Abstract:
Disclosed is a reverse power supply method, comprising: a power supply adapter mixing a digital subscriber line (xDSL) signal with direct current (DC), and transmitting the mixed signal to an xDSL central office device via a subscriber line; the xDSL central office device separating the mixed signal to acquire the DC required by the xDSL central office device. Also disclosed are a power supply adapter and xDSL central office device.

Description:
TECHNICAL FIELD 
       [0001]    The disclosure relates to a related technology for reverse power supply in the field of communication, and in particular to a reverse power supply method, a power supply adapter, x Digital Subscriber Line (xDSL) central office equipment and a storage medium. 
       BACKGROUND 
       [0002]    A Power Over Ethernet (POE) system includes two parts, i.e. Power Supply Equipment (PSE) and a Powered device (PD). Under a normal condition, POE refers to power supply from central office equipment to terminal equipment, and reverse power supply refers to power supply from the terminal equipment to the central office equipment. At present, all systems adopting a reverse power supply technology are Ethernet-based, and for a place where no Ethernet cables are arranged or it is inconvenient to arrange Ethernet cables, it is impossible to directly adopt a POE technology. 
         [0003]    Very-high-data-rate Digital Subscriber Line (VDSL) is a VDSL access manner, a VDSL2 standard has been released at present, and VDSL2 may provide a 100 Mbps symmetric bandwidth within a short distance, may well support an ordinary data service, an interactive game, a Voice over Internet Phone (VOIP) service, an Internet Protocol Television (IPTV), a High-Definition TV (HDTV) and the like, and is particularly suitable for a commercial user and a high-end home user. VDSL central office equipment is usually mounted in a computer room and a corridor and outdoors, while VDSL terminal equipment is usually mounted in a house or office of a user, and both of them adopt independent power supply at present, which may bring inconvenience and also cause energy waste. 
       SUMMARY 
       [0004]    The disclosure is intended to provide a reverse power supply method, a power supply adapter, xDSL central office equipment and a storage medium. 
         [0005]    In order to achieve the purpose, the technical solutions of the disclosure are implemented as follows. 
         [0006]    The disclosure provides a reverse power supply method, which may include that:
       a power supply adapter mixes an xDSL signal and Direct Current (DC); and   the power supply adapter transmits a mixed signal to xDSL central office equipment through a subscriber line.       
 
         [0009]    In the solution, before the step that the power supply adapter mixes the xDSL signal and the DC, the method may further include that: the power supply adapter receives the xDSL signal sent by xDSL terminal equipment. 
         [0010]    In the solution, the step that the power supply adapter mixes the xDSL signal and the DC may include that: an Alternating Current-Direct Current (AC-DC) conversion circuit of the power supply adapter converts input AC into DC, and transfers the DC to a first xDSL separator of the power supply adapter, and the first xDSL separator mixes the DC and an input xDSL signal. 
         [0011]    In the solution, after the step that the first xDSL separator mixes the DC and the input xDSL signal, the method may further include that: a PSE control circuit of the power supply adapter detects whether there exists a PD, and determines whether to supply power to the PD according to a detection result. 
         [0012]    In the solution, the step that the power supply adapter mixes the xDSL signal and the DC may include that: the AC-DC conversion circuit of the power supply adapter converts input AC into DC, and transfers the DC to a first filter circuit of the power supply adapter, and the first filter circuit mixes the DC and an input xDSL signal. 
         [0013]    In the solution, after the step that the first filter circuit mixes the DC and the input xDSL signal, the method may further include that: the PSE control circuit of the power supply adapter detects whether there exists a PD, and determines whether to supply power to the PD according to a detection result. 
         [0014]    In the solution, after the step that the power supply adapter transmits the mixed signal to the xDSL central office equipment through the subscriber line, the method may further include that: the xDSL central office equipment separates the mixed signal to acquire DC required by the xDSL central office equipment. 
         [0015]    In the solution, the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment may include that: a second xDSL separator of the xDSL central office equipment separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to a DC-DC conversion circuit of the xDSL central office equipment, and the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment. 
         [0016]    In the solution, the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment may include that: a second filter circuit of the xDSL central office equipment separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit in the xDSL central office equipment, and the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment. 
         [0017]    The disclosure provides a reverse power supply method, which may include that:
       xDSL central office equipment separates a received mixed signal; and   the xDSL central office equipment acquires DC required by the xDSL central office equipment,   herein the mixed signal may be a signal mixed from an xDSL signal and DC and transmitted to the xDSL central office equipment through a subscriber line by a power supply adapter.       
 
         [0021]    In the solution, the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment may include that: a second xDSL separator of the xDSL central office equipment separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to a DC-DC conversion circuit of the xDSL central office equipment, and the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment. 
         [0022]    In the solution, the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment may include that: a second filter circuit of the xDSL central office equipment separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit in the xDSL central office equipment, and the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment. 
         [0023]    The disclosure provides a power supply adapter, which may include: an AC-DC conversion circuit and a first xDSL separator, in which:
       the AC-DC conversion circuit may be configured to convert input AC into DC, and transfer the DC to the first xDSL separator; and   the first xDSL separator may be configured to mix the DC and an input xDSL signal.       
 
         [0026]    In the solution, the power supply adapter may further include a PSE control circuit, configured to detect whether there exists a PD, and determine whether to supply power to the PD according to a detection result. 
         [0027]    The embodiments of the disclosure further provide a power supply adapter, which may include: an AC-DC conversion circuit and a first filter circuit, in which:
       the AC-DC conversion circuit may be configured to convert input AC into DC, and transfer the DC to the first filter circuit; and   the first filter circuit may be configured to mix the DC and an input xDSL signal.       
 
         [0030]    In the solution, the power supply adapter may further include a PSE control circuit, configured to detect whether there exists a PD, and determine whether to supply power to the PD according to a detection result. 
         [0031]    The disclosure provides xDSL central office equipment, which may include: a second xDSL separator and a DC-DC conversion circuit, in which:
       the second xDSL separator may be configured to separate a received mixed signal to acquire an xDSL signal and DC, and transfer the DC to the DC-DC conversion circuit; and   the DC-DC conversion circuit may be configured to convert the DC into DC required by the xDSL central office equipment,   herein the mixed signal may be a signal mixed from the xDSL signal and the DC and transmitted to the xDSL central office equipment through a subscriber line by a power supply adapter.       
 
         [0035]    In the solution, the xDSL central office equipment may further include a PD detection circuit and an xDSL signal processing circuit, in which:
       the PD detection circuit may be configured to provide detection about whether there exists a PD; and   the xDSL signal processing circuit may be configured to process xDSL service data according to the xDSL signal.       
 
         [0038]    The disclosure provides xDSL central office equipment, which may include: a second filter circuit and a DC-DC conversion circuit, in which:
       the second filter circuit may be configured to separate a received mixed signal to acquire an xDSL signal and DC, and transfer the DC to the DC-DC conversion circuit; and   the DC-DC conversion circuit may be configured to convert the DC into DC required by the xDSL central office equipment,   herein the mixed signal may be a signal mixed from the xDSL signal and the DC and transmitted to the xDSL central office equipment through a subscriber line by a power supply adapter.       
 
         [0042]    In the solution, the xDSL central office equipment may further include a resistance-capacitance detection circuit and an xDSL signal processing circuit, in which:
       the resistance-capacitance detection circuit may be configured to provide detection about whether there exists a PD; and   the xDSL signal processing circuit may be configured to process xDSL service data according to the xDSL signal.       
 
         [0045]    The disclosure provides a storage medium having stored therein computer programs configured to execute the abovementioned reverse power supply method. 
         [0046]    According to the reverse power supply method, power supply adapter and xDSL central office equipment provided by the embodiments of the disclosure, the power supply adapter mixes the xDSL signal and the DC, and transmits the mixed signal to the xDSL central office equipment through the subscriber line. In such a manner, it is possible to provide power from power supply equipment arranged in a house of a user to small-sized xDSL central office equipment arranged in a corridor or outdoors under the condition that xDSL access is adopted for a place where there is no Ethernet cable or it is inconvenient to arrange an Ethernet cable but there is a subscriber line, and power is supplied to the central office equipment arranged outdoors when the user requires communication, and may be cut off when the user does not require communication, so that convenience, power saving, working reliability, control flexibility, low power consumption and high rate are ensured. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0047]      FIG. 1  is a flowchart of a reverse power supply method according to embodiment 1 of the disclosure; 
           [0048]      FIG. 2  is a flowchart of a reverse power supply method according to embodiment 2 of the disclosure; 
           [0049]      FIG. 3  is a flowchart of a reverse power supply method according to embodiment 3 of the disclosure; 
           [0050]      FIG. 4  is a flowchart of a reverse power supply method according to embodiment 4 of the disclosure; 
           [0051]      FIG. 5  is a structure diagram of a power supply adapter according to embodiment 1 of the disclosure; 
           [0052]      FIG. 6  is a structure diagram of a power supply adapter according to embodiment 2 of the disclosure; 
           [0053]      FIG. 7  is a structure diagram of xDSL central office equipment according to embodiment 1 of the disclosure; 
           [0054]      FIG. 8  is a structure diagram of xDSL central office equipment according to embodiment 2 of the disclosure; 
           [0055]      FIG. 9  is a structure diagram of a reverse power supply system according to embodiment 1 of the disclosure; and 
           [0056]      FIG. 10  is a structure diagram of a reverse power supply system according to embodiment 2 of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0057]    The disclosure will be further described below with reference to the drawings and embodiments in detail. 
         [0058]    In an embodiment of the disclosure, a power supply adapter mixes an xDSL signal and DC, and transmits a mixed signal to xDSL central office equipment through a subscriber line; and the xDSL central office equipment separates the mixed signal to acquire DC required by the xDSL central office equipment. 
         [0059]    Here, the xDSL signal may be: an Asymmetric Digital Subscriber Line (ADSL) signal, a Rate Automatic adapt Digital Subscriber Line (RADSL) signal, a VDSL signal, a Symmetric Digital Subscriber Line (SDSL) signal, a High-speed Digital Subscriber Line (HDSL) signal, a new-generation bandwidth standard G.fast signal (which is also transmitted by adopting a twisted pair at a rate capable of maximally reaching 1 Gbit/s) and the like, and the xDSL signal is preferably a VDSL signal. 
         [0060]      FIG. 1  is a flowchart of a reverse power supply method according to embodiment 1 of the disclosure, and as shown in  FIG. 1 , a flow of the reverse power supply method of the embodiment includes the following steps. 
         [0061]    Step  101 : a power supply adapter mixes an xDSL signal and DC;
       here, the xDSL signal is configured to transmit service data; the xDSL signal may be: an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal;   before the step that the power supply adapter mixes the xDSL signal and the DC, the method further includes that: the power supply adapter receives the xDSL signal sent by xDSL terminal equipment through an xDSL link; and here, the xDSL terminal equipment may be a modem, an uplink interface supports xDSL/xDSL2, and a downlink interface supports Gigabit Ethernet/Fast Ethernet (GE/FE), a Wireless Local Area Network (WLAN), Plain Old Telephone Service (POTS), a Universal Serial Bus (USB) and the like.       
 
         [0064]    Furthermore, a structure of the power supply adapter may include: an AC-DC conversion circuit and a first xDSL separator;
       correspondingly, the step that the power supply adapter mixes the xDSL signal and the DC includes that: the AC-DC conversion circuit converts input AC into DC, and transfers the DC to the first xDSL separator, and the first xDSL separator mixes the DC and an input xDSL signal, which is equivalent to superimposition of the xDSL signal to the DC;   here, a mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports; and   the step that the first xDSL separator mixes the DC and the input xDSL signal includes that: a filter circuit in the first xDSL separator filters a noise signal and high-frequency signal in the DC, and directly mixes the DC in which the noise signal and high-frequency signal are filtered and the input xDSL signal.       
 
         [0068]    Furthermore, the power supply adapter further includes a PSE control circuit;
       correspondingly, after the step that the first xDSL separator mixes the DC and the input xDSL signal, the method further includes that: the PSE control circuit detects whether there exists a PD, and determines whether to supply power to the PD according to a detection result; when the PD is detected, that is, xDSL central office equipment is consistent with a POE standard, it is necessary to supply power to the xDSL central office equipment, and the mixed signal is controlled to be output to the xDSL central office equipment; when no PD is detected, that is, the xDSL central office equipment is inconsistent with the POE standard, the mixed signal is forbidden to be output; here, it is important to note that it may be considered that the DC has been mixed with the input xDSL signal after the power supply adapter is powered on and the PSE control circuit may detect whether there exists the PD after power gets stable, so that the DC has been mixed with the input xDSL signal when the PSE control circuit detects whether there exists the PD; and   the step that the PSE control circuit detects whether there exists the PD includes that: the PSE control circuit detects whether characteristic resistance of a PD detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met.       
 
         [0071]    Furthermore, another structure of the power supply adapter may include: an AC-DC conversion circuit and a first filter circuit;
       correspondingly, the step that the power supply adapter mixes the xDSL signal and the DC includes that: the AC-DC conversion circuit converts input AC into DC, and transfers the DC to the first filter circuit, and the first filter circuit mixes the DC and an input xDSL signal;   here, the mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports; and   the step that the first filter circuit mixes the DC and the input xDSL signal includes that: the first filter circuit filters a noise signal and high-frequency signal in the DC, and directly mixes the DC in which the noise signal and high-frequency signal are filtered and the input xDSL signal.       
 
         [0075]    Furthermore, the power supply adapter may further include a PSE control circuit, connected with the first filter circuit;
       correspondingly, after the step that the first filter circuit mixes the DC and the input xDSL signal, the method further includes that: the PSE control circuit detects whether there exists a PD, and determines whether to supply power to the PD according to a detection result; when the PD is detected, that is, the xDSL central office equipment is consistent with the POE standard, it is necessary to supply power to the xDSL central office equipment, and the mixed signal is controlled to be output to the xDSL central office equipment; when no PD is detected, that is, the xDSL central office equipment is inconsistent with the POE standard, the mixed signal is forbidden to be output; and   the step that the PSE control circuit detects whether there exists the PD includes that: the PSE control circuit detects whether characteristic resistance of a resistance-capacitance detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met.       
 
         [0078]    Furthermore, the AC-DC conversion circuit in the embodiment of the disclosure may convert a 220V AC voltage into a 40V˜60V DC voltage, the 220V AC voltage is converted into a 57V AC voltage in the embodiment, and the AC-DC conversion circuit includes: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the first xDSL separator includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor;   the blocking capacitor may be a 400V/0.022 uF capacitor;   the first filter circuit includes: a differential mode inductor and a filter capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor; and   the PSE control circuit mainly includes a PSE control chip and a Transient Voltage Suppressor (TVS) protector, herein the PSE control chip may adopt MAX5971.       
 
         [0083]    Step  102 : the power supply adapter transmits the mixed signal to the xDSL central office equipment through a subscriber line;
       here, the xDSL central office equipment may be a Digital Subscriber Line Access Multiplexer (DSLAM), accesses a backbone network in an uplink direction, and accesses xDSL terminal equipment in a downlink direction; the subscriber line is a copper-core twisted pair, and a line diameter may be 0.4 mm or 0.5 mm;   after the step that the power supply adapter transmits the mixed signal to the xDSL central office equipment through the subscriber line, the method further includes that: the xDSL central office equipment separates the mixed signal to acquire DC required by the xDSL central office equipment;   here, when the power supply adapter includes the AC-DC conversion circuit, the PSE control circuit and the first xDSL separator, the xDSL central office equipment correspondingly includes a second xDSL separator, the PD detection circuit and a DC-DC conversion circuit;   the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment includes that: the second xDSL separator separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit, and the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment; the input mixed signal is a mixed signal input through a signal input port of the xDSL central office equipment; and the signal input port of the xDSL central office equipment may be RJ11,   herein, the step that the second xDSL separator separates the input mixed signal includes that: the high-frequency xDSL signal and low-frequency DC in the input mixed signal are separated to acquire the xDSL signal and the DC by a filter circuit in the second xDSL separator; and here, a frequency of the DC is far lower than a frequency of the xDSL signal, so that the xDSL signal is a high-frequency signal relative to the DC.       
 
         [0089]    Furthermore, after the step that the xDSL signal and the DC are required, the method further includes that: the second xDSL separator transmits the xDSL signal to an xDSL signal processing circuit in the xDSL central office equipment, and the xDSL signal processing circuit processes xDSL service data. 
         [0090]    Furthermore, when the power supply adapter includes the AC-DC conversion circuit and the first filter circuit, the xDSL central office equipment correspondingly includes a second filter circuit and a DC-DC conversion circuit;
       the step that the xDSL central office equipment separates the mixed signal to acquire the DC required by the xDSL central office equipment includes that: the second filter circuit separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit; the DC-DC conversion circuit converts the DC into the DC required by the xDSL central office equipment; the input mixed signal is a mixed signal input through the signal input port of the xDSL central office equipment; and the signal input port of the xDSL central office equipment may be RJ11; and   here, the step that the second filter circuit separates the input mixed signal includes that: the high-frequency xDSL signal and low-frequency DC in the input mixed signal are separated to acquire the xDSL signal and the DC by the second filter circuit.       
 
         [0093]    Furthermore, after the step that the xDSL signal and the DC are acquired, the method further includes that: the second filter circuit transmits the xDSL signal to the xDSL signal processing circuit in the xDSL central office equipment, and the xDSL signal processing circuit processes xDSL service data. 
         [0094]    Furthermore, when the power supply adapter further includes the PSE detection circuit, the xDSL central office equipment correspondingly further includes the resistance-capacitance detection circuit. 
         [0095]    Furthermore, the second xDSL separator in the embodiment of the disclosure may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; 
         [0096]    the second filter circuit may include: a differential mode inductor and a filter capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor;
       the PD detection circuit includes a PD chip and a characteristic resistor, herein the PD chip may be MAX5969, and the characteristic resistor may be a 24.9 kΩ resistor;   the DC-DC conversion circuit mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into 12V/3.3V/1.8V/1.2V DC required by the xDSL central office equipment;   the resistance-capacitance detection circuit mainly includes a characteristic resistor and a characteristic capacitor, herein the characteristic resistor may be a 24.9 kΩ resistor, and the characteristic capacitor may be a 100V/0.1 uF capacitor; and   the xDSL signal processing circuit mainly includes an xDSL chipset.       
 
         [0101]      FIG. 2  is a flowchart of a reverse power supply method according to embodiment 2 of the disclosure, and in the embodiment, an xDSL signal is a VDSL signal, and xDSL central office equipment is VDSL central office equipment; and as shown in  FIG. 2 , a flow of the reverse power supply method of the embodiment includes the following steps. 
         [0102]    Step  201 : VDSL terminal equipment transmits a VDSL signal to a power supply adapter;
       here, the step that the VDSL terminal equipment transmits the VDSL signal to the power supply adapter is specifically implemented as follows: the VDSL terminal equipment transmits the VDSL signal to the power supply adapter through a VDSL link;   the VDSL signal is configured to transmit service data; and the VDSL terminal equipment may be a modem, an uplink interface supports VDSL/VDSL2, and a downlink interface supports GE/FE, a WLAN, POTS, a USB and the like.       
 
         [0105]    Step  202 : the power supply adapter mixes the VDSL signal and DC;
       here, the power supply adapter in the embodiment of the disclosure includes: an AC-DC conversion circuit, a PSE control circuit and a first VDSL separator;   the step specifically includes that: the AC-DC conversion circuit of the power supply adapter converts input AC into DC, and transfers the DC to the first VDSL separator, and the first VDSL separator mixes the DC and an input VDSL signal, which is equivalent to superimposition of the VDSL signal to the DC;   here, a mixed signal is a VDSL+DC signal, and is output through a signal output port of the power supply adapter; the input VDSL signal is a VDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports; and   the step that the first VDSL separator mixes the DC and the input VDSL signal includes that: a filter circuit in the first VDSL separator filters a noise signal and high-frequency signal in the DC, and directly mixes the DC in which the noise signal and high-frequency signal are filtered and the input VDSL signal.       
 
         [0110]    The AC-DC conversion circuit in the embodiment of the disclosure may convert a 220V AC voltage into a 40V˜60V DC voltage, the 220V AC voltage is converted into a 57V AC voltage in the embodiment, and the AC-DC conversion circuit includes: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the first VDSL separator includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; the first VDSL separator is required to allow at least a 350 mA current to pass through; and   the blocking capacitor is a 400V/0.022 uF capacitor.       
 
         [0113]    Step  203 : the power supply adapter detects resistance and capacitance of a PD detection circuit in the VDSL central office equipment to determine whether there exists a PD, Step  204  is executed if YES, and Step  206  is executed if NO;
       the step specifically includes that: the PSE control circuit in the power supply adapter detects whether characteristic resistance of the PD detection circuit in the VDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD, that is, the VDSL central office equipment is a PD consistent with a POE standard, when judgment conditions of the resistance and the capacitance are met, and when the judgment conditions of the resistance and the capacitance are not met, determines that the VDSL central office equipment is a PD inconsistent with the POE standard, and determines whether to supply power to the PD according to a detection result;   the PSE control circuit mainly includes a PSE control chip and a TVS protector, herein the PSE control chip adopts MAX5971; and   the PD detection circuit includes a PD chip and a characteristic resistor, herein the PD chip may be MAX5969, and the characteristic resistor may be a 24.9 kΩ resistor.       
 
         [0117]    Step  204 : the power supply adapter controls the mixed signal to be transmitted to the VDSL central office equipment through a subscriber line;
       here, the subscriber line is a copper-core twisted pair, a line diameter may be 0.4 mm or 0.5 mm, and a length of the subscriber line does not exceed 100 meters; and   the VDSL central office equipment may be a DSLAM, accesses a backbone network in an uplink direction, and accesses xDSL terminal equipment in a downlink direction.       
 
         [0120]    Step  205 : the VDSL central office equipment separates the mixed signal to acquire DC required by the VDSL central office equipment, and processes VDSL service data according to the VDSL signal;
       here, the VDSL central office equipment includes a second VDSL separator, the PD detection circuit and a DC-DC conversion circuit;   the step that the VDSL central office equipment separates the mixed signal to acquire the DC required by the VDSL central office equipment includes that: the second VDSL separator of the VDSL central office equipment separates the input mixed signal to acquire the VDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit, and the DC-DC conversion circuit converts the DC into the DC required by the VDSL central office equipment; here, the 57V DC is converted into the 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment; the input mixed signal is a mixed signal input through a signal input port of the VDSL central office equipment; the signal input port of the VDSL central office equipment may be RJ11,   herein the step that the second VDSL separator separates the input mixed signal includes that: the high-frequency VDSL signal and low-frequency DC in the input mixed signal are separated to acquire the VDSL signal and the DC by a filter circuit in the second VDSL separator; here, a frequency of the VDSL signal is usually between 500 KHz and 30 MHz, while a frequency of the DC is far lower than the frequency of the VDSL signal, so that the VDSL signal is a high-frequency signal relative to the DC;   the step that the VDSL central office equipment processes the VDSL service data according to the VDSL signal is specifically implemented as follows: a VDSL signal circuit in the VDSL central office equipment processes the VDSL service data according to the VDSL signal; here, the VDSL signal circuit mainly includes a VDSL chipset; and   the second VDSL separator includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; and the second VDSL separator is required to allow at least a 350 mA current to pass through.       
 
         [0126]    The DC-DC conversion circuit mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; and the DC-DC conversion circuit in the embodiment of the disclosure may convert the 40V˜60V DC into the 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment. 
         [0127]    Step  206 : the processing flow is ended. 
         [0128]      FIG. 3  is a flowchart of a reverse power supply method according to embodiment 3 of the disclosure, and in the embodiment, an xDSL signal is a VDSL signal, and xDSL central office equipment is VDSL central office equipment; and as shown in  FIG. 3 , a flow of the reverse power supply method of the embodiment includes the following steps. 
         [0129]    Step  301 : VDSL terminal equipment transmits a VDSL signal to a power supply adapter;
       here, the VDSL terminal equipment transmits the VDSL signal to the power supply adapter through a VDSL link;   the VDSL signal is configured to transmit service data; and the VDSL terminal equipment may be a modem, an uplink interface supports VDSL/VDSL2, and a downlink interface supports GE/FE, a WLAN, POTS, a USB and the like.       
 
         [0132]    Step  302 : the power supply adapter mixes the VDSL signal and DC, and transmits a mixed signal to VDSL central office equipment through a subscriber line;
       here, the VDSL central office equipment may be a DSLAM, accesses a backbone network in an uplink direction, and accesses xDSL terminal equipment in a downlink direction;   the power supply adapter in the embodiment of the disclosure includes: an AC-DC conversion circuit and a first filter circuit;   the step that the power supply adapter mixes the VDSL signal and the DC includes that: the AC-DC conversion circuit of the power supply adapter converts input AC into DC, and transfers the DC to the first filter circuit; the first filter circuit mixes the DC and an input VDSL signal; here, the mixed signal is a VDSL+DC signal, and is output through a signal output port of the power supply adapter; the input VDSL signal is a VDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports,   herein the step that the first filter circuit mixes the DC and the input VDSL signal includes that: a first filter circuit filters a noise signal and high-frequency signal in the DC, and mixes the DC in which the noise signal and high-frequency signal are filtered and the input VDSL signal;   the AC-DC conversion circuit in the embodiment of the disclosure may convert a 220V AC voltage into a 40V˜60V DC voltage; the AC-DC conversion circuit includes: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;   the first filter circuit includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor;   the blocking capacitor may be a 400V/0.022 uF capacitor;   the subscriber line is a copper-core twisted pair, and a line diameter may be 0.4 mm or 0.5 mm; and a length of the subscriber line may maximally reach 300 meters.       
 
         [0141]    Step  303 : the VDSL central office equipment separates the mixed signal to acquire DC required by the VDSL central office equipment, and processes VDSL service data according to the VDSL signal;
       here, the VDSL central office equipment includes a second filter circuit and a DC-DC conversion circuit;   the step that the VDSL central office equipment separates the mixed signal to acquire the DC required by the VDSL central office equipment includes that: the second filter circuit of the VDSL central office equipment separates the input mixed signal to acquire the VDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit; the DC-DC conversion circuit converts the DC into the DC required by the VDSL central office equipment; here, the input mixed signal is a mixed signal input through the signal input port of the VDSL central office equipment; 57V DC is converted into 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment in the embodiment of the disclosure; the signal input port of the VDSL central office equipment may be RJ11;   the second filter circuit includes: a differential mode inductor and a filter capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor;   the DC-DC conversion circuit mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; and the DC-DC conversion circuit in the embodiment of the disclosure may convert the 40V˜60V DC into the 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment.       
 
         [0146]    The step that the VDSL central office equipment processes the VDSL service data according to the VDSL signal is specifically implemented as follows: a VDSL signal circuit in the VDSL central office equipment processes the VDSL service data according to the VDSL signal; and here, the VDSL signal circuit mainly includes a VDSL chipset. 
         [0147]      FIG. 4  is a flowchart of a reverse power supply method according to embodiment  4  of the disclosure, and in the embodiment, an xDSL signal is a VDSL signal, and xDSL central office equipment is VDSL central office equipment; and as shown in  FIG. 4 , a flow of the reverse power supply method of the embodiment includes the following steps. 
         [0148]    Step  401 : VDSL terminal equipment transmits a VDSL signal to a power supply adapter;
       here, the VDSL terminal equipment transmits the VDSL signal to the power supply adapter through a VDSL link;   the VDSL signal is configured to transmit service data; and the VDSL terminal equipment may be a modem, an uplink interface supports VDSL/VDSL2, and a downlink interface supports GE/FE, a WLAN, POTS, a USB and the like.       
 
         [0151]    Step  402 : the power supply adapter mixes the VDSL signal and DC;
       here, the power supply adapter in the embodiment of the disclosure includes: an AC-DC conversion circuit, a PSE control circuit and a first filter circuit;   the step specifically includes that: the AC-DC conversion circuit of the power supply adapter converts input AC into DC, and transfers the DC to the first filter circuit, and the first filter circuit mixes the DC and an input VDSL signal, which is equivalent to superimposition of the VDSL signal to the DC; here, a mixed signal is a VDSL+DC signal, and is output through a signal output port of the power supply adapter; the input VDSL signal is a VDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports;   the AC-DC conversion circuit in the embodiment of the disclosure may convert a 220V AC voltage into a 40V˜60V DC voltage; the AC-DC conversion circuit includes: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;   the blocking capacitor is a 400V/0.022 uF capacitor; and   the first filter circuit includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor.       
 
         [0157]    Step  403 : the power supply adapter detects a resistance-capacitance detection circuit in the VDSL central office equipment to determine whether there exists a PD, Step  404  is executed if YES, and Step  406  is executed if NO;
       the step specifically includes that: the PSE control circuit in the power supply adapter detects whether characteristic resistance of the resistance-capacitance detection circuit in the VDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD, that is, the VDSL central office equipment is a PD consistent with a POE standard, when judgment conditions of the resistance and the capacitance are met, and when the judgment conditions of the resistance and the capacitance are not met, determines that the VDSL central office equipment is a PD inconsistent with the POE standard, and determines whether to supply power to the PD according to a detection result;   the PSE control circuit mainly includes a PSE control chip and a TVS protector, herein the PSE control chip adopts MAX5971; and   the resistance-capacitance detection circuit mainly includes a characteristic resistor and a characteristic capacitor, herein the characteristic resistor may be a 24.9 kΩ resistor, and the characteristic capacitor may be a 100V/0.1 uF capacitor.       
 
         [0161]    Step  404 : the power supply adapter controls the mixed signal to be transmitted to the VDSL central office equipment through a subscriber line;
       here, the subscriber line is a copper-core twisted pair, a line diameter may be 0.4 mm or 0.5 mm, and a length of the subscriber line may maximally reach 300 meters; and   the VDSL central office equipment may be a DSLAM, accesses a backbone network in an uplink direction, and accesses xDSL terminal equipment in a downlink direction.       
 
         [0164]    Step  405 : the VDSL central office equipment separates the mixed signal to acquire DC required by the VDSL central office equipment, and processes VDSL service data according to the VDSL signal;
       here, the VDSL central office equipment includes a second filter circuit, the resistance-capacitance detection circuit and a DC-DC conversion circuit;   the step that the VDSL central office equipment separates the mixed signal to acquire the DC required by the VDSL central office equipment includes that: the second filter circuit of the VDSL central office equipment separates the input mixed signal to acquire the VDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit, and the DC-DC conversion circuit converts the DC into the DC required by the VDSL central office equipment; here, 57V DC is converted into 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment; the input mixed signal is a mixed signal input through a signal input port of the VDSL central office equipment; the signal input port of the VDSL central office equipment may be RJ11,   herein the step that the second filter circuit separates the input mixed signal includes that: the high-frequency VDSL signal and low-frequency DC in the input mixed signal are separated to acquire the VDSL signal and the DC by the second filter circuit; here, a frequency of the VDSL signal is usually between 500 KHz and 30 MHz, while a frequency of the DC is far lower than the frequency of the VDSL signal, so that the VDSL signal is a high-frequency signal relative to the DC;   the step that the VDSL central office equipment processes the VDSL service data according to the VDSL signal is specifically implemented as follows: a VDSL signal circuit in the VDSL central office equipment processes the VDSL service data according to the VDSL signal; here, the VDSL signal circuit mainly includes a VDSL chipset; and   the second filter circuit includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor.       
 
         [0170]    The DC-DC conversion circuit mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; and the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into the 12V/3.3V/1.8V/1.2V DC required by the VDSL central office equipment. 
         [0171]    Step  406 : the processing flow is ended. 
         [0172]      FIG. 5  is a structure diagram of a power supply adapter according to embodiment 1 of the disclosure; and as shown in  FIG. 5 , a structure of the power supply adapter of the embodiment of the disclosure includes: an AC-DC conversion circuit  51  and a first xDSL separator  52 , in whch:
       the AC-DC conversion circuit  51  is configured to convert input AC into DC, and transfer the DC to the first xDSL separator  52 ;   the first xDSL separator  52  is configured to mix the DC and an input xDSL signal;   here, the operation that the first xDSL separator  52  mixes the DC and the input xDSL signal includes that: a filter circuit in the first xDSL separator  52  filters a noise signal and high-frequency signal in teh DC, and mixes the DC in which the noise signal and high-frequency signal are filtered and an input xDSL signal, herein a mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter may be RJ11 ports, herein the xDSL signal may be: an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal or the like, and the xDSL signal is preferably a VDSL signal.       
 
         [0176]    Furthermore, the power supply adapter further includes a PSE control circuit  53 , connected with the first xDSL separator  52  and configured to detect whether there exists a PD and determine whether to supply power to the PD according to a detection result;
       the operation that the PSE control circuit  53  detects whether there exists the PD includes that: the PSE control circuit detects whether resistance of a PD detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met.       
 
         [0178]    Furthermore, when the xDSL signal in the embodiment is a VDSL signal, the AC-DC conversion circuit  51  converts a 22V AC voltage into a 40V˜60V DC voltage, and the AC-DC conversion circuit may include: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the first xDSL separator  52  may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; the first xDSL separator is required to allow at least a 350 mA current to pass through;   the blocking capacitor may be a 400V/0.022 uF capacitor; and   the PSE control circuit  53  mainly includes a PSE control chip and a TVS protector, herein the PSE control chip may adopt MAX5971.       
 
         [0182]      FIG. 6  is a structure diagram of a power supply adapter according to embodiment 2 of the disclosure; and as shown in  FIG. 6 , a structure of the power supply adapter of the embodiment of the disclosure includes: an AC-DC conversion circuit  61  and a first filter circuit  62 , in which:
       the AC-DC conversion circuit  61  is configured to convert input AC into DC, and transfer the DC to the first filter circuit  62 ;   the first filter circuit  62  is configured to mix the DC and an input xDSL signal;   here, a mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter and passes through a blocking capacitor; the signal input port of the power supply adapter and the signal output port of the power supply adapter may both be RJ11 ports, herein the xDSL signal may be: an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal; and   the operation that the first filter circuit  62  mixes the DC and the input xDSL signal includes that: the first filter circuit  62  filters a noise signal and high-frequency signal in the DC, and mixes the DC in which the noise signal and high-frequency signal are filtered and the input xDSL signal.       
 
         [0187]    Furthermore, the power supply adapter may further include a PSE control circuit  63 , connected with the first filter circuit  62  and configured to detect whether there exists a PD and determine whether to supply power to the PD according to a detection result; when the PD is detected, that is, xDSL central office equipment is consistent with a POE standard, it is necessary to supply power to the xDSL central office equipment, and the mixed signal is controlled to be output to the xDSL central office equipment; when no PD is detected, that is, the xDSL central office equipment is inconsistent with the POE standard, the mixed signal is forbidden to be output;
       here, the operation that the PSE control circuit  63  detects whether there exists the PD includes that: the PSE control circuit  63  detects whether characteristic resistance of a resistance-capacitance detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met.       
 
         [0189]    Furthermore, when the xDSL signal in all of the embodiments of the disclosure is a VDSL signal, the AC-DC conversion circuit  61  converts a 22V AC voltage into a 40V˜60V DC voltage, the 22V AC voltage is converted into a 57V DC voltage in the embodiment, and the AC-DC conversion circuit includes: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the blocking capacitor may be a 400V/0.022 uF capacitor;   the first filter circuit  62  may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; and   the PSE control circuit  63  mainly includes a PSE control chip and a TVS protector, herein the PSE control chip may adopt MAX5971.       
 
         [0193]      FIG. 7  is a structure diagram of xDSL central office equipment according to embodiment 1 of the disclosure; and as shown in  FIG. 7 , a structure of the xDSL central office equipment of the embodiment of the disclosure includes: a second xDSL separator  71  and a DC-DC conversion circuit  72 , in which:
       the second xDSL separator  71  is configured to separate a mixed signal to acquire an xDSL signal and DC, and transfer the DC to the DC-DC conversion circuit;   the DC-DC conversion circuit  72  is configured to convert the DC into DC required by the xDSL central office equipment,   herein the mixed signal is a signal mixed from the xDSL signal and the DC and transmitted to the xDSL central office equipment through a subscriber line by a power supply adapter;   here, the mixed signal may be: an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal;   the operation that the second xDSL separator  71  separates the mixed signal to acquire the xDSL signal and the DC includes that: the high-frequency xDSL signal and low-frequency DC in the input mixed signal are separated to acquire the xDSL signal and the DC by a filter circuit in the second xDSL separator  71 ; and here, a frequency of the DC is far lower than a frequency of the xDSL signal, so that the xDSL signal is a high-frequency signal relative to the DC.       
 
         [0199]    Furthermore, the xDSL central office equipment further includes a PD detection circuit  73  and an xDSL signal processing circuit  74 , and the PD detection circuit is positioned between the second xDSL separator  71  and the DC-DC conversion circuit  72 , in which:
       the PD detection circuit  73  is configured to provide detection about whether there exists a PD; and   the xDSL signal processing circuit  74  is configured to process xDSL service data according to the xDSL signal.       
 
         [0202]    Furthermore, the second xDSL separator  71  in the embodiment of the disclosure may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; the second xDSL separator is required to allow at least a 350 mH current to pass through;
       the DC-DC conversion circuit  72  mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into 12V/3.3V/1.8V/1.2V DC required by the xDSL central office equipment;   the PD detection circuit  73  may include a PD chip and a characteristic resistor, herein the PD chip may be MAX5969, and the characteristic resistor may be a 24.9 kΩ resistor; and   the xDSL signal processing circuit  74  may include a VDSL chipset.       
 
         [0206]      FIG. 8  is a structure diagram of xDSL central office equipment according to embodiment 2 of the disclosure; and as shown in  FIG. 8 , a structure of the xDSL central office equipment of the embodiment of the disclosure includes: a second filter circuit  81  and a DC-DC conversion circuit  82 , in which:
       the second filter circuit  81  is configured to separate a mixed signal to acquire an xDSL signal and DC, and transfer the DC to the DC-DC conversion circuit  82 ;   the DC-DC conversion circuit  82  is configured to convert the DC into DC required by the xDSL central office equipment,   herein the mixed signal is a signal mixed from the xDSL signal and the DC and transmitted to the xDSL central office equipment through a subscriber line by a power supply adapter;       
 
         [0210]    here, the xDSL signal may be an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal;
       the operation that the second filter circuit  81  separates the mixed signal to acquire the xDSL signal and the DC includes that: the high-frequency xDSL signal and low-frequency DC in the input mixed signal are separated to acquire the xDSL signal and the DC by a filter circuit in the second filter circuit  81 ; and here, a frequency of the DC is far lower than a frequency of the xDSL signal, so that the xDSL signal is a high-frequency signal relative to the DC.       
 
         [0212]    Furthermore, the xDSL central office equipment further includes a resistance-capacitance detection circuit  83  and an xDSL signal processing circuit  84 , and the resistance-capacitance detection circuit  83  is positioned between the second filter circuit  81  and the DC-DC conversion circuit  82 , in which:
       the resistance-capacitance detection circuit  83  is configured to provide detection about whether there exists a PD; and   the xDSL signal processing circuit  84  is configured to process xDSL service data according to the xDSL signal.       
 
         [0215]    Furthermore, the second filter circuit  81  in the embodiment of the disclosure may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor;
       the DC-DC conversion circuit  82  mainly includes a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into 12V/3.3V/1.8V/1.2V DC required by the xDSL central office equipment;   the resistance-capacitance detection circuit  83  mainly includes a characteristic resistor and a characteristic capacitor, herein the characteristic resistor may be a 24.9 kΩ resistor, and the characteristic capacitor may be a 100V/0.1 uF capacitor; and   the xDSL signal processing circuit  84  may include a VDSL chipset.       
 
         [0219]      FIG. 9  is a structure diagram of a reverse power supply system according to embodiment 1 of the disclosure; and as shown in  FIG. 9 , a structure of the reverse power supply system of the embodiment of the disclosure includes: a power supply adapter  91 , a subscriber line  92  and xDSL central office equipment  93 , in which:
       the power supply adapter  91  is configured to mix an xDSL signal and DC, and transmit a mixed signal to the xDSL central office equipment  93  through the subscriber line  92 ;   the subscriber line  92  is configured to transmit the mixed signal to the xDSL central office equipment  93 ;   the xDSL central office equipment  93  is configured to separate the mixed signal to acquire DC required by the xDSL central office equipment; and   here, the xDSL signal may be an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal.       
 
         [0224]    Furthermore, the system further includes xDSL terminal equipment  94 , configured to transmit the xDSL signal to the power supply adapter  91  through an xDSL link; the xDSL signal is configured to transmit service data; the xDSL terminal equipment  94  may be a modem, an uplink interface supports VDSL/VDSL2, and a downlink interface supports GE/FE, a WLAN, POTS, a USB and the like; the xDSL central office equipment  93  may be a DSLAM, accesses a backbone network in an uplink direction, and accesses the xDSL terminal equipment in a downlink direction; and the subscriber line  92  is a copper-core twisted pair, a line diameter may be 0.4 mm or 0.5 mm, and a maximum length of the subscriber line  92  in the embodiment does not exceed 100 meters. 
         [0225]    Furthermore, the power supply adapter  91  includes: an AC-DC conversion circuit  911  and a first xDSL separator  912 , in which:
       the AC-DC conversion circuit  911  is configured to convert input AC into DC, and transfer the DC to the first xDSL separator  912 ;   the first xDSL separator  912  is configured to mix the DC and an input xDSL signal;   the operation that the power supply adapter  91  mixes the xDSL signal and the DC includes that: the AC-DC conversion circuit  911  converts the input AC into DC, and transfers the DC to the first xDSL separator  912 ; the first xDSL separator  912  mixes the DC and the input xDSL signal, which is equivalent to superimposition of the xDSL signal to the DC; here, the mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter  91 ; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter  91  and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter  91  may be RJ11 ports.       
 
         [0229]    Furthermore, the power supply adapter  91  further includes a PSE control circuit  913 , configured to detect whether there exists a PD, determine whether to supply power to the PD according to a detection result, control the mixed signal to be output to the PD when the PD is detected, and forbid the mixed signal to be output when no PD is detected. 
         [0230]    The operation that the PSE control circuit  913  detects whether there exists the PD includes that: the PSE control circuit  913  detects whether characteristic resistance of a PD detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met. 
         [0231]    Furthermore, the AC-DC conversion circuit  911  in the embodiment may convert a 220V AC voltage into a 40V˜60V DC voltage, and the AC-DC conversion circuit  911  may include: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the first xDSL separator  912  may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor;   the blocking capacitor may be a 400V/0.022 uF capacitor; and   the PSE control circuit  913  mainly includes a PSE control chip and a TVS protector, herein the PSE control chip may adopt MAX5971.       
 
         [0235]    Furthermore, the xDSL central office equipment  93  includes: a second xDSL separator  931  and a DC-DC conversion circuit  932 , in which:
       the second xDSL separator  931  is configured to separate the mixed signal to acquire the xDSL signal and the DC;   the DC-DC conversion circuit  932  is configured to convert the DC into DC required by the xDSL central office equipment  93 ;   the operation that the xDSL central office equipment  93  separates the mixed signal to acquire the DC required by the xDSL central office equipment includes that: the second xDSL separator  931  separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit  932 ; the DC-DC conversion circuit  932  converts the DC into the DC required by the xDSL central office equipment  93 ;   furthermore, the xDSL central office equipment  93  further includes the PD detection circuit  933  and an xDSL signal processing circuit  934 , in which:   the PD detection circuit  933  is configured to provide detection about whether there exists a PD; and   the xDSL signal processing circuit  934  is configured to process the xDSL service data according to the xDSL signal separated from the mixed signal by the second xDSL separator  931 .       
 
         [0242]    Furthermore, the second xDSL separator  931  in the embodiment of the disclosure may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH, 2 mH and 0.7 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; 
         [0243]    the DC-DC conversion circuit  932  may include a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into 12V/3.3V/1.8V/1.2V DC required by the xDSL central office equipment; and
       the PD detection circuit  933  includes a PD chip and a characteristic resistor, herein the PD chip may be MAX5969, and the characteristic resistor may be a 24.9 kΩ resistor.       
 
         [0245]    The xDSL signal processing circuit  934  may include a VDSL chipset. 
         [0246]      FIG. 10  is a structure diagram of a reverse power supply system according to embodiment 2 of the disclosure; and as shown in  FIG. 10 , a structure of the reverse power supply system of the embodiment of the disclosure includes: a power supply adapter  101 , a subscriber line  102  and xDSL central office equipment  103 , in which:
       the power supply adapter  101  is configured to mix an xDSL signal and DC, and transmit a mixed signal to the xDSL central office equipment  103  through the subscriber line  102 ;   the subscriber line  102  is configured to transmit the mixed signal to the xDSL central office equipment  103 ;   the xDSL central office equipment  103  is configured to separate the mixed signal to acquire DC required by the xDSL central office equipment; and   here, the xDSL signal may be an ADSL signal, an RADSL signal, a VDSL signal, an SDSL signal, an HDSL signal, a G.fast signal and the like, and the xDSL signal is preferably a VDSL signal.       
 
         [0251]    Furthermore, the system further includes xDSL terminal equipment  104 , configured to transmit the xDSL signal to the power supply adapter  101  through an xDSL link; the xDSL signal is configured to transmit service data; the xDSL terminal equipment  104  may be a modem, an uplink interface supports VDSL/VDSL2, and a downlink interface supports GE/FE, a WLAN, POTS, a USB and the like; the xDSL central office equipment  103  may be a DSLAM, accesses a backbone network in an uplink direction, and accesses the xDSL terminal equipment in a downlink direction; and the subscriber line  102  is a copper-core twisted pair, a line diameter may be 0.4 mm or 0.5 mm, and a length of the subscriber line  92  in the embodiment may maximally reach 300 meters. 
         [0252]    Furthermore, the power supply adapter  101  includes: an AC-DC conversion circuit  1011  and a first filter circuit  1012 , in which:
       the AC-DC conversion circuit  1011  is configured to convert input AC into DC, and transfer the DC to the first filter circuit  1012 ;   the first filter circuit  1012  is configured to mix the DC and an input xDSL signal;   the operation that the power supply adapter  101  mixes the xDSL signal and the DC includes that: the AC-DC conversion circuit  1011  converts the input AC into DC, and transfers the DC to the first filter circuit  1012 ; the first filter circuit  1012  mixes the DC and the input xDSL signal; here, the mixed signal is an xDSL+DC signal, and is output through a signal output port of the power supply adapter  101 ; the input xDSL signal is an xDSL signal which is input through a signal input port of the power supply adapter  101  and passes through a blocking capacitor; and the signal input port and signal output port of the power supply adapter  101  may be RJ11 ports.       
 
         [0256]    Furthermore, the power supply adapter  101  may further include a PSE control circuit  1013 , configured to detect whether there exists a PD, determine whether to supply power to the PD according to a detection result, control the mixed signal to be output to the PD when the PD is detected, and forbid the mixed signal to be output when no PD is detected. 
         [0257]    The operation that the PSE control circuit  1013  detects whether there exists the PD includes that: the PSE control circuit  1013  detects whether characteristic resistance of a PD detection circuit in the xDSL central office equipment is within a set resistance range, for example, whether it is between 23.75 kΩ and 26.25 kΩ, and whether capacitance is within a set capacitance range, for example, whether it is between 0.05 uF and 0.12 uF, determines that there exists the PD when judgment conditions of the resistance and the capacitance are met, and determines that there exists no PD when the judgment conditions of the resistance and the capacitance are not met. 
         [0258]    Herein, the AC-DC conversion circuit  1011  may convert a 220V AC voltage into a 40V˜60V DC voltage, and the AC-DC conversion circuit  1011  may include: a common mode inductor, a bridge rectifier, a transformer, an AC-DC control chip, a filter inductor, a filter capacitor and the like, herein the common mode inductor may be a 35 mH common mode inductor, the bridge rectifier may be MB6S, the transformer may be RD246-7, the AC-DC control chip may be THX201 and the filter inductor may be a 3 uH inductor;
       the first filter circuit  1012  includes: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF capacitor; and   the PSE control circuit  1013  mainly includes a PSE control chip and a TVS protector, herein the PSE control chip may adopt MAX5971.       
 
         [0261]    Furthermore, the xDSL central office equipment  103  includes: a second filter circuit  1031  and a DC-DC conversion circuit  1032 , in which:
       the second filter circuit  1031  is configured to separate the mixed signal to acquire the xDSL signal and the DC;   the DC-DC conversion circuit  1032  is configured to convert the DC into DC required by the xDSL central office equipment  93 ;   the operation that the xDSL central office equipment  103  separates the mixed signal to acquire the DC required by the xDSL central office equipment  103  includes that: the second filter circuit  1031  separates the input mixed signal to acquire the xDSL signal and the DC, and transfers the DC to the DC-DC conversion circuit  1032 ; the DC-DC conversion circuit  1032  converts the DC into the DC required by the xDSL central office equipment  103 .       
 
         [0265]    Furthermore, the xDSL central office equipment  103  further includes an xDSL signal processing circuit  1033 , configured to process the xDSL service data according to the xDSL signal separated from the mixed signal by the second xDSL separator  1031 . 
         [0266]    Furthermore, the xDSL central office equipment  103  may further include a resistance-capacitance detection circuit  1034 , positioned between the second filter circuit  1031  and the DC-DC conversion circuit  1032  and configured to provide detection about whether there exists a PD. 
         [0267]    Furthermore, the second filter circuit  1031  in the embodiment of the disclosure may include: a differential mode inductor and a capacitor, herein the differential mode inductor may be an 8 mH differential mode inductor, and the capacitor may be a 400V/0.047 uF filter capacitor;
       the DC-DC conversion circuit  1032  may include a DC-DC control chip and a transformer, herein the DC-DC control chip may adopt ISL6722, and the transformer may adopt PA2649; and the DC-DC conversion circuit in the embodiment of the disclosure may convert 40V˜60V DC into 12V/3.3V/1.8V/1.2V DC required by the xDSL central office equipment.       
 
         [0269]    The xDSL signal processing circuit  1033  may include a VDSL chipset; and
       the resistance-capacitance detection circuit  1034  mainly includes a characteristic resistor and a characteristic capacitor, herein the characteristic resistor may be a 24.9 kΩ resistor, and the characteristic capacitor may be a 100V/0.1 uF capacitor.       
 
         [0271]    The embodiment of the disclosure further records a storage medium having stored therein computer programs configured to execute the reverse power supply methods of each of the abovementioned embodiment. 
       INDUSTRIAL APPLICABILITY 
       [0272]    According to the embodiments of the disclosure, the mixed signal is transmitted to the xDSL central office equipment through the subscriber line. In such a manner, it is possible to provide power from power supply equipment arranged in a house of a user to small-sized xDSL central office equipment arranged in a corridor or outdoors under the condition that xDSL access is adopted for a place where there is no Ethernet cable or it is inconvenient to arrange an Ethernet cable but there is a subscriber line is solved, and power is supplied to the central office equipment arranged outdoors when the user requires communication, and may be cut off when the user does not require communication, so that convenience, power saving, working reliability, control flexibility, low power consumption and high rate are ensured. 
         [0273]    The above are only the preferred embodiments of the disclosure and not intended to limit the scope of protection of the disclosure.