Power supplies, power systems, and electrical equipment

Abstract

A power supply device, a power supply system, and an electrical device are provided that can supply a first power supply voltage to the electrical device. [Solution] A power supply device supplies power to an electrical device via a cable. The power supply device includes a constant-voltage power supply unit that supplies a constant power supply voltage to the electrical device, a power supply control unit that controls the constant-voltage power supply unit, and a current detection unit that detects a current in a power supply line that electrically connects the constant-voltage power supply unit and the electrical device. The constant-voltage power supply unit is configured to be able to change the magnitude of the power supply voltage supplied to the electrical device. When the constant-voltage power supply unit is supplying a first power supply voltage V1 to the electrical device and a current value CT detected by the current detection unit is greater than a first current value C1, the power supply control unit causes the constant-voltage power supply unit to maintain the supply of the first power supply voltage V1 to the electrical device.

Description

[Technical Field]

[0001] The present disclosure relates to a power supply device, a power supply system, and an electrical device. [Background technology]

[0002] A power supply device that supplies a power supply voltage to an electrical device via a cable is known (for example, see Patent Document 1). In Patent Document 1, a control device supplies a power supply voltage to a camera device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-300462 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the power consumption of electrical devices tends to increase as their functionality improves. If the power supply voltage supplied to such electrical devices is low, the electrical devices may not be able to fully perform their functions. [Means for solving the problem]

[0005] (1) A power supply device that solves the above problem is a power supply device that supplies power to an electrical device via a cable, and includes a constant-voltage power supply unit that supplies a constant-voltage power supply voltage to the electrical device, a power supply control unit that controls the constant-voltage power supply unit, and a current detection unit that detects a current in a power supply line that electrically connects the constant-voltage power supply unit and the electrical device, wherein the constant-voltage power supply unit is configured to be able to change the magnitude of the power supply voltage supplied to the electrical device, and the power supply control unit causes the constant-voltage power supply unit to maintain the supply of the first power supply voltage to the electrical device when the current value detected by the current detection unit is greater than a first current value while the constant-voltage power supply unit is supplying a first power supply voltage to the electrical device.

[0006] According to the above configuration, when the current value of the power supply line is greater than the first current value while the first power supply voltage is being supplied to the electrical device, the first power supply voltage is maintained. Therefore, when a current greater than the first current value flows through the first power supply voltage, the first power supply voltage can be supplied to the electrical device.

[0007] (2) In the power supply device described in (1) above, when the constant voltage power supply unit is supplying the first power supply voltage to the electrical equipment and the current value is equal to or greater than a second current value that is greater than the first current value, the power supply control unit causes the constant voltage power supply unit to stop supplying the power supply voltage to the electrical equipment.

[0008] When the current value of the power supply line is large, there is a risk of an overcurrent occurring. According to the above configuration, when the current value of the power supply line is equal to or greater than the second current value, the supply of the power supply voltage to the electric device can be stopped.

[0009] (3) In the power supply device described in (1) or (2) above, when the constant voltage power supply unit is supplying the first power supply voltage to the electrical equipment and the current value is equal to or less than the first current value, the power supply control unit causes the constant voltage power supply unit to supply a second power supply voltage greater than the first power supply voltage to the electrical equipment.

[0010] According to the above configuration, when the current value in the power supply line is equal to or less than the first current value while the first power supply voltage is being supplied to the electrical device, the second power supply voltage higher than the first power supply voltage is supplied to the electrical device. This makes it possible to supply the second power supply voltage higher than the first power supply voltage to electrical devices that cannot be powered by the first power supply voltage.

[0011] (4) In the power supply device described in (3) above, when the constant voltage power supply unit is supplying a second power supply voltage to the electrical equipment and the current value is equal to or less than a third current value, the power supply control unit causes the constant voltage power supply unit to stop supplying the power supply voltage to the electrical equipment.

[0012] According to the above configuration, when the current value of the power supply line is equal to or less than the third current value while the second power supply voltage is being supplied to the electric device, the supply of the power supply voltage to the electric device can be stopped.

[0013] (5) A power supply device according to any one of (1) to (4) above, wherein when the power supply device is connected to the electrical equipment, the constant voltage power supply unit supplies a test voltage smaller than the first power supply voltage before supplying the first power supply voltage to the electrical equipment, and the power supply control unit causes the constant voltage power supply unit to supply the first power supply voltage to the electrical equipment when the current value is equal to or smaller than a fourth current value while the constant voltage power supply unit is supplying the test voltage to the electrical equipment.

[0014] According to this configuration, when the test voltage is being supplied, if the current value in the power supply line is equal to or less than the fourth current value, the supply of the first power supply voltage is started. In other words, when the test voltage is being supplied, if the current value in the power supply line is greater than the fourth current value, the supply of the first power supply voltage is not started. This makes it possible to detect abnormalities such as short circuits in electrical equipment.

[0015] (6) A power supply device according to any one of (1) to (5) above, wherein the cable is a coaxial cable, the electrical device is a camera device, and receives a video signal from the camera device via the coaxial cable.

[0016] According to this configuration, the power supply device can receive the video captured by the camera device via the coaxial cable.

[0017] (7) A power supply system that solves the above problem includes the power supply device according to any one of (1) to (6) above, and an electric device that receives a power supply voltage from the power supply device.

[0018] According to this configuration, a power supply voltage suitable for the power consumption of the electrical equipment can be supplied from the power supply device to the electrical equipment.

[0019] (8) An electrical device that solves the above problem is an electrical device that receives a constant power supply voltage from a power supply device, wherein the power supply device supplies a first power supply voltage to the electrical device, and if the electrical device does not start up until a determination period has elapsed since the supply of the first power supply voltage began, starts supplying a second power supply voltage that is greater than the first power supply voltage to the electrical device, and the electrical device is equipped with an appliance control unit that controls the electrical device, and a voltage detection unit that detects the power supply voltage as an appliance-side power supply voltage, and the electrical device starts up after a reference period that is greater than the determination period has elapsed after detecting that the appliance-side power supply voltage is greater than or equal to a startup power supply voltage, and the startup power supply voltage is less than the first power supply voltage.

[0020] According to this configuration, the electric device starts up after a reference period has elapsed since it was detected that the device-side power supply voltage is equal to or greater than the startup power supply voltage. Because the reference period is longer than the determination period, the electric device does not start up until the power supply device starts supplying the second power supply voltage after the device-side power supply voltage of the electric device becomes equal to or greater than the startup power supply voltage. Therefore, the electric device can receive the second power supply voltage from the power supply device.

[0021] (9) An electrical device that solves the above problem is an electrical device that operates on a constant power supply voltage and includes an equipment control unit that controls the electrical device and a voltage detection unit that detects the power supply voltage as an equipment-side power supply voltage, and does not start up if the equipment-side power supply voltage is lower than a third power supply voltage, and starts up if the equipment-side power supply voltage is equal to or higher than the third power supply voltage.

[0022] According to this configuration, the electrical device can be started up when supplied with a device-side power supply voltage equal to or higher than the third power supply voltage, and can be prevented from starting up when supplied with a device-side power supply voltage lower than the third power supply voltage.

[0023] (10) In the electrical device described in (9) above, a drive unit is provided that is driven by the power supply voltage, and the device control unit does not supply the power supply voltage to the drive unit when the device-side power supply voltage is lower than the third power supply voltage, and starts supplying the power supply voltage to the drive unit when the device-side power supply voltage is equal to or higher than the third power supply voltage.

[0024] With this configuration, if the device-side power supply voltage is lower than the third power supply voltage, the power supply voltage is not supplied to the drive unit, but if the device-side power supply voltage is equal to or higher than the third power supply voltage, the power supply voltage is supplied to the drive unit, so that the electrical device can be driven by a power supply voltage equal to or higher than the third power supply voltage.

[0025] (11) An electrical device that solves the above problem is an electrical device that is configured to be connectable to the power supply device described in (3) or (4) above and that receives a constant power supply voltage from the power supply device, and that includes an equipment control unit that controls the electrical device and a voltage detection unit that detects the power supply voltage as an equipment-side power supply voltage, and that does not start up when the equipment-side power supply voltage is lower than a third power supply voltage and starts up when the equipment-side power supply voltage is equal to or higher than the third power supply voltage, and that is configured so that when the power supply voltage supplied from the power supply device is the first power supply voltage, the current value detected by the current detection unit of the power supply device is equal to or lower than the first current value, and that the third power supply voltage is greater than the first power supply voltage and less than the second power supply voltage.

[0026] According to this configuration, the electric device does not start up when the first power supply voltage is supplied from the power supply device, but can start up when the second power supply voltage is supplied from the power supply device. Furthermore, when the power supply voltage supplied from the power supply device to the electrical device is the first power supply voltage, the current value detected by the power supply device is equal to or less than the first current value, which allows the power supply device to supply a different power supply voltage to the electrical device and to another electrical device that has a current value greater than the first current at the first power supply voltage.

[0027] (12) In the electrical device according to any one of (8) to (11) above, the electrical device is a camera device.

[0028] With this configuration, the camera device can be started up by the power supply voltage of the power supply device. [Effects of the Invention]

[0029] The power supply device, the power supply system, and the electrical equipment are capable of supplying a first power supply voltage to the electrical equipment. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a block diagram showing an example of the configuration of a power supply system according to a first embodiment. [Figure 2] 2 is a flowchart of a process executed by a power supply control unit in FIG. [Figure 3] 2 is a flowchart of a process executed by the device control unit of FIG. 1. [Figure 4] 4 is a timing chart showing changes in power supply voltage, device-side power supply voltage, and current value when a first electrical device is connected to the power supply device of FIG. [Figure 5] 10 is a timing chart showing changes in power supply voltage, device-side power supply voltage, and current value when a second electrical device is connected to the power supply device of FIG. [Figure 6] 10 is a timing chart showing changes in power supply voltage, device-side power supply voltage, and current value when a second electrical device is connected to the power supply device in the power supply system according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0031] First Embodiment A power supply system 1, a power supply device 10, and an electrical device 20 according to this embodiment will be described with reference to FIGS. 1 to 5. FIG.

[0032] <Power supply system> 1 , the power supply system 1 includes a power supply device 10 and an electric device 20. The electric device 20 is supplied with a power supply voltage PV from the power supply device 10. The power supply device 10 supplies power to the electric device 20. The power supply system 1 includes one or more electric devices 20. When the power supply system 1 includes multiple electric devices 20, the power supply device 10 supplies power to each of the multiple electric devices 20.

[0033] The power supply system 1 includes a cable 30 that connects a power supply device 10 and an electrical device 20. The cable 30 is a coaxial cable 30A. The electrical device 20 is a camera device 20A. The power supply device 10 is also called a drive unit. A system in which the power supply device 10 and the camera device 20A are connected by a single coaxial cable 30A is also called a one-cable system. In the coaxial cable 30A, the power supply voltage PV supplied by the power supply device 10 and the video signal output by the camera device 20A are superimposed.

[0034] Power supply device 10 supplies a constant power supply voltage PV to camera device 20A. Camera device 20A extracts power supply voltage PV from coaxial cable 30A and outputs a video signal to coaxial cable 30A. Power supply device 10 receives the video signal from camera device 20A via coaxial cable 30A. Power supply device 10 outputs the received video signal to video device 40, such as a recorder or display.

[0035] The electric device 20 is configured to be connectable to the power supply device 10, and is supplied with a constant power supply voltage PV from the power supply device 10. The electric device 20 operates on the constant power supply voltage PV. The electric device 20 includes a plurality of types of electric devices with different power consumptions. One of the electric devices 20 is a first electric device. The other electric device 20 is a second electric device 20X. The second electric device 20X is an electric device with higher performance than the first electric device. The power consumption of the second electric device 20X is greater than the power consumption of the first electric device. In FIG. 1, the second electric device 20X is illustrated as an example of the electric device 20.

[0036] However, as the performance of the electrical device 20 improves, the power consumption of the electrical device 20 tends to increase. If the power supply voltage PV supplied to the electrical device 20 is insufficient, the performance of the electrical device 20 may be limited. For example, if the electrical device 20 is a camera device 20A, functions such as the swivel of the imaging unit 24 and the zoom-in and zoom-out of the imaging unit 24 may be limited.

[0037] In the power supply system 1, a first electric device and a second electric device 20X may be used together. For the reasons described above, if the power supply voltage PV for operating the first electric device is supplied to the second electric device 20X, the power supply voltage PV for the second electric device 20X may be insufficient. On the other hand, if the power supply voltage PV for operating the second electric device 20X is supplied to the first electric device, the power supply voltage PV may be too high for the first electric device, which may place an electrical load on the first electric device. The longer the wiring distance of the coaxial cable 30A, the more difficult it becomes to determine whether the electric device 20 connected to the end of the coaxial cable 30A is the first electric device or the second electric device 20X, making incorrect connection more likely. The power supply system 1 can supply an appropriate power supply voltage PV to the first electric device or the second electric device 20X.

[0038] <Power supply> 1 supplies power to an electrical device 20 via a cable 30. The power supply device 10 includes a constant voltage power supply unit 11, a power supply control unit 12, and a current detection unit 13.

[0039] The constant voltage power supply unit 11 supplies a constant power supply voltage PV to the electric device 20. For example, AC power is supplied to the constant voltage power supply unit 11 from an external power supply 50. The external power supply 50 is, for example, a commercial power supply. The constant voltage power supply unit 11 has a power supply circuit that generates DC power from AC current to be supplied to the electric device 20. The power supply circuit generates the constant power supply voltage PV.

[0040] The power supply device 10 is provided with one or more power supply terminals 14. Cables 30 are connected to the power supply terminals 14. When multiple power supply terminals 14 are provided, different cables 30 are connected to each of the power supply terminals 14.

[0041] The constant voltage power supply unit 11 is configured to be able to change the magnitude of the power supply voltage PV supplied to the electrical device 20. The constant voltage power supply unit 11 supplies to the electrical device 20 one of a first power supply voltage V1, a second power supply voltage V2 that is greater than the first power supply voltage V1, and a test voltage Vt that is less than the first power supply voltage V1. The constant voltage power supply unit 11 has a first power supply 11A that generates the first power supply voltage V1, a second power supply 11B that generates the second power supply voltage V2, and a third power supply 11C that generates the test voltage Vt.

[0042] The first power supply voltage V1 is, for example, 26.4 V. When the constant voltage power supply unit 11 supplies the first power supply voltage V1, a power supply voltage PV of 24.2 V is applied to the power supply side terminal 14. The second power supply voltage V2 is, for example, 38 V. When the constant voltage power supply unit 11 supplies the second power supply voltage V2, a power supply voltage PV of 36 V is applied to the power supply side terminal 14. The test voltage Vt is, for example, 9 V. When the constant voltage power supply unit 11 supplies the test voltage Vt, a power supply voltage PV of 7 V is applied to the power supply side terminal 14.

[0043] When the power supply device 10 is connected to the electrical equipment 20, the constant voltage power supply unit 11 supplies the test voltage Vt before supplying the first power supply voltage V1 to the electrical equipment 20. When the power supply device 10 is turned on, the constant voltage power supply unit 11 applies the test voltage Vt to the power supply side terminal 14.

[0044] The power supply device 10 includes, for example, a power supply line 15. The power supply line 15 electrically connects the constant voltage power supply unit 11 and the electrical device 20. One end of the power supply line 15 is connected to the constant voltage power supply unit 11, and the other end of the power supply line 15 is connected to the power supply side terminal 14.

[0045] A video separation unit 16 is provided on the power supply line 15. The video separation unit 16 has a circuit that separates a video signal from the power supply voltage PV of the power supply line 15. The video separation unit 16 outputs the video signal separated from the power supply voltage PV to the video device 40.

[0046] The constant voltage power supply unit 11 has a switching unit 17 that connects any one of the first power supply 11A, the second power supply 11B, and the third power supply 11C to the power supply line 15. The switching unit 17 has, for example, a relay circuit.

[0047] The power supply control unit 12 is configured with one or more central processing units (CPUs) or one or more micro processing units (MPUs). The power supply control unit 12 controls the constant voltage power supply unit 11. Specifically, the power supply control unit 12 controls the power supply voltage PV that the constant voltage power supply unit 11 supplies to the electrical device 20. The power supply control unit 12 has a control circuit that controls the switching unit 17 of the constant voltage power supply unit 11. This control circuit causes the switching unit 17 to switch the connection destination of the power supply line 15 among the first power supply 11A, the second power supply 11B, and the third power supply 11C.

[0048] The current detection unit 13 detects the current in the power supply line 15. The current detection unit 13 has an ammeter. The current detection unit 13 detects the current from, for example, a voltage drop across a resistor provided in the power supply line 15. The current detection unit 13 outputs the detected current value CT to the power supply control unit 12.

[0049] The power supply control unit 12 controls the power supply voltage PV that the constant voltage power supply unit 11 supplies to the electrical device 20 in accordance with the current value CT detected by the current detection unit 13. The power supply control unit 12 may use, as the current value CT, the maximum value of the current output from the current detection unit 13 over a predetermined period, or may use the average value of the current output from the current detection unit 13 over a predetermined period.

[0050] The power supply device 10 supplies a first power supply voltage V1 to the electric device 20. If the electric device 20 does not start up until a determination period T1 has elapsed since the supply of the first power supply voltage V1 started, the power supply device 10 starts supplying a second power supply voltage V2 to the electric device 20 (see FIG. 5). The power supply device 10 determines the start-up state of the electric device 20 based on the current value CT. If the current value CT is greater than a predetermined current value CT, the power supply device 10 determines that the electric device 20 is started up.

[0051] When a predetermined condition related to the current value CT is satisfied while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to maintain the supply of the first power supply voltage V1 to the electric device 20. On the other hand, when another predetermined condition related to the current value CT is satisfied while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the second power supply voltage V2 to the electric device 20.

[0052] When the current value CT is greater than the first current value C1 while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to maintain the supply of the first power supply voltage V1 to the electric device 20. For example, when the current value CT is equal to or less than the first current value C1 while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the second power supply voltage V2 to the electric device 20. The first current value C1 is set to a value that allows detection that the first electric device is operating and the second electric device 20X is not operating. The first current value C1 is, for example, 30 mA.

[0053] When the current value CT is equal to or greater than the second current value C2 while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20. The second current value C2 is greater than the first current value C1. The second current value C2 is set to, for example, a value that can detect an overcurrent in the electric device 20. The second current value C2 is, for example, 300 mA.

[0054] When the current value CT is equal to or less than the third current value C3 while the constant voltage power supply unit 11 is supplying the second power supply voltage V2 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20. The third current value C3 is set to, for example, a value that can detect that the electric device 20 is not connected to the cable 30 connected to the power supply device 10. The third current value C3 is, for example, equal to the first current value C1.

[0055] When the current value CT is equal to or less than the fourth current value C4 while the constant voltage power supply unit 11 is supplying the test voltage Vt to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the first power supply voltage V1 to the electric device 20. When the current value CT is greater than the fourth current value C4 while the constant voltage power supply unit 11 is supplying the test voltage Vt to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20. The fourth current value C4 is set to, for example, a value that allows detection of a short circuit in the electric device 20. The fourth current value C4 is, for example, equal to the first current value C1.

[0056] When the current value CT is greater than the fifth current value C5 while the constant voltage power supply unit 11 is supplying the second power supply voltage V2 to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20. The fifth current value C5 is set to, for example, a value that can detect an overcurrent in the electric device 20. In one example, the fifth current value C5 is equal to the second current value C2.

[0057] The control executed by the power supply control unit 12 will be described with reference to Fig. 2. The power supply control unit 12 executes the process of Fig. 2 when the power supply device 10 is connected to the electrical device 20. Alternatively, the power supply control unit 12 may execute the process of Fig. 2 when the power supply device 10 is turned on.

[0058] In S11, when the power supply device 10 is connected to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the test voltage Vt to the electric device 20. In S12, the power supply control unit 12 determines whether the current value CT is equal to or less than the fourth current value C4. If the current value CT is equal to or less than the fourth current value C4, in S13, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the first power supply voltage V1 to the electric device 20, and the process proceeds to S14. If the current value CT is not equal to or less than the fourth current value C4 in S12, that is, if the current value CT is greater than the fourth current value C4, the power supply control unit 12 stops the supply of the power supply voltage PV in S21 and ends the process of FIG. 2.

[0059] In S14, it is determined whether the current value CT is smaller than the second current value C2. If the current value CT is not smaller than the second current value C2, that is, if the current value CT is equal to or greater than the second current value C2, the power supply control unit 12 stops the supply of the power supply voltage PV in S21 and ends the processing of FIG. 2. If the current value CT is smaller than the second current value C2, the power supply control unit 12 determines in S15 whether the current value CT is greater than the first current value C1. If the current value CT is greater than the first current value C1, the power supply control unit 12 ends the processing of FIG. 2 while causing the constant voltage power supply unit 11 to continue supplying the first power supply voltage V1 in S16.

[0060] If the current value CT is not greater than the first current value C1 in S15, that is, if the current value CT is equal to or less than the first current value C1, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the second power supply voltage V2 in S17. The power supply control unit 12 determines whether the current value CT is less than the fifth current value C5 in S18. If the current value CT is less than the fifth current value C5, the power supply control unit 12 proceeds to S19. If the current value CT is not less than the fifth current value C5, that is, if the current value CT is equal to or greater than the fifth current value C5, the power supply control unit 12 stops the supply of the power supply voltage PV in S21 and ends the processing of FIG. 2.

[0061] In S19, the power supply control unit 12 determines whether the current value CT is greater than the third current value C3. If the current value CT is greater than the third current value C3, in S20 the power supply control unit 12 causes the constant voltage power supply unit 11 to maintain the second power supply voltage V2, and ends the processing of Fig. 2. If the current value CT is not greater than the third current value C3, that is, if the current value CT is equal to or less than the third current value C3, in S21 the power supply control unit 12 stops the supply of the power supply voltage PV, and ends the processing of Fig. 2.

[0062] <Electrical equipment> 1 illustrates an example of the configuration of a second electric device 20X. The configuration of the second electric device 20X as the electric device 20 will be described below. The second electric device 20X includes a device control unit 21 and a voltage detection unit 22.

[0063] The device control unit 21 is configured with one or more CPUs or one or more MPUs. The device control unit 21 controls the electrical device 20. Specifically, the device control unit 21 controls the power supply to the drive unit 23, which will be described later. The device control unit 21 has a control circuit that controls the power supply to the drive unit 23.

[0064] The voltage detection unit 22 detects the power supply voltage PV as the device-side power supply voltage PVR. The voltage detection unit 22 has a voltmeter. The voltage detection unit 22 detects the power supply voltage PV at the device-side terminal 26 as the device-side power supply voltage PVR. The device-side terminal 26 is connected to the power supply-side terminal 14 of the power supply device 10 by a cable 30. The voltage detection unit 22 outputs the detected device-side power supply voltage PVR to the device control unit 21.

[0065] The second electric device 20X includes a driving unit 23. The driving unit 23 is driven by a power supply voltage PV. The driving unit 23 includes an imaging unit 24. The imaging unit 24 has an imaging sensor such as an image sensor or a microphone. The imaging unit 24 may be a high-performance camera such as a high-sensitivity camera or an infrared camera. The driving unit 23 may include components such as a motor that moves the viewpoint of the imaging unit 24 and moves a lens for zooming the imaging unit 24.

[0066] The second electric device 20X has an image superimposing unit 25. The imaging unit 24 outputs an image signal relating to the captured image to the image superimposing unit 25. The image superimposing unit 25 has a circuit that superimposes the image signal captured by the imaging unit 24 on the power supply voltage PV supplied from the power supply device 10.

[0067] The second electric device 20X does not start up when the device-side power supply voltage PVR is lower than the startup power supply voltage VS, but starts up when the device-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS. The drive unit 23 starts up when the power supply voltage PV is supplied to the drive unit 23. The second electric device 20X starts up when the power supply voltage PV is supplied to the drive unit 23 in this manner. The device control unit 21 does not supply the power supply voltage PV to the drive unit 23 when the device-side power supply voltage PVR is lower than the startup power supply voltage VS, but starts supplying the power supply voltage PV to the drive unit 23 when the device-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS.

[0068] The startup power supply voltage VS is set to a value smaller than the value of the first power supply voltage V1 dropped in the coaxial cable 30A. When the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, an equipment-side power supply voltage PVR equal to or greater than the startup power supply voltage VS is supplied to the second electrical device 20X. The startup power supply voltage VS is set to a value larger than the test voltage Vt. The startup power supply voltage VS is, for example, 10V.

[0069] The state in which the second electric appliance 20X is activated refers to a state in which the drive unit 23 can operate with power. On the other hand, when the second electric appliance 20X is not activated, even if the power supply voltage PV is supplied to the electric appliance 20, power is not supplied to the drive unit 23. In other words, when the second electric appliance 20X is not activated, the drive unit 23 does not operate. When the second electric appliance 20X is not activated, power is not supplied to the drive unit 23, but power is supplied to the appliance control unit 21 and the voltage detection unit 22. When the second electric appliance 20X is not activated, power is consumed by the appliance control unit 21 and the voltage detection unit 22. When the second electric appliance 20X is not activated, the power consumed by the second electric appliance 20X is, for example, 1 W or less.

[0070] The second electric device 20X is configured such that when the second electric device 20X is not activated, the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or less than the first current value C1. The second electric device 20X is connected in series to the power supply line 15 of the power supply device 10 via a cable 30. When the second electric device 20X is not activated, the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or less than the first current value C1. On the other hand, when the second electric device 20X is activated, the current value CT detected by the current detection unit 13 of the power supply device 10 is greater than the first current value C1.

[0071] The second electric device 20X starts up after a reference period T2 has elapsed since it was detected that the device-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS (see FIG. 5). The second electric device 20X remains in an inactive state until the reference period T2 has elapsed since it was detected that the device-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS. Specifically, the device control unit 21 does not supply power to the drive unit 23 during the reference period T2.

[0072] The reference period T2 is set to a period longer than the period from when the device-side power supply voltage PVR becomes equal to or greater than the startup power supply voltage VS until the power supply voltage PV of the power supply device 10 becomes equal to or greater than the second power supply voltage V2. The reference period T2 is longer than the determination period T1. The period obtained by adding the first boost period to the reference period T2 is longer than the period obtained by adding the second boost period to the determination period T1. The reference period T2 is preferably longer than the period obtained by adding the second boost period to the determination period T1. The first boost period is defined as the period from when the power supply voltage PV starts to boost from the test voltage Vt to the first power supply voltage V1 in order for the power supply device 10 to supply the first power supply voltage V1 until the device-side power supply voltage PVR becomes equal to or greater than the startup power supply voltage VS. The second boost period is defined as the period from when the power supply voltage PV starts to boost from the first power supply voltage V1 to the second power supply voltage V2 in order for the power supply device 10 to supply the second power supply voltage V2 until the power supply voltage PV becomes equal to the second power supply voltage V2.

[0073] During the reference period T2, the second electric device 20X is not activated, so the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or less than the first current value C1. After the reference period T2 has elapsed, the device control unit 21 starts supplying the power supply voltage PV to the drive unit 23. As a result, the current value CT detected by the current detection unit 13 of the power supply device 10 becomes greater than the first current value C1.

[0074] The control executed by the device control unit 21 of the second electric device 20X will be described with reference to Fig. 3. When the power supply voltage PV is supplied from the power supply device 10 to the second electric device 20X while the second electric device 20X is not activated, the device control unit 21 repeatedly executes the process of Fig. 3.

[0075] In S31, the device control unit 21 determines whether the device-side power supply voltage PVR is equal to or greater than the startup power supply voltage VS. The device control unit 21 acquires the device-side power supply voltage PVR at the device-side terminal 26 from the voltage detection unit 22. If the device-side power supply voltage PVR is equal to or greater than the startup power supply voltage VS, the device control unit 21 determines in S32 whether a reference period T2 has elapsed since the device-side power supply voltage PVR became equal to or greater than the startup power supply voltage VS. The device control unit 21 has, for example, a timer function for measuring time. If the reference period T2 has not elapsed, the device control unit 21 repeats the process of S32 until the reference period T2 has elapsed. After the reference period T2 has elapsed, in S33, the device control unit 21 starts supplying the power supply voltage PV to the drive unit 23, and ends the process of FIG. 3. That is, in S33, the second electrical device 20X starts up. If, in S31, the device-side power supply voltage PVR is not equal to or greater than the startup power supply voltage VS, that is, if the device-side power supply voltage PVR is lower than the startup power supply voltage VS, the device control unit 21 ends the process of FIG. 3.

[0076] The first electric device is configured similarly to the second electric device 20X except for the following points. When the appliance-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS, the first electric appliance starts up regardless of whether the reference period T2 has elapsed.

[0077] <Changes in power supply voltage supplied by the power supply unit> Changes in the power supply voltage PV supplied by the power supply device 10 to the electric device 20 will be described with reference to Figures 4 and 5. Figure 4 shows the changes in the power supply voltage PV, the device-side power supply voltage PVR, and the current value CT over time t after the first electric device is connected to the power supply device 10. Figure 5 shows the changes in the power supply voltage PV, the device-side power supply voltage PVR, and the current value CT over time t after the second electric device 20X is connected to the power supply device 10.

[0078] A case where a first electrical device is connected to the power supply device 10 will be described with reference to Fig. 4. In Fig. 4, the change in the power supply voltage PV at the power supply device 10 is shown by a solid line, and the change in the device-side power supply voltage PVR at the first electrical device is shown by a two-dot chain line. The left vertical axis represents the power supply voltage PV at the power supply device 10, and the right vertical axis represents the device-side power supply voltage PVR at the first electrical device.

[0079] Time t0 is the time when the first electric device is connected to the power supply device 10. When the first electric device is connected to the power supply device 10 at time t0, the power supply device 10 starts supplying the test voltage Vt to the first electric device. The power supply device 10 continues to supply the test voltage Vt until time t1. During the period from time t0 to time t1, short circuits and incorrect connections are detected.

[0080] Time t1 is, for example, four seconds after time t0. If current value CT is equal to or less than fourth current value C4 until time t1, power supply device 10 starts supplying first power supply voltage V1 from time t1. Power supply device 10 continues supplying first power supply voltage V1 until time t3.

[0081] At time t2, when the appliance-side power supply voltage PVR of the first electrical appliance becomes equal to or higher than the startup power supply voltage VS, the first electrical appliance starts up, causing the current value CT to increase.

[0082] Time t3 is the time when a determination period T1 has elapsed since time t1. The determination period T1 is, for example, 2 seconds. If, at time t3, the current value CT is greater than the first current value C1 and less than the second current value C2, the power supply device 10 continues to supply the first power supply voltage V1 after time t3. The current value CT at time t3 is the average or maximum value of the current values ​​CT from time t1 to time t3. The current value CT at time t3 may be the current value CT detected at time t3.

[0083] A case where a second electric device 20X is connected to the power supply device 10 will be described with reference to Fig. 5. In Fig. 5, the change in the power supply voltage PV of the power supply device 10 is indicated by a solid line, and the change in the device-side power supply voltage PVR of the second electric device 20X is indicated by a two-dot chain line. The left vertical axis represents the power supply voltage PV of the power supply device 10, and the right vertical axis represents the device-side power supply voltage PVR of the second electric device 20X.

[0084] At time t0, when the second electric device 20X is connected to the power supply device 10, the power supply device 10 starts supplying the test voltage Vt to the second electric device 20X. The power supply device 10 continues to supply the test voltage Vt until time t1.

[0085] If the current value CT is equal to or less than the fourth current value C4 until time t1, the power supply device 10 starts supplying the first power supply voltage V1 from time t1. The power supply device 10 continues to supply the first power supply voltage V1 until time t3.

[0086] At time t2, when the power supply voltage PV of the second electric device 20X becomes equal to or higher than the startup power supply voltage VS, the second electric device 20X enters a startup standby state in which it does not start from time t2 until the reference period T2 has elapsed. The second electric device 20X determines the elapse of the reference period T2 using a timer function or the like. Because the second electric device 20X is in an inactive state until the reference period T2 has elapsed, the current value CT in the power supply device 10 is maintained at or below the first current value C1. The period from time t1 to time t2 corresponds to a first voltage step-up period.

[0087] At time t3, when the current value CT is equal to or less than the first current value C1, the power supply device 10 starts supplying the second power supply voltage V2. For example, the power supply device 10 increases the voltage from the first power supply voltage V1 to the second power supply voltage V2 in less than one second. The period from time t3 to when the power supply voltage PV becomes the second power supply voltage V2 corresponds to the second voltage increase period.

[0088] Time t4 is the time when a reference period T2 has elapsed since time t2. The reference period T2 is, for example, 3 seconds. At time t4, the second electric device 20X is started up. As a result of the second electric device 20X being started up, the current value CT becomes greater than the third current value C3. Because the current value CT becomes greater than the third current value C3, the power supply device 10 continues to supply the second power supply voltage V2.

[0089] After time t4, if the current value CT becomes equal to or greater than the fifth current value C5 or equal to or less than the third current value C3, the power supply device 10 stops supplying the power supply voltage PV.

[0090] <Operation of this embodiment> The operation of this embodiment will be described. When the current value CT is greater than the first current value C1 while the power supply device 10 is supplying the first power supply voltage V1 to the electric device 20, the power supply device 10 maintains the supply of the first power supply voltage V1. Therefore, when the power supply device 10 is connected to the first electric device, the supply of the first power supply voltage V1 is maintained.

[0091] <Effects of the embodiment> The effects of this embodiment will be described. (1-1) The power supply device 10 supplies power to the electric device 20 via the cable 30. The power supply device 10 includes a constant voltage power supply unit 11, a power supply control unit 12, and a current detection unit 13. The constant voltage power supply unit 11 supplies a constant power supply voltage PV to the electric device 20. The power supply control unit 12 controls the constant voltage power supply unit 11. The current detection unit 13 detects a current in a power supply line 15. The power supply line 15 electrically connects the constant voltage power supply unit 11 and the electric device 20. The constant voltage power supply unit 11 is configured to be able to change the magnitude of the power supply voltage PV supplied to the electric device 20. When the constant voltage power supply unit 11 is supplying a first power supply voltage V1 to the electric device 20 and the current value CT detected by the current detection unit 13 is greater than the first current value C1, the power supply control unit 12 causes the constant voltage power supply unit 11 to maintain the supply of the first power supply voltage V1 to the electric device 20.

[0092] According to the above configuration, when the first power supply voltage V1 is supplied to the electric device 20, if the current value CT of the power supply line 15 is greater than the first current value C1, the first power supply voltage V1 is maintained. Therefore, when a current greater than the first current value C1 flows in the first power supply voltage V1, the first power supply voltage V1 can be supplied to the electric device 20.

[0093] (1-2) When the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electrical equipment 20 and the current value CT is equal to or greater than a second current value C2 that is greater than the first current value C1, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electrical equipment 20.

[0094] There is a risk of an overcurrent occurring if the current value CT of the power supply line 15 is large. According to the above configuration, when the current value CT of the power supply line 15 is equal to or greater than the second current value C2, the supply of the power supply voltage PV to the electric device 20 can be stopped.

[0095] (1-3) When the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electrical equipment 20 and the current value CT is equal to or less than the first current value C1, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the second power supply voltage V2, which is greater than the first power supply voltage V1, to the electrical equipment 20.

[0096] According to the above configuration, when the current value CT of the power supply line 15 is equal to or less than the first current value C1 while the first power supply voltage V1 is being supplied to the electric device 20, the second power supply voltage V2 higher than the first power supply voltage V1 is supplied to the electric device 20. This makes it possible to supply the second power supply voltage V2 higher than the first power supply voltage V1 to the electric device 20 that cannot be supplied with power by the first power supply voltage V1.

[0097] (1-4) When the constant voltage power supply unit 11 is supplying the second power supply voltage V2 to the electrical equipment 20 and the current value CT is equal to or less than the third current value C3, the power supply control unit 12 causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electrical equipment 20.

[0098] According to the above configuration, when the second power supply voltage V2 is being supplied to the electric device 20 and the current value CT of the power supply line 15 is equal to or less than the third current value C3, the supply of the power supply voltage PV to the electric device 20 can be stopped.

[0099] (1-5) When the power supply device 10 is connected to the electric device 20, the constant voltage power supply unit 11 supplies a test voltage Vt that is smaller than the first power supply voltage V1 before supplying the first power supply voltage V1 to the electric device 20. When the current value CT is equal to or smaller than the fourth current value C4 while the constant voltage power supply unit 11 is supplying the test voltage Vt to the electric device 20, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the first power supply voltage V1 to the electric device 20.

[0100] According to this configuration, when the test voltage Vt is being supplied, the supply of the first power supply voltage V1 is started if the current value CT of the power supply line 15 is equal to or less than the fourth current value C4. In other words, when the test voltage Vt is being supplied, the supply of the first power supply voltage V1 is not started if the current value CT of the power supply line 15 is greater than the fourth current value C4. This makes it possible to detect abnormalities such as short circuits in the electrical device 20.

[0101] (1-6) The cable 30 is a coaxial cable 30A. The electrical device 20 is a camera device 20A. The power supply device 10 receives a video signal from the camera device 20A via the coaxial cable 30A.

[0102] According to this configuration, the power supply device 10 can receive the video captured by the camera device 20A via the coaxial cable 30A.

[0103] (1-7) The power supply system 1 includes a power supply device 10 and an electric device 20. The electric device 20 is supplied with a power supply voltage PV from the power supply device 10.

[0104] According to this configuration, the power supply device 10 can supply the electric device 20 with a power supply voltage PV that is suitable for the power consumption of the electric device 20.

[0105] (1-8) The electric device 20 is supplied with a constant power supply voltage PV from the power supply device 10. The power supply device 10 supplies a first power supply voltage V1 to the electric device 20. If the electric device 20 does not start up until a determination period T1 has elapsed since the supply of the first power supply voltage V1 began, the power supply device 10 starts supplying a second power supply voltage V2 to the electric device 20. The electric device 20 includes an electric device control unit 21 and a voltage detection unit 22. The electric device control unit 21 controls the electric device 20. The voltage detection unit 22 detects the power supply voltage PV as an electric device-side power supply voltage PVR. The electric device 20 starts up after a reference period T2, which is greater than the determination period T1, has elapsed after detecting that the electric device-side power supply voltage PVR is equal to or greater than the startup power supply voltage VS. The startup power supply voltage VS is smaller than the first power supply voltage V1.

[0106] With this configuration, the electric device 20 starts up after the reference period T2 has elapsed since it was detected that the device-side power supply voltage PVR is equal to or higher than the startup power supply voltage VS. Because the reference period T2 is longer than the determination period T1, the electric device 20 does not start up until the power supply device 10 starts supplying the second power supply voltage V2 after the device-side power supply voltage PVR of the electric device 20 becomes equal to or higher than the startup power supply voltage VS. Therefore, the electric device 20 can receive the second power supply voltage V2 from the power supply device 10.

[0107] (1-9) The electrical device 20 is a camera device 20A.

[0108] According to this configuration, the camera device 20A can be started up by the power supply voltage PV of the power supply device 10.

[0109] Second Embodiment A power supply system 1, a power supply device 10, and an electrical device 20 according to a second embodiment will be described with reference to Figures 1 and 6. In this embodiment, components common to the first embodiment are assigned the same reference numerals as those in the first embodiment, and descriptions of overlapping components will be omitted.

[0110] In the first embodiment, the second electric device 20X starts up after a reference period T2 has elapsed since it was detected that the device-side power supply voltage PVR is equal to or greater than the startup power supply voltage VS. In this embodiment, the second electric device 20X does not start up if the device-side power supply voltage PVR is smaller than the third power supply voltage V3, but starts up if the device-side power supply voltage PVR is equal to or greater than the third power supply voltage V3. The device control unit 21 does not supply the power supply voltage PV to the drive unit 23 if the device-side power supply voltage PVR is smaller than the third power supply voltage V3, and starts supplying the power supply voltage PV to the drive unit 23 if the device-side power supply voltage PVR is equal to or greater than the third power supply voltage V3.

[0111] The third power supply voltage V3 is set to a value smaller than the value of the second power supply voltage V2 dropped in the coaxial cable 30A. The second electric device 20X starts up when the power supply device 10 supplies the second power supply voltage V2. When the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the device-side power supply voltage PVR is smaller than the third power supply voltage V3. When the power supply voltage PV supplied from the power supply device 10 is the second power supply voltage V2, the device-side power supply voltage PVR of the electric device 20 is equal to or greater than the third power supply voltage V3. The third power supply voltage V3 is set to a value equal to or smaller than the second power supply voltage V2. The third power supply voltage V3 is set to a value greater than the first power supply voltage V1. The third power supply voltage V3 is, for example, 28V.

[0112] The second electrical device 20X is configured so that when the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or less than the first current value C1. When the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the device-side power supply voltage PVR is lower than the third power supply voltage V3, and therefore no power is supplied to the drive unit 23. Therefore, the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or less than the first current value C1. On the other hand, when the power supply voltage PV supplied from the power supply device 10 is the second power supply voltage V2, the device-side power supply voltage PVR is equal to or greater than the third power supply voltage V3, and therefore power is supplied to the drive unit 23. Therefore, the current value CT detected by the current detection unit 13 of the power supply device 10 is greater than the first current value C1.

[0113] The first electric device of this embodiment is configured similarly to the second electric device 20X of this embodiment, except for the following points. The first electric device does not start up when the device-side power supply voltage PVR is lower than a fourth power supply voltage V4, but starts up when the device-side power supply voltage PVR is equal to or higher than the fourth power supply voltage V4. The fourth power supply voltage V4 is set to a value lower than the third power supply voltage V3. The device control unit of the first electric device does not supply the power supply voltage PV to the drive unit of the first electric device when the device-side power supply voltage PVR is lower than the fourth power supply voltage V4, but starts supplying the power supply voltage PV to the drive unit of the first electric device when the device-side power supply voltage PVR is equal to or higher than the fourth power supply voltage V4. The power consumption of the drive unit of the first electric device is lower than the power consumption of the drive unit 23 of the second electric device 20X. The fourth power supply voltage V4 may be the same value as the startup power supply voltage VS of the first embodiment.

[0114] The fourth power supply voltage V4 is set to a value smaller than the value of the first power supply voltage V1 dropped in the coaxial cable 30A. The first electrical device starts up when the power supply device 10 supplies the first power supply voltage V1. When the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the device-side power supply voltage PVR is equal to or greater than the fourth power supply voltage V4. The fourth power supply voltage V4 is set to a value smaller than the first power supply voltage V1. The fourth power supply voltage V4 is set to a value greater than the test voltage Vt.

[0115] The first electrical device is configured so that when the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the current value CT detected by the current detection unit 13 of the power supply device 10 is greater than the first current value C1. The first current value C1 is set to a value smaller than the current value CT in the power supply line 15 of the power supply device 10 when the first electrical device is activated, for example. When the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the device-side power supply voltage PVR is equal to or greater than the fourth power supply voltage V4, and therefore power is supplied to the drive unit 23. Therefore, the current value CT detected by the current detection unit 13 of the power supply device 10 is greater than the first current value C1.

[0116] A case where a second electric device 20X of this embodiment is connected to the power supply device 10 will be described with reference to Fig. 6. In Fig. 6, the change in the power supply voltage PV of the power supply device 10 is indicated by a solid line, and the change in the device-side power supply voltage PVR of the second electric device 20X is indicated by a two-dot chain line. The left vertical axis represents the power supply voltage PV of the power supply device 10, and the right vertical axis represents the device-side power supply voltage PVR of the first electric device.

[0117] At time t0, when the second electric device 20X is connected to the power supply device 10, the power supply device 10 starts supplying the test voltage Vt to the second electric device 20X. The power supply device 10 continues to supply the test voltage Vt until time t1.

[0118] If the current value CT is equal to or less than the fourth current value C4 until time t1, the power supply device 10 starts supplying the first power supply voltage V1 from time t1. The power supply device 10 continues to supply the first power supply voltage V1 until time t3.

[0119] At time t2, even if the device-side power supply voltage PVR becomes equal to or higher than the fourth power supply voltage V4, the second electric device 20X does not start up. The current value CT remains equal to or lower than the first current value C1 until time t3. Note that, when the first electric device of this embodiment is connected to the power supply device 10, the first electric device starts up at time t2.

[0120] At time t3, when the current value CT is equal to or less than the first current value C1, the power supply device 10 starts supplying the second power supply voltage V2.

[0121] At time t5, when the appliance-side power supply voltage PVR becomes greater than the third power supply voltage V3, the second electrical appliance 20X starts up, causing the current value CT to become greater than the third current value C3. Because the current value CT becomes greater than the third current value C3, the power supply device 10 continues to supply the second power supply voltage V2.

[0122] After time t3, while the second power supply voltage V2 is being supplied, if the current value CT is equal to or greater than the fifth current value C5 or equal to or less than the third current value C3, the power supply device 10 terminates the supply of the power supply voltage PV.

[0123] <Effects of the embodiment> The effects of this embodiment will be described. (2-1) The electric device 20 operates on a constant power supply voltage PV. The electric device 20 includes an electric device control unit 21 and a voltage detection unit 22. The electric device control unit 21 controls the electric device 20. The voltage detection unit 22 detects the power supply voltage PV as an electric device-side power supply voltage PVR. The electric device 20 does not start up if the electric device-side power supply voltage PVR is lower than a third power supply voltage V3, and starts up if the electric device-side power supply voltage PVR is equal to or higher than the third power supply voltage V3.

[0124] According to this configuration, the electric device 20 is activated when supplied with an electric device-side power supply voltage PVR equal to or higher than the third power supply voltage V3, and is prevented from activating when supplied with an electric device-side power supply voltage PVR lower than the third power supply voltage V3.

[0125] (2-2) The electric device 20 includes a drive unit 23. The drive unit 23 is driven by an electric device-side power supply voltage PVR. When the electric device-side power supply voltage PVR is smaller than a third power supply voltage V3, the device control unit 21 does not supply the power supply voltage PV to the drive unit 23, and when the electric device-side power supply voltage PVR is equal to or greater than the third power supply voltage V3, the device control unit 21 starts supplying the power supply voltage PV to the drive unit 23.

[0126] According to this configuration, when the device-side power supply voltage PVR is smaller than the third power supply voltage V3, the power supply voltage PV is not supplied to the drive unit 23, and when the device-side power supply voltage PVR is equal to or greater than the third power supply voltage V3, the power supply voltage PV is supplied to the drive unit 23. Therefore, the electric device 20 can be driven by the power supply voltage PV that is equal to or greater than the third power supply voltage V3.

[0127] (2-3) The electric device 20 is configured to be connectable to the power supply device 10, and is supplied with a constant power supply voltage PV from the power supply device 10. The electric device 20 operates on the constant power supply voltage PV. The electric device 20 includes an electric device control unit 21 and a voltage detection unit 22. The electric device control unit 21 controls the electric device 20. The voltage detection unit 22 detects the power supply voltage PV as an electric device-side power supply voltage PVR. The electric device 20 does not start up when the electric device-side power supply voltage PVR is lower than a third power supply voltage V3, and starts up when the electric device-side power supply voltage PVR is equal to or higher than the third power supply voltage V3. The electric device 20 is configured such that when the power supply voltage PV supplied from the power supply device 10 is the first power supply voltage V1, the current value CT detected by the current detection unit 13 of the power supply device 10 is equal to or lower than the first current value C1. The third power supply voltage V3 is higher than the first power supply voltage V1 and lower than the second power supply voltage V2.

[0128] According to this configuration, the electric device 20 does not start up when the first power supply voltage V1 is supplied from the power supply device 10, but can start up when the second power supply voltage V2 is supplied from the power supply device 10. Furthermore, when the power supply voltage PV supplied from the power supply device 10 to the electric device 20 is the first power supply voltage V1, the current value CT detected by the power supply device 10 is equal to or less than the first current value C1. This allows the power supply device 10 to supply a different power supply voltage PV to the electric device 20 and to another electric device 20 for which the current value CT is greater than the first current value C1 at the first power supply voltage V1.

[0129] <Modification> The above-described embodiments are examples of possible forms of the power supply system 1, the power supply device 10, and the electrical device 20, and are not intended to limit the forms. The power supply system 1, the power supply device 10, and the electrical device 20 may take forms different from those illustrated in the above-described embodiments. Examples of such forms include forms in which part of the configuration of the above-described embodiments is replaced, modified, or omitted, or forms in which a new configuration is added to the embodiments. Modified examples of the embodiments are shown below.

[0130] The power supply control unit 12 in each embodiment causes the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20 when the current value CT is equal to or greater than the second current value C2 while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20. The power supply control unit 12 in this modification does not have to cause the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20 even when the current value CT is equal to or greater than the second current value C2 while the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20. In the power supply system 1 of this modification, the electric device 20 may be provided with a device that disconnects the electric device 20 from the power supply device 10 when the device-side power supply voltage PVR is greater than a predetermined device-side power supply voltage PVR.

[0131] In each embodiment, when the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20 and the current value CT is equal to or less than the first current value C1, the power supply control unit 12 causes the constant voltage power supply unit 11 to supply the second power supply voltage V2 to the electric device 20. In this modification, when the constant voltage power supply unit 11 is supplying the first power supply voltage V1 to the electric device 20 and the current value CT is equal to or less than the first current value C1, the power supply control unit 12 may cause the constant voltage power supply unit 11 to stop supplying the power supply voltage PV to the electric device 20. In this modification, it is possible to prevent the first power supply voltage V1, which is insufficient for the operation of the second electric device 20X, from being continuously supplied to the second electric device 20X.

[0132] In each embodiment, when the power supply device 10 is connected to the electrical device 20, the constant voltage power supply unit 11 supplies a test voltage Vt that is smaller than the first power supply voltage V1 before supplying the first power supply voltage V1 to the electrical device 20. However, the supply of the test voltage Vt may be omitted.

[0133] In each embodiment, the power supply device 10 is a drive unit, the electrical device 20 is a camera device 20A, and the cable 30 is a coaxial cable 30A on which the power supply voltage PV and a video signal are superimposed, but the cable 30 is not limited to this example. For example, the power supply device 10 may be a phantom power supply, the electrical device 20 may be a microphone, and the cable 30 may be a microphone cable.

[0134] In each embodiment, the constant voltage power supply unit 11 has a plurality of power supplies with different power supply voltages PV, but the power supply voltage PV may be switched by a variable power supply. [Explanation of symbols]

[0135] 1...power supply system, 10...power supply device, 11...constant voltage power supply section, 11A...first power supply, 11B...second power supply, 11C...third power supply, 12...power supply control section, 13...current detection section, 14...power supply side terminal, 15...power supply line, 16...image separation section, 17...switching section, 20...electrical equipment, 20A...camera device, 20X...second electrical equipment, 21...equipment control section, 22...voltage detection section, 23...drive section, 24...imaging section, 25...image superimposition section, 26...equipment side terminal, 30...cable, 30A...coaxial cable, 40...video device, 50...external power supply.

Claims

1. A power supply device that supplies power to an electrical device via a cable, a constant voltage power supply unit that supplies a constant power supply voltage to the electrical device; a power supply control unit that controls the constant voltage power supply unit; a current detection unit that detects a current in a power supply line that electrically connects the constant voltage power supply unit and the electrical device, the constant voltage power supply unit is configured to be able to change the magnitude of the power supply voltage supplied to the electrical device, The power supply control unit causes the constant voltage power supply unit to maintain the supply of the first power supply voltage to the electrical equipment when the current value detected by the current detection unit is greater than a first current value while the constant voltage power supply unit is supplying a first power supply voltage to the electrical equipment.

2. 2. The power supply device according to claim 1, wherein the power supply control unit causes the constant voltage power supply unit to stop supplying the power supply voltage to the electrical device when the current value is equal to or greater than a second current value that is greater than the first current value while the constant voltage power supply unit is supplying the first power supply voltage to the electrical device.

3. 2. The power supply device according to claim 1, wherein, when the current value is equal to or less than the first current value while the constant voltage power supply unit is supplying the first power supply voltage to the electrical device, the power supply control unit causes the constant voltage power supply unit to supply a second power supply voltage higher than the first power supply voltage to the electrical device.

4. 4. The power supply device according to claim 3, wherein the power supply control unit causes the constant voltage power supply unit to stop supplying the power supply voltage to the electrical device when the current value is equal to or less than a third current value while the constant voltage power supply unit is supplying the second power supply voltage to the electrical device.

5. when the power supply device is connected to the electrical equipment, the constant voltage power supply unit supplies a test voltage that is smaller than the first power supply voltage to the electrical equipment before supplying the first power supply voltage to the electrical equipment; 2. The power supply device according to claim 1, wherein the power supply control unit causes the constant voltage power supply unit to supply the first power supply voltage to the electrical equipment when the current value is equal to or less than a fourth current value while the constant voltage power supply unit is supplying the test voltage to the electrical equipment.

6. the cable is a coaxial cable, the electrical device is a camera device, The power supply device according to claim 1 , wherein the power supply device receives a video signal from the camera device via the coaxial cable.

7. The power supply device according to any one of claims 1 to 6; an electrical device that receives a power supply voltage from the power supply device.

8. An electrical device that receives a constant power supply voltage from a power supply device, the power supply device supplies a first power supply voltage to the electrical device, and if the electrical device does not start up until a determination period has elapsed since the supply of the first power supply voltage started, starts supplying a second power supply voltage higher than the first power supply voltage to the electrical device; a device control unit that controls the electrical device; a voltage detection unit that detects the power supply voltage as a device-side power supply voltage, After detecting that the power supply voltage of the device is equal to or higher than the startup power supply voltage, the device starts up after a reference period longer than the determination period has elapsed, The electrical device, wherein the startup power supply voltage is lower than the first power supply voltage.

9. An electrical device that operates on a constant power supply voltage, a device control unit that controls the electrical device; a voltage detection unit that detects the power supply voltage as a device-side power supply voltage, The electrical device does not start up when the device-side power supply voltage is lower than a third power supply voltage, and starts up when the device-side power supply voltage is equal to or higher than the third power supply voltage.

10. a drive unit driven by the power supply voltage, 10. The electrical device according to claim 9, wherein the device control unit does not supply the power supply voltage to the drive unit when the device-side power supply voltage is lower than the third power supply voltage, and starts supplying the power supply voltage to the drive unit when the device-side power supply voltage is equal to or higher than the third power supply voltage.

11. An electrical device configured to be connectable to the power supply device according to claim 3 and to receive a constant power supply voltage from the power supply device, a device control unit that controls the electrical device; a voltage detection unit that detects the power supply voltage as a device-side power supply voltage, The device does not start up when the device-side power supply voltage is lower than a third power supply voltage, and starts up when the device-side power supply voltage is equal to or higher than the third power supply voltage, when the power supply voltage supplied from the power supply device is the first power supply voltage, the current value detected by the current detection unit of the power supply device is equal to or less than a first current value, The third power supply voltage is greater than the first power supply voltage and less than the second power supply voltage.

12. The electrical device according to claim 8 , wherein the electrical device is a camera device.

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