Optical communication device and control method

Abstract

One embodiment of the present invention is a communication device comprising: an optical signal sending / receiving unit that sends and receives optical signals; and a sleep control unit that switches the operation mode of the optical signal sending / receiving unit between an active mode in which optical signals can be sent and received in a range in which the average consumed power of the optical communication device is less than the supplied-power supplied to the optical communication device, and a sleep mode in which optical signals are not sent or received.

Description

[Technical Field]

[0001] The present invention relates to an optical communication device and a control method. [Background technology]

[0002] 6 is a diagram showing an example of the configuration of an OLT (Optical Line Terminal) and an ONU (Optical Network Unit) in a PON (Passive Optical Network) used in an access system. The OLT is provided on the central office side, and the ONU is provided on the user side.

[0003] The OLT and ONUs are connected via a splitter. Downstream data from the OLT is distributed to each ONU via the splitter. Upstream data from the ONUs is combined by the splitter and sent to the OLT.

[0004] A typical ONU consumes around 1W to 10W of power, and even if it has a sleep mode function that disables communication, the power saving effect is limited. Also, unlike wireless communication, it is difficult to reduce power consumption in optical communication even by reducing the communication speed. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] IEEE 802.3az Energy Efficient Ethernet Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, it is difficult to supply power to an ONU by, for example, energy harvesting. Another method of supplying power to an ONU is optical power feeding, which transmits power feeding light through optical fiber and converts that light into electricity. However, with this type of optical power feeding, the power that can be supplied is limited to a few hundred milliwatts in order to avoid melting the optical fiber. Therefore, since an ONU cannot operate on batteries alone, for example, the installation location of the ONU is limited to places where sufficient power can be supplied.

[0007] In view of the above circumstances, an object of the present invention is to provide a technique that enables optical communication even in an environment where it is difficult to supply sufficient power. [Means for solving the problem]

[0008] One aspect of the present invention is an optical communication device comprising an optical signal transceiver unit that transmits and receives optical signals, and a sleep control unit that switches the operating mode of the optical signal transceiver unit between an active mode in which optical signals can be transmitted and received, and a sleep mode in which optical signals are not transmitted or received, within a range in which the average power consumption of the optical communication device is less than the supply power supplied to the optical communication device.

[0009] One aspect of the present invention is a control method for an optical communication device having an optical signal transceiver unit that transmits and receives optical signals, comprising a step of switching the operating mode of the optical signal transceiver unit between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which the average power consumption of the optical communication device is less than the supply power supplied to the optical communication device. [Effects of the Invention]

[0010] The present invention makes it possible to provide a technology that enables optical communication even in an environment where it is difficult to supply sufficient power. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a configuration of an optical communication system according to a first embodiment. [Figure 2] 10 is a flowchart showing the flow of processing by a sleep control unit. [Figure 3] FIG. 10 is a diagram illustrating a configuration of an optical communication system according to a second embodiment. [Figure 4] FIG. 10 is a diagram illustrating a configuration of an optical communication system according to a third embodiment. [Figure 5] 10 is a flowchart showing the flow of processing by a sleep control unit. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of an OLT and an ONU. DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. (First embodiment) 1 is a diagram showing the configuration of an optical communication system 1 according to the first embodiment. The optical communication system 1 is composed of an ONU (Optical Network Unit) 100 and an OLT (Optical Line Terminal) 200. A splitter and the like provided between the ONU 100 and the OLT 200 are omitted. Of these, the ONU 100 is an example of an optical communication device according to this embodiment.

[0013] The OLT 200 is a communication device provided on the central office side. The OLT 200 is composed of a communication unit 210, a data transmission / reception unit 220, and a multiplexer / demultiplexer 230. The communication unit 210 controls the data transmission / reception unit 220. The data transmission / reception unit 220 transmits and receives data in accordance with the control of the communication unit 210. The multiplexer / demultiplexer 230 outputs an optical signal transmitted from the data transmission / reception unit 220 to the ONU 100. The multiplexer / demultiplexer 230 also demultiplexes an optical signal received from the ONU 100 as necessary and outputs the demultiplexed signal to the data transmission / reception unit 220.

[0014] The ONU 100 is composed of a power supply circuit unit 110, a sleep control unit 120, a multiplexer / demultiplexer 130, and an optical signal transmitting / receiving unit 140. The power supply circuit unit 110 is supplied with power from an external power supply 300. The power supply circuit unit 110 charges a rechargeable battery 111 using the supplied power. The ONU 100 operates using the power stored in the rechargeable battery 111. The external power supply 300 is an energy harvesting device such as a solar cell, a vibration power generator, or a temperature difference power generator. The magnitude of the power supplied by the external power supply 300 will be described later.

[0015] The optical signal transmitting and receiving unit 140 transmits and receives optical signals to and from the OLT 200. The optical signal transmitting and receiving unit 140 is connected to the user equipment 400. The optical signal transmitting and receiving unit 140 transmits data output from the user equipment 400 to the OLT 200. The optical signal transmitting and receiving unit 140 transmits data received from the OLT 200 to the user equipment 400. The user equipment 400 is, for example, a sensing device, but is not limited to this.

[0016] The optical signal transmitting and receiving unit 140 is composed of a communication unit 141 and a data transmitting and receiving unit 142. The communication unit 141 controls the data transmitting and receiving unit 142. The data transmitting and receiving unit 142 transmits and receives data in accordance with the control of the communication unit 141. The multiplexer / demultiplexer 130 transmits the optical signal transmitted from the data transmitting and receiving unit 142 to the OLT 200. The multiplexer / demultiplexer 130 also outputs the optical signal received from the OLT 200 to the data transmitting and receiving unit 142.

[0017] The ONU 100 has an active mode in which optical signals can be transmitted and received, and a sleep mode in which optical signals are not transmitted or received. The sleep control unit 120 switches the operation mode between the active mode and the sleep mode within a range in which the average power consumption of the ONU 100 is less than the power supplied to the ONU 100. This will be specifically explained using mathematical expressions.

[0018] Let the power supplied from the external power source 300 be Po. This supplied power Po includes losses in the power supply circuit unit 110 and the rechargeable battery 111. Let the power consumption in the active mode be Pa, and the power consumption in the sleep mode be Ps. Let the operating time in the active mode be Ta, and the operating time in the sleep mode be Ts. Further, let Pa > Po > Ps. That is, the supplied power Po is smaller than the power consumption Pa in the active mode. Therefore, since it is impossible to operate in the active mode constantly, the ONU 100 is in an environment where it is difficult to supply sufficient power.

[0019] The sleep control unit 120 switches the operation mode between the active mode and the sleep mode within the range where Ta and Ts satisfy the following (conditional expression A). (Pa × Ta + Ps × Ts) / (Ta + Ts) < Po … (conditional expression A)

[0020] The left side of the conditional expression A indicates the average power consumption, and the right side indicates the supplied power. Therefore, the sleep control unit 120 switches the operation mode within the range where the average power consumption is less than the supplied power supplied to the ONU 100. Thus, the sleep control unit 120 adjusts the length of each of the active mode and the sleep mode.

[0021] <000009:An example of the adjustment method, adjustment method A, will be described. Adjustment method A is, for example, a method that uses a set value from the OLT 200. For example, assume that Ta:Ts = N:M is notified from the OLT 200 as a set value. When the set value satisfies the conditional expression A, the sleep control unit 120 switches the operation mode to the notified set value. On the other hand, when the set value does not satisfy the conditional expression A, the sleep control unit 120 switches the operation mode to a default set value that satisfies the conditional expression A.

[0022] Figure 2 is a flowchart showing the processing flow of the sleep control unit 120. In Figure 2, the sleep control unit 120 acquires the supplied power Po (step S101). The acquisition method is, for example, from a power meter (not shown) or by acquiring from the storage device a value indicating the supplied power Po stored in the storage device in advance.

[0023] The sleep control unit 120 acquires the power consumption Pa in the active mode (step S102). Since the power consumption Pa is considered to be almost constant, the sleep control unit 120 stores the power consumption Pa in advance in a storage device and acquires a value indicating the stored power consumption Pa from the storage device.

[0024] The sleep control unit 120 acquires the power consumption Ps in the sleep mode (step S103). Since the power consumption Ps is considered to be almost constant, the sleep control unit 120 stores the power consumption Ps in advance in a storage device and acquires a value indicating the stored power consumption Ps from the storage device.

[0025] The sleep control unit 120 sets Ta and Ts that satisfy conditional formula A (step S104). As a setting method, the above-mentioned method A can be mentioned.

[0026] According to the first embodiment, optical communication can be performed even in an environment where it is difficult to supply sufficient power (power supply by energy harvesting).

[0027] (Second embodiment) 3 is a diagram showing the configuration of an optical communication system 1 according to the second embodiment. The optical communication system 1 is composed of an ONU 100 and an OLT 200. A splitter and the like provided between the ONU 100 and the OLT 200 are omitted. Of these, the ONU 100 is an example of an optical communication device according to this embodiment.

[0028] The OLT 200 is a communication device provided on the central office side. The OLT 200 is composed of a communication unit 210, a data transceiver unit 220, a power supply optical transmitter unit 240, and a multiplexer / demultiplexer 230. The communication unit 210 controls the data transceiver unit 220. The data transceiver unit 220 transmits and receives data under the control of the communication unit 210. The power supply optical transmitter unit 240 outputs a signal for optical power feeding. The multiplexer / demultiplexer 230 multiplexes the optical signal transmitted from the data transceiver unit 220 with an optical signal indicating the power supply optical signal, and outputs the multiplexed signal to the ONU 100. The multiplexer / demultiplexer 230 also demultiplexes the optical signal received from the ONU 100 as necessary, and outputs the demultiplexed signal to the data transceiver unit 220.

[0029] The ONU 100 is composed of a power supply circuit unit 110, a sleep control unit 120, a multiplexer / demultiplexer 130, a photoelectric conversion unit 150, and an optical signal transmitting / receiving unit 140. The power supply circuit unit 110 is supplied with power from the photoelectric conversion unit 150. The power supply circuit unit 110 charges a rechargeable battery 111 using the supplied power. The ONU 100 operates using the power stored in the rechargeable battery 111. The magnitude of the power supplied by the photoelectric conversion unit 150 will be described later.

[0030] The optical signal transmitting and receiving unit 140 transmits and receives optical signals to and from the OLT 200. The optical signal transmitting and receiving unit 140 is connected to the user equipment 400. The optical signal transmitting and receiving unit 140 transmits data output from the user equipment 400 to the OLT 200. The optical signal transmitting and receiving unit 140 transmits data received from the OLT 200 to the user equipment 400. The user equipment 400 is, for example, a sensing device, but is not limited to this.

[0031] The optical signal transmitting and receiving unit 140 is composed of a communication unit 141 and a data transmitting and receiving unit 142. The communication unit 141 controls the data transmitting and receiving unit 142. The data transmitting and receiving unit 142 transmits and receives data under the control of the communication unit 141. The multiplexer / demultiplexer 130 transmits the optical signal transmitted from the data transmitting and receiving unit 142 to the OLT 200. The multiplexer / demultiplexer 130 also demultiplexes the optical signal received from the OLT 200 and outputs it to the data transmitting and receiving unit 142 and the photoelectric conversion unit 150.

[0032] The ONU 100 has an active mode in which optical signals can be transmitted and received, and a sleep mode in which optical signals are not transmitted and received. The sleep control unit 120 switches the operation mode between the active mode and the sleep mode within a range in which the average power consumption of the ONU 100 is less than the power supplied to the ONU 100.

[0033] In the second embodiment, Po in conditional formula A is replaced with Po, which represents the power supplied from the photoelectric conversion unit 150. This power supply Po includes losses in the power supply circuit unit 110 and the rechargeable battery 111. The above-described method A is also applicable to the second embodiment. Furthermore, the processing flow of the sleep control unit 120 in the second embodiment is the same as the flowchart shown in FIG. 2.

[0034] According to the second embodiment, it is possible to perform optical communication even in an environment where it is difficult to supply sufficient power (power supply by optical power supply). In the configuration of Fig. 3, the optical fiber for power supply and the optical fiber for communication are one optical fiber, but they may be separate optical fibers.

[0035] (Third embodiment) 4 is a diagram showing the configuration of an optical communication system 1 according to the third embodiment. The optical communication system 1 is composed of an ONU 100 and an OLT 200. A splitter and the like provided between the ONU 100 and the OLT 200 are omitted. Of these, the ONU 100 is an example of an optical communication device according to this embodiment.

[0036] The OLT 200 is a communication device provided on the central office side. The OLT 200 is composed of a communication unit 210, a data transceiver unit 220, a power supply optical transmitter unit 240, and a multiplexer / demultiplexer 230. The communication unit 210 controls the data transceiver unit 220. The data transceiver unit 220 transmits and receives data under the control of the communication unit 210. The power supply optical transmitter unit 240 outputs a signal for optical power feeding. The multiplexer / demultiplexer 230 multiplexes the optical signal transmitted from the data transceiver unit 220 with an optical signal indicating the power supply optical signal, and outputs the multiplexed signal to the ONU 100. The multiplexer / demultiplexer 230 also demultiplexes the optical signal received from the ONU 100 as necessary, and outputs the demultiplexed signal to the data transceiver unit 220.

[0037] The ONU 100 is composed of a power supply circuit unit 110, a sleep control unit 120, a multiplexer / demultiplexer 130, an optical / electrical conversion unit 150, and an optical signal transmitting / receiving unit 140. The power supply circuit unit 110 is supplied with power from the optical / electrical conversion unit 150. The power supply circuit unit 110 charges a rechargeable battery 111 using the supplied power. The ONU 100 operates using the power stored in the rechargeable battery 111. In the third embodiment, the user device 400 also operates using the power stored in the rechargeable battery 111. The magnitude of the power supplied by the optical / electrical conversion unit 150 will be described later.

[0038] The optical signal transmitting and receiving unit 140 transmits and receives optical signals to and from the OLT 200. The optical signal transmitting and receiving unit 140 is connected to the user equipment 400. The optical signal transmitting and receiving unit 140 transmits data output from the user equipment 400 to the OLT 200. The optical signal transmitting and receiving unit 140 transmits data received from the OLT 200 to the user equipment 400. The user equipment 400 is, for example, a sensing device, but is not limited to this.

[0039] The optical signal transmitting and receiving unit 140 is composed of a communication unit 141 and a data transmitting and receiving unit 142. The communication unit 141 controls the data transmitting and receiving unit 142. The data transmitting and receiving unit 142 transmits and receives data under the control of the communication unit 141. The multiplexer / demultiplexer 130 transmits the optical signal transmitted from the data transmitting and receiving unit 142 to the OLT 200. The multiplexer / demultiplexer 130 also demultiplexes the optical signal received from the OLT 200 and outputs it to the data transmitting and receiving unit 142 and the photoelectric conversion unit 150.

[0040] The ONU 100 has an active mode in which optical signals can be transmitted and received, and a sleep mode in which optical signals are not transmitted or received. The sleep control unit 120 switches the operation mode between the active mode and the sleep mode within a range in which the average power consumption of the ONU 100 is less than the power supplied to the ONU 100. This will be specifically explained using mathematical expressions.

[0041] The power supplied from the photoelectric conversion unit 150 is designated as Po. This power supply Po includes losses in the power supply circuit unit 110 and the rechargeable battery 111. The power consumption in active mode is designated as Pa. The power consumption in sleep mode is designated as Ps. The operating time in active mode is designated as Ta. The operating time in sleep mode is designated as Ts. Furthermore, Pa>Po>Ps. That is, the power supply Po is smaller than the power consumption in active mode, Pa. Therefore, since it is not possible to operate in active mode all the time, the ONU 100 is in an environment where it is difficult to supply sufficient power. It is also assumed that the user equipment 400 has an operation mode. These operation modes include a sleep mode in which power consumption is reduced, and an active mode in which power consumption is higher than in sleep mode. The operation modes of the user equipment 400 and the ONU 100 are synchronized. That is, when the operation mode of the ONU 100 is the sleep mode, the operation mode of the user equipment 400 is also the sleep mode. When the operation mode of the ONU 100 is the active mode, the operation mode of the user equipment 400 is also the active mode. The power consumption of the user equipment 400 in the active mode is defined as PA. The power consumption of the user equipment 400 in the sleep mode is defined as PS.

[0042] The sleep control unit 120 switches the operation mode between the active mode and the sleep mode within the range where Ta and Ts satisfy the following (conditional expression B). ((Pa + PA) × Ta + (Ps + PS) × Ts) / (Ta + Ts) < Po…(conditional expression B)

[0043] The left side of conditional expression B indicates the average power consumption of the ONU 100 and the user device 400 combined, and the right side indicates the supplied power. Therefore, the sleep control unit 120 switches the operation mode within the range where the average power consumption is less than the supplied power supplied to the ONU 100 and the user device 400. Thus, the sleep control unit 120 adjusts the length of each of the active mode and the sleep mode.

[0044] In the case of conditional expression B as well, the above-described method A can be applied. FIG. 5 is a flowchart showing the processing flow of the sleep control unit 120. In FIG. 5, the sleep control unit 120 acquires the supplied power Po (step S201). The acquisition method is, for example, from a power meter (not shown) or by acquiring from the storage device a value indicating the supplied power Po stored in the storage device in advance.

[0045] The sleep control unit 120 acquires the power consumptions Pa and PA in the active mode (step S202). Since the power consumptions Pa and PA are considered to be substantially constant, the sleep control unit 120 stores the power consumptions Pa and PA in the storage device in advance and acquires from the storage device the values indicating the stored power consumptions Pa and PA.

[0046] The sleep control unit 120 acquires the power consumptions Ps and PS in the sleep mode (step S203). Since the power consumptions Ps and PS are considered to be substantially constant, the sleep control unit 120 stores the power consumptions Ps and PS in the storage device in advance and acquires from the storage device the values indicating the stored power consumptions Ps and PS.

[0047] The sleep control unit 120 sets Ta and Ts that satisfy conditional formula B (step S204). As a setting method, the above-mentioned method A and the like can be mentioned.

[0048] According to the third embodiment, optical communication can be performed even in an environment where it is difficult to supply sufficient power (power supply by optical power supply). Furthermore, optical communication can be performed even when power is supplied to the user device 400.

[0049] In the third embodiment, power is supplied by optical power supply, but power may be supplied by energy harvesting, as in the first embodiment. In addition, in the configuration of Fig. 4, the optical fiber for power supply and the optical fiber for communication are one optical fiber, but they may be separate optical fibers.

[0050] The sleep control unit 120 may be configured using a processor such as a CPU (Central Processing Unit) and a memory. In this case, the sleep control unit 120 functions as the sleep control unit 120 when the processor executes a program. Note that all or part of the functions of the sleep control unit 120 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, and a semiconductor storage device (e.g., a solid-state drive (SSD)), as well as storage devices such as a hard disk or semiconductor storage device built into a computer system. The program may be transmitted via a telecommunications line.

[0051] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0052] The present invention is applicable to optical communication devices that operate in environments where it is difficult to supply sufficient power. [Explanation of symbols]

[0053] 1...optical communication system, 110...power supply circuit unit, 111...rechargeable battery, 120...sleep control unit, 130, 230...multiplexer / demultiplexer, 140...optical signal transmitting / receiving unit, 141, 210...communication unit, 142, 220...data transmitting / receiving unit, 150...photoelectric conversion unit, 240...power supply optical transmitting unit, 300...external power supply, 400...user device

Claims

1. An optical communication device, an optical signal transmitting and receiving unit that transmits and receives optical signals; a sleep control unit that switches the operation mode of the optical signal transmitting and receiving unit between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with The power supply is smaller than the power consumption in the active mode and larger than the power consumption in the sleep mode, the sleep control unit switches the operation mode between the active mode and the sleep mode within a range in which the average power consumption based on the operation time in the active mode and the operation time in the sleep mode is less than the supply power. Optical communication equipment.

2. An optical communication device, an optical signal transmitting and receiving unit that transmits and receives optical signals; a sleep control unit that switches the operation mode of the optical signal transmitting and receiving unit between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with When the supplied power is Po, the power consumption in active mode is Pa, the power consumption in sleep mode is Ps, the operating time in active mode is Ta, the operating time in sleep mode is Ts, and Pa > Po > Ps, the sleep control unit switches the operation mode between an active mode and a sleep mode within a range in which the Ta and the Ts satisfy (Pa×Ta+Ps×Ts) / (Ta+Ts)<Po. Optical communication equipment.

3. An optical communication device, an optical signal transmitting and receiving unit that transmits and receives optical signals; a sleep control unit that switches the operation mode of the optical signal transmitting and receiving unit between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with When the optical communication device supplies power to another device that communicates using the optical communication device, the supplied power is Po, the power consumption in active mode is Pa, the power consumption in sleep mode is Ps, the power consumption of the other device in active mode is PA, the power consumption of the other device in sleep mode is PS, the operating time in active mode is Ta, and the operating time in sleep mode is Ts, and Pa > Po > Ps, the sleep control unit switches the operation mode between an active mode and a sleep mode within a range in which Ta and Ts satisfy ((Pa+PA)×Ta+(Ps+PS)×Ts) / (Ta+Ts)<Po. Optical communication equipment.

4. a power supply unit that charges a rechargeable battery using the supplied power, The optical communication device according to claim 1 , wherein the optical communication device operates using power stored in the rechargeable battery.

5. 4. The optical communication device according to claim 1, wherein the power supply is supplied by power supply light transmitted from a communication destination of the optical communication device.

6. A control method for an optical communication device including an optical signal transmitting and receiving unit that transmits and receives optical signals, switching the operation mode of the optical signal transceiver between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with The power supply is smaller than the power consumption in the active mode and larger than the power consumption in the sleep mode, In the switching step, the operation mode is switched between the active mode and the sleep mode within a range in which the average power consumption based on the operation time in the active mode and the operation time in the sleep mode is less than the supply power. Control method.

7. A control method for an optical communication device having an optical signal transmitting and receiving unit that transmits and receives optical signals, comprising: switching the operation mode of the optical signal transceiver between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with When the supplied power is Po, the power consumption in active mode is Pa, the power consumption in sleep mode is Ps, the operating time in active mode is Ta, the operating time in sleep mode is Ts, and Pa > Po > Ps, In the switching step, the operation mode is switched between an active mode and a sleep mode within a range in which Ta and Ts satisfy (Pa×Ta+Ps×Ts) / (Ta+Ts)<Po. Control method.

8. A control method for an optical communication device having an optical signal transmitting and receiving unit that transmits and receives optical signals, comprising: switching the operation mode of the optical signal transceiver between an active mode in which optical signals can be transmitted and received and a sleep mode in which optical signals are not transmitted or received, within a range in which average power consumption of the optical communication device is less than the supply power supplied to the optical communication device; Equipped with When the optical communication device supplies power to another device that communicates using the optical communication device, the supplied power is Po, the power consumption in active mode is Pa, the power consumption in sleep mode is Ps, the power consumption of the other device in active mode is PA, the power consumption of the other device in sleep mode is PS, the operating time in active mode is Ta, and the operating time in sleep mode is Ts, and Pa > Po > Ps, In the switching step, the operation mode is switched between an active mode and a sleep mode within a range in which Ta and Ts satisfy ((Pa+PA)×Ta+(Ps+PS)×Ts) / (Ta+Ts)<Po. Control method.

Images