 has three terminals: a negative terminal 19 of secondary battery 12, a positive terminal 18, and a charge / discharge line terminal 20, which is also the output terminal of control switch 14. A preliminary charging circuit 7 is added and connected to positive terminal 18.

[0011] The battery module 5 has three terminals: a negative terminal 22 and a positive terminal 21 of the secondary battery 15, and a charge / discharge line terminal 23 which is also the output terminal of the control switch 17. A pre-charging circuit 7 is connected to the positive terminal 21. The output of the pre-charging circuit 7 is connected to the positive terminal 18 through a first element, and to the positive terminal 21 through a second element. The first element is formed by connecting a resistor 9 and a diode 8 in series. The second element is formed by connecting a resistor 11 and a diode 10 in series. A load circuit 6 is connected to an output terminal 26 and a ground terminal 27 of the power supply device 1.

[0012] The operation will be described below. First, normal operation will be described. Power supplied from the power supply input terminal 24 is input to the charging circuit 28, which outputs the voltage and current required to charge the secondary batteries 12, 15 through the charging switch 2. In the initial state, if the secondary batteries 12, 15 are normal and charged to near their rated voltage, the voltage detectors 13, 16 can drive the control switches 14, 17. The control switches 14, 17 are turned on, and the secondary batteries 12, 15 are charged through terminals 20, 23. When charging is completed, the charging switch 2 is opened, and since the voltage of the secondary batteries 12, 15 is higher than the rated voltage, the control switches 14, 17 remain on, and the same voltage as the positive terminals 18, 21 of the secondary batteries 12, 15 is output to terminals 20, 23. When the output switch 3 is connected in this state, current is supplied from the secondary batteries 12, 15 to the load circuit 6 through terminal 26, enabling backup operation.

[0013] Second, we will explain the operation when the secondary batteries 12, 15 are normal but undercharged. When the charge stored in the secondary batteries 12, 15 is insufficient, the voltage drops as the amount of charge stored in the secondary batteries 12, 15 decreases, causing the voltage detectors 13, 16 to switch the control switches 14, 17 from ON to OFF. Power from the power input terminal 24 is supplied to the pre-charging circuit 7, which outputs a voltage approximately equal to the rated voltage of the secondary batteries 12, 15. This voltage is supplied directly to the positive terminals 18, 21 of the secondary batteries 12, 15 through resistors 9, 11 and diodes 8, 10. When the voltage of the secondary batteries 12, 15 rises to near the rated voltage due to the current supply from the pre-charging circuit 7, the voltage detectors 13, 16 drive the control switches 14, 17 to the ON state, and charging begins with current from the charging circuit 28.

[0014] Third, we will explain the operation when secondary battery 12 is normal and secondary battery 15 is defective due to an internal short circuit. In this case, the voltage of secondary battery 15 will be approximately 0.4 (V) or less, so voltage detector 16 cannot drive control switch 17, control switch 17 will be in the OFF state, no current will pass through terminal 23, and operation can continue with the battery capacity of first battery module 4 only.

[0015] Furthermore, when the accumulated charge in the secondary battery 12 becomes low and the charging operation begins, the charging current from the pre-charging circuit 7 is supplied to the secondary battery 12 through resistor 9, diode 8, and positive terminal 18. The charging current from the pre-charging circuit 7 is supplied to the secondary battery 15 through resistor 11, diode 10, and positive terminal 21, but because the secondary battery 15 is short-circuited, the voltage of the voltage detector 16 does not rise, the control switch 17 remains OFF, and the current from the charging circuit 28 operates to be supplied only to the secondary battery 12. Furthermore, because the charging current from the pre-charging circuit 7 is limited by resistor 11, the current supplied to the secondary battery 12 does not decrease and the voltage of the secondary battery 12 does not fail to rise.

[0016] 2 is a diagram showing a specific circuit configuration of the first battery module 4. The voltage detector 13 has an N-channel MOS transistor 31. In this embodiment, the voltage detector 13 is composed of the N-channel MOS transistor 31 and a parasitic diode 32. The control switch 14 has a P-channel MOS transistor 33. In this embodiment, the control switch 14 is composed of the P-channel MOS transistor 33 and a parasitic diode 34. Resistors 35 and 36 supply a bias current for operation. If the voltage of the secondary battery 12 is Vb and the threshold voltage for turning on the MOS transistor 31 is Vth, the gate voltage of the MOS transistor 31 is supplied via resistor (first resistor) 35.

[0017] Vth<Vb (1) In the case of formula (1), the MOS transistor 31 is turned on, and conduction occurs between the drain and source. Because the voltage of the secondary battery 12 is supplied to the drain of the MOS transistor 31 through the parasitic diode 34 and resistor (second resistor) 36, current flows through the resistor 36, causing the gate potential of the MOS transistor 33 to drop below the source potential, turning the MOS transistor 33 on and establishing conduction between the drain and source. As a result, the terminal 18 and the terminal 20 are connected.

[0018] On the other hand, when the voltage of the secondary battery 12 drops and equation (2) holds, Vth>Vb (2), the MOS transistor 31 turns OFF, and terminal 18 and terminal 20 are connected only by the parasitic diode 34. Comparing the voltage at terminal 20 with the voltage at terminal 18, the voltage at terminal 20 is higher, so the parasitic diode 34 is in a reverse bias state, preventing current from flowing from terminal 20 to terminal 18, and power from other normal battery modules is not consumed.

[0019] Although the embodiment shown in FIGS. 1 and 2 shows two battery modules connected in parallel, a plurality of battery modules can be connected in parallel, and there is no limit to the number of connections.

[0020] 2, there are no particular limitations on the Vth of the selected MOS transistor and the Vb of the selected secondary battery. As an example, when a sulfide-based all-solid-state battery having an operating voltage of about 2.3 V and charged at a voltage of about 2.6 V is used as the secondary battery, a MOS transistor with a Vth of 1.8 (V) to 2.5 (V) is selected for optimal operation.

[0021] Figure 3 is a diagram showing one example of an application form of the power supply device according to the embodiment. The power supply device 1 is equipped with a first battery module 4 and a second battery module 5. The battery module 4 in Figure 2 has three terminals 18, 19, and 20, and in Figure 3, the electrical contacts on the battery module side are designated 18a, 19a, and 20a, respectively. The electrical contacts on the power supply device 1 side are designated 18b, 19b, and 20b, respectively, and are mechanically connected via the contacts with the same numbers, allowing for easy replacement of the battery modules in the event of a malfunction.

[0022] 4 is a diagram showing the overall configuration of a power supply device according to a second embodiment of the present invention. The power supply device 101 includes a charging circuit 28, a charging switch 2, an output switch 3, a first battery module 4, a second battery module 5, a pre-charging circuit 7, diodes 8 and 10, resistors 9 and 11, a power input terminal 24, an output terminal 26, ground terminals 25 and 27, and a pre-charging input terminal 29. The first battery module 4 includes a secondary battery 12, a voltage detector 13, a control switch 14, a positive terminal 18, a negative terminal 19, and a charge / discharge line terminal 20. The second battery module 5 includes a secondary battery 15, a voltage detector 16, a control switch 17, a positive terminal 21, a negative terminal 22, and a charge / discharge line terminal 23. A load circuit 6 is connected to the output terminal 26 and ground terminal 27 of the power supply device 101.

[0023] Since the operation is the same as that of the embodiment shown in Figure 1, a description will be omitted and only the differences between Figures 1 and 4 will be explained. The pre-charging circuit 7 operates by supplying current from the pre-charging circuit 7 to raise the voltage of the secondary batteries 12, 15 to near their rated voltage when the storage capacity of the secondary batteries 12, 15 decreases and the control switches 14, 17 cannot be driven. Furthermore, the voltage detectors 13, 16 drive the control switches 14, 17 to the ON state, allowing charging to be performed using current from the charging circuit 28. The pre-charging circuit 7 is necessary for the initial charging of the secondary batteries 12, 15, but does not operate once charging is complete and the secondary batteries 12, 15 are in an appropriate charge / discharge cycle so as not to be over-discharged. Therefore, providing a terminal 29 on the power supply device 101 and configuring the pre-charging circuit 7 as an external circuit provides an advantageous configuration for reducing the cost of the device.

[0024] FIG. 5 shows the overall configuration of a power supply device according to a third embodiment of the present invention. The power supply device 102 comprises a charging circuit 28, a charging switch 2, an output switch 3, a first battery module 4, a second battery module 5, diodes 8 and 10, resistors 9 and 11, a power input terminal 24, an output terminal 26, and ground terminals 25 and 27. The first battery module 4 comprises a secondary battery 12, a voltage detector 13, a control switch 14, a positive terminal 18, a negative terminal 19, and a charge / discharge line terminal 20. The second battery module 5 comprises a secondary battery 15, a voltage detector 16, a control switch 17, a positive terminal 21, a negative terminal 22, and a charge / discharge line terminal 23. A load circuit 6 is connected to the output terminal 26 and the ground terminal 27 of the power supply device 102. The power supply device 102 is provided with pre-charging input terminals 103 and 104, and the output of the pre-charging circuit 7 is connected to the power supply device 102 via the pre-charging input terminals 103 and 104.

[0025] Since the operation is the same as that of the embodiment shown in Fig. 1, a description thereof will be omitted and only the differences between Fig. 1 and Fig. 5 will be explained. The operation of the pre-charging circuit 7 is such that, when the storage capacity of the secondary batteries 12, 15 decreases and the control switches 14, 17 cannot be driven, the voltage of the secondary batteries 12, 15 is increased to near the rated voltage by the current supplied from the pre-charging circuit 7, and the voltage detectors 13, 16 drive the control switches 14, 17 to the ON state, allowing charging to be performed by the current from the charging circuit 28. The pre-charging circuit 7 is necessary for the initial charging of the secondary batteries 12, 15, but does not operate once charging is complete and in an appropriate charge / discharge cycle where the secondary batteries 12, 15 are not over-discharged. Therefore, by configuring the pre-charging circuit 7, diodes 8, 10, and resistors 9, 11 as external components, the cost of the device can be reduced.

[0026] The configuration of Figure 5 is more advantageous in terms of cost than the configuration of Figure 4 because it reduces the number of parts in the power supply device 102. In addition, it has the advantage of being easy to maintain because it can directly measure the voltage of the secondary battery.

[0027] In the above embodiment, a semiconductor switch element is provided on the positive electrode side of each secondary battery and connected to the main circuit, and the semiconductor switch element is directly controlled by the voltage of each secondary battery, so that even if an individual secondary battery suddenly shorts out, it can be quickly disconnected from the main circuit. Also, a semiconductor switch element is provided on the positive electrode side of each secondary battery and connected to the main circuit, and the semiconductor switch element is directly controlled by the voltage of each secondary battery. If the voltage of an individual secondary battery drops below a predetermined voltage, the secondary battery is electronically disconnected from the main circuit, and if the voltage of the secondary battery recovers, the secondary battery is electronically connected to the main circuit. This allows an individual secondary battery to be quickly disconnected from the main circuit even if it suddenly shorts out.

[0028] In any of the above-described embodiments, even if the charge / discharge characteristics of the secondary battery deteriorate over time, or if a secondary battery that was problem-free at the time of manufacture suddenly becomes unusable due to an internal short circuit or the like, the secondary battery can be automatically disconnected from the charge / discharge circuit, thereby providing a significant advantage in that it is possible to obtain an output voltage as a power supply. An example of an electronic device incorporating the power supply device of the present invention is an absolute encoder used in an industrial robot. The motor (e.g., a servo motor) of the robot's operating axis is equipped with an absolute encoder, and by supplying power to the encoder using this power supply device, the motor's movement can be constantly monitored even when the controller's power is cut off, enabling smooth startup without a return to the origin when the system is started or when recovering from an emergency stop.

[0029] Furthermore, the technology according to this embodiment can provide a charge / discharge system with excellent energy efficiency, which contributes to the achievement of "9. Build resilient infrastructure, promote inclusive and sustainable industrialization, promote inclusive and sustainable technological development, and make sustainable use of resources" and "11. Make cities and towns sustainable and livable" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0030] Although various embodiments have been described above in detail, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are detailed descriptions of the entire system in order to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0031] 1... power supply device, 28... charging circuit, 12, 15... secondary battery, 13, 16... voltage detector, 14, 17... control switch, 7... pre-charging circuit, 8, 10... diode, 9, 11... resistor

Claims

1. A power supply device comprising: a secondary battery; a voltage detector that detects the voltage of the secondary battery; and a control unit controlled by the voltage detector, wherein the secondary battery and the control unit are connected in series to form a battery module, and a charging circuit that charges the secondary battery is connected in parallel to a plurality of the battery modules.

2. A power supply device according to claim 1, wherein the control unit is a control switch, the battery module has three terminals: a negative terminal of the secondary battery, a positive terminal, and an output terminal of the control switch, and the positive terminal is connected to a pre-charging circuit.

3. A power supply device according to claim 2, wherein the output of said pre-charging circuit is connected to said positive terminal through an element in which a resistor and a diode are connected in series.

4. A power supply device according to claim 2, wherein the voltage detector is composed of an N-channel MOS transistor, and the control switch is composed of a P-channel MOS transistor.

5. A power supply device according to claim 4, wherein the positive terminal of the secondary battery is connected to the drain terminal of the P-channel MOS transistor and to the gate terminal of the N-channel MOS transistor via a first resistor, a second resistor is connected in parallel to the gate and source terminals of the P-channel MOS transistor, the drain terminal of the N-channel MOS transistor is connected to the gate terminal of the P-channel MOS transistor, and the source terminal of the P-channel MOS transistor is configured as the output terminal of the control switch.

6. The power supply device according to claim 5, wherein the secondary battery is an all-solid-state battery using a sulfide-based solid electrolyte.

7. The power supply device according to claim 5, wherein the secondary battery is an all-solid-state battery using an oxide-based solid electrolyte.

8. A power supply device according to claim 2, comprising a pre-charging terminal, wherein the battery module comprises three terminals: a negative terminal of the secondary battery, a positive terminal, and an output terminal of the control switch, and wherein an element comprising a resistor and a diode connected in series is connected between the positive terminal and the pre-charging terminal.

9. Electronic equipment comprising: a motor; an absolute encoder; a secondary battery; a voltage detector that detects the voltage of the secondary battery; and a control unit controlled by the voltage detector, wherein the secondary battery and the control unit are connected in series to form a battery module; a power supply device is formed by connecting a plurality of the battery modules in parallel to a charging circuit that charges the secondary battery; the rotating shaft of the motor and the input shaft of the absolute encoder are mechanically connected; and the power supply device is connected to the power terminal of the absolute encoder.

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