Patent Publication Number: US-2023138316-A1

Title: Alternating current transmission circuit and socket

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application claims priority of 202122635624.9, filed on Oct. 29, 2021; 202122635077.4 , filed on Oct. 29, 2021; 202122719481.X, filed on November 06,2021; 202111593751.5, Dec. 23, 2021; 202123278188.0 Dec. 23, 2021; which is incorporated herein by reference in its entireties. 
     FIELD 
     The subject matter herein generally relates to electronic devices, and particularly relates to an alternating current transmission circuit and a socket. 
     BACKGROUND 
     An Alternating current (AC) transmission circuit is widely used in people’s daily life. In order to facilitate control, an AC transmission circuit with a switching device is developed. However, the switching device will have a problem of zero crossing shutdown, which will lead to sudden change of the current at an output terminal of the AC transmission circuit, and then produce a peak voltage in electrical equipment electrically connected with the output terminal of the AC transmission circuit. Therefore, it is easy to damage the switching device and even lead to potential safety hazards. 
     SUMMARY 
     In order to solve above-mentioned technology problems of sudden change of the current when the switching device of AC transmission circuit is turned off at zero crossing in existing technologies, the present disclosure provides an AC transmission circuit and a socket. 
     A solution to solve the technological problems of the present disclosure is to provide an alternating current transmission circuit. The alternating current transmission circuit includes a power supply circuit; and a switch circuit coupled with the power supply circuit. The switch circuit includes a main control circuit, a surge detection circuit, and a first switch device connected in series in the power supply circuit. The main control circuit is signal connected with the first switch device and configured to control on-off of the power supply circuit by controlling the first switch device. An input terminal of the surge detection circuit is connected with the power supply circuit, and an output terminal of the surge detection circuit is connected with the main control circuit. 
     Preferably, the surge detection circuit includes a varistor, the varistor is connected to the power supply circuit and the main control circuit. 
     Preferably, the switch circuit further includes an AC voltage detection circuit, the AC voltage detection circuit is connected to the power supply circuit and configured to detect voltages of the power supply circuit, an output terminal of the AC voltage detection circuit is connected with the main control circuit. 
     Preferably, input voltage of the power supply circuit is lower than a present voltage threshold, the main control circuit controls the first switch device to be turned on. 
     Preferably, the first switch device includes a TRIAC, the switch circuit further includes a switch isolation control circuit, the TRIAC is connected with the main control circuit through the switch isolation control circuit. 
     Preferably, the switch isolation control circuit includes an optocoupler. 
     Preferably, the first switch device is a TRIAC, the main control circuit is signal connected with the first switch device and configured to control on-off of the power supply circuit through the first switch device. The switch circuit further includes a temperature detection circuit connected with the main control circuit and configured to detect temperature of the alternating current transmission circuit. 
     Preferably, the temperature detection circuit configured to detect temperature of the TRIAC and feed back the detected temperature to the main control circuit, the main control circuit controls on-off of the TRIAC according to the detected temperature. 
     Preferably, the main control circuit stores preset an overheat threshold, when the detected temperature is beyond the overheat threshold, the main control circuit controls the TRIAC to be turned off. 
     Preferably, the switch circuit further includes a switch control circuit, the switch control circuit controls on-off of the TRIAC through the main control circuit, the switch control circuit is one or more of a touch switch, a voice switch, a remote control switch or a push switch. 
     Preferably, the switch circuit further includes a display circuit connected with the main control circuit. 
     Another solution to solve the technological problems of the present disclosure is to provide an alternating current transmission circuit, which includes a power supply circuit; and a switch circuit coupled with the power supply circuit. The switch circuit includes a main control circuit, a first switch device connected in series in the power supply circuit, and a snubber circuit connected in parallel with the first switch circuit. The main control circuit controls on-off of the power supply circuit by controlling on-off of the first switch device. The snubber circuit is configured to compensate current of the power supply circuit when the first switch device is turns off at zero-crossing. 
     Preferably, the first switch device is one or more of a TRIAC, a relay, and a MOS transistor. 
     Preferably, the snubber circuit includes a second switch device, one terminal of the second switch device is connected with the main control circuit, the other terminal of the second switch device is connected with the power supply circuit. 
     Preferably, the second switch device includes a relay and a MOS transistor, the main control circuit is connected with the relay through the MOS transistor and controls on-off of the relay by controlling the MOS transistor. 
     Preferably, the alternating current transition circuit further includes a voltage detection circuit configured to detect alternating current voltages and phases at an input terminal of the power supply circuit, an input terminal of the voltage detection circuit is connected with the power supply circuit, an output terminal of the voltage detection circuit is connected with the main control circuit. 
     Preferably, the voltage detection circuit includes a transformer and a full bridge MOS circuit, a primary coil of the transformer is connected with the power supply circuit, a secondary coil of the transformer is connected with the main control circuit through the full bridge MOS circuit. 
     Preferably, the switch circuit further includes a voltage-stabilizing circuit, an input terminal of the voltage-stabilizing circuit is connected with the power supply circuit, an output terminal of the voltage-stabilizing circuit is connected with the main control circuit and the snubber circuit. 
     Still another solution to solve the technological problems of the present disclosure is to provide a socket, which includes a socket body and a circuit structure arranged in the socket body. The circuit structure is the alternating current transmission circuit described above. 
     Comparing to the existing technologies, the alternating current transmission circuit provided by the present disclosure has following advantages: 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the switching circuit includes a main control circuit, a surge detection circuit and a first switching device connected in series to the power supply circuit. The main control circuit is signal connected with the first switching device and controls the on-off of the power supply circuit through the first switching device. Through the design of coupling the first switching device to the power supply circuit, the problem of easy ignition at the switch in the AC transmission circuit is effectively avoided, so as to improve safety and reliability of the AC transmission circuit. In addition, the design of controlling the on-off of the AC transmission circuit through the first switching device makes the service life of the switching circuit in the AC transmission circuit longer, so as to prolong the service life of the switching circuit of the AC transmission circuit. In addition, the switching circuit further includes the surge detection circuit, which can detect the high-voltage surge, lightning stroke and other abnormalities inputted by the power supply circuit. First, it can prevent internal components from being damaged by abnormal external voltage, so as to ensure the normal operation of the AC transmission circuit. Second, it can electrically isolate the power supply circuit and the switching circuit through the transformer, Thus, safety of the AC transmission circuit is improved. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the surge detection circuit includes a varistor. When the power supply circuit inputs high voltages, the varistor is conducted. The main control circuit determines whether there is a high voltage is inputted by detecting whether the varistor is conducted. Therefore, the main control circuit can accurately detect the voltage in the power supply circuit, and timely controls on-off of the first switch device so as to control on-off of the power supply circuit according to the voltage in the power supply circuit, thereby protecting the AC transmission circuit from voltage surges. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the AC voltage detection circuit can detect the voltage inputted by the power supply circuit. Furthermore, when the AC voltage detection circuit detects that the voltage inputted by the power supply circuit is within the present voltage threshold, the main control circuit controls on-off of the first switch device so as to ensure normal power supply of the power supply circuit. When the main control circuit determines that the AC voltage detection circuit detects that the voltage inputted by the power supply circuit is beyond the preset voltage threshold (that is, the voltage inputted by the power supply circuit is abnormal), the main control circuit controls the first switch device to be turned off, so as to control the power supply circuit to stop power supply. By the main control circuit and the AC voltage detection circuit, it further ensures safety and reliability of the AC transmission circuit. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the first switch device includes the TRIAC. The switch circuit further includes the switch isolation control circuit, and the TRIAC is connected to the main control circuit through the switch isolation control circuit. The switch isolation control circuit can electrically isolate the power supply circuit and the main control circuit, which can protect the main control circuit from being damaged due to voltage surges in the power supply circuit, so as to prolong service life of the AC transmission circuit. Furthermore, the design that the power supply circuit and the main control circuit are electrically isolated can prevent direct connection between the high voltage and the main control circuit, so as to further improve safety when users control on-off of the AC transmission circuit artificially. Furthermore, the design that the switch isolation control circuit includes the optocoupler further ensures reliable isolation control of the TRIAC by the main control circuit, so as to improve safety and reliability of the main control circuit. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the first switch device is the TRIAC. The main control circuit is signal connected with the TRIAC and configured to control on-off of the power supply circuit by the TRIAC. By the design that the TRIAC is coupled to the power supply circuit, it can effectively avoid ignition at the switch device in the AC transmission circuit. Therefore, it can improve safety and reliability of the AC transmission circuit. Additionally, by the design that the TRIAC controls on-off the AC transmission circuit, it can make service life of the switch circuit of the AC transmission device longer, thereby prolonging service life of the switch circuit of the AC transmission device. Furthermore, the AC transmission circuit further includes the temperature detection circuit. The temperature detection circuit can detect temperature of the AC transmission circuit and feeds back detected temperature to the main control circuit so as to control on-off of the power supply circuit. Furthermore, by presetting an overheat temperature threshold of the TRIAC in advance, when the main control circuit determines that the temperature of the TRIAC detected by the temperature detection circuit is beyond the overheat temperature threshold, it means that the temperature of the TRIAC is too high and the AC transmission circuit is abnormal at this time. Then, the main control circuit controls the power supply circuit to stop power supply. By arrangement of the main control circuit and the temperature detection circuit, it further ensures safety and reliability of the AC transmission circuit. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the switch control circuit facilitates convenient control of the on-off of the AC transmission circuit for users. The switch control circuit can be a touch switch, a voice switch, a remote-control switch or a push switch, which makes use of the AC transmission circuit more intelligent, thereby improving convenience of the AC transmission circuit. If the switch control circuit is a push switch, it may be cost saving. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the display circuit can visually show working information of the AC transmission circuit, which further improve convenience of the AC transmission circuit. 
     The AC transmission circuit provided by the embodiments of the present disclosure, includes the power supply circuit and the switch circuit coupled with the power supply circuit. The switch circuit further includes the main control circuit and the first switch device coupled to the power supply circuit. The main control circuit is signal connected with the first switch device and configured to control on-off of the power supply circuit through the first switch device. The design that the main control circuit controls on-off of the power supply circuit through the first switch device can allow users to control on-off of the power supply circuit according to actual need. Furthermore, the switch circuit further includes a snubber circuit connected in parallel with the first switch device. When the first switch device turns off at zero-crossing, the snubber circuit is configured to compensate for current of the power supply circuit. That is, when the first switch device turns off at zero-crossing, the snubber circuit is conducted to allow current pass therethrough so as to prevent sudden change of the current at the output terminal of the power supply circuit, which can avoid voltage surges in the electric appliance connected to the power supply circuit due to sudden change of the current at the output terminal of the power supply circuit. By the design that the first switch device is connected in parallel with the snubber circuit, when the first switch device turns off at zero-crossing, it can avoid voltage surges due to sudden change of the current in the AC transmission circuit so as to make the AC transmission circuit output complete wave diagram. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the first switch device is one or more of a TRIAC, a relay or a MOS transistor. The design setting the first switching device as a semiconductor switch that is not physically opened and closed, a problem prone to ignite along on/off of a physical switch can be effectively avoided, so as to improve safety and reliability of the AC transmission circuit. Therefore, service life of the switching circuit in the AC transmission circuit is longer, and the safety of the power supply circuit in the AC transmission circuit is improved. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the second switch circuit includes a second switch device. One end of the second switch device is connected with the main control circuit, and the other end of the second switch device is connected with the power supply circuit. The snubber circuit can be controlled to be conducted through the second switch device and then to compensate for the current of the power supply circuit. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the second switch device includes the relay and the MOS transistor. The main control circuit is connected with the relay through the MOS transistor and configured to control on-off of the relay by controlling the MOS transistor, which can improve response speed of the second switch device. When the first switch device is turned off at zero-crossing, the main control circuit controls the snubber circuit is conducted by the MOS transistor and the relay so as to control the snubber circuit to timely compensate the current of the power supply circuit. Furthermore, the relay in the snubber circuit can make the snubber circuit electrically isolate the power supply circuit and the main control circuit, so as to effectively protect the main control circuit from being damaged due to high voltages in the power supply circuit, Therefore, it can further improve safety and reliability of the AC transmission circuit. 
     The AC transmission circuit provided by the embodiments of the present disclosure further includes a voltage detection circuit, which detects the AC voltages and phases at the input terminal of the power supply circuit. The input terminal of the voltage detection circuit is connected with the power supply circuit, and the output end of the voltage detection circuit is connected with the main control circuit. The voltage detection circuit can more accurately detect the voltages and phases of the voltage of the AC power supply inputted by the power supply circuit, and can more timely and accurately detect the positive and negative peaks of the voltage of the power supply circuit, so as to reduce the difference between the detected voltage of the voltage detection circuit and the actual voltage. Furthermore, it can more accurately detect the AC voltage inputted by the AC transmission circuit, so that the main control circuit can control the switching circuit in time according to the input voltage of the power supply circuit. In addition, by more accurately detecting the voltage and phase of the AC inputted by the AC transmission current, the connection of the snubber circuit can be controlled in time to ensure that the snubber circuit can compensate the current in time. That is, the voltage detection circuit further avoids possibility of sudden change of current in the power supply circuit, and can further ensure the safety and reliability of AC transmission circuit. 
     In the AC transmission circuit provided by the embodiments of the present disclosure, the voltage detection circuit includes a transformer and a full bridge MOS circuit. The primary coil of the transformer is connected with the power supply circuit, and the secondary coil of the transformer is connected with the main control circuit through the full bridge MOS circuit. When the power supply circuit inputs high voltages, the voltage of the primary coil of the transformer increase. At this time, the voltages of the secondary coil of the transformer decrease. The transformer can electrically isolate the power supply circuit and the switch circuit. Furthermore, the secondary coil of the transformer is connected with the main control circuit through the full bridge MOS circuit. The full bridge MOS circuit can detect and switch the alternating current inputted by the power supply circuit, can sort out positive peaks and negative peaks of the alternating current, and can provides voltage signals for detection of voltages and phases. The voltage drop detected by the full bridge MOS circuit is smaller, which can further improve accuracy of voltage detection. In addition, the full bridge MOS circuit is used to detect the voltage, which improves accuracy of the voltage detection circuit, and further ensures the safety and reliability of the AC transmission circuit. 
     The AC transmission circuit provided by the embodiments of the present disclosure includes a voltage-stabilizing circuit. An input terminal of the voltage-stabilizing circuit is connected with the power supply circuit, and an output terminal of the voltage-stabilizing circuit is connected to the main control circuit and the snubber circuit. Through the design that the switch circuit includes the voltage-stabilizing circuit, the voltage-stabilizing circuit provides power to the main control circuit and the snubber circuit. 
     The socket provided by the embodiments of the present disclosure have same advantages with the AC transmission circuit, which is not repeated here. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view of a first circuit module of an alternating current (AC) transmission circuit according to a first embodiment of the present disclosure. 
         FIG.  2    is a schematic view of a second circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  3    is a schematic view showing principle of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  4    is a schematic view showing principle of a main control circuit of the AC transmission circuit according to the first embodiment. 
         FIG.  5    is a schematic view showing principle of a voltage-stabilizing circuit of the AC transmission circuit according to the first embodiment. 
         FIG.  6    is a waveform diagram showing output current of an AC transmission circuit in prior art. 
         FIG.  7    is a waveform diagram showing output current of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  8    is a schematic view of a third circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  9    is a schematic view of a fourth circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  10    is a schematic view of a fifth circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  11    is a schematic view of a sixth circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  12    is a schematic view of a seventh circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  13    is a schematic view showing principle of a voltage detection circuit of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  14    is a schematic view of a eighth circuit module of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  15    is a schematic view showing principle of a switch isolation control circuit of the AC transmission circuit according to the first embodiment of the present disclosure. 
         FIG.  16    is a schematic view of a first circuit module of an AC transmission circuit according to a second embodiment of the present disclosure. 
         FIG.  17    is a schematic view of a second circuit module of the AC transmission circuit according to the second embodiment of the present disclosure. 
         FIG.  18    is a schematic view showing principle of the AC transmission circuit according to the second embodiment of the present disclosure. 
         FIG.  19    is a schematic view showing principle of a main control circuit of the AC transmission circuit according to the second embodiment. 
         FIG.  20    is a schematic view showing principle of an AC voltage detection circuit of the AC transmission circuit according to the second embodiment of the present disclosure. 
         FIG.  21    is a schematic view showing principle of a surge detection circuit of the AC transmission circuit according to the second embodiment of the present disclosure. 
         FIG.  22    is a schematic view showing principle of a switch isolation control circuit of the AC transmission circuit according to the second embodiment of the present disclosure. 
         FIG.  23    is a schematic view of a first circuit module of an AC transmission circuit according to a third embodiment of the present disclosure. 
         FIG.  24    is a schematic view of a second circuit module of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  25    is a schematic view showing principle of a switch circuit of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  26    is a schematic view showing principle of a main control circuit of the AC transmission circuit according to the third embodiment. 
         FIG.  27    is a schematic view showing principle of a power supply circuit of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  28    is a schematic view showing principle of a switch isolation control circuit of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  29    is a schematic view showing principle of a switch control circuit of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  30    is a schematic view showing principle of a display circuit of the AC transmission circuit according to the third embodiment of the present disclosure. 
         FIG.  31    is a schematic view of a socket according to a fourth embodiment of the present disclosure. 
     
    
    
     In the drawings:
       1 . alternating current transmission circuit;  2 . alternating current transmission circuit;  3 . alternating current transmission circuit;  4 . socket;     11 . power supply circuit;  12 . switch circuit;  13 . voltage detection circuit;  20 . power supply circuit;  21 . switch circuit;  31 . power supply circuit;  32 . switch circuit;  41 . socket body;  42 . circuit structure;     121 . first switch device;  122 . main control circuit;  123 . voltage-stabilizing circuit;  124 . buffer circuit;  125 . switch isolation control circuit;  211 . main control circuit;  212 . first switch device;  213 . surge detection circuit;  214 . AC voltage detection circuit;  215 . warning circuit;  216 . temperature detection circuit;  217 . switch isolation control circuit;  218 . voltage-stabilizing circuit;  321 . switch control circuit;  322 . main control circuit;  323 . TRIAC;  324 . switch isolation control circuit;  325 . display circuit;  326 . rectifier circuit;  327 . temperature detection circuit;  328 . warning circuit;     1241 . second switch device;  1211 . TRIAC   

     DETAILED DESCRIPTION 
     In order for making objects, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below in combination with the attached drawings and exemplary embodiments. It should be understood that the exemplary embodiments described herein are only used to explain the present disclosure and are not used to limit the present disclosure. 
     Referring to  FIGS.  1  and  2   , a first embodiment of the present disclosure provides an AC transmission circuit  1 . The AC transmission circuit  1  includes a power supply circuit  11  and a switch circuit  12  coupled with the power supply circuit  11 . The switch circuit  12  includes a main control circuit  122 , a first switch device  121  connected in series to the power supply circuit  11 , and a snubber circuit  124  connected in parallel to the first switch device  121 . The main control circuit  122  The main control circuit  122  controls on-off of the power supply circuit  11  by controlling on-off of the first switching device  121 . When the first switching device  121  turns off at zero-crossing, the snubber circuit  124  compensates current of the power supply circuit  11 . 
     Additionally, Referring to  FIGS.  2  and  5   , the switch circuit  12  provided by the first embodiment of the present disclosure further includes a voltage-stabilizing circuit  123 . An input terminal of the voltage-stabilizing circuit  123  is connected to the power supply circuit  11 , an output terminal of the voltage-stabilizing circuit  123  are connected to both the main control circuit  122  and the snubber circuit  124 . 
     It should be understood, part of alternating current of the power supply circuit  11  provided by the first embodiment of the present disclosure is transmitted to the voltage-stabilizing circuit  123 , and the other part of alternating current of the power supply circuit  11  supplies power to electrical equipment electrically connected to an output terminal of the power supply circuit  11  through the output terminal. The voltage stabilizing circuit  123  supplies power to the main control circuit  122  and the snubber circuit  124 . 
     The voltage stabilizing circuit  123  of the present disclosure can be an input circuit connected to a primary input terminal, and the input circuit includes an AC input, a primary rectifier and a primary filter connected successively. Then, the primary input power supply is provided to the voltage stabilizing circuit  123 , a load to be charged is connected to a secondary output terminal, and the secondary output terminal provides charging power supply to the load. 
     Referring to  FIGS.  2  and  3   , the power supply circuit  11  provided by the first embodiment of the present disclosure includes an AC input terminal and an output terminal. It should be understood, the AC input terminal is configured to input AC, and the output terminal is configured to output AC or direct current (DC). The AC input terminal provides power supply to a whole socket. 
     Specifically, the power supply circuit  11  provided by the first embodiment of the present disclosure includes a varistor MOV 1  configured to remove surge voltage in an AC power supply, a capacitor C 2  configured to filter out clutter, and a resistor R 1 . The varistor MOV 1  is connected between the L line and the N line of the AC power supply. 
     It should be understood, the main control circuit  122  is signal connected to the first switch device  121  and controls on-off of the first power supply circuit  11  by the first switch device  121 , which allows the main control circuit  122  to control on-off of the power supply circuit  11  on demand. That is, when AC is inputted into the main control circuit  122 , the main control circuit  122  controls on-off of the first switch  121  so as to control on-off of the power supply circuit  11 . 
     Optionally, the first switching device  121  can be a combination of one or more of TRIACs, relays and MOS tubes. Specifically, in the first embodiment of the present disclosure, the first switching device  121  is a TRIAC. 
     It should be understood, by setting the first switching device  121  as a semiconductor switch that is not physically opened and closed, a problem prone to ignite at a switch in an AC transmission circuit is effectively avoided, so as to improve safety and reliability of the AC transmission circuit  1 , and further to prolong service life of the switching circuit  12  in the AC transmission circuit  1 . Thus, the safety of the power supply circuit  11  of the AC transmission circuit  1  is improved. 
     It should be understood, the main control circuit  122  of the present disclosure can be a single chip microcomputer, a microcontroller, a field programmable gate array, a general array logic or any combination thereof. 
     Specifically, referring to  FIGS.  2  and  4   , the main control circuit  122  of the present disclosure can be a microcontroller. The main control circuit  122  can be QFN20 having  21  pins. 
     Additionally, referring to  FIG.  6   , in the prior art, since the switch will turn off at zero-crossing, which may cause a sudden change of the output current of the power supply circuit when the switch turns off at zero-crossing, thus, a voltage surge may occur at the output terminal of the power supply circuit and/or the equipment connected to the output terminal of the power supply circuit. Therefore, turning off of the switch at zero-crossing may cause damage of the power supply circuit and/or the electronic equipment connected to the power supply circuit, and cause wave diagram of output current incomplete. 
     Additionally, referring to  FIG.  7   , the AC transmission circuit  1  can output complete wave by compensating for current of the power supply circuit  11 . 
     It should be understood, the snubber circuit  124  is configured to compensate for current of the power supply circuit  11 . That is, when the first switch turns off at zero-crossing, the main control circuit  122  controls the snubber circuit  124  to be switched on. 
     It should be understood, by arranging the snubber circuit  124  and the first switch device  121  in parallel, when the first switch device  121  turns off at zero-crossing, the main control circuit  122  controls the snubber circuit  124  to be switched on, so that current at the input terminal of the power supply circuit  11  can be transmitted to the output terminal through the snubber circuit  124 . Therefore, it can avoid sudden change of the output current of the power supply circuit  11  so as to solve problems that voltage surges occur at circuits or electronic equipment electrically connected to the power supply circuit  11 . Therefore, by compensating for current of the power supply circuit  11  when the first switch device  121  turns off at zero-crossing, it can avoid voltage surges due to sudden change of current. 
     Additionally, referring to  FIG.  8   , the snubber circuit  124  includes a second switch device  1241 . One terminal of the second switch device  1241  is connected to the main control circuit  122 , the other terminal of the second switch device  1241  is connected to the power supply circuit  11 . 
     It should be understood, the main control circuit  122  controls the second switch device  1241  to be switched on so as to controls the snubber circuit  124  to compensate for the current of the power supply circuit  11 . 
     Additionally, the second switch device  1241  includes a relay and/or a metal oxide semiconductor (MOS) tube. 
     Referring to  FIG.  9   , as an exemplary embodiment of the present disclosure, the second switch device  1241  provided by the first embodiment of the present disclosure includes a relay. The second switch device  1241  further includes a MOS transistor. The main control circuit  122  is connected to the relay through the MOS transistor and controls on-off of the relay by controlling the MOS transistor. 
     Specifically, referring to  FIGS.  3  and  9   , the snubber circuit  124  provided by the first embodiment of the present disclosure includes a relay K 1 , a MOS transistor Q 2 , a resistor R 5  and a resistor R 7 . The gate of MOS transistor Q 2  is connected with an eighteenth pin (that is, PA 7  pin) of the main control circuit  122  through the resistor R 5 ; The drain of the MOS transistor Q 2  is connected with one terminal of the relay K 1 , the other terminal of relay K 1  is connected with the power supply circuit  11 , the source of MOS transistor Q 2  is grounded, one terminal of the resistor R 7  is connected with the gate of MOS transistor Q 2 , and the other terminal of the resistor R 7  is connected with GND. 
     It should be understood, the design that the main control circuit  122  controls the on-off of the relay K 1  through the MOS transistor Q 2  can improve response speed of the second switching device  1241 . When the first switching device  121  is turned off at zero-crossing, turning on of the snubber circuit  124  is controlled through the MOS tube Q 2  and the relay K 1 , so that the snubber circuit  124  can timely compensate for the current of the power supply circuit  11 . In addition, the design of arranging the relay K 1  in the snubber circuit  124 , so that the snubber circuit  124  can also electrically isolate the power supply circuit  11  from the main control circuit  122 , so as to effectively avoid the problem that the main control circuit  122  is damaged by the high voltage in the power supply circuit  11 , and to further improve the safety and reliability of the AC power transmission circuit  1 . 
     It should be understood, when the first switch device  121  turns off at zero-crossing, the main control circuit  122  controls the MOS transistor Q 2  to be turned on so as to control the relay K 1  to be turned on to compensate for the current of the power supply circuit  11 . When the first switch device  121  turns on, the main control circuit  122  controls the MOS transistor Q 2  to be turned off, so as to the relay K 1  to be turned off to turn off compensation for the current of the power supply circuit  11 . 
     Referring to  FIG.  10   , as another exemplary embodiment, the second switch device  1241  provided by the first embodiment of the present disclosure includes a MOS transistor. The second switch device  1241  further includes an isolation control element, The MOS transistor and the power supply circuit  11  are connected and the MOS transistor is signal connected to the main control circuit  122  through the isolation control element. 
     It should be understood, through the design that the second switch device  1241  includes the MOS transistor can improve response speed of the second switch device  1241 . Since the MOS transistor itself cannot isolate elements, the MOS transistor is signal connected to the main control circuit  122  through the isolation control element. The design that the MOS transistor is connected to the main control circuit  122  through the isolation control element can electrically isolate the power supply circuit  11  and the main control circuit  122  so as to prevent the main control circuit  122  from being damaged due to direct connection between the power supply circuit  11  and the main control circuit  122 . 
     Additionally, referring to  FIGS.  11  and  12   , the AC transmission circuit  1  provided by the first embodiment of the present disclosure further includes a voltage detection circuit  13 . The voltage detection circuit  13  detects the AC voltage and phase at the input terminal of the power supply circuit  11 . An input terminal of the voltage detection circuit  13  is connected to the power supply circuit  11 , and an output terminal of the voltage detection circuit  13  is connected to the main control circuit  122 . 
     It should be understood, detection of the AC voltage and the phase of the AC power supply of the power supply circuit  11  by the voltage detection circuit  13  allows the main control circuit  122  to timely control the switch circuit  12  based on an input voltage of the power supply circuit  11 . In an exemplary embodiment, when the voltage detection circuit  13  detects that the input voltage of the power supply circuit  11  is too large, the main control circuit  122  can immediately control the switch circuit  12  to be switched off so as to prevent the AC transmission circuit  1  and/or the electronic equipment connected to the power supply circuit  11  from being damaged due to over large voltage. When the voltage detection circuit  13  detects that the input voltage of the power supply circuit  11  returns to normal, the main control circuit  122  can also timely control the switch circuit  12  to be switched on so as to make the power supply circuit  11  to return to normal work states. Furthermore, detection of the AC voltage and the phase of the AC power supply of the power supply circuit  11  by the voltage detection circuit  13  allows the main control circuit  122  to timely control the switch circuit  12  to be turned on based on magnitude and phase of the input voltage of the power supply circuit  11 , so as to ensure timely compensation for the current of the power supply circuit by the snubber circuit  124 . That is, the voltage detection circuit  13  can further prevent sudden change of the current of the power supply circuit  11  so as to further improve safety and reliability of the AC transmission circuit  1 . 
     If a diode is used to detect the voltage at the input terminal of the AC transmission circuit  1 , voltage drop of detected voltage is relatively large, which will lead to the detected voltage value being lower than actual voltage value and detected waveform being lower than expected waveform. Therefore, the present disclosure adopts a full bridge MOS circuit to detect the voltage and phase at the input terminal of the AC transmission circuit, which can make the voltage value detected by the voltage detection circuit  13  closer to the actual voltage value, so as to greatly improve accuracy of voltage detection. 
     It should be understood, the full bridge MOS circuit can more accurately detect voltage of the AC power supply of the power supply circuit  11 , timely and accurately detect positive and negative peaks of the voltage of the power supply circuit  11 , so as to reduce difference between the voltage value detected by the voltage detection circuit  13  and the actual voltage value, and then more accurately detect the voltage of the AC power supply of the AC transmission circuit  1 . In addition, the safety and reliability of the AC transmission circuit  1  can be further ensured by more accurately detecting the voltage and phase of the AC power supply of the AC transmission circuit  1 . 
     Additionally, referring to  FIGS.  12  and  13   , the voltage detection circuit  13  includes a transformer and a full bridge MOS circuit. The primary coil of the transformer is connected with the power supply circuit  11 , and the secondary coil of the transformer is connected with the main control circuit  122  through the full bridge MOS circuit. 
     Specifically, referring to  FIG.  13   , the voltage detection circuit  13  of the present disclosure at least includes a transformer T 1 , a MOS transistor Q 4 , a MOS transistor Q 5 , a MOS transistor Q 6  and a MOS transistor Q 7 . A first terminal and a second terminal of the primary coil of the transformer T 1  are connected between the L line and the N line of the AC power supply. A third terminal of the secondary coil of the transformer T 1  is connected with the drain of the MOS transistor Q 5 , the drain of the MOS transistor Q 4 , the gate of the MOS transistor Q 6  and the gate of the MOS transistor Q 7 . A fourth terminal of the secondary coil of the transformer T 1  is connected with the drain of the MOS transistor Q 6 , the drain of the MOS transistor Q 7 , the gate of the MOS transistor Q 4  and the gate of the MOS transistor Q 5 . The source of the MOS transistor Q 5  and the source of the MOS transistor Q 6  are connected to GND. The source of the MOS transistor Q 4  is connected to a second pin (that is, PA 3  pin) of the main control circuit  122 . The source of the MOS transistor Q 4  is connected to GND through a resistor R 15  and a resistor R 17 . The source of the MOS transistor Q 7  is connected to a third pin (that is, PA 2  pin) of the main control circuit  122 . The source of the MOS transistor Q 7  is connected to GND through a resistor R 14  and a resistor R 16 . 
     Specifically, when a voltage at the third terminal of the secondary coil of the transformer T 1  is a positive voltage, the voltage at the fourth terminal of the secondary coil of the transformer T 1  is a negative voltage. The voltage flows through the MOS transistor Q 4  to the main control circuit  122  and GND. At this time, the MOS transistor Q 4  is inputted with high level, the MOS transistor Q 4  is turned on, the MOS transistor Q 6  and the MOS transistor Q 7  form a closed loop, and they are not turned on. When the high level is inputted at the third terminal of the secondary coil of transformer T 1 , the MOS transistor Q 4  is always on. Because the MOS transistor Q 4  itself has a parasitic diode, its internal resistance is very small after the MOS transistor Q 4  is turned on, so the voltage drop of the detected voltage will be small, and then the detected voltage signal will be outputted to the main control circuit  122  through the source of the MOS transistor Q 4 . The source of MOS transistor Q 4  is connected to GND through the resistor R 15  and the resistor R 17 . 
     when a voltage at the third terminal of the secondary coil of the transformer T 1  is a negative voltage, the voltage at the fourth terminal of the secondary coil of the transformer T 1  is a positive voltage. The voltage flows through the MOS transistor Q 7  to the main control circuit  122  and GND. At this time, the MOS transistor Q 7  is turned on, the MOS transistor Q 5  and the MOS transistor Q 4  form a closed loop, and they are not turned on. When the high level is inputted at the fourth terminal of the secondary coil of transformer T 1 , the voltage at the drain of the MOS transistor Q 7  is a positive voltage, a voltage at the gate of the MOS transistor Q 7  is a negative voltage, there is a voltage difference between the drain and the gate of the MOS Q 7 , and the MOS Q 7  is turned on. Because the MOS transistor Q 7  itself has a parasitic diode, its internal resistance is very small after the MOS transistor Q 7  is turned on, so the voltage drop of the detected voltage will be small, and then the detected voltage signal will be outputted to the main control circuit  122  through the source of the MOS transistor Q 7 . The source of MOS transistor Q 7  is connected to GND through the resistor R 15  and the resistor R 17 . 
     It should be understood, when the power supply circuit  11  inputs high voltage, the voltage at the primary coil of the transformer T 1  is increased, at same time, the voltage at the secondary coil of the transformer T 1  is decreased. Furthermore, the secondary coil of the transformer T 1  is connected to the main control circuit  122  through the full bridge MOS circuit. The full bridge MOS circuit can detect and switch the AC power supply inputted by the power supply circuit  11 , sort out the positive and negative peaks of the AC power supply, and provide voltage signals for voltage and phase detection. The voltage drops at the input terminal of AC transmission circuit  1  detected by the full bridge MOS circuit is smaller, which can further improve accuracy of voltage detection. In addition, detecting the voltage through the full bridge MOS circuit improves accuracy of the voltage detection circuit  13 , which can further ensure safety and reliability of the AC transmission circuit  1 . 
     Additionally, referring to  FIG.  14   , the first switch device  121  includes a TRIAC  1211 . The switch circuit  12  further includes a switch isolation control circuit  125 . The TRIAC  1211  is connected to the main control circuit  122  through the switch isolation control circuit  125 . The switch isolation control circuit  125  of the present disclosure includes an optocoupler. 
     It should be understood, the switch isolation control circuit  125  can electrically isolate the power supply circuit  11  and the main control circuit  122  so as to prevent the main control circuit from being damaged due to surge voltage in the power supply circuit  11 , thus prolonging service life of the AC transmission circuit. Furthermore, the design that the power supply circuit  11  is electrically isolated from the main control circuit  122   can prevent direct connection between the high voltage AC and the main control circuit  122 , which can further improve safety when users control on-off of the AC transmission circuit  1  artificially. Furthermore, the switch isolation control circuit  125  includes the optocoupler, which can further ensure isolation control of the TRIAC  1211  by the main control circuit  122 , thereby improving safety of the main control circuit  122 . 
     Additionally, when the TRIAC  1211  is connected to high voltage, it is necessary to isolate the power supply circuit  11  and the main control circuit  122 . The optocoupler of the present disclosure has a good isolation function. By setting the optocoupler, the optocoupler is used to directly isolate low voltage and high voltage of the power supply circuit  11  from the main control circuit  122 . When the TRIAC  1211  is connected to the high voltage, the duration during which the TRIAC  1211  is turned on can be controlled through the optocoupler, so as to isolate the high voltage of the TRIAC  1211 . Thus, the main control circuit  122  is safer and more reliable. 
     Specifically, referring to  FIG.  15   , the switch isolation control circuit  125  at least includes an optocoupler U 1 , its type is MOC3041 and has a zero-crossing detection circuit inside. The optocoupler U 1  controls on-off of the TRIAC according to detection result of the zero-crossing circuit so as to achieve turning off of the TRIAC at zero-crossing. 
     As stated above, the power supply circuit  11  inputs AC power supply, part of which is transmitted to the voltage-stabilizing circuit  123  and the voltage-stabilizing circuit  123  provides power to the main control circuit  122  and the snubber circuit  124 . Another part of the AC power supply is transmitted to electronic equipment connected with the output terminal through the output terminal. The main control circuit  122  controls on-off of the power supply circuit  11  by controlling on-off of the first switch device  121 . The snubber circuit  124  is connected in parallel with the first switch device  121 . When the first switch device  121  is turned off at zero-crossing, the main control circuit  122  controls the snubber circuit  124  to compensate for the current of the power supply circuit  11 . The voltage detection circuit  13  can detect voltage values and phases of the voltage at the input terminal of the power supply circuit  11 . The voltage detection circuit  13  includes a transformer and a full bridge MOS circuit. The transformer can electrically isolate the power supply circuit  11  and the switch circuit  12 . The voltage drop at the input terminal of the AC transmission circuit  1  detected by the full bridge MOS circuit is smaller. The switch isolation control circuit  125  is configured to electrically isolate the power supply circuit  11  and the main control circuit  122 , which can prevent direct connection between high voltage AC and the main control circuit when the AC transmission circuit  1  inputs high voltage. The switch isolation control circuit  125  further includes an optocoupler configured to provide further reliable isolation of the TRIAC  1211 . 
     Referring to  FIGS.  16  and  17   , a second embodiment of the present disclosure provides an AC transmission circuit  2 . The AC transmission circuit  2  includes a power supply circuit  20  and a switch circuit  21  coupled to the power supply circuit  20 . The switch circuit  21  includes a main control circuit  211 , surge detection circuit  213 , and a first switch device  212  connected in series to the power supply circuit  20 . The main control circuit  211  is signal connected to the first switch device  212  and controls on-off of the power supply circuit  20  by controlling the first switch device  212 . An input terminal of the surge detection circuit  213  is connected to the power supply circuit  20 , and an output terminal of the surge detection circuit  213  is connected to the main control circuit  211 . 
     It should be understood, the switch circuit  21  provided by the second embodiment of the present disclosure includes a main control circuit  211  and the first switch device  212  connected in series to the power supply circuit  20 . The main control circuit  211  is signal connected to the first switch device  212  and controls on-off of the power supply circuit  20  by controlling the first switch device  212 . By the design that the first switch device  20  is coupled to the power supply circuit  20 , it can effectively avoid ignition at the switch device in the AC transmission circuit  2 . Therefore, it can improve safety and reliability of the AC transmission circuit  2 . 
     Additionally, by the design that the first switch device  212  controls on-off the AC transmission circuit  2 , it can make service life of the switch circuit  21  of the AC transmission device  2  more longer, thereby prolonging service life of the switch circuit  21  of the AC transmission device  2 . 
     Additionally, the switch circuit  21  provided by the second embodiment of the present disclosure includes a voltage-stabilizing circuit  218 . The voltage-stabilizing circuit  218  is connected to the main control circuit  211  and provides power to the main control circuit  211 . 
     It should be understood, the voltage-stabilizing circuit  218  in the second embodiment of the present disclosure can be an input circuit connected to a primary input terminal. The input circuit is an input circuit of a conventional Primary-Side-Regulation (PSR) system, and includes an AC input, a primary rectifier and a primary filter connected successively. Then, the primary input power supply is provided to the voltage stabilizing circuit  218 , a load to be charged is connected to a secondary output terminal, and the secondary output terminal provides charging power supply to the load. 
     It should be noted, part of the power supply inputted by the power supply circuit  20  of the second embodiment of the present disclosure is transmitted to the voltage-stabilizing circuit  218 , another part of the power supply is configured to provide power to a socket. The voltage-stabilizing circuit  218  provides power to the main control circuit  211 , the surge detection circuit  213 , an AC voltage detection circuit  214 , a warning circuit  215 , a temperature detection circuit  216 , and a switch isolation control circuit  217 . 
     Referring to  FIGS.  17  and  18   , the power supply circuit  20  of the second embodiment of the present disclosure includes an AC input and an AC output. It should be understood, the AC input is configured to input AC power supply, and the AC output is configured to output AC power supply and provides power to the socket. 
     The switch circuit  21  of the second embodiment of the present disclosure includes the surge detection circuit  213 , a resistor R 1 , a capacitor C 2 , the first switch device  212  and the main control circuit  211 . The resistor R 1  and the capacitor C 2  are connected in series to form a RC (resistance capacitance) absorber, which can protect the first switching device  212  from breakdown. The surge detection circuit  213  is connected to the power supply circuit  20 . The first switch device  212  is coupled to the power supply circuit  20 . The first switch device  212  and the surge detection circuit  213  are connected to the main control circuit  211 . 
     It should be understood, when the AC power supply is inputted, the main control circuit  211  controls on-off of the first switch device  212  so as to control on-off of the power supply circuit  20 . 
     It should be noted, the first switch device  212  of the second embodiment can be a TRIAC, a relay and/or a MOS transistor. The design setting the first switching device  121  as a semiconductor switch that is not physically opened and closed, a problem prone to ignite along on/off of a physical switch can be effectively avoided, so as to improve safety and reliability of the AC transmission circuit  2 . If the first switch device  212  is a TRIAC, the problem that it is prone to ignite at a switch in an AC transmission circuit can be efficiently solved, so as to improve safety and reliability of the AC transmission circuit  2 . Furthermore, the design that the on-off of the AC transmission circuit  2  is controlled by the TRIAC can make service life of the switching circuit  21  in the AC transmission circuit  2  longer, thus, the service life of the switching circuit  21  in the AC transmission circuit  2  is improved. 
     It should be understood, the switch circuit  21  further includes a surge detection circuit  213 , which can detect abnormal conditions including voltage surges and breakdown, and protect internal components from damage when the voltage goes abnormal so as to ensure normal working of the AC transmission circuit  2 . 
     It should be understood, the main control circuit  211  of the second embodiment can be a single chip microcomputer, a microcontroller, a field programmable gate array, a general array logic or any combination thereof. 
     Specifically, referring to  FIG.  19   , the main control circuit  211  of the second embodiment of the present disclosure can be a QFN20 chip U 4 . It is an 8-bit microcontroller (MCU) based on a low-power platform, which makes it very suitable for any battery operation application. It also has 8 KB flash memory, 0.5 KB ram, 16 digital I / O pins, 4 x 16 bit timer, 3 PCA channels and other peripheral communication devices. 
     The main control chip U 4  is configured to control on-off of the first switch device  212 . The main control chip U 4  is further configured to receive detected signals from the surge detection circuit  213  and the AC voltage detection circuit  214 . The main control chip U 4  is further configured to receive detected temperature information from the temperature detection circuit  216 . 
     Additionally, referring to  FIGS.  18  and  21   , the surge detection circuit  213  of the second embodiment of the present disclosure at least includes a varistor MOV 1  and a transformer T 1 . The varistor MOV 1  is connected to the power supply circuit  20 . The primary coil of the transformer T 1  is connected to the power supply circuit  20  through the varistor MOV 1 . The secondary coil of the transformer T 1  is connected to the main control circuit  211 . That is, the varistor MOV 1  is connected to the main control circuit  211  through the transformer T 1 . Through such arrangements, the transformer T 1  can electrically isolate the power supply circuit  20  and the switch circuit  21  so as to improve safety of the AC transmission circuit  2 . Furthermore, when the power supply circuit  20  inputs high voltage, the varistor MOV 1  is conducted. The main control circuit  211  detects whether there is high voltage is inputted by detecting whether the varistor is conducted. Therefore, the main control circuit  211  can accurately detects inputted voltage, and timely controls on-off of the first switch device  212  according to the inputted voltage to control on-off of the power supply circuit  20 , which can protect the AC transmission circuit from voltage surges. 
     Specifically, the surge detection circuit  213  of the second embodiment of the present disclosure includes a varistor MOV 1 , a transformer T 1 , an AC-AC transformer D 4 , a resistor R 16 , a resistor R 17 , a resistor R 18 , a resistor R 19 , and a triode Q 3 . One terminal of the varistor MOV 1  is connected to the power supply circuit  20 , the other terminal of the varistor MOV 1  is connected with the primary coil of the transformer T 1 . The secondary coil of the transformer T 1  is connected with one terminal of the AC-AC transformer D 4 . The other terminal of the AC-AC transformer D 4  is connected with one terminal of the resistor R 18 . The one terminal of the resistor R 18  is connected with one terminal of the resistor R 17 , the other terminal of the resistor R 18  is connected to GND. The other terminal of the resistor R 17  is connected to one terminal of the resistor R 19 , the other terminal of the resistor R 19  is connected to GND. The emitter of the triode Q 3  is connected to GND, the base of the triode Q 3  is connected with the resistor R 17  and the resistor R 19 . The collector of the triode Q 3  is connected with PA 4  pin of the main control circuit  211 . 
     It should be understood, when the power supply circuit  20  inputs low voltage, the varistor MOV 1  remains open and is not conducted. At this time, the first switch device  212  is turned on. When the power supply circuit  20  inputs high voltage, the varistor MOV 1  is conducted. At this time, inputted voltage and current increase. Before breakdown of the first switching device  212 , the current of the secondary coil of the transformer T 1  changes accordingly under the function of the transformer T 1 , which makes the potential at the base of the triode Q 3  changes from low level to high level, and the triode Q 3  changes from off state to on state. The main control circuit  211  detects on-off state of the triode Q 3  and controls on-off of the first switching device  212  according to the on-off state of the three-stage transistor Q 3 , so as to protect the electrical equipment connected with the power supply circuit  20  or the components in the AC transmission circuit  21  from damage due to the high voltage outputted through the power supply circuit  20  the high voltage of the input voltage from damaging the through the power supply circuit  20 . Through such arrangements, safety of the AC transmission circuit  2  is improved. It should be understood that the low voltage is relative to the high voltage, where the low voltage refers to the voltage less than the on threshold of the varistor MOV 1 , and the high voltage refers to the voltage greater than or equal to the on threshold of the varistor MOV 1 . Optionally, in the embodiment of the present disclosure, the on threshold of the varistor MOV 1  is 1000V When the input voltage is greater than 1000V, the varistor MOV 1  is on. 
     Additionally, referring to  FIGS.  18  and  20   , the switch circuit  21  of the second embodiment of the present disclosure further includes an AC voltage detection circuit  214 . The AC voltage detection circuit  214  is connected to the power supply circuit  20  to detect the voltage of the power supply circuit  20 . An output terminal of the AC voltage detection circuit  214  is connected to the main control circuit  211 . 
     Specifically, the AC voltage detection circuit  214  includes a resistor R 27 , a resistor R 28 , a transformer T 2 , a diode ZD 3 , and a capacitor C 10 . The primary coil of the transformer T 2  is connected with the input terminal of the power supply circuit  20 . The resistor R 27  and the resistor R 28  are connected in series and are connected with the primary coil of the transformer T 2 . The secondary coil of the transformer T 2  is connected with the diode ZD 3 . The positive pole of the diode ZD 3  is connected with the capacitor C 10 . 
     It should be understood, the AC voltage detection circuit  214  is configured to detect the voltage inputted by the power supply circuit  20 . When the AC voltage detection circuit detects that the voltage inputted by the power supply circuit  20  is normal, the main control circuit  211  controls the first switch device  212  to be turned on so as to ensure normal power supply of the power supply circuit  20 . When the AC voltage detection circuit detects that the voltage inputted by the power supply circuit  20  is abnormal, the main control circuit  211  controls the first switch device  212  to be turned off so as to control the power supply circuit  20  to stop providing power. Through such arrangements, it further ensures safety and reliability of the AC transmission circuit  2 . 
     Additionally, the main control circuit  211  stores a preset threshold voltage value. When the voltage inputted by the power supply circuit  20  is within the preset threshold voltage value, the main control circuit  211  controls the first switch device  212  to be turned on. In the embodiment, the present threshold voltage value is 90 V~250 V 
     It should be noted, when the power adapter is American Standard, the voltage threshold is 100 V ~ 120 V When the power adapter is GB, Chinese or European standard, the voltage threshold is 200 V ~ 240 V 
     It should be understood, when the AC input is within the preset threshold voltage value, the first switch device  212  is on. When the AC input beyond the preset threshold voltage value, the main control circuit  211  controls the first switch device  212  to be turned off. At this time, the power supply circuit  20  stop providing power. By design that the AC voltage detection circuit  214  detects whether the AC input is in the normal operating range and the main control circuit  211  controls on-off of the first switch device  212 , it can prevent users from artificially controlling the on-off of the AC transmission circuit  2 , so as to further improve safety of AC transmission circuit  2 . 
     Additionally, referring to  FIGS.  17  and  22   , the switch circuit  21  of the second embodiment of the present disclosure further includes a switch isolation control circuit  217 . The first switch device  212  is connected to the main control circuit  211  through the switch isolation control circuit  217 . In the embodiment, the switch isolation control circuit  217  can include an optocoupler. 
     It should be understood, by arranging the switch isolation control circuit  217 , the main control circuit  211  controls the first switch device  212  through the switch isolation control circuit  217 , which can electrically isolate the power supply circuit  20  and the main control circuit  211  so as to protect the main control circuit  211  from being damaged by the voltage surge in the power supply circuit  20 . Thus, it can prolong service life of the AC transmission circuit  2 . Furthermore, the design that the power supply circuit  20  is electrically isolated from the main control circuit  211  can prevent direct connection between the high voltage AC and the main control circuit  211 , which can further improve safety when users control on-off of the AC transmission circuit  1  artificially. 
     Additionally, when the TRIAC  1211  is connected to high voltages, it is necessary to isolate the power supply circuit  20  and the main control circuit  211 . The optocoupler of the present disclosure has a good isolation function. By setting the optocoupler, the optocoupler is used to directly isolate low voltage and high voltage of the power supply circuit  20  from the main control circuit  211 . When the first switch device  212  is connected to the high voltage, the duration during which the first switch device  212  is turned on can be controlled through the optocoupler, so as to isolate the high voltage of the first switch device  212 . Thus, the main control circuit  211  is safer and more reliable. 
     Specifically, the switch isolation control circuit  217  includes an optocoupler U 1 , a resistor R 1 , a resistor R 2 , a resistor R 3 , a resistor R 4 , a resistor R 5 , a resistor R 6 , a resistor R 7 , and a triode Q 2 . 
     The optocoupler U 1  has six pins. A positive pole (that is pin  1 ) of the optocoupler U 1  is connected to a 5 V voltage through the resistor R 4 . The collector of the triode Q 2  is coupled with a negative pole (that is pin  2 ) of a light emitter of the optocoupler U 1 . The emitter of the triode Q 2  is connected to GND. The base of the triode Q 2  is coupled to with the pin PA 7  of the main control circuit U 4  through the resistor R 7 . The resistor R 7  is connected series with one terminal of the resistor R 6 , and the other terminal of the resistor R 6  is connected to GND. 
     One terminal (pin  6 ) of a light receiver of the optocoupler U 1  is coupled with the AC input through the resistor R 3  and the resistor R 4 , the other terminal (pin  4 ) of the light receiver of the optocoupler U 1  is connected with the TRIAC Q 1  and the resistor R 5 . The resistor R 5  and the TRIAC Q 1  are connected in series. Pin  5  and pin  3  of the optocoupler U 1  remains suspended. 
     It should be understood, a work process of the switch isolation control circuit  217  is as follow: the optocoupler U 1  is MOC3041 and has a zero-crossing detection circuit. When corresponding current is inputted into the optocoupler U 1 , the voltage value between pin  6  and pin  4  of the optocoupler U 1  slightly crosses zero, and the TRIAC inside the optocoupler U 1  is turned on. When the main control chip U 4  collects electrical signals that AC voltage crosses zero, it triggers the main control chip U 4  to generate an event interrupt, which triggers the first switch device  212 . Therefore, the first switch device  212  is turned on. When 0 mA current is inputted into the optocoupler U 1 , the TRIAC inside the optocoupler U 1  is turned off. After the main control chip U 4   receives signals that the TRIAC inside the optocoupler U 1  is turned off, the main control chip U 4  transmits off signal to the first switch device  212 , so as to control the first switch device  212  to be turned off, and then the power supply circuit  20  stops power supply. 
     Furthermore, the switch circuit  21  of the second embodiment of the present disclosure further includes a temperature detection circuit  216  configured to detect temperature of the AC transmission circuit  2 . The temperature detection circuit  216  is connected to the main control circuit  211 . 
     It should be understood, the temperature detection circuit  216  at least includes a thermistor. 
     It should be understood, the temperature detection circuit  216  detects temperature of the first switch device  212  and feedbacks detected temperature to the main control circuit  211 . The main control circuit  211  controls on-off of the first switch device  212  according to the detected temperature. 
     It should be understood, the temperature detection circuit  216  is configured to detect temperature of the first switch device  212  and transmits detected temperature to the main control circuit  211 . 
     In specific application, by presetting an overheat temperature threshold of the first switch device  212  in advance, when the main control circuit  211  determines that the temperature of the first switch device  212  detected by the temperature detection circuit  216  is beyond the overheat temperature threshold, it means that the temperature of the first switch device  212  is too high and the AC transmission circuit  2  is abnormal at this time. Then, the main control circuit  211  sends an off signal to the first switch device  212 . At this time, the first switch device  212  is turned off so as to control the power supply circuit  20  to stop power supply. 
     Optionally, the preset overheat temperature threshold is 70° C.~110° C. Preferably, the preset overheat temperature threshold is 80° C.∼100° C. 
     Furthermore, the switch circuit  21  of the second embodiment of the present disclosure further includes a warning circuit  215 . The main control circuit  211  is signal connected with the warning circuit  215  and controls the warning circuit  215  to output warning signals. 
     It should be understood, when the surge detection circuit  213  detects abnormal conditions such as voltage surges or lightning, when the AC voltage detection circuit  214  detects that the AC input is beyond threshold voltage value or when the temperature detection circuit  216  detects that the temperature of the AC transmission circuit  2  is abnormal, the warning circuit  215  outputs warning signals. 
     It should be noted, the warning circuit of the second embodiment of the present disclosure includes a buzzer, an audible and visual alarm, a light alarm, etc. If the warning circuit  215  is a buzzer, when the main control circuit outputs a high level, the buzzer will output sounds. 
     As stated above, the power supply  20  inputs AC power supply, part of which is transmitted to the voltage-stabilizing circuit  218 . The voltage-stabilizing circuit  218  provides power to the main control circuit. The other part of the AC power supply is transmitted to the socket so as to provide power to the socket. The main control circuit  211  controls on-off of the power supply circuit  20  by controlling on-off of the first switch device  212 . The surge detection circuit  213  is configured to detect abnormal conditions such as voltage surges and lightning so as to prevent internal components from being damaged under the abnormal conditions. The AC voltage detection circuit  214  can detect voltage values of the input voltage inputted by the power supply circuit  20 . When the AC voltage detection circuit  214  detects that the voltage values of the input voltage inputted by the power supply circuit  20  is normal, the main control circuit  211  controls the first switch device  212  to be turned on so as to ensure normal power supply of the power supply circuit  20 . When the AC voltage detection circuit  214  detects that the voltage values of the input voltage inputted by the power supply circuit  20  is abnormal, the main control circuit  211  controls the first switch device  212  to be turned off so as to control the power supply circuit  20  to stop power supply. The temperature detection circuit  216  is configured to detect the temperature of the first switch device  212 . When the main control circuit  212  determines that the temperature detection circuit  216  detects that the temperature of the first switch device is too high, which indicates that the AC transmission circuit  2  is abnormal. At this time, the main control circuit  211  controls the first switch device  212  to be turned off so as to control the power supply circuit  20  to stop power supply. The switch isolation control circuit  217  is configured to electrically isolate the power supply circuit  20  and the main control circuit  211 . When the AC input is high voltage, the switch isolation control circuit  217  can avoid direct electrical connection between the high voltage AC and the main control circuit  211 . The switch isolation control circuit  217  further includes an optocoupler, which can further provide reliable isolation of the first switch device  212 . When the AC transmission circuit  2  is abnormal, the warning circuit  215  outputs warning signals. 
     Referring to  FIGS.  23  and  24   , a third embodiment of the present disclosure provides an AC transmission circuit  3 . The AC transmission circuit  3  includes a power supply circuit  31  and a switch circuit  32  coupled to the power supply circuit  31 . The switch circuit  32  further includes a main control circuit  322  and a TRIAC  323  coupled to the power supply circuit  31 . The main control circuit  322  is signal connected to the TRIAC  323  and controls on-off the power supply circuit  31  through the TRIAC  323 . 
     It should be understood, the TRIAC  323  of the third embodiment of the present disclosure is structurally equivalent to two unidirectional thyristors connected reversely. The TRIAC  323  has a function of bidirectional conduction. The advantage of TRIAC  323  is that the TRIAC  323  has a simple control circuit and there is no reverse withstand voltage problem. Therefore, it is especially suitable for an AC contactless switch. The TRIAC  323  is connected in series on the power supply circuit  31 , and the TRIAC  323  is signal connected with the main control circuit  322 . When the AC transmission circuit  3  inputs high-voltage AC, the on-off of the TRIAC  323  can be controlled by the main control circuit  322 , and then the on-off of the power supply circuit  31  can be controlled. He TRIAC  323  is an AC semiconductor switch that is not physically opened and closed, a problem prone to ignite along on/off of a physical switch can be effectively avoided, so as to improve safety. It should be understood that the TRIAC  323  can also be other AC semiconductor switches with same characteristics, such as MOS transistors, relays and other elements. 
     Referring to  FIGS.  24  and  25   , the switch circuit  32  of the third embodiment of the present disclosure includes TRIAC Q 1 , a capacitor C 1 , a varistor MOV 1  and a R-C absorb resistor. The capacitor C 1  is connected in parallel with the varistor MOV 1 . The varistor MOV 1  is connected in parallel with the R-C absorb resistor. It should be noted, the R-C absorb resistor is consisted of a resistor R 1  and a capacitor C 2  connected in series and configured to protect the TRIAC Q 1  from breakdown. The TRIAC Q 1  is coupled with the power supply circuit  31 . 
     A work flow of the switch circuit  32  of the embodiment is: when the AC power supply is inputted, the AC power supply flows through the TRIAC  323 , the main control circuit  322  controls on-off of the TRIAC  323  so as to control on-off of the power supply circuit  31 . 
     Referring to  FIGS.  24  and  26   , the main control circuit  322  of the third embodiment of the present disclosure includes a main control chip U 4  having a model of QFN20. It is an 8-bit microcontroller (MCU) based on a low-power platform, which makes it very suitable for any battery operation application. It also has 8 KB flash memory, 0.5 KB ram, 16 digital I/O pins, 4 x 16 bit timer, 3 PCA channels and other peripheral communication devices. 
     The main control chip U 4  is configured to collect touch information control on-off of the first switch device  212 . The main control chip U 4  is responsible for collecting touch information at a touch sensing part in the switch control circuit  321  and controlling the TRIAC Q 1  accordingly. The main control chip U 4  is further configured to control on-off of the TRIAC Q 1 . The main control chip U 4  is further configured to transmit detected signals including voltages, current and power in the AC transmission circuit  3  to the display circuit. The main control chip U 4  is further configured to receive detected temperature information from the temperature detection circuit. 
     Referring to  FIGS.  24  and  27   , the rectifier circuit  326  of the third embodiment of the present disclosure includes a rectifier bridge BD 1 , a transformer T 2 , a primary chip U 3 , a capacitor C 3 , a filter capacitor EC 1 , a filter capacitor EC 2  and a filter capacitor EC 3 , a diode D 1 , a diode D 2  and a diode D 3 , a resistor R 8 , a resistor r9, a resistor R 10  and a resistor R 11 . 
     It should be understood, the transformer T 2  of the third embodiment of the present disclosure has a primary input terminal Ti, a primary output terminal To1 and a secondary output terminal To2. 
     Specifically, the primary coil of the transformer T 2  is connected with the rectifier bridge BD 1 . The rectifier bridge BD 1  is connected with the filter capacitor EC 2 . A positive pole of the filter capacitor EC 2  is connected with the capacitor C 3 . The capacitor C 3  is connected with the resistor R 8  in parallel. The capacitor C 3  is connected in series with the resistor R 10  and the diode D 2 . The resistor R 8  is connected between the resistor R 10  and the diode D 2 . 
     It should be understood, the AC power supply passes through the rectifier bridge BD 1  for primary rectification, then passes through the filter capacitor EC 2  for primary filtering, and then passes through the primary input terminal. 
     Specifically, in the embodiment, the primary input terminal Ti is connected with an input circuit. The input circuit is an input circuit of a conventional Primary-Side-Regulation (PSR) system, and includes an AC input, a primary rectifier and a primary filter connected successively. Then, the primary input power supply is provided to the transformer T 2 , a load to be charged is connected to the secondary output terminal To2, and the secondary output terminal To2 provides charging power supply to the load. 
     Furthermore, pin HV of the primary chip U 3  is connected with the primary input terminal Ti of the transformer T 2 . The FB pin of a primary chip U 3  is voltage divided and connected to the primary output terminal to1 of the transformer T 2 . The FB pin of the primary chip U 3  is also successively connected with the resistor R 11 , the diode D 3  and the filter capacitor EC 3 . The node between the diode D 3  and the filter capacitor EC 3  is also connected with the VCC pin of the primary chip U 3 . 
     It is understandable that the design that the HV pin of the primary chip U 3  is connected to the primary input Ti of the transformer T 2  to detect the input voltage of the primary coil of the transformer T 2 , so that the primary chip U 3  can determine the input voltage, then adjust on-time of a built-in switch, adjust a switching frequency of the built-in switch at the same time, and adjust demagnetization time of the transformer T 2  so as to achieve constant current output of the transformer T 2 . 
     By the design that the pin FB of the primary chip U 3  is connected with the primary output terminal To1 of the transformer T 2 , the pin FB of the primary chip U 3  detects output voltage of the transformer T 2  according to an interact induction principle. 
     Furthermore, in the embodiment, the secondary coil of the transformer T 2  is connected with a rectifier-filter unit configured to rectify and filter output current of the secondary coil of the transformer T 2 . 
     Additionally, the rectifier-filter unit can include a diode D 1  connected to the secondary coil and configured to rectify the output current of the secondary coil. A positive pole of the diode D 1  is connected to the filter capacitor EC 1 . The output current of the secondary coil is filtered by the filter capacitor EC 1  and then is outputted. 
     It should be understood, the secondary coil of the transformer T 2  is connected to the diode D 1  to rectify the output current of the secondary coil, and the filter capacitor EC 1  is connected after the diode D 1  to filter rectified output current. Filtered output current is then outputted to the electronic equipment. 
     A work flow of the rectifier circuit  326  of the third embodiment is: obtain charging requirements of the load to be charged, control the transformer T 2  to make the secondary output terminal To2 to output constant current or voltage according to the charging requirements, the constant current or voltage can be adjustable. 
     It should be understood, the rectifier circuit  326  of the third embodiment provides power to the main control circuit  322 , the switch isolation control circuit  324 , the switch control circuit  324 , the temperature detection circuit  327 , the display circuit  325 , and the warning circuit  328 . 
     Referring to  FIGS.  24  and  28   , the switch circuit  32  of the third embodiment further includes the switch isolation control circuit  324 . The TRIAC  323  is connected to the main control circuit  322  through the switch isolation control circuit  324 . The switch isolation control circuit  324  in this embodiment includes an optocoupler. 
     It should be understood, the main control circuit  322  in this embodiment is configured to control operations of the AC transmission circuit  3 . By arranging the switch isolation control circuit  324 , the main control circuit  322  can controls the TRIAC  323  through the switch isolation control circuit  324 , which can isolate the power supply circuit  31  and the main control circuit  322  so as to protect the main control circuit  322  from being damaged by the voltage surges in the power supply circuit., thereby prolonging service life of the AC transmission circuit  3 . The design that the power supply circuit  31  and the main control circuit  322  is electrically isolated can avoid direct connection between high voltages and the main control circuit  322 , which can further improve safety when users control on-off of the AC transmission circuit  1  artificially. 
     Additionally, when the TRIAC  323  is connected to high voltages, it is necessary to it is necessary to isolate the power supply circuit  31  and the main control circuit  322 . The optocoupler of the present disclosure has a good isolation function. By setting the optocoupler, the optocoupler is used to directly isolate low voltage and high voltage of the power supply circuit  31  from the main control circuit  322 . When the TRIAC  323  is connected to the high voltages, on-time of the TRIAC  323  (the duration during which the TRIAC  323  is turned on) can be controlled through the optocoupler, so as to isolate the high voltages of the TRIAC  323 . Thus, the main control circuit  322  is safer and more reliable. 
     Specifically, the switch isolation control circuit  324  includes an optocoupler U 1 , a resistor R 1 , a resistor R 2 , a resistor R 3 , a resistor R 4 , a resistor R 5 , a resistor R 6 , a resistor R 7 , and a triode Q 2 . 
     The optocoupler U 1  has six pins. A positive pole (that is pin  1 ) of a light emitter of the optocoupler U 1  is connected to a 5 V voltage through the resistor R 4 . The collector of the triode Q 2  is coupled with a negative pole (that is pin  2 ) of the light emitter of the optocoupler U 1 . The emitter of the triode Q 2  is connected to GND. The base of the triode Q 2  is coupled to with the pin PA 7  of the main control circuit U 4  through the resistor R 7 . The resistor R 7  is connected series with one terminal of the resistor R 6 , and the other terminal of the resistor R 6  is connected to GND. 
     One terminal (pin  6 ) of a light receiver of the optocoupler U 1  is coupled with the AC input through the resistor R 3  and the resistor R 4 , the other terminal (pin  4 ) of the light receiver of the optocoupler U 1  is connected with the TRIAC Q 1  and the resistor R 5 . The resistor R 5  and the TRIAC Q 1  are connected in series. Pin  5  and pin  3  of the optocoupler U 1  remains suspended. 
     It should be understood, a work process of the switch isolation control circuit  324  is as follow: the optocoupler U 1  is MOC3041 and has a zero-crossing detection circuit. When corresponding current is inputted into the optocoupler U 1 , the voltage value between pin  6  and pin  4  of the optocoupler U 1  slightly crosses zero, and the TRIAC inside the optocoupler U 1  is turned on. When the main control chip U 4  collects electrical signals that AC voltage crosses zero, it triggers the main control chip U 4  to generate an event interrupt, which triggers the TRIAC Q 1 . Therefore, the TRIAC Q 1  is turned on. When 0 mA current is inputted into the optocoupler U 1 , the TRIAC inside the optocoupler U 1  is turned off. After the main control chip U 4  receives signals that the TRIAC inside the optocoupler U 1  is turned off, the main control chip U 4  transmits off signal to the TRIAC Q 1 , so as to control the TRIAC Q 1  to be turned off. 
     Referring to  FIGS.  24  and  29   , the switch circuit  32  of the third embodiment of the present disclosure further includes the switch control circuit  321  connected with the main control circuit  322 . The main control circuit  322  controls on-off of the TRIAC  323  through the switch control circuit  321 . 
     It should be understood, by arranging the switch control circuit  321 , the main control circuit  322  controls on-off of the TRIAC  323  through the switch control circuit  321 . 
     Optionally, the switch control circuit  321  may be but not limited to, a combination of one or more of a touch switch, a voice switch, a remote control switch and a push switch. Specifically, in the embodiment, the switch control circuit  321  is a touch switch. 
     It should be understood, the switch control circuit  321  of the third embodiment of the present disclosure controls on-off of the TRIAC  323  by a touch switch, which is convenient for controlling on-off the AC transmission circuit  3 . In addition, comparing with conventional physical switches, the touch switch is safer and the service life thereof will be longer. 
     Specifically, the switch control circuit  321  includes a touch switch chip U 2  having a model of SD8223LB. Sd82231b is a touch and proximity sensing switch having a single key, which is used to replace a traditional mechanical switch. It has six pins. Further, the switch control circuit  321  of this embodiment also includes a peripheral circuit connected to the touch switch chip U 2 , and pin  1  of the touch switch chip U 2  is connected with pin PA12 of the main control chip U 4 . 
     The peripheral circuit includes a resistor R 12 , a resistor R 13 , a resistor R 14  and a resistor R 15 , a capacitor C 4 , and a capacitor C 5 . A pin  6  of the touch switch chip U 2  is connected with a 5V voltage through the resistor R 13 . A pin  4  of the touch switch chip U 2  is connected with one terminal of the resistor R 15 . The other terminal of the resistor R 15  is connected in series with one terminal of the capacitor C 4 . The other terminal of the capacitor C 4  is connected to GND. A pin  1  of the touch switch chip U 1  is connected with a 3.3 V voltage through the resistor R 12 . A pin  3  of the touch switch chip U 2  is connected with the resistor R 14  and the capacitor C 5 . The Capacitor C 5  is connected to GND. A pin  2  of the touch switch chip U 2  is connected to GND. 
     It should be understood, a work flow of the switch control circuit  321  of this embodiment is as follow: when the touch switch is touched or the proximity switch is approached, the switch control circuit  321  transmits corresponding signals to the main control chip U 4  so as to control on-off of the TRIAC Q 1 . 
     Referring to  FIGS.  24  and  30   , the switch circuit  32  further includes a display circuit  325  configured to display working modes and working states of the AC transmission circuit  3 . 
     It should be understood, the display circuit  325  and the main control circuit  322  are connected. The main control circuit  322  controls the display circuit  325  to display working modes of the AC transmission circuit  3 . 
     Specifically, the display circuit  325  includes a resistor R 20 , a resistor R 21 , a light emitting diode LED 1 , a light emitting diode LED 2  and a light emitting diode LED 3 . One terminal of the light emitting diode LED 1  is connected with a 5V voltage, and the other terminal of the light emitting diode LED 2  is connected with pin PB 1  of the main control chip U 4  through the resistor R 21 . One terminal of the light emitting diode LED 3  is connected with a 5 V power, and the other terminal of the light emitting diode LED 3  is connected with pin PB 2  of the main control chip U 4 . 
     It should be understood, when power supply is inputted into the display circuit  325 , the 5V voltage forms a path through the resistors and then LEDs are lighted on. 
     It should be noted, lights of different colors can be used to indicate different operating modes of the AC transmission circuit  3 . For example, a red light is used to indicate an abnormal state of the AC transmission circuit  3 , at this time, the TRIAC  323  is abnormal. A green light is used to indicate a normal state of the AC transmission circuit  3 , at this time, each component in the AC transmission circuit  3  is in a normal working state. A blue light is used to indicate that the AC transmission circuit  3  does not work, at this time, the AC transmission circuit  3  is in a closed state. 
     It should be understood, the display circuit  325  includes a display screen, which can be a combination of one or more of a LED screen, a CRT screen, or an OLED screen. The display circuit  325  is connected with the main control chip U 4 , which allows the display circuit  325  to timely display working information of the AC transmission circuit  3  collected by the main control chip U 4 . It should be noted, working information can be voltage, current, power, or their combination of the AC transmission circuit  3 . Through such arrangements, voltages, current, powers or power consumption of the AC transmission circuit can be timely displayed on the display screen, which is convenient for users to obtain the working information of the AC transmission circuit  3 . 
     Additionally, displayed power values can indicate current total power consumption of the AC transmission circuit. The display screen of the present disclosure shows the power value, so that users can understand power of an electric appliance and use the electric appliance within the allowable range. As for power consumption, watt hours can be displayed, which indicates power information of the electric appliance when users use the electric appliance for a long time. Furthermore, the power charge information can be preset. According to the power charge information and power consumption, real-time power charge can be displayed to tell the user that the power charge has been generated, so that the user can have an intuitive understanding of the power charge and remind the user to save power. 
     As stated above, when AC power supply is inputted, one part of which is transmitted to the power supply circuit  31 . The power supply circuit  31  provides power to the main control circuit  32 . The other part of the AC power supply is transmitted to a female socket so as to provide power to the female socket. The main control circuit  32  controls on-off of the power supply circuit  31  by controlling the TRIAC  323 . The switch isolation control circuit  324  is configured to electrically isolate the power supply circuit  31  and the main control circuit  323 . When the AC power supply is high voltage, it can avoid direct connection between the high voltage AC and the main control circuit  323 . Furthermore, the switch isolation control circuit  324  further includes an optocoupler, which can provide further reliable isolation of the TRIAC  323 . The power supply circuit  31  provides power to the main control circuit  323 . The display circuit  325  is configured to display information collected by the main control circuit  323 . The display circuit  325  display working modes or working states of the AC transmission circuit  3 . 
     Referring to  FIG.  31   , a fourth embodiment of the present disclosure provides a socket  4  including a socket body  41  and a circuit structure  42  arranged in the socket body  41 . The circuit structure  42  may be the AC transmission circuit  1  of the first embodiment, the AC transmission circuit  2  of the second embodiment, or the AC transmission circuit  3  of the third embodiment. 
     It should be understood, the socket  4  provided by the fourth embodiment of the present disclosure has same advantages with the AC transmission circuit  1  of the first embodiment, the AC transmission circuit  2  of the second embodiment, or the AC transmission circuit  3  of the third embodiment. 
     The above description only describes embodiments of the present disclosure, and is not intended to limit the present disclosure, various modifications and changes can be made to the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present disclosure are intended to be included within the scope of the present disclosure.