Patent Publication Number: US-2010123527-A1

Title: Network transformer to reduce electromagnetic interference

Description:
FIELD OF THE INVENTION 
     The present invention relates to a network transformer and particularly to a network transformer to reduce electromagnetic interference (EMI). 
     BACKGROUND OF THE INVENTION 
     A conventional network transformer usually is installed between a client interface and a network transceiver chip to transmit data to other ends connected to a network through coupling of internal electromagnetic field. It also has internal coils coupled to do filtering to boost signal intensity to prevent different voltages or currents to pass through different network equipment to cause damages of the equipment resulting from network connection. 
     Refer to  FIG. 1  for a conventional network transformer and its circuit structure. The network transformer  100  has a transformation unit  200 , a choke coil  300  connecting to the transformation unit  200  and an induction coil  400  connecting to the choke coil  300 . The transformation unit  200  receives input power S 100  and input information S 101  from network equipment (not shown in the drawing) and transforms to generate output power S 200 . The induction coil  400  induces and generates output information S 201  so that AC power of the output power  200  is blocked by the choke coil  300 , and the output power S 200  and output information S 201  are sent together to another network equipment (not shown in the drawing). Therefore, information can be transmitted and electric power also can be transformed. 
     Although the conventional network transformer  100  can transmit information and transform electric power, it cannot isolate high frequency signals of the output power S 200  and output information S 201 . The high frequency signals generate electromagnetic radiation and results in EMI. 
     SUMMARY OF THE INVENTION 
     Therefore, the primary object of the present invention is to solve the aforesaid disadvantage by eliminating the high frequency signals to reduce EMI. 
     The present invention provides a network transformer to reduce EMI. It is connected to two network equipment to transmit data. It has a transformation unit, a plurality of high frequency signal attenuation elements electrically connected to the transformation unit and a plurality of high frequency signal channel elements connecting to the high frequency signal attenuation elements. The transformation unit transforms input power and input information of one network equipment to output power and output information, and sends the output power and output information to the high frequency signal attenuation elements to reduce high frequency noises of the output information and output power. Then the attenuated output information and output power are transmitted to the load of the other network equipment. By bridging the high frequency signal channel elements between the high frequency signal attenuation elements and the load, high frequency signals of the output information and output power can be integrated and grounded through the high frequency signal channel elements. Thus the high frequency signals can be eliminated, and EMI can be reduced. 
     In short, the invention provides the high frequency signal attenuation elements to attenuate the high frequency signals of the output power and output information, and integrate and ground the attenuated output power and output information of high frequency signals through the high frequency signal channel elements. Hence the load received the output power and output information is not affected by the high frequency signals. And EMI also can be reduced. 
     The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic circuit diagram of a conventional network transformer. 
         FIG. 2  is a schematic circuit diagram of a first embodiment of the invention. 
         FIG. 3  is a schematic circuit diagram of a second embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIG. 2 , the network transformer  1  to reduce EMI according to the invention has a plurality of pins at two sides connecting to two network equipment (not shown in the drawing) to transmit data. It includes a transformation unit  10 , a plurality of high frequency signal attenuation elements  30  and a plurality of high frequency signal channel elements  40 . The transformation unit  10  receives input power S 10  and input information S 11  from one network equipment (not shown in the drawing) and transforms them to output power S 20  and output information S 21 . The high frequency signal attenuation elements  30  are electrically connected to the transformation unit  10 , and receive the output power S 20  and output information S 21 , and reduce high frequency noises of the output information S 21  and output power S 20 . Then the attenuated output information S 21  and output power S 20  are transmitted to the load of the other network equipment (not shown in the drawing). The high frequency signal channel elements  40  are installed between the high frequency signal attenuation elements  30  and the load to receive high frequency signals S 30  of the output information S 21  and output power S 20 , and integrate and ground the high frequency signals S 30 . Therefore, the high frequency signals can be eliminated, and EMI also can be reduced. 
     The transformation unit  10  has a primary coil  11  and a secondary coil  12 . The primary coil  11  receives the input power S 10  and input information S 11 , and the secondary coil  12  induces the output power S 20  and output information S 21 . The output power S 20  and output information S 21  are transmitted from the secondary coil  12  to the high frequency signal attenuation elements  30  which are inductors in this embodiment to reduce the high frequency noises of the output power S 20  and output information S 21 , especially the noises between 30 MHz and 3 GHz. Thus radiation waves generated by the high frequency noises can be greatly reduced. Then the attenuated output power S 20  and output information S 21  are transmitted to the load of the other network equipment. The high frequency signal channel elements  40  are coupled in parallel with a channel linking the high frequency signal attenuation elements  30  and the load. The network transformer  1  has a ground pin  50  connecting to the high frequency signal channel elements  40 . In this embodiment, the high frequency signal channel elements  40  are capacitors of a high frequency and low impedance. Hence the high frequency signals S 30  are transmitted to the high frequency signal channel elements  40  and isolated before the attenuated output power S 20  and output information S 21  are sent to the load. Then the high frequency signals S 30  of the output power S 20  and output information S 21  are integrated and grounded through the high frequency signal channel elements  40 . 
     Moreover, in response to different information transmission requirements of the network equipment, another embodiment of the invention can be provided as shown in  FIG. 3 . In this embodiment, the network transformer  1  includes a choke coil  20  connecting to the transformation unit  10  and high frequency signal attenuation elements  30 . The transformation unit  10  has a primary coil  11  to receive input power S 10  and input information S 11 , and a secondary coil  12  to generate output power S 20  and output information S 21 . The output power S 20  is transmitted to the choke coil  20  to block AC power of the output power S 20 . Then the output power S 20  and output information S 21  pass through the high frequency signal attenuation elements  30  to reduce high frequency noises thereof, thereafter are sent to the load of the other equipment. Through the high frequency signal channel elements  40 , the high frequency signals S 30  of the output power S 20  and output information S 21  are integrated and transmitted to the ground pin  50  and the high frequency signals S 30  to be isolated. 
     As a conclusion, the invention mainly provides high frequency signal attenuation elements  30  to reduce high frequency noises of output power S 20  and output information S 21 , and high frequency signal channel elements  40  to integrate and ground high frequency signals S 30  of the attenuated output power S 20  and output information S 21 . Therefore, the load receiving the output power S 20  and output information S 21  is not affected by the high frequency signals S 30 , and EMI can be reduced. 
     While the preferred embodiments of the invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention.