Backup power supply device and electronic apparatus

Abstract

The present invention protects a secondary battery without consuming the original battery capacity of the secondary battery by a device such as a microcomputer, and suppresses wasteful power consumption of the secondary battery during output short circuit and storage. A voltage conversion circuit is provided for converting the voltage of a secondary battery into a backup voltage required by a semiconductor memory, and a voltage monitoring circuit for monitoring an output voltage is provided on the output side of the voltage conversion circuit. The operation of the voltage conversion circuit is stopped when the result of the voltage monitoring is a short-circuit state or a state close to the short-circuit state.

Description

Backup Power Supplies and Electronic Equipment

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

[0002] In electronic devices with semiconductor memory, in order to preserve the information stored in the semiconductor memory even if the main power source is lost, it is common to install a circuit that backs up the semiconductor memory using a power source other than the main power source, such as a primary battery, as a backup power source. When using a primary battery for backup, alkaline batteries, lithium batteries, etc. are generally used, but when using alkaline batteries, they must be replaced periodically (approximately every year).

[0003] When lithium batteries are used, there is little self-discharge over the long term, but if the device is stopped for several periods per year, the battery will be consumed and there is a concern that the battery capacity will decrease, so it becomes necessary to check the remaining battery charge periodically, and maintenance work will be required approximately every three years. To solve this problem, a method is used in which a backup system is created using secondary batteries in addition to the battery.

[0004] When a secondary battery is used, the secondary battery is charged by an external power source during normal use, and the secondary battery is used to back up the semiconductor memory while the power is off. However, when a secondary battery is used, it is packaged with, for example, a microcomputer (MCU) to manage the charging and discharging of the secondary battery, and monitors the terminal voltage (cell voltage), charging and discharging current, battery temperature, etc. of the secondary battery to detect abnormalities, and when an abnormality is detected, it protects the secondary battery by shutting off a switch element inserted in series in the charging and discharging path of the secondary battery.

[0005] The microcomputer also plays an intelligent role in managing the remaining charge capacity of the secondary battery by integrating the charge / discharge current of the secondary battery, and in determining the battery life by managing the number of repeated charge / discharge cycles, etc. Technology for performing backup operation using an intelligent secondary battery is described, for example, in Patent Document 1 listed below.

[0006] JP 2010-218743 A

[0007] However, the disclosure of Patent Document 1 has a first problem in that the use of a microcomputer consumes the original battery capacity of the secondary battery, thereby reducing the actual capacity of the secondary battery.

[0008] In addition, in order to reduce unnecessary power consumption of the secondary battery, the microcomputer is stopped or put into hibernation, but this is a complex system that requires processing a start-up signal to resume operation from a stopped state, and there is a second problem in that if the microcomputer latches up, it may not be able to perform its intended backup operation.

[0009] Furthermore, if the secondary battery is not charged for a long period of time, the battery capacity of the secondary battery will become zero, which presents a third problem in that initial charging will be necessary after long-term storage.

[0010] In order to solve the first problem, one embodiment of the present invention provides a voltage conversion circuit that converts the voltage of a secondary battery into the backup voltage required by a semiconductor memory, and a voltage monitoring circuit that monitors the output voltage on the output side of the voltage conversion circuit.If the result of the voltage monitoring indicates a short-circuit state or a state close to such a state, control is performed to stop the operation of the voltage conversion circuit, thereby protecting the secondary battery and reducing unnecessary power consumption.

[0011] To solve the second problem, in order to restart the backup operation, a voltage is applied to the voltage monitoring circuit with an extremely simple circuit by power input from the main power supply side, thereby restoring the voltage conversion circuit to a recovery state.

[0012] To solve the third problem, during long-term storage, the voltage conversion output can be short-circuited to stop the operation of the voltage conversion circuit, thereby reducing the slight power consumption in a no-load state.

[0013] According to the present invention, it is possible to protect the secondary battery from over-discharge, to suppress unnecessary power consumption of the secondary battery when it is not in use, and to back up the semiconductor memory.

[0014] 1 is a configuration diagram of a first embodiment of a backup 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 backup power supply device according to an embodiment of the present invention; FIG. 3 is a configuration diagram of a second embodiment of a backup power supply device according to an embodiment of the present invention;

[0015] 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.

[0016] A typical backup power supply refers to an uninterruptible power supply such as a UPS (Uninterruptible Power Supply) that maintains the operation of the entire system, but the backup power supply defined here is a power supply that backs up the power supply for part of a device in order to prevent the loss of position information data when the system stops operating, such as data retention in semiconductor memory or information from encoders that determine the position of mechanically operating devices, when the system suddenly stops operating or stops for equipment maintenance, etc.

[0017] 1 is a diagram showing the overall configuration of a backup power supply according to one embodiment of the present invention. Electronic equipment 9 includes a system power supply 10, a diode 12, a semiconductor memory 11, a semiconductor memory power terminal 19, a power output terminal 13 for charging the power terminal, and a backup power input terminal 14.

[0018] Electronic device 9 has an internal system power supply unit 10 that outputs a voltage of, for example, 3.6 (V) to drive semiconductor memory 11. Backup power supply input terminal 14 is connected to semiconductor memory power supply terminal 19 via diode 12, and a voltage lower than that of terminal 19, for example, a voltage of 3.5 (V), is input. A voltage of, for example, 3.3 (V) is supplied to power supply terminal charging power output terminal 13.

[0019] The backup power supply 1 comprises a secondary battery 3, a voltage conversion circuit 6, a power input terminal 7, a backup output terminal 8, a voltage monitoring circuit 101, a diode 106, and a resistor 105. The backup power supply 1 further comprises a charging circuit 2, which charges the secondary battery 3. The voltage conversion circuit 6 comprises a secondary battery input terminal 18 and an enable control terminal 102.

[0020] The secondary battery 3 is a sulfide-based all-solid-state battery. The voltage conversion circuit 6 converts the voltage of the secondary battery to a predetermined voltage. The voltage monitoring circuit 101 is composed of a voltage detection terminal 103 and a common ground terminal 104. The enable control terminal 102 is connected to the output side of the voltage monitoring circuit 101, and the voltage monitoring circuit 101 monitors the output voltage of the voltage conversion circuit 6. A diode 106 and a resistor 105 are connected in series. The diode 106 and the resistor 105 connected together may be referred to as an element. The input voltage of the charging circuit 2 is configured to be lower than the output voltage of the voltage conversion circuit 6.

[0021] Next, the operation will be described. When the electronic device 9 is operating, a predetermined voltage is supplied from the power input terminal 7 of the backup power supply 1 to the charging circuit 2, which charges the secondary battery 3. During charging, voltage is input from terminal 18 to the voltage conversion circuit, terminal 102 is enabled, and 3.5 (V) is output to terminal 8 via the voltage conversion circuit 6. Because the voltage at terminal 7 is lower than the voltage at terminal 8, diode 106 is reverse biased and is electrically cut off.

[0022] When electronic device 9 is not operating, charging circuit 2 does not charge, and the voltage of the secondary battery is output to terminal 18, and the same operation is performed. In this case, terminal 7 is at ground potential, but diode 106 remains in a cut-off state, and the 3.5 (V) supplied from terminal 14 drops by the forward voltage drop (hereinafter referred to as VF) of diode 12. For example, when VF = 0.7 (V), 2.8 (V) is supplied to semiconductor memory 11, and data loss in the semiconductor memory can be prevented.

[0023] If there is a malfunction on the system side, for example if terminal 14 is short-circuited, the voltage at terminal 103 will drop to approximately 0 (V), and control will be performed to change enable control terminal 102 from the OPEN state to the ground potential. When enable control terminal 102 is in the ground state, operation of voltage conversion circuit 6 will stop, and voltage output to terminal 8 will stop. In this state, current flowing from secondary battery 3 to voltage conversion circuit 6 will stop, making it possible to prevent unnecessary power consumption from secondary battery 3.

[0024] When the system power supply 10 is in an operating state, a short-circuit current flows from terminal 14 via terminal 7, diode 106, and resistor 105. However, by appropriately setting the resistance of resistor 105, for example, to about 1 kΩ, this current can be suppressed to about 3.3 mA. When the system malfunction is resolved, the potential at terminal 103 immediately rises to 3.3 V, and the enable control terminal 102 output from the voltage monitoring circuit 101 becomes open again. This causes the voltage conversion circuit 6 to start operating, and the potential at terminal 8 returns to 3.5 V, allowing backup operation to continue. A specific configuration example of the voltage monitoring circuit 101 will be described using FIG. 2.

[0025] 2 is a diagram showing a specific configuration of a first embodiment of a charging device according to the present invention. Voltage monitoring circuit 101 is composed of resistors 110 and 111, a reference voltage source 112, a voltage comparator 113, an N-channel MOS transistor 114, a ground terminal 104, a voltage detection terminal 103, and an enable control terminal 102. Next, the voltage monitoring operation will be described.

[0026] The voltage input from voltage detection terminal 103 is divided by resistors 110 and 111 and compared with the voltage of reference voltage source 112. If the voltage is smaller, the output of voltage comparator 113 is on, and if the voltage is larger, the output is off. For example, if the voltage of the reference voltage source is 1.0 (V) and resistors 110 and 111 have the same value, during normal operation the divided voltage value is 1.75 (V), the output of voltage comparator 113 is off, and the drain terminal of N-channel MOS transistor 114, i.e., enable control terminal 102, is in an open state. When the output is short-circuited, the divided voltage value is 0 (V), the output of voltage comparator 113 is in an on state, and the drain terminal of N-channel MOS transistor 114, i.e., enable control terminal 102, is grounded.

[0027] If the set values ​​of resistors 110 and 111 and the ground voltage of reference voltage source 112 are set under the above conditions, when the voltage value at terminal 8 is, for example, 2.1 (V), the voltage divided by resistors 110 and 111 will be 1.05 (V), which is higher than the voltage value of reference voltage source 112, 1.0 (V), and therefore enable control terminal 102 will not be grounded. If some kind of abnormality occurs on the system side, the output current from backup power supply 1 increases, and the output voltage drops, making it impossible to deal with this situation. To prevent this situation, it is necessary to optimize the set values ​​of resistors 110 and 111 and the set voltage of reference voltage source 112. As an example, if the detected voltage of terminal 8 is Vdet, the set voltage of reference voltage source 112 is Vref, the resistance value of resistor 110 is R110, and the resistance value of resistor 111 is R111, then this can be achieved by setting them so that the following holds: Vdet×R111 / (R110+R111)=Vref (1).

[0028] The effect of this embodiment is that it is possible to minimize power consumption of the secondary battery 3. When the secondary battery 3 is fully charged and removed from the electronic device 9 for storage, voltage output at the terminal 8 is not required, so once it is short-circuited, the operation of the voltage conversion circuit 6 stops, and no power is consumed by the secondary battery 3. When the secondary battery 3 is incorporated into the electronic device 9, voltage can be supplied from the power supply input terminal 7 to enable voltage output from the voltage conversion circuit 6.

[0029] In this embodiment, the voltage conversion circuit 6 has been described as having an input terminal 18 and an enable control terminal 102, and as a circuit that converts the voltage input from the input terminal 18 into a predetermined voltage and outputs it, and that activates or stops the voltage conversion operation and voltage output operation according to the control information of the enable control terminal 102. The voltage conversion circuit 6 does not necessarily have to have a voltage conversion function, and may simply have a function of activating or stopping the voltage output operation according to the control information of the enable control terminal 102 for the voltage from the input terminal 18. In this case, the effects include reducing unnecessary power consumption of the secondary battery 3 due to a short circuit at the voltage of the terminal 8, and reducing unnecessary power costs when the secondary battery 3 is stored away from the electronic device 9.

[0030] 3 is a diagram showing the overall configuration of a backup power supply according to a second embodiment of the present invention. Electronic equipment 9 is composed of a system power supply 10, a diode 12, a semiconductor memory 11, a semiconductor memory power terminal 19, a power output terminal 13 for charging the power terminal, and a backup power input terminal 14.

[0031] Electronic device 9 has an internal system power supply unit 10 that outputs a voltage of, for example, 3.6 (V) to drive semiconductor memory 11. Backup power supply input terminal 14 is connected to semiconductor memory power supply terminal 19 via diode 12, and a voltage lower than that of terminal 19, for example, a voltage of 3.5 (V), is input. A voltage of, for example, 3.3 (V) is supplied to power supply terminal charging power output terminal 13.

[0032] The backup power supply device 1 has a charging circuit 2, a secondary battery 3, a primary battery 4, a battery selection circuit 5, a voltage conversion circuit 6, a power input terminal 7, a backup output terminal 8, a voltage monitoring circuit 101, a diode 106, and a resistor 105. The voltage conversion circuit 6 is composed of a secondary battery input terminal 18 and an enable control terminal 102. The voltage monitoring circuit 101 is composed of a voltage detection terminal 103 and a common ground terminal 104. The battery selection circuit 5 is composed of a secondary battery input terminal 15, a primary battery input terminal 17, and a common ground terminal 16. The primary battery 4 is a lithium battery.

[0033] Next, the operation will be described. When the electronic device 9 is operating, a predetermined voltage is supplied from the power input terminal 7 of the backup power supply 1 to the charging circuit 2, which charges the secondary battery 3. During charging, the input voltage from terminal 15 is selected by the battery selection circuit 5 and output to terminal 18, and then input to the voltage conversion circuit 6, terminal 102 is enabled, and 3.5 (V) is output to terminal 8 via the voltage conversion circuit 6. Because the voltage at terminal 7 is lower than the voltage at terminal 8, the diode 106 is reverse biased and is electrically cut off.

[0034] When electronic device 9 is not in operation, charging circuit 2 does not perform charging operation, and the voltage of the secondary battery is output to terminal 15, selected by battery selection circuit 5, and output to terminal 18, and the same operation is performed. In this case, terminal 7 is at ground potential, but diode 106 remains in a cut-off state, and the 3.5 (V) supplied from terminal 14 drops by the forward voltage drop (hereinafter referred to as VF) of diode 12; for example, if VF = 0.7 (V), 2.8 (V) is supplied to semiconductor memory 11, and loss of data in the semiconductor memory can be prevented.

[0035] When the electronic device 9 is not in operation and the secondary battery 3 has no remaining battery capacity, the battery selection circuit 5 outputs the voltage of the primary battery 4 connected to terminal 17 to terminal 18, and performs the same operation. The battery selection circuit 5 is configured as a circuit that selects the secondary battery 3 first, then the primary battery 4, in that order.

[0036] An example of an electronic device 9 equipped with a backup power supply is an absolute encoder used in an industrial robot. An absolute encoder is mounted on the motor (e.g., servo motor) of the robot's operating axis, and by supplying backup power to the encoder using a battery or the like, the motor's movement is constantly monitored even when the controller's power is cut off, enabling smooth startup without returning to the origin when the system is started or when recovering from an emergency stop.

[0037] In any of the embodiments described above, it is possible to reduce unnecessary power consumption of the secondary battery when the output is short-circuited, and when the backup power supply device 1 is removed from the electronic device 9, the output can be short-circuited to preserve the accumulated charge in the secondary battery 3. Furthermore, since no mechanical switch is required, it has the advantage of being easy to make the backup device drip-proof and waterproof.

[0038] 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 innovation and foster resilience" and "11. Make cities and towns inclusive and sustainable" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0039] 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.

[0040] REFERENCE SIGNS LIST 1 backup power supply device, 2 charging circuit, 3 secondary battery, 6 voltage conversion circuit, 101 voltage monitoring circuit, 105 resistor, 106 diode

Claims

1. A backup power supply device comprising: a secondary battery; a voltage conversion circuit that converts the voltage of the secondary battery into a predetermined voltage; a voltage monitoring circuit that monitors the output voltage of the voltage conversion circuit; and an element comprising a diode and a resistor connected in series.

2. A backup power supply device according to claim 1, wherein the voltage conversion circuit has an enable control terminal, and the enable control terminal is connected to the output side of the voltage monitoring circuit.

3. A backup power supply device according to claim 2, wherein the element in which the diode and the resistor are connected in series is connected to the input side of a charging circuit that charges the secondary battery and to the output side of the voltage conversion circuit.

4. A backup power supply device according to claim 3, wherein the input voltage of said charging circuit is lower than the output voltage of said voltage conversion circuit.

5. A backup power supply device according to claim 4, wherein the secondary battery is a sulfide-based all-solid-state battery.

6. A backup power supply device comprising: a primary battery; a secondary battery; a battery selection circuit that selects the voltage of the primary battery or the secondary battery; a voltage conversion circuit that converts the voltage selected by the battery selection circuit into a predetermined voltage; a voltage monitoring circuit that monitors the output voltage of the voltage conversion circuit; and an element comprising a diode and a resistor connected in series.

7. A backup power supply device according to claim 6, wherein the primary battery is a lithium battery, and the secondary battery is a sulfide-based all-solid-state battery.

8. A backup power supply device according to claim 7, wherein the battery selection circuit is configured as a circuit that selects the secondary battery and then the primary battery in that order with priority.

9. Electronic equipment comprising: a motor; an absolute encoder; a secondary battery; a voltage conversion circuit that converts the voltage of the secondary battery to a predetermined voltage; a voltage monitoring circuit that monitors the output voltage of the voltage conversion circuit; and an element comprising a diode and a resistor connected in series, wherein the voltage conversion circuit has an enable control terminal that is connected to the output side of the voltage monitoring circuit; the element comprising the diode and the resistor connected in series is connected to the input side of a charging circuit that charges the secondary battery and the output side of the voltage conversion circuit; the rotating shaft of the motor and the input shaft of the absolute encoder are mechanically connected; and the output side of the voltage conversion circuit is connected to the power supply terminal of the absolute encoder.

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