JP7523007B2 - Power receiving terminal device and power receiving system - Google Patents

Description

This invention relates to a power receiving terminal device that receives a power supply voltage from a preceding device and supplies the power supply voltage to a succeeding device, and a power receiving system that is configured by connecting the power receiving terminal devices.

Patent Document 1, which will be described later, discloses an invention relating to a telephone system using PoE (Power over Ethernet (registered trademark)) technology, which is constructed by connecting IP (Internet Protocol) telephones (telephone terminals) to each power supply port of a power supply hub device. In this telephone system, the IP telephones are connected to the power supply hub device with LAN cables, and power is supplied to the IP telephones from the power supply hub device. This eliminates the need to install batteries in the IP telephones. In addition, since the IP telephones do not need to receive power supply voltage from an AC outlet (commercial power source), they can be installed in various locations regardless of the location of the AC outlet, allowing for a flexible telephone system to be constructed.

JP 2019-106632 A

In general, in power supply equipment (PSE (Power Sourcing Equipment)) such as a power supply hub device, the number of power receiving devices (PD (Powered Device)) that can be connected to one power supply port is limited, for example, to a total power consumption of 15.4 W (watts). If multiple IP telephones are connected to one power supply port of a power supply hub, exceeding the allowable power consumption, it is possible that all IP telephones connected to that power supply port will become unusable. For this reason, when building a system with power supply equipment and power receiving devices, it is necessary to know the power consumption of each power receiving device to be connected to one power supply port and to know the total power consumption of those power receiving devices.

However, it is troublesome to keep track of the power consumption of each power receiving device, such as an IP telephone. In addition, it is possible that the power consumption of a power receiving device cannot be confirmed or an error occurs in calculating the total power consumption of the power receiving devices, resulting in connecting more power receiving devices to one power supply port than the allowable power consumption. For this reason, when building a telephone system using a power supply hub device, such as the telephone system disclosed in the above-mentioned Patent Document 1, the general rule is to connect only one IP telephone to one power supply port of the power supply hub device.

Normally, the power consumption of one IP phone is much lower than the total power consumption of all power-receiving devices that can be connected to one power supply port, making it possible to build a telephone system that operates stably without running out of power. However, in this case, IP phones can only be installed as many as the power supply ports on the power supply hub, and when connecting many IP phones, such as in a large office, many power supply hubs are required. Also, when installing IP phones in a location relatively far from the main unit, cables must be run from the power supply hub, creating the problem of limited flexibility in wiring.

In view of the above, the object of this invention is to enable only the number of devices that can be reliably operated to be connected to one power supply port of a power supply device without bothering the operator, thereby enabling the flexible construction of a highly reliable system.

In order to solve the above problem, the power supply/receiving terminal device of the present invention according to claim 1 comprises:
a voltage detection means for detecting a voltage value of a power supply voltage received from a preceding device;
a notification information providing means for providing, when the voltage value detected by the voltage detection means is equal to or greater than a predetermined minimum value, notification information notifying the preceding device;
a voltage limiting means for lowering the power supply voltage received from the preceding device by a predetermined voltage value and supplying the power to the succeeding device;
a stop instruction means for outputting a stop instruction for instructing to stop the supply of power supply voltage to the downstream device when the voltage value detected by the voltage detection means is less than the predetermined minimum value;
a first stop means for stopping the supply of power supply voltage to the downstream device when the stop instruction is output from the stop instruction means;
a determination means for receiving notification information notified from the subsequent stage device, the notification information being information with the same content as the notification information notified to the previous stage device by the notification information providing means, and determining whether or not the notification information exists;
and second stopping means for stopping the supply of power supply voltage to the downstream device when the determining means determines that the notification information has not been provided.

According to the power supply terminal device of the invention described in claim 1, the voltage detection means detects the voltage value of the power supply voltage received from the upstream device, and if the voltage value is equal to or greater than a predetermined minimum value, the notification information providing means provides notification information to the upstream device. This allows the upstream device to know that sufficient power supply voltage is being supplied, and allows the supply of power supply voltage to continue.

The power supply voltage received from the preceding device is limited by the voltage limiting means to a predetermined voltage value and then supplied to the succeeding device. If the voltage value detected by the voltage detection means is less than a predetermined minimum value, the stop instruction means instructs the supply of power supply voltage to the succeeding device to be stopped, and in response, the first stop means stops the supply of power supply voltage to the succeeding device.

The determination means also receives notification information (information having the same content as the notification information notified to the preceding device by the notification information providing means) supplied from the subsequent device, and determines whether the notification information has been received. If the determination means determines that the notification information from the subsequent device has not been received, the second stopping means stops the supply of power supply voltage to the subsequent device. In other words, if the detected voltage value is less than a predetermined minimum value, or if the predetermined notification information is not provided from the subsequent device, the configuration is such that the supply of power supply voltage to the subsequent device can be automatically stopped.

This invention makes it possible to connect only the number of devices that will reliably operate to one power supply port without bothering the operator. This allows for the flexible construction of a highly reliable system that functions stably.

1 is a block diagram for explaining a configuration example of a power supply and reception system according to an embodiment; 1 is a diagram for explaining a telephone system (power supply system) configured with a PoE hub device and an IP telephone terminal. 1 is a diagram for explaining a configuration example of a PoE hub device according to an embodiment; 1 is a block diagram for explaining a configuration example of an IP telephone terminal according to an embodiment; 2 is a block diagram for explaining the configuration of a power receiving circuit and a power supply circuit of the IP telephone terminal according to the embodiment; FIG. 1 is a diagram for explaining a negotiation procedure (PoE sequence) for determining whether or not a device can be powered by PoE technology. 10 is a sequence diagram for explaining a process performed in the telephone system (power supply/reception system) according to the embodiment. FIG. 5 is a flowchart illustrating a process executed in an IP telephone terminal according to the embodiment.

Below, an embodiment of a device and system according to the present invention will be described with reference to the drawings. Digital interfaces exist that are capable of transmitting data and supplying a power supply voltage (driving voltage). For example, PoE technology based on the IEEE802.3af standard or the IEEE802.3at standard using a LAN cable, a digital interface based on the IEEE1394 standard, and a digital interface based on the USB standard are known.

This invention is applicable to electronic devices that are connected using a digital interface cable capable of transmitting and receiving data and supplying power voltage, and that allows a so-called daisy chain connection that connects devices in series, and to systems that use such electronic devices. For this reason, in the embodiment described below, PoE technology is applied, and the device and system according to this invention will be specifically described using an example in which a system is constructed by connecting the LAN ports of each device with a LAN cable. Note that in this specification, PoE is an abbreviation for Power over Ethernet (registered trademark), USB is an abbreviation for Universal serial Bus, and LAN is an abbreviation for Local Area Network.

[Example of power supply system configuration]
Fig. 1 is a block diagram for explaining a configuration example of a power supply system according to an embodiment of the present invention, which is configured by applying the PoE technology. As shown in Fig. 1, PoE power receiving devices 2(1) to 2(4) are daisy-chained to one power supply port of the PoE power supply device 1. PoE power receiving devices 3(1) to 3(4) are daisy-chained to another power supply port of the PoE power supply device 1, and PoE power receiving devices 4(1) to 4(4) are daisy-chained to the other power supply port.

The PoE power supply device 1 is connected to a higher-level device (not shown), and transmits and receives data between the higher-level device and the PoE power supply device. It also receives power voltage from an AC outlet and supplies it to a PoE power receiving device connected to its own power supply port. Each of the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), and 4(1)-4(4) has a power receiving port and power receiving circuit that receives power voltage from the previous device, and a power supply circuit and power supply port that supplies power voltage to the next device. Each device is daisy-chained as shown in FIG. 1 by connecting the power supply port of the previous device to the power receiving port of its own device, forming a system.

Therefore, each of the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), and 4(1)-4(4) does not have a battery installed, but can receive power from the preceding device to supply power to each part of the device, and can also supply power to the following device. In other words, each of the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), and 4(1)-4(4) has both the function of receiving power from the preceding device and the function of supplying power to the following device. Therefore, each of the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), and 4(1)-4(4) can be flexibly installed without being influenced by the position of the AC outlet.

In addition, each of the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), and 4(1)-4(4), which will be described in detail later, has a function that automatically limits the number of PoE power receiving devices that can be connected to one power supply port of the PoE power supply device 1 to an appropriate number. This allows the worker building the system to easily build a highly reliable power receiving system by connecting an appropriate number of PoE power receiving devices to one power supply port of the PoE power supply device without having to worry about the power consumption of the power receiving devices.

The PoE power supply device 1 is specifically a so-called repeater device such as a PoE hub device, and the PoE power receiving devices 2(1)-2(4), 3(1)-3(4), 4(1)-4(4) are various electronic devices that can be connected to a LAN. Examples of PoE power receiving devices include IP telephone terminals, wireless LAN access points, network cameras, and personal computers. Specific examples of the device and system of this invention are described below. In the following, an example is described in which IP telephone terminals 2(1)-2(4) as PoE power receiving terminal devices are daisy-chained to a PoE hub device 1 as a PoE power supply device to configure a telephone system as a power supply and transmission system.

[Power supply system configured with PoE hub device and IP telephone terminal]
2 is a diagram for explaining a telephone system configured with a PoE hub device 1 and IP telephone terminals 2(1)-2(4). As shown in FIG. 2, the telephone system of this embodiment is configured by daisy-chaining the IP telephone terminals 2(1)-2(4) to the PoE hub device 1. As described later, the PoE hub device 1 has a power supply port, and each of the IP telephone terminals 2(1)-2(4) has a power receiving port, a power receiving circuit, a power supply circuit, and a power supply port. Each of the IP telephone terminals 2(1)-2(4) is daisy-chained by connecting the power supply port of the preceding device to the power receiving port of the own device, as shown in FIG. 2, to configure the telephone system.

The PoE hub device 1 is connected to a main device, such as a Session Initiation Protocol (SIP) server (not shown), which is connected to an IP network. This allows IP telephone terminals 2(1)-2(4) to be connected to the main device via the PoE hub device 1 and to make and receive calls, thereby conducting telephone conversations through a call line connected through the IP network. However, in this embodiment, the IP telephone terminals 2(1)-2(4) cooperate with the IP telephone terminals connected before and after them, so that the number of IP telephone terminals that can be connected to one power supply port of the PoE hub device 1 can be automatically limited to an appropriate number.

As will be described in more detail later, in this embodiment, each of the IP telephone terminals 2(1)-2(4) lowers the power supply voltage supplied to the subsequent stage device by a fixed value (4V in this embodiment) as shown in FIG. 2. Therefore, as shown in FIG. 2, the power supply voltage supplied to the subsequent stage device decreases each time it passes through IP telephone terminals 2(1)-2(4), and when the power supply voltage falls below a predetermined minimum value (40V in this embodiment), the supply of power supply voltage to the subsequent stage device is stopped. This causes the IP telephone terminal that has stopped supplying power supply voltage to the subsequent stage device to be electrically disconnected from the other IP telephone terminal that is the subsequent stage device.

In this way, this embodiment has a function that allows up to three IP telephone terminals to be connected to one power supply port as IP telephone terminals that can function properly. For this reason, in FIG. 2, four IP telephone terminals 2(1) to 2(4) are connected to the PoE hub device 1, but the number of IP telephone terminals that can actually function is automatically limited to three, IP telephone terminals 2(1) to 2(3).

In the following, we will first explain an example of the configuration of the PoE hub device 1, and then explain an example of the configuration of the IP telephone terminals 2(1) to 2(4). In this embodiment, each of the IP telephone terminals 2(1) to 2(4) has the same configuration. Therefore, in the following, except when it is necessary to distinguish between them, the IP telephone terminals 2(1) to 2(4) will be collectively referred to as the IP telephone terminal 2.

<Configuration Example of PoE Hub Device>
3 is a diagram for explaining a configuration example of a PoE hub device 1 as a PoE power supply device. The PoE hub device 1 has a plurality of power supply ports. However, for the sake of simplicity, FIG. 3 shows a portion including one downstream device side port (power supply port) 102 and a corresponding upstream device side port 101. The LAN cable connecting the devices is configured with four twisted pair wires, in which eight insulated coated conductors numbered 1 to 8 are twisted together in pairs. Specifically, the twisted pair wires are configured by pairing each wire, such as 1 and 2, 3 and 6, 4 and 5, and 7 and 8.

There are two types of PoE technology (power supply technology) that transmit and receive data and supply power voltage through such LAN cables: Alternative A and Alternative B. In either case, twisted pair wires 1 and 2 and twisted pair wires 3 and 6 are used for data communication. In the case of the Alternative A method, power is supplied by superimposing the power voltage on the twisted pair wires 1 and 2 and twisted pair wires 3 and 6 used for data communication. Therefore, in the case of the Alternative A method, twisted pair wires 4 and 5 and twisted pen wires 7 and 8 are open (free). In contrast, in the case of the Alternative B method, power is supplied through twisted pair wires 4 and 5 and twisted pen wires 7 and 8, which are not used for data. Therefore, in the case of Alternative B, there are no open (vacant) twisted pairs.

The PoE hub device 1 may use either the Alternative A method or the Alternative B method. However, as described later, the connection between the IP telephone terminals 2(1) to 2(4) uses the Alternative A method. For this reason, in this embodiment, the connection between the PoE hub device 1 and the IP telephone terminal 2(1) is also assumed to be made using the Alternative A method. As shown in FIG. 3, the PoE hub device 1 has a front-stage device port 101 and a rear-stage device port 102 as ports (connection ends) to which a LAN cable is connected. In the front-stage device port 101 and the rear-stage device port 102, the eight terminals numbered and indicated by circles correspond to the eight insulated conductors of the LAN cable, numbered 1 to 8. Therefore, the twisted pair wires numbered 1 and 2 are used as the transmission line (TX), and the twisted pair wires numbered 3 and 6 are used as the reception line (RX) to perform data communication.

Furthermore, as shown in FIG. 3, for example, a power supply voltage of 48V (volts) formed based on a commercial power supply from an AC outlet is applied to the twisted pair wires No. 1 and No. 2 and the twisted pair wires No. 3 and No. 6 of the downstream device side port 102. This makes it possible to superimpose the power supply voltage on the communication data being sent and received, and to supply the power supply voltage to the downstream device connected to the downstream device side port 102. In other words, the downstream device side port 102 of the PoE hub device 1 functions as a power supply port. In this way, in the upstream device side port 101 and the downstream device side port 102 of the PoE hub device 1, the pair of terminals No. 1 and No. 2 and the pair of terminals No. 3 and No. 6 are used as data communication terminals. Furthermore, in the downstream device side port 102, the pair of terminals No. 1 and No. 2 and the pair of terminals No. 3 and No. 6 are also used as power supply terminals for the power supply voltage.

In this way, the PoE hub device 1 relays data communication between the main device connected to the upstream device port 101 and the IP telephone terminal 2 connected to the downstream device port 102. Furthermore, the PoE hub device 1 supplies power supply voltage to the downstream device connected to the downstream device port 102, which functions as a power supply port.

<Example of the configuration of an IP telephone terminal>
Fig. 4 is a block diagram for explaining a configuration example of the IP telephone terminal 2. As shown in Fig. 4, the IP telephone terminal 2 includes a front-stage device port 201 and a rear-stage device port 204, the front-stage device port 201 is connected to a power receiving circuit 202, and the rear-stage device port 204 is connected to a power supplying circuit 203. That is, the front-stage device port 201 functions as a power receiving port, and the rear-stage device port 204 functions as a power supplying port. The power receiving circuit 202 and the power supplying circuit 203 are connected to each other, and these two circuits function as a LAN I/F (Interface).

The upstream device side port 201 and downstream device side port 204 are configured in the same manner as the upstream device side port 101 and downstream device side port 102 of the PoE hub device 1 described with reference to FIG. 3, as will be described in detail later. The IP telephone terminal 2 receives and supplies power supply voltage using the Alternative A method of PoE technology. Therefore, the power receiving circuit 202 receives the power supply voltage applied through the upstream device side port and applies it to the power supply unit 206.

The power supply unit 206 generates a drive current to be supplied to each unit according to the power supply voltage applied from the power receiving circuit 202, and supplies the drive current to each unit. This enables the IP telephone terminal 2 to function. The power receiving circuit 202 also supplies the power supply voltage applied through the front-stage device side port directly to the power supply circuit 203. The power supply circuit 203 converts the power supply voltage applied thereto into a power supply voltage for power supply, and supplies power to another IP telephone terminal 2, which is a rear-stage device, through the rear-stage device side port 204.

Although the details will be described later, the power supply circuit 203 has a function of stopping the supply of power supply voltage to the downstream device, and when the supply of power supply voltage to the downstream device is stopped, it notifies the control unit 220 described later. This allows the control unit 220 to notify the user that the supply of power supply voltage to the downstream device has been stopped via the display 213 described later, etc.

The power receiving circuit 202 also extracts the received data addressed to itself received through the upstream device side port 201 and supplies it to the packet processing unit 205. The power receiving circuit 202 also sends the transmission data from its own device supplied from the packet processing unit 205 to the upstream device side through the upstream device side port 201. The received data received through the upstream device side port 201 is provided to the downstream device via the power receiving circuit 202 → power supply circuit 203 → downstream device side port 204 in this order. Conversely, the transmission data from the downstream device received through the downstream device side port 204 is provided to the upstream device via the power supply circuit 203 → power receiving circuit 202 → upstream device side port 201 in this order.

The control unit 220 is a microprocessor formed by connecting a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a non-volatile memory, etc. through a CPU bus (not shown). The control unit 220 controls each part of the IP telephone terminal 2. The packet processing unit 205 performs decomposition/generation processing of various data such as control data and voice data that are packetized and transmitted/received.

The handset 207 has a speaker (receiver) and a microphone (transmitter). The codec 208 receives the voice data that has been decomposed into packets by the packet processing unit 205, compresses and expands it to convert it into an analog voice signal, and supplies it to the speaker of the handset 207 in the off-hook state. As a result, the voice from the other party is emitted from the speaker of the handset 207. The codec 208 also converts the analog voice signal picked up by the microphone of the off-hook handset 207 into a digital signal, compresses the data, and supplies it to the packet processing unit 205. The packet processing unit 205 packetizes the voice data from the codec 208 and transmits it to the other party via the power receiving circuit 202 and the front-stage device side port 201.

Although not shown in FIG. 4, the IP telephone terminal 2 is provided with a hook switch. This allows the IP telephone terminal 2 to detect when the handset 207 is placed in a specified position on the IP telephone terminal 2 (on-hook state) and when the handset 207 is picked up from the specified position on the IP telephone terminal 2 (off-hook state) and to notify the control unit 220. The sound emission unit 209, under the control of the control unit 220, mainly emits a ringtone when a call is received, but in addition to the ringtone, it can also emit a warning sound and audible error messages and operation guidance.

The operation input unit 210 and the operation input I/F (Inter Face) 211 accept operation input from the user and provide the accepted information to the control unit 220. Although not shown, the operation input unit 210 is provided with several function keys such as a numeric keypad, a call key, a response key, and a hold key, as well as several flexible keys. The display controller 212 and the display 213 perform a process of displaying various information on the display screen of the display 213 under the control of the control unit 220. The display 213 can display various information such as the entered telephone number of the other party, the telephone number and name of the caller, guidance messages, and warning messages, and, as described above, also displays a notice that the supply of power voltage to downstream devices has been stopped.

Figure 5 is a block diagram for explaining the configuration of the power receiving circuit 202 and power supply circuit 203 of the IP telephone terminal 2. As shown in Figure 5, the front-stage device side port (power receiving port) 201 and the back-stage device side port (power supply port) 204 have eight terminals, as indicated by circles numbered 1 to 8. These terminals 1 to 8 correspond to the insulated conductors 1 to 8 of the LAN cable. Therefore, as described above, the IP telephone terminal 2 is capable of data communication (receiving and transmitting data) and receiving/supplying power supply voltage through the twisted pair wires 1 and 2 and the twisted pair wires 3 and 6.

Terminals 1 and 2 and terminals 3 and 6 of the upstream device side port 201 are connected to terminals 1 and 2 and terminals 3 and 6 of the downstream device side port 204 via the communication processing unit 2021, voltage detection unit 2022, supply switching unit 2032, and voltage limiting unit 2033. Therefore, communication data from the upstream device can be provided to the downstream device, and communication data from the downstream device can be provided to the upstream device, via the upstream device side port 201, power receiving circuit 202, power supply circuit 203, and downstream device side port 204.

The power supply voltage applied through terminals 1 and 2 and terminals 3 and 6 of the upstream device port 201 is supplied to the downstream device through terminals 1 and 2 and terminals 3 and 6 of the downstream device port 204, which are connected through the above-mentioned power receiving circuit and power supply circuit. Furthermore, the power receiving circuit 202 and power supply circuit 203 between the upstream device port 201 and the downstream device port 204 not only relay communication data and power supply voltage as described above, but also have the following functions.

As shown in FIG. 5, the power receiving circuit 202 includes a communication processing unit 2021, a voltage detection unit 2022, a notification information providing unit 2023, and a supply stop instruction unit 2024. The communication processing unit 2021 extracts the received data addressed to the device itself from the received data received through terminals 1 and 2, and supplies the extracted data to the packet processing unit 205. The communication processing unit 2021 also transmits the transmission data from the device itself, which is supplied from the packet processing unit 205, to the upstream device through terminals 3 and 6 of the upstream device side port 201. This makes it possible to retrieve the received data addressed to the device itself and send the transmission data from the device itself through the packet processing unit 205.

The voltage detection unit 2022 applies the power supply voltage received through terminals 1 and 2 and terminals 3 and 6 of the upstream device side port 201 to the power supply unit 206. As described above, the power supply unit 206 forms a power supply current to be supplied to each part of the IP telephone terminal 2 by applying the power supply voltage, and supplies it to each part. Furthermore, the voltage detection unit 2022 detects the voltage value of the power supply voltage received through terminals 1 and 2 and terminals 3 and 6 of the upstream device side port 201, and notifies the notification information provision unit 2023 and the supply stop instruction unit 2024 of the voltage value.

When the voltage value from the voltage detection unit 2022 is equal to or greater than a predetermined minimum value, the notification information providing unit 2023 forms predetermined notification information and provides it to the preceding device through lines (terminals) 7 and 8, which are vacant in the Alternative A system. That is, when the voltage value of the power supply voltage received by the device itself is sufficient for normal operation, notification information notifying this is provided to the preceding device. In this embodiment, the predetermined minimum value of the power supply voltage is, for example, 40V (volts). The notification information may be any information that is predetermined, but for example, company product notification information such as a manufacturer code and a product model number that indicates that the product is the company's own product is used. As a result, when the notification information is notified by the subsequent device, the preceding device can know that it is supplying sufficient power supply voltage and that the subsequent device is the company's own product.

Conversely, if no notification information is sent from the subsequent device, it is possible to recognize that sufficient power supply voltage is not being supplied or that the subsequent device is not one of the company's products, and it becomes possible to stop the supply of power supply voltage to the subsequent device. The subsequent device is able to recognize that it is not one of the company's products because it will not provide notification information if it is not one of the company's products. Also, even if some notification information is sent, if it is not the specified product notification information that can identify it as one of the company's products, such as a manufacturer code or product number, the subsequent device can determine that it is not one of the company's products. In this way, the reason that power supply voltage is not provided to the subsequent device even if it is not one of the company's products is that it is not possible to accurately grasp the power consumption of the subsequent device, and therefore it is not possible to guarantee that it will operate properly even if the power supply voltage is above a specified minimum value.

In addition, in this embodiment, if the voltage value from the voltage detection unit 2022 is equal to or greater than a predetermined maximum value, the notification information providing unit 2023 does not provide the predetermined notification information to the preceding device. The predetermined maximum voltage value is determined to be, for example, 48V (volts). When a power supply voltage of 48V is supplied to the IP telephone terminal 2 in this embodiment, the IP telephone terminal 2 can be determined to be the first PoE power receiving device directly connected to the PoE hub device 1. In this case, there is no need to stop the supply of power supply voltage from the PoE hub device 1, so notification information is not provided.

However, when a power supply voltage of 48V is supplied to the IP telephone terminal 2 and the specified notification information is not provided to the preceding device, a normal PoE sequence is used to determine whether or not the IP telephone terminal 2 can supply power via PoE. Here, the PoE sequence for negotiation performed between devices compatible with PoE technology is explained. Figure 6 is a diagram explaining the negotiation procedure (PoE sequence) for determining whether or not a device can be supplied with power via PoE technology.

When any electronic device (back-end device) is connected to the power supply port 102 of the PoE hub device 1, the PoE sequence shown in FIG. 6A is executed. The PoE hub device 1 first applies two different voltages in the range of 2.8V to 10V to the back-end device and measures the current. In the case of a back-end device that can supply power supply voltage using PoE technology, a 25 kΩ (kilo-ohms) resistor is built in for detection purposes. Therefore, if a current value corresponding to 25 kΩ is detected, the PoE hub device 1 can determine that the back-end device connected to the PoE hub device 1 is a PoE power receiving device that can supply power supply voltage using PoE technology.

If it is determined that the subsequent device is a PoE receiving device that can receive power voltage using PoE technology, the PoE hub device 1 then applies a voltage in the range of 15.5V to 20.5V to the subsequent device and measures the current. The measured current value is used to identify the power consumption class to which the subsequent device belongs. As shown in FIG. 6B, the power consumption class can be determined according to the detected current and is divided into five levels, from class 0 to class 4. However, this only determines the power consumption class to which the subsequent device belongs, i.e., the minimum and maximum power consumption that the subsequent device can consume, and does not determine the power consumption of the subsequent device itself. After 400 ms (milliseconds) have elapsed since the process of determining the power consumption class of the subsequent device began, the supply of power voltage to the subsequent device begins. Note that, as shown in FIG. 6A, it takes several hundred milliseconds for the power supply voltage to be stably supplied.

Next, the supply stop instruction unit 2024 will be described. As described above, the voltage value of the power supply voltage detected by the voltage detection unit 2022 is also supplied to the supply stop instruction unit 2024. When the voltage value from the voltage detection unit is less than a predetermined minimum value (e.g., 40V), the supply stop instruction unit 2024 forms a stop instruction to instruct the power supply voltage to be stopped from being supplied to the downstream device, and supplies this to the supply switching unit 2032 of the power supply circuit 203. When the voltage value of the received power supply voltage is less than the predetermined minimum value (less than 40V in this embodiment), it is not possible to supply a power supply voltage sufficient for the downstream device to operate, so it is necessary not to supply power supply voltage to the downstream device.

In this way, the power receiving circuit 202 is equipped with a communication processing unit 2021 and a voltage detection unit 2022, and can take in received data addressed to the device itself and send out transmitted data from the device itself, as well as receive power supply voltage from the preceding device to supply drive power to each unit. Furthermore, the power receiving circuit 202 is equipped with a notification information providing unit 2023, so that if the voltage value of the received power supply voltage is equal to or higher than a predetermined minimum value, the notification information is notified to the preceding device, allowing for simple and quick negotiation. Also, the power receiving circuit 202 is equipped with a supply stop instruction unit 2024, so that if the power supply voltage is below a predetermined minimum value, an instruction to stop the supply of power supply voltage to the subsequent device can be quickly issued.

On the other hand, as shown in FIG. 5, the power supply circuit 203 includes a notification information discrimination unit 2031, a supply switching unit 2032, and a voltage limiting unit 2033. When any device is connected to the downstream device side port 204, the notification information discrimination unit 2031 acquires notification information notified from the downstream device through terminals 7 and 8. Furthermore, when the specified notification information is not notified (cannot be acquired because it is not notified), the notification information discrimination unit 2031 supplies a stop instruction to the supply switching unit 2032 to instruct the supply of power voltage to be stopped. In other words, when notification information is not provided from the downstream device, either a sufficient power voltage is not being supplied to the downstream device or the downstream device is not a company product, and in this case, power voltage is not supplied to the downstream device.

When the notification information discrimination unit 2031 detects whether the downstream device is a company's product or not by using notification information such as a manufacturer code or product number, it provides a memory for storing and holding the manufacturer code and product number. By comparing the information held in this memory with the notification information provided, it becomes possible to determine whether the downstream device is a company's product or not.

The supply switching unit 2032 stops supplying the power supply voltage supplied through the voltage detection unit 2022 to the voltage limiting unit 2033 when a stop instruction is provided from the supply stop instruction unit 2024 and when a stop instruction is provided from the notification information discrimination unit 2031. That is, when a stop instruction is notified from either the supply stop instruction unit 2024 or the notification information discrimination unit 2031, the supply switching unit 2032 stops supplying the power supply voltage to the voltage limiting unit 2033. As a result, if the power supply voltage supplied from the upstream device is not equal to or greater than a predetermined minimum value, the supply of the power supply voltage to the downstream device is stopped, and also if notification information is not provided from the downstream device, the supply of the power supply voltage to the downstream device is stopped.

When the power supply voltage is supplied without being stopped by the supply switching unit 2032, the voltage limiting unit 2033 limits the power supply voltage to be lowered by a predetermined value, and applies the limited power supply voltage to terminals 1 and 2 and terminals 3 and 6 of the downstream device side port. As a result, a power supply voltage lowered by a predetermined value, in this embodiment by 4Vb as described above, is supplied to the downstream device. In this embodiment, the voltage limiting unit 2033 lowers the applied power supply voltage by 4V and applies it to terminals 1 and 2 and terminals 3 and 6 of the downstream device side port.

The reason why the voltage limiting unit 2033 reduces the power supply voltage by 4V and processes the power supply to the downstream device is to limit the number of IP telephone terminals 2 that can be connected to one power supply port of the PoE hub device 1 to an appropriate number (three in this embodiment). In this embodiment, as shown in FIG. 2, the power supply voltage is reduced by 4V each time the signal passes through an IP telephone terminal 2. Therefore, as shown in FIG. 2, a power supply voltage of 48V is supplied to IP telephone terminal 2(1), a power supply voltage of 44V is supplied to IP telephone terminal 2(2), and a power supply voltage of 40V is supplied to IP telephone terminal 2(3).

Furthermore, a power supply voltage of 36V is supplied to the IP telephone terminal 2 (4), but if the power supply voltage becomes less than 40V due to the power consumption of each IP telephone terminal 2, the specified notification information is not provided to the preceding device. In addition, since the power supply voltage supplied to the IP telephone terminal 2 (4) to which a power supply voltage of 36V is supplied is less than 40V, power supply voltage is not supplied even if a subsequent device is connected to the subsequent device side port 204 of the IP telephone terminal 2 (4) itself. Therefore, in the case of the telephone system shown in FIG. 2, power supply voltage is not supplied from the IP telephone terminal 2 (3) and the IP telephone terminal 2 (4). Therefore, the power supply port of the PoE hub device 1 is limited to three IP telephone terminals 2 daisy-chained. In other words, it is possible to automatically limit the number of IP telephone terminals 2 connected to one power supply port of the PoE hub device 1 to three IP telephone terminals 2 that can be guaranteed to operate reliably.

As can be seen from the above explanation, when the received power supply voltage is less than a predetermined minimum value, the function of notifying the supply stop instruction unit 2024 of the stop instruction to the supply switching unit 2032 to stop power supply realizes the function of stopping the supply of power supply voltage from the own device to the subsequent device. Also, notifying the preceding device of notification information through the notification information providing unit 2023 realizes the function of stopping the supply of power supply voltage from the preceding device by the function of the notification information determining unit 2031 and supply switching unit 2032 of the preceding device. In other words, it is possible to control the power receiving function and the power supply function separately.

[Telephone System Operation]
Fig. 7 is a sequence diagram for explaining the processing performed in the telephone system (power supply system) of the embodiment shown in Fig. 2, which is configured by the above-mentioned PoE hub device 1 and IP telephone terminals 2(1)-2(4). As shown in Fig. 2, the telephone system is constructed by connecting the PoE hub device 1 and the IP telephone terminals 2(1)-2(4), and each device is powered on.

When an electronic device is connected to the downstream device side port (power supply port) 102 of the PoE hub device 1, as described with reference to FIG. 6, the PoE hub device 1 executes a normal negotiation procedure (PoE sequence) to determine whether the device can be powered by PoE technology (step S1). The PoE hub device 1 executes the PoE sequence, and based on the current value of the current flowing through the IP telephone terminal 2 (1) connected to the device, determines whether the IP telephone terminal 2 (1) is a device that can be powered by PoE technology, and ends the PoE negotiation (step S2). In this embodiment, since the IP telephone terminal 2 (1) is a PoE power receiving device that supports PoE technology, it is determined that power can be supplied by PoE technology, and the supply of 48V power supply voltage from the PoE hub device 1 to the IP telephone terminal 2 (1) is started (step S3). Note that in FIG. 7, "negotiation" is abbreviated to "nego".

Although omitted in FIG. 7, the voltage value of the power supply voltage is also detected in IP telephone terminal 2 (1), but in this case, the voltage value of the received power supply voltage is 48V. Therefore, the notification information providing unit 2023 does not function to notify the preceding device of the specified notification information, and the supply stop instruction unit 2024 does not issue a stop instruction to the supply switching unit 2032 to stop the supply of power supply voltage to the subsequent device. Therefore, in IP telephone terminal 2 (1), the voltage limiting unit 2033 functions and starts supplying a power supply voltage of 44V for power supply, which is formed by reducing the received power supply voltage of 48V by 4V, to IP telephone terminal 2 (2) connected to the power supply port 204 (step S4).

In the IP telephone terminal 2 (2), the voltage detection unit 2022 functions to detect the voltage value of the power supply voltage (step S5). The voltage detection unit 2022 of the IP telephone terminal 2 (2) notifies the notification information providing unit 2023 and the supply stop instruction unit 2024 of the detected voltage value. In this case, the detected voltage value is not equal to or greater than the predetermined maximum value of 48 V, nor is it less than the predetermined minimum value of 40 V. Therefore, the notification information providing unit 2023 of the IP telephone terminal 2 (2) forms the predetermined notification information and provides it to the IP telephone terminal 2 (1), which is the preceding device, through terminals 7 and 8 of the power receiving port 201 (step S6). The IP telephone terminal 2 (1) can determine that the notification information has been provided by the notification information determining unit 2031, by receiving the predetermined notification information from the IP telephone terminal 2 (2), which is the following device. As a result, IP telephone terminal 2(1) continues to supply power to IP telephone terminal 2(2) without stopping the supply of 44V power supply voltage (step S7).

In addition, the supply stop instruction unit 2024 of the IP telephone terminal 2(2) does not issue a stop instruction to the supply switching unit 2032 because the voltage value of the power supply voltage is not less than the specified minimum value of 40V. Therefore, in the IP telephone terminal 2(2), the voltage limiting unit 2033 functions and starts supplying a power supply voltage of 40V for power supply, which is formed by reducing the received power supply voltage of 44V by 4V, to the IP telephone terminal 2(3) connected to its own power supply port 204 (step S8). In the IP telephone terminal 2(3), the voltage detection unit 2022 functions and detects the voltage value of the power supply voltage (step S9).

The voltage detection unit 2022 of the IP telephone terminal 2 (3) notifies the notification information providing unit 2023 and the supply stop instruction unit 2024 of the detected voltage value. In this case, the detected voltage value is not equal to or greater than the predetermined maximum value of 48V, nor is it less than the predetermined minimum value of 40V. Therefore, the notification information providing unit 2023 of the IP telephone terminal 2 (3) forms the predetermined notification information and provides it to the IP telephone terminal 2 (2), which is the preceding device, through terminals 7 and 8 of the power receiving port 201 (step S10). By receiving the predetermined notification information from the IP telephone terminal 2 (3), which is the following device, the IP telephone terminal 2 (2) can determine that notification information has been provided in the notification information determining unit 2031. Therefore, the IP telephone terminal 2 (2) continues to supply power to the IP telephone terminal 2 (3) without stopping the supply of the 40V power supply voltage (step S11).

The supply stop instruction unit 2024 of the IP telephone terminal 2 (3) does not issue a stop instruction to the supply switching unit 2032 because the voltage value of the power supply voltage is not less than the specified minimum value of 40V. Therefore, in the IP telephone terminal 2 (3), the voltage limiting unit 2033 functions to start supplying a power supply voltage of 36V to the IP telephone terminal 2 (4) connected to its own power supply port 204, which is formed by reducing the received power supply voltage of 40V by 4V (step S12). In the IP telephone terminal 2 (4), the voltage detection unit 2022 functions to detect the voltage value of the power supply voltage (step S13).

The voltage detection unit 2022 of the IP telephone terminal 2 (4) notifies the notification information providing unit 2023 and the supply stop instruction unit 2024 of the detected voltage value. In this case, the detected voltage value is not the specified maximum value of 48V, and is less than the specified minimum value of 40V. Therefore, the notification information providing unit 2023 of the IP telephone terminal 2 (3) does not provide the specified notification information to the IP telephone terminal 2 (3), which is the preceding device. Since the IP telephone terminal 2 (3) has not received the specified notification information from the IP telephone terminal 2 (4), which is the following device, the notification information determining unit 2031 supplies a stop instruction to the supply switching unit 2032. As a result, the supply of power supply voltage from the IP telephone terminal 2 (3) to the IP telephone terminal 2 (4) is stopped (step S14).

The supply stop instruction unit 2024 of the IP telephone terminal 2 (4) receives the notification that the voltage value is 36V, and because the power supply voltage received by the IP telephone terminal 2 (4) is less than the specified minimum value of 40V, issues a stop instruction to the supply switching unit 2032 of the IP telephone terminal 2 (4). As a result, even if a downstream device is connected to the power supply port 204 of the IP telephone terminal 2 (4), the supply switching unit 2032 of the IP telephone terminal 2 (4) will not output the power supply voltage. Therefore, the power supply voltage from the upstream device, IP telephone terminal 2 (3), will not be supplied to the downstream device.

[Summary of the operation of IP telephone terminal 2]
Next, the processing performed by the IP telephone terminal 2, which is the PoE power receiving device of this embodiment, will be summarized. Fig. 8 is a flow chart for explaining the processing executed by the IP telephone terminal 2 of the embodiment. The processing shown in Fig. 8 is executed by each IP telephone terminal 2 when, as shown in Fig. 2, the PoE hub device 1 and the IP telephone terminal 2 are connected by a LAN cable, the PoE hub device 1 is powered on to enable power supply, and each IP telephone terminal 2 is powered on.

The voltage detection unit 2022 of the power receiving circuit 202 of the IP telephone terminal 2 detects the voltage value V of the power supply voltage received through the upstream device side port (power receiving port) 201, and notifies the detected voltage value V to the notification information providing unit 2023 and the supply stop instruction unit 2024 (step S101). In this case, the voltage detection unit 2022 detects and notifies the voltage value V of the power supply voltage after the power supply voltage is applied to the device itself, enabling it to operate, and the voltage value V of the applied power supply voltage becomes a constant value.

The notification information providing unit 2023 and the supply stop instruction unit 2024 determine whether the voltage value V of the received power supply voltage is equal to or greater than a predetermined maximum value Hth (e.g., 48 V) (step S102). When it is determined in the determination process of step S102 that the voltage value V is equal to or greater than the predetermined maximum value Hth, there is no need to notify the preceding device of the predetermined notification information, and there is no need to stop the supply of power supply voltage to the subsequent device. For this reason, the notification information providing unit 2023 and the supply stop instruction unit 202 do not perform any processing, and instead proceed to the processing from step S107 described below.

In the determination process of step S102, it is determined that the voltage value V is not equal to or greater than the predetermined maximum value Hth. In this case, the notification information providing unit 2023 and the supply stop instruction unit 2024 further determine whether the voltage value V of the received power supply voltage is equal to or greater than a predetermined minimum value Lth (e.g., 40 V) (step S103). In the determination process of step S103, it is determined that the voltage value V of the received power supply voltage is less than the predetermined minimum value Lth. In this case, the notification information providing unit 2023 does not provide the predetermined notification information, and the supply stop instruction unit 2024 notifies the supply switching unit 2032 of a supply stop instruction (step S104). The supply switching unit 2032, which has received the stop instruction, stops the output of the power supply voltage to the subsequent stage (step S105). After this, the process shown in FIG. 8 is terminated.

In this way, by not providing the predetermined notification information to the upstream device, the supply of insufficient power supply voltage to the device itself can be stopped. Also, by notifying the supply switching unit of a stop instruction, the supply switching unit 2032 can stop the supply of insufficient power supply voltage to the downstream device. Meanwhile, in the determination process of step S103, it is determined that the voltage value V of the received power supply voltage is equal to or greater than the predetermined minimum value Lth. In this case, the notification information providing unit 2023 forms predetermined notification information (notification information to be provided to the upstream device) and provides it to the upstream device through the 7th and 8th terminals of the upstream device side port 201 (step S106). Note that in step S106, since the power supply voltage to the downstream device is not in a state of being stopped, the supply stop instruction unit 2024 does not issue a stop instruction to the supply switching unit 2032.

After the process of step S106, and if it is determined in the determination process of step S102 that the voltage value V is equal to or greater than the predetermined maximum value Hth, the supply of power supply voltage to the downstream device is started (step S107). In step S107, the voltage limiting unit 2033 functions to form a power supply voltage for power supply that is a predetermined value (4 V in this embodiment) lower than the received power supply voltage. This power supply voltage for power supply that is formed is supplied to the other IP telephone terminal 2, which is the downstream device, through terminals 1 and 2 and terminals 3 and 6 of the downstream device side port (power supply port) 204.

Then, the notification information determination unit 2031 of the IP telephone terminal 2 functions to acquire the specified notification information (notification information provided from the subsequent stage device) provided through terminals 7 and 8 of the subsequent stage device side port 204 (step S108). The process of step S108 takes into account the processing delay in the subsequent stage device, and performs the notification information acquisition process for a specified period of time, for example, several seconds. Next, the notification information determination unit 2031 determines whether or not the specified notification information is present (whether or not the specified notification information has been provided) (step S109).

In other words, the notification information received from the subsequent stage device indicates the same content as the notification information provided to the subsequent stage device through the notification information providing unit 2023 of the own device. Therefore, when it is determined in the determination process of step S109 that there is specified notification information, it can be determined that the subsequent stage device is a company product that is receiving a sufficient supply of power voltage. In this case, the notification information determination unit 2031 does nothing and continues the supply of power voltage to the subsequent stage device that began in step S105 (step S110). After this, the process shown in FIG. 8 is terminated.

Also, when it is determined in the determination process of step S109 that there is no specific notification information, it can be determined that the downstream device is not receiving a sufficient supply of power supply voltage or is not a product of the company. In this case, the notification information determination unit 2031 forms an instruction to stop the supply of power supply voltage and supplies this to the supply switching unit 2032 (step S111). As a result, the supply switching unit 2032 stops the supply of power supply voltage to the downstream device and does not supply power supply voltage to the downstream device (step S112), and ends the process shown in this Figure 8.

The process shown in Figure 8 is executed by each of the IP telephone terminals 2(1) to 2(4) in the telephone system shown in Figure 2. As a result, in the case of the telephone system of this embodiment, it is possible to limit the number of IP telephone terminals 2(1) to 2(3) to one power supply port of the PoE hub device 1 so that they can be connected to one port. In this case, even if IP telephone terminal 2(4) is physically connected to the rear of IP telephone terminal 2(3), no power supply voltage is supplied and the terminals are electrically disconnected, so that it is possible to avoid a state in which the IP telephone terminals 2(1) to 2(3) become unusable due to an overconnection.

In addition, when the IP telephone terminal 2 (3) stops the supply of power voltage to the downstream device, the supply switching unit 2032 of the power supply circuit 203 notifies the control unit 220 of the IP telephone terminal 2 that the supply of power voltage to the downstream device has been stopped. As a result, the control unit 220 displays a display message such as "The supply of power voltage to the downstream device has been stopped" or "The downstream device cannot be connected" on the display 213, or emits a voice message with the same content from the sound emission unit 209. As a result, in the case of the telephone system shown in FIG. 2, by outputting a message through the IP telephone terminal 2 (3), the user can be clearly notified that the IP telephone terminal 2 (4) cannot be connected after the P telephone terminal 2 (3).

The notification that the IP telephone terminal 2 cannot be connected to the downstream can be given by an alarm sound, lighting or blinking of an LED (Light Emitting Diode), etc. In this way, in this embodiment, it is possible to clearly indicate through the IP telephone terminal 2 (3) that the power supply voltage is not supplied to the downstream device, the IP telephone terminal 2 (4). Therefore, the user can take measures such as reconnecting the IP telephone terminal 2 (4) to the main device via a different route, and thus avoid a state in which the IP telephone terminal 2 (4) cannot be used. In other words, even if more IP telephone terminals 2 than the allowable number are connected to one power supply port of the PoE hub device 1, it is possible to grasp from which point the allowable number is exceeded, and therefore it becomes easy to appropriately reconnect the IP telephone terminals 2 that exceed the allowable number.

[Effects of the embodiment]
As described above, according to the power receiving device of this embodiment, each of the power receiving devices cooperates with the preceding device and the subsequent device, and it is possible to limit the number of power receiving devices to be connected to one power supply port of the PoE power supply device. This makes it possible to easily build a highly reliable power receiving system in which appropriate power receiving devices are connected to one power supply port without knowing the total power consumption of electronic devices that can be connected to one power supply port of the PoE power supply device or the power consumption of each of the power receiving devices.

[Modification]
In the above-mentioned embodiment, the predetermined maximum value of the power supply voltage is 48V, the predetermined minimum value is 40V, and the power supply voltage for power supply is 4V lower than the received power supply voltage. However, these voltage values are only examples, and appropriate values can be set according to the performance of the PoE power supply device and the power consumption of the PoE power receiving device. Therefore, depending on the power consumption of the PoE power receiving device, it is possible to connect a larger number of PoE power receiving devices to one power supply port of the PoE power supply device, or conversely, it is possible to further limit the number of devices connected to one power supply port.

In the above embodiment, a telephone system is constructed by connecting multiple IP telephone terminals 2 to the PoE hub device 1, but the present invention is not limited to this. The present invention can be applied to a power supply system constructed by connecting a wireless LAN access point, a network camera, a personal computer, etc. as a PoE power supply receiving device to a PoE power supply device.

In the above embodiment, as explained with reference to FIG. 5, the supply switching unit 2032 is provided on the power supply circuit 203 side, but this is not limited to the above. The supply switching unit 2032 may be provided in the power receiving circuit 202, for example, after the voltage detection unit 2022. Therefore, the configuration of the power receiving circuit and power supply circuit shown in FIG. 5 is one example, and various modifications and improvements are possible.

The power receiving circuit 202 and the power supply circuit 203 described with reference to FIG. 5 can also be created using technology such as a programmable logic device (PLD). A PLD is an integrated circuit that allows the user to define and change the internal logic circuit after manufacturing, and can flexibly configure a power receiving circuit and a power supply circuit with the desired functions.

In the above embodiment, the power supply voltage is received and supplied using the Alternative A method of PoE technology. This is because the specified notification information is sent to the upstream device using the free twisted pair wires No. 7 and No. 8. However, this is not limited to this.

For example, the devices may be connected using the Alternative B method of PoE technology, and the power supply voltage may be supplied by superimposing it on the twisted pair wires No. 4 and No. 5 and the twisted pair wires No. 7 and No. 8. In this case, the voltage detection unit 2022 detects the voltage value of the power supply voltage superimposed on the twisted pair wires No. 4 and No. 5 and the twisted pair wires No. 7 and No. 8. The supply switching unit 2032 switches whether or not the power supply voltage superimposed on the twisted pair wires No. 4 and No. 5 and the twisted pair wires No. 7 and No. 8 is output to the subsequent stage.

The voltage limiting means limits the power supply voltage superimposed on the twisted pair wires No. 4 and No. 5 and the twisted pair wires No. 7 and No. 8. The specified notification information is superimposed on the twisted pair wires No. 7 and No. 8 and provided to the upstream device, and is configured to be extracted by the upstream device. When the devices are connected using the Alternative B method of PoE technology, the specified notification information may be mixed with or superimposed on the transmission data sent on the twisted pair wires No. 3 and No. 6 and provided to the upstream device, and extracted by the upstream device.

In other words, the power supply device and the power receiving device, and the power receiving device and the power receiving device may be connected using any interface as long as the interface is capable of receiving and supplying power from the power supply voltage and is capable of daisy chain connection. In this case, it is sufficient to have the following functions (1) to (5) described with reference to FIG. 5. That is, the interface is provided with (1) a function of detecting the voltage value of the power supply voltage, (2) a function of providing predetermined notification information according to the detected voltage value, and (3) a function of controlling the supply of the power supply voltage according to the detected voltage value. In addition, the interface is provided with (4) a function of detecting notification information from a downstream device, and (5) a function of controlling the supply of the power supply voltage according to the presence or absence of notification information from the downstream device.

[others]
As can be seen from the above description of the embodiment, the functions of the voltage detection means, notification information providing means, and voltage limiting means in the claims are realized by the voltage detection unit 2022, notification information providing unit 2023, and voltage limiting unit 2033 of the IP telephone terminal 2 in the embodiment. Also, the functions of the stop instruction means, determination means, first and second stop means in the claims are realized by the supply stop instruction unit 2024, notification information determination unit 2031, and supply switching unit 2032 of the IP telephone terminal 2 in the embodiment.

The method of performing the processing shown in the flowchart of FIG. 8 corresponds to one embodiment of the power receiving method according to the present invention, which is performed by the power receiving device.

1...PoE power supply device (PoE hub device), 101...preceding device side port, 102...subceding device side port, 2, 2(1)-2(4)...PoE power receiving device (IP telephone terminal), 201...preceding device side port (power receiving port), 202...power receiving circuit, 2021...communication processing unit, 2022...voltage detection unit, 2023...notification information providing unit, 2024...supply stop instruction unit, 203...power supply circuit, 2031...notification information determination unit, 2032...supply cut replacement unit, 2033...voltage limiting unit, 204...back-end device side port (power supply port), 205...packet processing unit, 206...power supply unit, 207...handset, 208...codec, 209...sound emission unit, 210...operation input unit, 211...operation input I/F, 212...display controller, 213...display, 220...control unit, 3(1)-3(4)...PoE power receiving device, 4(1)-4(4)...PoE power receiving device

Claims (5)

a voltage detection means for detecting a voltage value of a power supply voltage received from a preceding device;
a notification information providing means for providing, when the voltage value detected by the voltage detection means is equal to or greater than a predetermined minimum value, notification information notifying the preceding device;
a voltage limiting means for lowering the power supply voltage received from the preceding device by a predetermined voltage value and supplying the power to the succeeding device;
a stop instruction means for outputting a stop instruction for instructing to stop the supply of power supply voltage to the downstream device when the voltage value detected by the voltage detection means is less than the predetermined minimum value;
a first stop means for stopping the supply of power supply voltage to the downstream device when the stop instruction is output from the stop instruction means;
a determination means for receiving notification information notified from the subsequent stage device, the notification information being information with the same content as the notification information notified to the previous stage device by the notification information providing means, and determining whether or not the notification information exists;
and a second stopping means for stopping the supply of power supply voltage to the downstream device when the determining means determines that the notification information has not been provided. The power supply terminal device according to claim 1,
The power receiving terminal device according to claim 1, wherein, when the voltage value detected by the voltage detection means is equal to or greater than a predetermined maximum value, the notification information providing means does not provide the notification information to the upstream device. The power supply terminal device according to claim 1 or 2,
The power supply voltage is received/supplied using the Alternative A method of PoE technology.
The power receiving terminal device according to claim 1, wherein the notification information providing means notifies the preceding device of the notification information through an unused line of a LAN cable. A power supply system including two or more power supply/reception devices connected in series,
Each of the power supply/reception devices is
a voltage detection means for detecting a voltage value of a power supply voltage received from a preceding device;
a notification information providing means for providing, when the voltage value detected by the voltage detection means is equal to or greater than a predetermined minimum value, notification information notifying the preceding device;
a voltage limiting means for lowering the power supply voltage received from the preceding device by a predetermined voltage value and supplying the power to the succeeding device;
a stop instruction means for outputting a stop instruction for instructing to stop the supply of power supply voltage to the downstream device when the voltage value detected by the voltage detection means is less than the predetermined minimum value;
a first stop means for stopping the supply of power supply voltage to the downstream device when the stop instruction is output from the stop instruction means;
a determination means for receiving notification information notified from the subsequent stage device, the notification information being information with the same content as the notification information notified to the previous stage device by the notification information providing means, and determining whether or not the notification information exists;
and a second stopping means for stopping the supply of power supply voltage to the downstream device when the determining means determines that the notification information has not been provided. The power supply/reception system according to claim 4,
The power supply terminal devices are configured to receive/supply power from/to each other using an Alternative A method of PoE technology,
A power receiving terminal device, characterized in that the notification information providing means of the power receiving terminal device in the rear stage and the determination means of the power receiving terminal device in the front stage are connected through an unused line of a LAN cable.

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