Patent Publication Number: US-2005141247-A1

Title: Transformer with a plurality of coils in the secondary side

Description:
FIELD OF THE INVENTION  
      The present invention relates to a transformer, and in particular to a transformer; wherein a secondary side of the transformer includes two coils. Each of the coils has one grounded end. The currents of the two grounded ends of the two coils are opposite. The two coils are coupled to the same coil or different coils of the primary side of the transformer. Each the two coils has a non-grounded end. The two non-grounded ends are connected to two ends of a load. A voltage difference of the two non-grounded ends is the sum of the voltage differences of the two coils.  
     BACKGROUND OF THE INVENTION  
      With reference to  FIG. 1 , a prior art DC to AC inventor is illustrated. In this prior art, a DC input  1  serves for inputting DC current. An inductor L 1  is used to filter the high frequency components to transfer to the DC input end  1 . A push pull pair includes a transistor Q 5  and a transistor Q 6 , where transistor Q 5  is an NPN transistor and transistor Q 6  is a PNP transistor. The base of the transistor Q 5  is connected to the inductor L 1  through a resistor R 13  and the base of the transistor Q 6  is connected to the inductor L 1  through a resistor R 12 . The emitters of the two transistors are grounded. The collectors of the two transistors are connected to the two ends of a capacitor C 14 . Thereby, the two transistors are impossible to be “on” at the same time. That is to say that at a time, only one transistor turns on.  
      The prior art circuit further comprises a transformer PT 1 . A primary side of the transistor PT 1  include three coils, Y 11 , Y 12  and Y 13 . Each of the coils Y 11  and Y 12  has an end connected to the collectors of the transistor Q 5  and transistor Q 6  and the other ends of the coils Y 11  and Y 12  are connected to the DC inputs. The two ends of the coils Y 13  are connected to the bases of two transistors Q 5  and Q 6 . Thereby, the primary side sides of the transformer is formed as an oscillating circuit by the coils Y 11 -Y 13  and the capacitor C 14 .  
      The positive cycle of the oscillating circuit will actuate the transistor Q 5  and turn off the transistor Q 6 . Contrary, the negative cycle of the oscillating circuit will actuate the transistor Q 6  and turn off the transistor Q 5 . Thereby, outputs of the push-pull circuit are AC current.  
      The secondary side of the transformer PT 1  includes only one coil Y 2 . The coil ratios of the primary side to the secondary side are several tens to several hundreds. Thereby, the secondary sides of the transformer can output voltages of several hundreds to several thousands. One end of the coil Y 2  is grounded and the other end is connected to one end of the capacitor C 10  so as to filter out the DC components.  
      A load can be connected to the other end of the capacitor C 10  and the ground so that the AC voltage from the secondary coil is applied to the load. For example, the load may be a cold cathode ray tube. Thereby, the voltage from the coil at the secondary side can be applied to the cold cathode ray tube so as to make the cold cathode ray tube to light up.  
      However above said prior art provides only one voltage which is too high to be damage the DC to AC inverter or the load installed at the secondary side of the transformer.  
     SUMMARY OF THE INVENTION  
      Accordingly, the primary object of the present invention is to provide a transformer. A secondary side of the transformer includes two coils. Each of the coils has one grounded end. The currents of the two grounded ends of the two coils are opposite. The two coils are coupled to the same coil or different coils of the primary side of the transformer. Each the two coils has a non-grounded end. The two non-grounded ends are connected to two ends of a load. A voltage difference of the two non-grounded ends is the sum of the voltage differences of the two coils.  
      Furthermore, the present invention further provides a DC to AC inverter which comprises: a DC input for inputting DC current; an inductor for filtering the high frequency components; a push pull transistor pair including a first transistor and a second transistor, where the first transistor is an NPN transistor and the second transistor is a PNP transistor; the emitters of the two transistors are connected; the collectors of the two transistors being connected to two ends of a capacitor set; transformer having a primary side and a secondary side; the primary side of the transistor including three first coils; each of two selected first coils having an end connected to the collectors of the first and second transistors and the other ends of the first coils being connected to the DC inputs; the two ends of the other first coils being connected to the bases of two transistors; and the secondary side of the transformer includes two second coils coupled to the primary side.  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  shows the circuit diagram of the prior art DC to AC inverter.  
       FIG. 2  shows the circuit diagram of a DC to AC inverter in the first embodiment of the present invention.  
       FIG. 3  shows the wave diagram in the first embodiment of the present invention, wherein voltages at two ends for connecting a load are measured.  
       FIG. 4  shows the circuit diagram of a DC to AC inverter in the second embodiment of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      In the following, the preferred embodiment of the present invention will be described with reference to the drawings. In all the specification, like elements are numerated by the same numbers.  
      Referring to  FIG. 2 , the first preferred embodiment of the present invention will be described herein.  
      A DC input  1  serves for inputting DC current. An inductor L 2  is used to filter the high frequency components to transfer to the DC input end  1 . A push pull pair includes a transistor Q 11  and a transistor Q 12 , where for example, the transistor Q 11  may be an NPN transistor and the transistor Q 12  may be a PNP transistor. The base of the transistor Q 11  is connected to the inductor L 2  through a resistor set R 43  and the base of the transistor Q 12  is connected to the inductor L 2  through a resistor set R 45 . In this embodiment, each of the resistor sets R 43  and R 45  include three parallel connected resistors which are used to reduce the electric load so as to prevent from damage. The emitters of the two transistors are grounded. The collectors of the two transistors are connected to the two ends of two capacitor C 12  and C 13  which are connected in parallel. Thereby, the two transistors are impossible to be “on” at the same time. That is to say that at a time, only one transistor turns on.  
      The circuit further comprises a transformer T. A primary side of the transistor T include three coils, Y 11 , Y 12  and Y 13 . Each of the coils Y 11  and Y 12  has an end connected to the collectors of the transistor Q 11  and transistor Q 12  and the other ends of the coils Y 11  and Y 12  are connected to the DC inputs. The two ends of the coils Y 13  are connected to the bases of two transistors Q 11  and Q 12 . Thereby, the primary side of the transformer is formed as an oscillating circuit by the coils Y 11 -Y 13  and the capacitor C 12 .  
      The positive cycle of the oscillating circuit will actuate the transistor Q 11  and turn off the transistor Q 12 . Contrary, the negative cycle of the oscillating circuit will actuate the transistor Q 12  and turn off the transistor Q 11 . Thereby, outputs of the push-pull circuit are AC current.  
      The secondary side of the transformer includes two coils Y 21  and Y 22 . The coil ratios of the primary side to the secondary side are several tens to several hundreds. Thereby, the secondary sides of the transformer can output voltages of several hundreds to several thousands. One end of each of the coils Y 21  and Y 22  is grounded and the other end is connected to one end of each of a plurality of capacitors C 19 , C 20 , C 21  for coil Y 21  and a plurality of capacitors C 22 , C 23 , C 24  for coil Y 22  so as to filter out the DC components. The other ends of the coils Y 21  and Y 22  are grounded. The other ends of the capacitors C 19  and C 22  are connected to a first load, the other ends of the capacitors C 20  and C 23  are connected to a second load, and the other ends of the capacitors C 19  and C 22  are connected to a third load. The loads may be for example, cold cathode ray tubes. Thereby, the voltage from the coil at the secondary side can be applied to the cold cathode ray tubes so as to make the cold cathode ray tubes light up.  
      Referring to  FIG. 3 ,  FIG. 3  shows the wave diagram in the first embodiment of the present invention, wherein the voltages of two points between two sides of a load are measured by two channels, channel 2 and channel 3 and thus two voltage waves are shown in the drawings. The RMS (root mean square) voltages of the channels 2 and 3 are 545V and 664V. Moreover, the two voltage waves have opposite phases (that is, the phase differences of the two waves are 180 degrees. This is the exact result of push-pull transistor pair. Thus if the load is a cold cathode ray tube. The voltage difference at two sides of the cold cathode ray tube is the addition of the voltage wave with a peak value of 1209.  
       FIG. 4  shows the circuit diagram of a DC to AC inverter in the second embodiment of the present invention. A DC input  1  serves for inputting DC current. An inductor L 3  is used to filter the high frequency components to transfer to the DC input end  1 . A push pull pair includes a transistor Q 13  and a transistor Q 14 , where transistor Q 13  is an NPN transistor and transistor Q 14  is a PNP transistor. The base of the transistor Q 13  is connected to the collector of transistor Q 14  through a resistor set R 60  and the base of the transistor Q 14  is connected to the collector of the transistor Q 13  through a resistor set R 63 . In this embodiment, each of the resistor sets R 63  and R 60  include three parallel connected resistors which are used to reduce the electric load so as to prevent from damage. The emitters of the two transistors are grounded. The collectors of the two transistors are connected to the two ends of two capacitor C 36  and C 37  which are connected in parallel. Thereby, the two transistors are impossible to be “on” at the same time. That is to say that at a time, only one transistor turns on.  
      The circuit further comprises a transformer T. A primary side of the transistor T include two coils, Y 15 , and Y 16 . Each of the coils Y 15  and Y 16  has an end connected to the collectors of the transistor Q 13  and transistor Q 14  and the other ends of the coils Y 15  and Y 16  are connected to the DC inputs. One end of the coil Y 15  is connected to the collector of the transistor Q 13 , and the other end thereof is connected to the inductor L 3 . One end of the coil Y 16  is connected to the collector of the transistor Q 14 , and the other end thereof is connected to the inductor L 3 .  
      The positive cycle of the oscillating circuit will actuate the transistor Q 13  and turn off the transistor Q 14 . Contrary, the negative cycle of the oscillating circuit will actuate the transistor Q 14  and turn off the transistor Q 13 . Thereby, outputs of the push-pull circuit are AC current.  
      The secondary side of the transformer includes two coils Y 23  and Y 24 . The coil ratios of the primary side to the secondary side are several tens to several hundreds. Thereby, the secondary sides of the transformer can output voltages of several hundredth to several thousandth. One end of each of the coils Y 23  and Y 24  is grounded and the other end is connected to one end of each of a plurality of capacitors C 42 , C 43 , C 44  for coil Y 23  and a plurality of capacitors C 45 , C 46 , C 47  for coil Y 24  so as to filter out the DC components. The other ends of the coils Y 23  and Y 24  are grounded. The other ends of the capacitors C 42  and C 45  are connected to a first load, the other ends of the capacitors C 43  and C 46  are connected to a second load, and the other ends of the capacitors C 44  and C 47  are connected to a third load. The loads may be for example, cold cathode ray tubes. Thereby, the voltage from the coil at the secondary side can be applied to the cold cathode ray tubes so as to make the cold cathode ray tubes light up.  
      The present invention is thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.