Abstract:
A surge protection circuit includes a surge protection unit and an interface electrically connected to each other. The surge protection unit includes an internal connection terminal block, three varistors and one discharge tube. The three varistors are electrically connected to the internal connection terminal block, where two varistors are electrically connected to the discharge tube. The discharge tube is also electrically connected to the internal connection terminal block and is grounded. The surge protection circuit can avoid connecting a varistor to the discharge tube in series and reduce a residual voltage of the surge protection circuit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application No. PCT/CN2011/074998, filed on May 31, 2011, which claims priority to Chinese Patent Application No. 201020620604.3, filed on Nov. 22, 2010, both of which are hereby incorporated by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present utility model relates to the field of electronic communications, and in particular, to a surge protection circuit. 
     BACKGROUND 
     In the field of electronic communications, a protection technology is required to ensure stable and reliable operation of communication equipment. For example, a surge protection circuit disposed at a power port or a signal port of the communication equipment can ensure stable and reliable operation of the communication equipment in a severe electromagnetic environment. 
     Referring to  FIG. 1 , the prior art provides a surge protection circuit, including a surge protection unit S 1  (as shown in a dotted box), a four-row external connection terminal block S 2 , and a conversion terminal block S 3 . The surge protection unit S 1  includes an internal connection terminal block S 11 , a first varistor S 12 , a second varistor S 13 , a third varistor S 14 , a fourth varistor S 15 , and a discharge tube S 16 . The internal connection terminal block S 11  includes a first internal connection terminal L 11 , a second internal connection terminal L 12 , a third internal connection terminal L 13 , and a fourth internal connection terminal N 1 . One end of the first varistor S 12 , one end of the second varistor S 13 , and one end of the third varistor S 14  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively; and the other ends of the varistors are connected in parallel together and electrically connected to one end of the fourth varistor S 15  and the fourth internal connection terminal N 1 . The other end of the fourth varistor S 15  is electrically connected to one end of the discharge tube S 16 , and the other end of the discharge tube S 16  is grounded. The four-row external connection terminal block S 2  includes a first external connection terminal L 21 , a second external connection terminal L 22 , a third external connection terminal L 23 , and a fourth external connection terminal N 2 . The conversion terminal block S 3  includes a first conversion terminal A, a second conversion terminal B, a third conversion terminal C, and a fourth conversion terminal D. The first external connection terminal L 21 , the second external connection terminal L 22 , the third external connection terminal L 23 , and the fourth external connection terminal N 2  are electrically connected to the first conversion terminal A, the second conversion terminal B, the third conversion terminal C, and the fourth conversion terminal D, respectively. 
     Through the surge protection circuit, a 220 V three-phase power distribution manner, a 220 V single-phase power distribution manner, and a 110 V dual live wire power distribution manner can be implemented. In the 220 V three-phase power distribution manner shown in  FIG. 1 , the first conversion terminal A, the second conversion terminal B, the third conversion terminal C, and the fourth conversion terminal D are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , and the fourth internal connection terminal N 1  through cables, respectively; and then a 220 V phase wire L 1 , a 220 V phase wire L 2 , and a 220 V phase wire L 3  are electrically connected to the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23 , respectively; and a phase wire N is electrically connected to the fourth external connection terminal N 2 . In the 220 V single-phase power distribution manner shown in  FIG. 2 , the internal connection terminals L 11 , L 12  and L 13  are electrically connected to the conversion terminal A through cables, and the fourth internal connection terminal N 1  is electrically connected to the fourth conversion terminal D through a cable. A 220 V phase live wire L is electrically connected to the first external connection terminal L 21 , and a phase wire N is electrically connected to the fourth external connection terminal N 2 . In the 110 V dual live wire power distribution manner shown in  FIG. 3 , the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  are electrically connected to the second conversion terminal B through cables, and the fourth internal connection terminal N 1  is electrically connected to the third conversion terminal C. A 110 V phase live wire L 1  and a 110 V phase live wire L 2  are electrically connected to the second external connection terminal L 22  and the third external connection terminal L 23 , respectively. 
     In normal circumstances, for any one of the foregoing power distribution manners, the voltage across the first varistor S 12 , the second varistor S 13 , and the third varistor S 14  is 220 V or 110 V. The higher the voltage across a varistor is, the smaller the resistance value of the varistor, and the lower the voltage across a varistor is, the larger the resistance value of the varistor is. In this case, resistance values of the first varistor S 12 , the second varistor S 13 , and the third varistor S 14  are very large. Currents shunted by the first varistor S 12 , the second varistor S 13 , and the third varistor S 14  from the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  are nearly zero, and most of currents on the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  are transmitted to the communication equipment. After the phase wire L 1 , L 2 , L 3  or L externally connected to the surge protection circuit is struck by lightning, the voltage of the first internal connection terminal L 11 , the second internal connection terminal L 12  or the third internal connection terminal L 13  becomes very high, and the voltages across the first varistor S 12 , the second varistor S 13 , and the third varistor S 14  become very high accordingly. In this case, the resistance values of the first varistor S 12 , the second varistor S 13  and the third varistor S 14  become very small. The first varistor S 12 , the second varistor S 13 , and the third varistor S 14  shunt most of the currents on the first internal connection terminal L 11 , the second internal connection terminal L 12  and the third internal connection terminal L 13 , respectively, onto the discharge tube S 16 , and the discharge tube S 16  releases the currents to a grounded place. The currents transmitted by the first internal connection terminal L 11 , the second internal connection terminal L 12  and the third internal connection terminal L 13  to the communication equipment are small. In this way, a surge protection function is implemented. 
     During implementation of the present utility model, it is found that the prior art at least has the following problems: 
     After lightning strike, the currents on the first varistor S 12 , the second varistor S 13 , and the third varistor S 14  are very large, a parallel current obtained after the three varistors are connected in parallel is greater, it is hard to find a fourth varistor S 15  capable of bearing the parallel current. In addition, a residual voltage of the surge protection circuit includes a voltage of the fourth varistor S 15  and a voltage of the discharge tube S 16 , and therefore, the residual voltage of the surge protection circuit is high. 
     SUMMARY 
     In order to avoid connecting a varistor to a discharge tube in series and reduce a residual voltage of a surge protection circuit, the present utility model provides a surge protection circuit. The technical solution is as follows: 
     A surge protection circuit includes: 
     a surge protection unit and an interface, where the surge protection unit is electrically connected to the interface, 
     the surge protection unit includes an internal connection terminal block, three varistors and one discharge tube, and 
     the three varistors are electrically connected to the internal connection terminal block, two varistors of the three varistors are electrically connected to the discharge tube, and the discharge tube is electrically connected to the internal connection terminal block and is grounded. 
     It is avoided that a varistor is connected to the discharge tube  15  in series, and a residual voltage of the surge protection circuit includes a voltage of the discharge tube only, thereby reducing the residual voltage of the surge protection circuit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of implementation of a 220 V three-phase power distribution manner by using a surge protection circuit provided by the prior art; 
         FIG. 2  is a schematic diagram of implementation of a 220 V single-phase power distribution manner by using a surge protection circuit provided by the prior art; 
         FIG. 3  is a schematic diagram of implementation of a 110 V dual live wire power distribution manner by using a surge protection circuit provided by the prior art; 
         FIG. 4  is a schematic diagram of implementation of 220 V three-phase power distribution by using a surge protection circuit provided by Embodiment 1 of the present utility model; 
         FIG. 5  is a schematic diagram of implementation of 220 V single-phase power distribution by using the surge protection circuit provided by Embodiment 1 of the present utility model; 
         FIG. 6  is a schematic diagram of implementation of 110 V dual live wire power distribution by using the surge protection circuit provided by Embodiment 1 of the present utility model; 
         FIG. 7  is a schematic diagram of implementation of 220 V three-phase power distribution by using a surge protection circuit provided by Embodiment 2 of the present utility model; 
         FIG. 8  is a schematic diagram of implementation of 220 V single-phase power distribution by using the surge protection circuit provided by Embodiment 2 of the present utility model; 
         FIG. 9  is a schematic diagram of implementation of 110 V dual live wire power distribution by using a surge protection circuit provided by Embodiment 3 of the present utility model; 
         FIG. 10  is a schematic diagram of implementation of 220 V single-phase power distribution by using the surge protection circuit provided by Embodiment 3 of the present utility model; 
         FIG. 11  is a schematic diagram of implementation of 220 V three-phase power distribution by using a surge protection circuit provided by Embodiment 4 of the present utility model; 
         FIG. 12  is a schematic diagram of the surge protection circuit provided by Embodiment 4 of the present utility model; 
         FIG. 13  is a schematic diagram of implementation of 220 V single-phase power distribution by using the surge protection circuit provided by Embodiment 4 of the present utility model; 
         FIG. 14  is a schematic diagram of implementation of 110 V dual live wire power distribution by using the surge protection circuit provided by Embodiment 4 of the present utility model; 
         FIG. 15  is a schematic diagram of implementation of 220 V three-phase power distribution by using a surge protection circuit provided by Embodiment 5 of the present utility model; 
         FIG. 16  is a schematic diagram of implementation of 220 V single-phase power distribution by using the surge protection circuit provided by Embodiment 5 of the present utility model; and 
         FIG. 17  is a schematic diagram of implementation of 110 V dual live wire power distribution by using the surge protection circuit provided by Embodiment 5 of the present utility model. 
     
    
    
     DETAILED DESCRIPTION 
     To illustrate the objectives, technical solutions and advantages of the present utility model more clearly, the embodiments of the present utility model are further described in the following with reference to the accompanying drawings. 
     Embodiment 1 
     As shown in  FIG. 4 , an embodiment of the present utility model provides a surge protection circuit, including: 
     a surge protection unit  1  and a six-row external connection terminal block  2 , where the surge protection unit  1  includes an internal connection terminal block  11 , a first varistor  12 , a second varistor  13 , a third varistor  14 , and a discharge tube  15 , and the internal connection terminal block  11  includes a first internal connection terminal L 11 , a second internal connection terminal L 12 , a third internal connection terminal L 13 , a fourth internal connection terminal L 1   p , a fifth internal connection terminal N 1 , and a sixth internal connection terminal N 11 , and the six-row external connection terminal block  2  includes a first external connection terminal L 21 , a second external connection terminal L 22 , a third external connection terminal L 23 , a fourth external connection terminal L 2   p , a fifth external connection terminal N 2 , and a sixth external connection terminal N 21 . 
     One end of the first varistor  12 , one end of the second varistor  13 , and one end of the third varistor  14  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the fourth internal connection terminal L 1   p , respectively. The other end of the first varistor  12  is electrically connected to the fifth internal connection terminal N 1 . The other end of the second varistor  13  and the other end of the third varistor  14  are connected together in parallel, and are electrically connected to one end of the discharge tube  15  and the sixth internal connection terminal N 11 , and the other end of the discharge tube  15  is grounded. The first external connection terminal L 21 , the second external connection terminal L 22 , the third external connection terminal L 23 , the fourth external connection terminal L 2   p , the fifth external connection terminal N 2 , and the sixth external connection terminal N 21  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , the fifth internal connection terminal N 1 , and the sixth internal connection terminal N 11 , respectively. 
     Further, the surge protection unit  1  may also include three filter inductors, that is, a first filter inductor  16 , a second filter inductor  17 , and a third filter inductor  18 , where the first filter inductor  16 , the second filter inductor  17 , and the third filter inductor  18  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively. 
     Referring to  FIG. 4 , this embodiment provides a cabinet, including the surge protection circuit provided by this embodiment and a cabinet body  6 , where the surge protection circuit is electrically connected to a port of the cabinet body  6  directly. The port of the cabinet body  6  includes a power port or a signal port. For example, the cabinet body  6  includes a first power port PSU 1 , a second power port PSU 2 , and a third power port PSU 3 , where the first power port PSU 1  is electrically connected to the first filter inductor  16  and the fifth internal connection terminal N 1  in the surge protection unit  1 , the second power port PSU 2  is electrically connected to the second filter inductor  17  and the fifth internal connection terminal N 1  in the surge protection unit  1 , and the third power port PSU 3  is electrically connected to the third filter inductor  18  and the fifth internal connection terminal N 1  in the surge protection unit  1 . In addition, a socket may also be externally connected to the cabinet, where the socket is electrically connected to the first filter inductor  16  and the sixth internal connection terminal N 11  in the surge protection unit  1 . When detection equipment is used to detect the surge protection circuit, the socket may supply power to the detection equipment. 
     Through the surge protection circuit provided by this embodiment, a 220 V three-phase power distribution manner, a 220 V single-phase power distribution manner, and a 110 V dual live wire power distribution manner can be implemented. 
     In a circuit structure of the 220 V three-phase power distribution manner shown in  FIG. 4 , short connection sheets S are used to electrically connect the fifth internal connection terminal N 1  and the sixth internal connection terminal N 11  together, and electrically connect the third internal connection terminal L 13  and the fourth internal connection terminal L 1   p  together. The 220 V three-phase wires L 1 , L 2  and L 3  are electrically connected to the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23 , respectively; and a phase wire N is electrically connected to the sixth external connection terminal N 21 . 
     If the phase wires L 1 , L 2 , and L 3  are struck by lightning, voltages of the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , and the fourth internal connection terminal L 1   p  become very high, and voltages of the first varistor  12 , the second varistor  13 , and the third varistor  14  become very high accordingly. Resistance values of the first varistor  12 , the second varistor  13 , and the third varistor  14  become very small, so that the first varistor  12 , the second varistor  13 , and the third varistor  14  shunt most of currents on the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively, onto the discharge tube  15 , and the discharge tube  15  releases the currents to a grounded place. In this way, a surge protection function is implemented. 
     In a circuit structure of the 220 V single-phase power distribution manner shown in  FIG. 5 , short connection sheets S are used to electrically connect the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  together, and electrically connect the fifth internal connection terminal N 1  and the sixth internal connection terminal N 11  together. A 220 V phase wire L is electrically connected to the first external connection terminal L 21 , and a phase wire N is electrically connected to the sixth external connection terminal N 21 . 
     If the phase wire L is struck by lightning, voltages of the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  become very high, and voltages of the first varistor  12  and the second varistor  13  become very high accordingly. In this case, resistance values of the first varistor  12  and the second varistor  13  become very small, so that the first varistor  12  and the second varistor  13  shunt most of currents of the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  onto the discharge tube  15 , and the discharge tube  15  releases the currents to a grounded place. In this way, a surge protection function is implemented. 
     In a circuit structure of the 110 V dual live wire power distribution manner shown in  FIG. 6 , short connection sheets S are used to electrically connect the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  together, and electrically connect the fourth internal connection terminal L 1   p  and the fifth internal connection terminal N 1  together. The 110 V dual live wires L 1  and L 2  are electrically connected to the first external connection terminal L 21  and the fifth external connection terminal N 2 , respectively; and a phase wire N is electrically connected to the sixth external connection terminal N 21 . 
     If the phase wires L 1  and L 2  are struck by lightning, voltages of the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , and the fifth internal connection terminal N 1  become very high, and voltages of the second varistor  13  and the third varistor  14  become very high. In this case, resistance values of the second varistor  13  and the third varistor  14  become very small, and the second varistor  13  and the third varistor  14  shunt most of currents of the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , and the fifth internal connection terminal N 1  onto the discharge tube  15 , and the discharge tube  15  releases the currents to a grounded place. In this way, a surge protection function is implemented. 
     The discharge tube  15  cannot be directly connected to a live wire. Referring to  FIG. 4 ,  FIG. 5 , and  FIG. 6 , the internal connection terminal block  11  includes a six-row internal connection terminal, and one end of the discharge tube  15  is electrically connected to the sixth internal connection terminal N 11 . During implementation of the 220 V three-phase power distribution manner, the 220 V single-phase power distribution manner, and the 110 V dual live wire power distribution manner, it can be avoided that the live wire is directly connected to the discharge tube  15 , and it is not required to connect a varistor to the discharge tube  15  in series. In addition, a residual voltage of the surge protection circuit is a voltage of the discharge tube  15 , so the residual voltage of the surge protection circuit is lower than a residual voltage of an existing surge protection circuit. 
     The six-row external connection terminal block  2  is electrically connected to the internal connection terminal block  11  directly. During implementation of different power distribution manners, it is only required to use the short connection sheets S to connect a part of the internal connection terminals together, and no space needs to be reserved between the six-row external connection terminal block  2  and the internal connection terminal block  11  for wiring, thereby reducing the volume of the surge protection circuit. 
     In this embodiment, it is not required to connect a varistor to the discharge tube  15  in series. In addition, the residual voltage of the surge protection circuit includes the voltage of the discharge tube only, thereby reducing the residual voltage of the surge protection circuit. 
     Embodiment 2 
     An embodiment of the present utility model provides a surge protection circuit, where the surge protection circuit can implement a 220 V three-phase power distribution manner and a 220 V single-phase power distribution manner. Referring to  FIG. 7 , the surge protection circuit includes a surge protection unit  1 , a four-row external connection terminal block S 2 , and a conversion terminal block  3 . 
     The surge protection unit  1  includes an internal connection terminal block  11 , a first varistor  12 , a second varistor  13 , a third varistor  14 , and a discharge tube  15 , where the internal connection terminal block  11  includes a first internal connection terminal L 11 , a second internal connection terminal L 12 , a third internal connection terminal L 13 , a fourth internal connection terminal L 1   p , a fifth internal connection terminal N 1 , and a sixth internal connection terminal N 11 . One end of the first varistor  12 , one end of the second varistor  13 , and one end of the third varistor  14  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the fourth internal connection terminal L 1   p , respectively. The other end of the first varistor  12  is electrically connected to the fifth internal connection terminal N 1 . The other end of the second varistor  13  and the other end of the third varistor  14  are connected together in parallel, and are electrically connected to the sixth internal connection terminal N 11  and one end of the discharge tube  15 , and the other end of the discharge tube  15  is grounded. 
     The four-row external connection terminal block S 2  includes a first external connection terminal L 21 , a second external connection terminal L 22 , a third external connection terminal L 23 , and a fourth external connection terminal N 2 . The conversion terminal block  3  includes a first conversion terminal L 31 , a second conversion terminal L 32 , a third conversion terminal L 33 , a fourth conversion terminal L 3   p , a fifth conversion terminal N 3 , and a sixth conversion terminal N 31 . The first conversion terminal L 31  and the second conversion terminal L 32  are electrically connected to the first external connection terminal L 21  and the second external connection terminal L 22 , respectively. The third conversion terminal L 33  and the fourth conversion terminal L 3   p  are electrically connected to the third external connection terminal L 23 . The fifth conversion terminal N 3  and the sixth conversion terminal N 31  are electrically connected to the fourth external connection terminal N 2 . 
     The conversion terminal block  3  and the internal connection terminal block  11  serve as a socket and a plug, respectively; or the conversion terminal block  3  and the internal connection terminal block  11  serve as a plug and a socket, respectively. Correspondingly, by inserting the conversion terminal block  3  into the internal connection terminal block  11 , the first conversion terminal L 31 , the second conversion terminal L 32 , the third conversion terminal L 33 , the fourth conversion terminal L 3   p , the fifth conversion terminal N 3 , and the sixth conversion terminal N 31  in the conversion terminal block  3  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , the fifth internal connection terminal N 1 , and the sixth internal connection terminal N 11  in the internal connection terminal block  11 , respectively. 
     The four-row external connection terminal block S 2  and the conversion terminal block  3  may be integrated onto a circuit board, and the conversion terminal block  3  may be directly inserted into the internal connection terminal block  11 , and may also be directly pulled out from the internal connection terminal block  11 . 
     Further, the surge protection unit  1  may also include three filter inductors, that is, a first filter inductor  16 , a second filter inductor  17 , and a third filter inductor  18 , where the first filter inductor  16 , the second filter inductor  17 , and the third filter inductor  18  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively. 
     Through the surge protection circuit provided by this embodiment, a 220 V three-phase power distribution manner and a 220 V single-phase power distribution manner can be implemented. 
     Referring to  FIG. 7 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V three-phase power distribution manner, that is, the 220 V three-phase wires L 1 , L 2 , and L 3  are electrically connected to the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23 , respectively; and a phase wire N is electrically connected to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V three-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 8 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V single-phase power distribution manner, that is, a short connection sheet S is used to electrically connect the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23  together, and a 220 V phase wire L is electrically connected to the first external connection terminal L 21 , and a phase wire N is electrically connected to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V single-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 7  and  FIG. 8 , the internal connection terminal block  11  includes a six-row internal connection terminal, and one end of the discharge tube  15  is electrically connected to the sixth internal connection terminal N 11 . During implementation of the 220 V three-phase power distribution manner and the 220 V single-phase power distribution manner, it can be avoided that the live wire is directly connected to the discharge tube  15 , and it is not required to connect a varistor to the discharge tube  15  in series. In addition, a residual voltage of the surge protection circuit is a voltage of the discharge tube  15 , so the residual voltage of the surge protection circuit is lower than a residual voltage of an existing surge protection circuit. 
     The conversion terminal block  3  is electrically connected to the internal connection terminal block  11  directly in an insertion manner. During implementation of different power distribution manners, it is only required to use the short connection sheet S to connect a part of the external connection terminals together, and no space needs to be reserved between the conversion terminal block  3  and the internal connection terminal block  11  for wiring, thereby reducing the volume of the surge protection circuit. 
     Referring to  FIG. 7 , this embodiment provides a cabinet. The cabinet includes the surge protection circuit provided by this embodiment and a cabinet body  6 . The surge protection circuit is electrically connected to a port of the cabinet body  6 . A socket may also be externally connected to the cabinet, and the socket is electrically connected to the surge protection circuit. The port of the cabinet body  6  includes a power port or a signal port. A specific connection relationship among the surge protection circuit, the power port or the signal port of the cabinet body  6  and the socket is the same as corresponding content in Embodiment 1, which is not described again herein. 
     In this embodiment, it is not required to connect a varistor to the discharge tube  15  in series. In addition, the residual voltage of the surge protection circuit includes the voltage of the discharge tube only, thereby reducing the residual voltage. 
     Embodiment 3 
     An embodiment of the present utility model provides a surge protection circuit, where the surge protection circuit can implement a 110 V dual live wire power distribution manner and a 220 V single-phase power distribution manner. Referring to  FIG. 9 , the surge protection circuit includes a surge protection unit  1 , a three-row external connection terminal block  4 , and a conversion terminal block  3 . 
     A structure of the surge protection unit  1  is the same as the structure of the surge protection unit  1  provided by Embodiment 2, which is not described again herein. 
     The three-row external connection terminal block  4  includes a first external connection terminal L 21 , a second external connection terminal L 22 , and a third external connection terminal N 2 . The conversion terminal block  3  includes a first conversion terminal L 31 , a second conversion terminal L 32 , a third conversion terminal L 33 , a fourth conversion terminal L 3   p , a fifth conversion terminal N 3 , and a sixth conversion terminal N 31 . The first conversion terminal L 31 , the second conversion terminal L 32 , and the third conversion terminal L 33  are electrically connected to the first external connection terminal L 21 . The fourth conversion terminal L 3   p  and the fifth conversion terminal N 3  are electrically connected to the second external connection terminal L 22 . The sixth conversion terminal N 31  is electrically connected to the third external connection terminal N 2 . 
     The conversion terminal block  3  and the internal connection terminal block  11  serve as a socket and a plug, respectively; or the conversion terminal block  3  and the internal connection terminal block  11  serve as a plug and a socket, respectively. Correspondingly, by inserting the conversion terminal block  3  into the internal connection terminal block  11 , the first conversion terminal L 31 , the second conversion terminal L 32 , the third conversion terminal L 33 , the fourth conversion terminal L 3   p , the fifth conversion terminal N 3 , and the sixth conversion terminal N 31  in the conversion terminal block  3  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , the fifth internal connection terminal N 1 , and the sixth internal connection terminal N 11  in the internal connection terminal block  11 , respectively. 
     The three-row external connection terminal block  4  and the conversion terminal block  3  may be integrated onto a circuit board, and the conversion terminal block  3  may be directly inserted into the internal connection terminal block  11 , and may also be directly pulled out from the internal connection terminal block  11 . 
     Further, the surge protection unit  1  may also include three filter inductors, that is, a first filter inductor  16 , a second filter inductor  17 , and a third filter inductor  18 , where the first filter inductor  16 , the second filter inductor  17 , and the third filter inductor  18  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively. 
     Through the surge protection circuit provided by this embodiment, a 110 V dual live wire power distribution manner and a 220 V single-phase power distribution manner can be implemented. 
     Referring to  FIG. 9 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 110 V dual live wire power distribution manner, that is, 110 V dual live wires L 1  and L 2  are electrically connected to the first external connection terminal L 21  and the second external connection terminal L 22 , respectively; and a phase wire N is electrically connected to the third external connection terminal N 2 . 
     In the circuit structure of the 110 V dual live wire power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 10 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V single-phase power distribution manner, that is, a short connection sheet S is used to electrically connect the second external connection terminal L 22  and the third external connection terminal N 2  together. A 220 V phase wire L is electrically connected to the first external connection terminal L 21 , and a phase wire N is electrically connected to the third external connection terminal N 2 . 
     In the circuit structure of the 220 V single-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 9  and  FIG. 10 , the internal connection terminal block  11  includes a six-row internal connection terminal, and one end of the discharge tube  15  is electrically connected to the sixth internal connection terminal N 11 . During implementation of 110 V dual live wire power distribution manner and the 220 V single-phase power distribution manner, it can be avoided that the live wire is directly connected to the discharge tube  15 , and it is not required to connect a varistor to the discharge tube  15  in series. In addition, a residual voltage of the surge protection circuit is a voltage of the discharge tube  15 , so the residual voltage of the surge protection circuit is lower than a residual voltage of an existing surge protection circuit. 
     The conversion terminal block  3  is electrically connected to the internal connection terminal block  11  in an insertion manner. During implementation of different power distribution manners, it is only required to use the short connection sheet S to connect a part of the external connection terminals together, and no space needs to be reserved between the conversion terminal block  3  and the internal connection terminal block  11  for wiring, thereby reducing the volume of the surge protection circuit. 
     Referring to  FIG. 9 , this embodiment provides a cabinet, including the surge protection circuit provided by this embodiment and a cabinet body  6 . The surge protection circuit is electrically connected to a port of the cabinet body  6 . A socket may also be externally connected to the cabinet, and the socket is electrically connected to the surge protection circuit. The port of the cabinet body  6  includes a power port or a signal port. A specific connection relationship among the surge protection circuit, the power port or the signal port of the cabinet body  6  and the socket is the same as corresponding content in Embodiment 1, which is not described again herein. 
     In this embodiment, it is not required to connect a varistor to the discharge tube  15  in series. In addition, the residual voltage of the surge protection circuit includes the voltage of the discharge tube only, thereby reducing the residual voltage of the surge protection circuit. 
     Embodiment 4 
     As shown in  FIG. 11 , an embodiment of the present utility model provides a surge protection circuit, including a surge protection unit  1 , a four-row external connection terminal block S 2 , and a rotation terminal  5 . 
     A structure of the surge protection unit  1  is the same as the structure of the surge protection unit  1  provided by Embodiment 1, which is not described again herein. 
     The four-row external connection terminal block S 2  includes a first external connection terminal L 21 , a second external connection terminal L 22 , a third external connection terminal L 23 , and a fourth external connection terminal N 2 . 
     Referring to  FIG. 12 , the rotation terminal  5  includes a rotation disk  51  and a fixed disk  52 . The rotation disk  51  includes a first contact a, a second contact b, a third contact c, a fourth contact d, a fifth contact e, a sixth contact f, a seventh contact g, an eighth contact h, a ninth contact  1 , a tenth contact  2 , an eleventh contact  3 , a twelfth contact  4 , a thirteenth contact  5 , a fourteenth contact  6 , a fifteenth contact  7 , and a sixteenth contact  8 . The first contact a is electrically connected to the fourth contact d. The second contact b, the fifth contact e, and the sixth contact f are electrically connected together. The third contact c, the seventh contact g, and the eighth contact h are electrically connected together. The ninth contact  1  is electrically connected to the twelfth contact  4 . The tenth contact  2 , the thirteenth contact  5 , and the fourteenth contact  6  are electrically connected together. The eleventh contact  3 , the fifteenth contact  7 , and the sixteenth contact  8  are electrically connected together. The fixed disk  52  includes a first contact A, a second contact B, a third contact C, a fourth contact D, a fifth contact E, a sixth contact F, a seventh contact G, an eighth contact H, and a ninth contact J. 
     The first internal connection terminal L 11 , the first external connection terminal L 21 , and the first contact A of the fixed disk  52  are electrically connected together. The second internal connection terminal L 12 , the third internal connection terminal L 13 , the fourth internal connection terminal L 1   p , the fifth internal connection terminal N 1 , and the sixth internal connection terminal N 11  are electrically connected to the fifth contact E, the sixth contact F, the seventh contact G, the eighth contact H, and the ninth contact J in the fixed disk  52 , respectively. The second external connection terminal L 22 , the third external connection terminal L 23 , and the fourth external connection terminal N 2  are electrically connected to the second contact B, the third contact C, and the fourth contact D, respectively. The rotation disk  51  is mounted on the fixed disk  52  and can be rotated on the fixed disk  52 . 
     Further, the surge protection unit  1  may also include three filter inductors, that is, a first filter inductor  16 , a second filter inductor  17 , and a third filter inductor  18 , where the first filter inductor  16 , the second filter inductor  17 , and the third filter inductor  18  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively. 
     Through the surge protection circuit provided by this embodiment, a 220 V three-phase power distribution manner, a 220 V single-phase power distribution manner, and a 110 V dual live wire power distribution manner can be implemented. 
     As shown in  FIG. 11 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V three-phase power distribution manner, that is, the rotation disk  51  is rotated so that the first contact a, the second contact b, the third contact c, the fourth contact d, the fifth contact e, the sixth contact f, the seventh contact g, and the eighth contact h are in electrical contact with the second contact B, the third contact C, the fourth contact D, the fifth contact E, the sixth contact F, the seventh contact G, the eighth contact H, and the ninth contact J on the fixed disk  52 , respectively. The 220 V three-phase wires L 1 , L 2 , and L 3  are electrically connected to the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23 , respectively. A phase wire N is electrically connected to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V three-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     As shown in  FIG. 13 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V single-phase power distribution manner, that is, the rotation disk  51  is rotated so that the first contact a, the second contact b, the third contact c, the fourth contact d, the fifth contact e, the sixth contact f, the seventh contact g, and the eighth contact h are in electrical contact with the second contact B, the third contact C, the fourth contact D, the fifth contact E, the sixth contact F, the seventh contact G, the eighth contact H, and the ninth contact J on the fixed disk  52 . Short connection sheets S are used to electrically connect the external connection terminals L 21 , L 22 , and L 23  together. A 220 V phase wire L is electrically connected to the first external connection terminal L 21 . A phase wire N is electrically connected to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V single-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     As shown in  FIG. 14 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 110 V dual live wire power distribution manner, that is, the rotation disk  51  is rotated so that the ninth contact  1 , the tenth contact  2 , the eleventh contact  3 , the twelfth contact  4 , the thirteenth contact  5 , the fourteenth contact  6 , the fifteenth contact  7 , and the sixteenth contact  8  are in electrical contact with the fourth contact D, the second contact B, the first contact A, the ninth contact J, the eighth contact H, the seventh contact G, the sixth contact F, and the fifth contact E on the fixed disk  52 , respectively. The 110 V dual live wires L 1  and L 2  are electrically connected to the first external connection terminal L 21  and the second external connection terminal L 22 , respectively. A phase wire N is electrically connected to the fourth external connection terminal N 2 . 
     In the circuit structure of the 110 V dual live wire power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 14 , the internal connection terminal block  11  includes a six-row internal connection terminal, and one end of the discharge tube  15  is electrically connected to the sixth internal connection terminal N 11 . During implementation of the 220 V three-phase power distribution manner, the 220 V single-phase power distribution manner, and the 110 V dual live wire power distribution manner, it can be avoided that the live wire is directly connected to the discharge tube  15 , and it is not required to connect a varistor to the discharge tube  15  in series. In addition, a residual voltage of the surge protection circuit is a voltage of the discharge tube  15 , so the residual voltage of the surge protection circuit is lower than a residual voltage of an existing surge protection circuit. 
     The four-row external connection terminal block S 2  and the rotation terminal  5  are electrically connected to the internal connection terminal block  11  directly. During implementation of different power distribution manners, it is only required to use the short connection sheet S to connect a part of the external connection terminals together, and no space needs to be reserved in the surge protection circuit for wiring, thereby reducing the volume of the surge protection circuit. 
     Referring to  FIG. 11 , this embodiment provides a cabinet, including the surge protection circuit provided by this embodiment and a cabinet body  6 . The surge protection circuit is electrically connected to a port of the cabinet body  6 . A socket may also be externally connected to the cabinet, and the socket is electrically connected to the surge protection circuit. The port of the cabinet body  6  includes a power port or a signal port. A specific connection relationship among the surge protection circuit, the power port or the signal port of the cabinet body  6  and the socket is the same as corresponding content in Embodiment 1, which is not described again herein. 
     In this embodiment, it is not required to connect a varistor to the discharge tube  15  in series. In addition, the residual voltage of the surge protection circuit includes the voltage of the discharge tube only, thereby reducing the residual voltage. In addition, different power distribution manners can be implemented by rotating the rotation disk, thereby being convenient for the user and improving user experience. 
     Embodiment 5 
     As shown in  FIG. 15 , an embodiment of the present utility model provides a surge protection circuit, including a surge protection unit  1  and a four-row external connection terminal block S 2 . 
     A structure of the surge protection unit  1  is the same as the structure of the surge protection unit  1  provided by Embodiment 1, which is not described again herein. 
     A structure of the four-row external connection terminal block S 2  is the same as the structure of four-row external connection terminal block S 2  provided by Embodiment 4, which is not described again herein. 
     A first external connection terminal L 21 , a third external connection terminal L 23 , and a fourth external connection terminal N 2  are electrically connected to a first internal connection terminal L 11 , a third internal connection terminal L 13 , and a sixth internal connection terminal N 11 , respectively. 
     Further, the surge protection unit  1  may also include three filter inductors, that is, a first filter inductor  16 , a second filter inductor  17 , and a third filter inductor  18 , where the first filter inductor  16 , the second filter inductor  17 , and the third filter inductor  18  are electrically connected to the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13 , respectively. 
     Through the surge protection circuit provided by this embodiment, a 220 V three-phase power distribution manner, a 220 V single-phase power distribution manner, and a 110 V dual live wire power distribution manner can be implemented. 
     As shown in  FIG. 15 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V three-phase power distribution manner, that is, short connection sheets S are used to connect the third internal connection terminal L 13  and the fourth L 1   p  together and connect the fifth internal connection terminal N 1  and the sixth internal connection terminal N 11  together. Cables are used to electrically connect the second external connection terminal L 22  to the second internal connection terminal L 12 , electrically connect 220 V three-phase wires L 1 , L 2 , and L 3  to the first external connection terminal L 21 , the second external connection terminal L 22 , and the third external connection terminal L 23 , respectively; and electrically connect a phase wire N to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V three-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     As shown in  FIG. 16 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 220 V single-phase power distribution manner, that is, short connection sheets S are used to connect the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  together and connect the fifth internal connection terminal N 1  and the sixth internal connection terminal N 11  together. Cables are used to electrically connect the second external connection terminal L 22  to the second internal connection terminal L 12 , electrically connect a 220 V phase wire L to the first external connection terminal L 21 , and electrically connect a phase wire N to the fourth external connection terminal N 2 . 
     In the circuit structure of the 220 V single-phase power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     As shown in  FIG. 17 , the surge protection circuit provided by this embodiment is used to implement a circuit structure of the 110 V dual live wire power distribution manner, that is, short connection sheets S are used to connect the fifth internal connection terminal N 1  and the fourth internal connection terminal L 1   p  together and connect the first internal connection terminal L 11 , the second internal connection terminal L 12 , and the third internal connection terminal L 13  together. Cables are used to electrically connect the second external connection terminal L 22  to the fifth internal connection terminal N 1 , electrically connect 110 V dual live wires L 1  and L 2  to the first external connection terminal L 21  and the second external connection terminal L 22 , respectively; and electrically connect a phase wire N to the fourth external connection terminal N 2 . 
     In the circuit structure of the 110 V dual live wire power distribution manner, the surge protection circuit can implement a surge protection function, and the specific implementation process is the same as a part of the content of Embodiment 1, which is not described again herein. 
     Referring to  FIG. 17 , the internal connection terminal block  11  includes a six-row internal connection terminal, and one end of the discharge tube  15  is electrically connected to the sixth internal connection terminal N 11 . During implementation of the 220 V three-phase power distribution manner, the 220 V single-phase power distribution manner, and the 110 V dual live wire power distribution manner, it can be avoided that the live wire is directly connected to the discharge tube  15 , and it is not required to connect a varistor to the discharge tube  15  in series. In addition, a residual voltage of the surge protection circuit is a voltage of the discharge tube  15 , so the residual voltage of the surge protection circuit is lower than a residual voltage of an existing surge protection circuit. 
     Referring to  FIG. 15 , this embodiment provides a cabinet, including the surge protection circuit provided by this embodiment and a cabinet body  6 . The surge protection circuit is electrically connected to a port of the cabinet body  6 . A socket may also be externally connected to the cabinet, and the socket is electrically connected to the surge protection circuit. The port of the cabinet body  6  includes a power port or a signal port. A specific connection relationship among the surge protection circuit, the power port or the signal port of the cabinet body  6  and the socket is the same as corresponding content in Embodiment 1, which is not described again herein. 
     In this embodiment, it is not required to connect a varistor to the discharge tube  15  in series. In addition, the residual voltage of the surge protection circuit includes the voltage of the discharge tube only, thereby reducing the residual voltage of the surge protection circuit. 
     The above descriptions are merely exemplary embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present utility model should be included within the scope of protection of the present utility model.