Patent Publication Number: US-2003230992-A1

Title: Fly back transformer

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention relates to a fly back transformer, and more particularly, to an improved fly back transformer capable of integrating a bleeder resistor to a high-voltage bobbin to downsize an article, reducing manufacturing cost, and readily drawing a focusing voltage during a process of winding high-voltage wires around a high-voltage bobbin so as to promptly conform with various article conditions.  
       [0003] 2. Description of the Related Art  
       [0004] As well known in the art, a Fly Back Transformer (hereinafter will be referred to as FBT) is an apparatus mounted within a Braun Tube or Cathode Ray Tube (CRT) in a TV set or monitor for multiplying a pulse voltage from a horizontal output circuit for tens of times to generate a DC high voltage.  
       [0005]FIG. 1 shows a high-voltage stabilizing circuit in use for a general FBT. The high-voltage stabilizing circuit comprises a horizontal output circuit P receiving a horizontal synchronous pulse and generating a sawtooth wave, the first coil L 1  with one end connected to an output terminal of the circuit P and the other end connected to a power source B+, the second coil L 2  connected with a plurality of high-voltage rectifier diodes D 1  to D 5  for generating a high voltage HV, a bleeder resistor B/R stabilizing the high voltage TV from a high-voltage terminal of the second coil L 2 , a focusing circuit F outputting a plurality of focusing voltages and the third low-voltage circuit L 3 .  
       [0006]FIG. 2 is an exploded perspective view of a typical FBT. As shown in FIG. 2, a low-voltage bobbin  110   a  has a low-voltage wire wound around the same for plural times to constitute the first coil. A high-voltage bobbin  110  has an inner central opening into which the low-voltage bobbin  110   a  is inserted in a superposing manner. A plurality of high-voltage wires  113  are wound around the high-voltage bobbin  110  to constitute the second coil and a plurality of high-voltage rectifier diodes (hereinafter will be referred to as diodes) are connected to the high-voltage bobbin  110  in series. A focusing section  130  has a focusing pack  131  internally receiving a bleeder resistor  132 . The focusing section  130  is mounted to one side of an FBT housing internally receiving the low- and high-voltage bobbins  110   a  and  110  and has a plurality of knobs for adjusting focusing voltages of a CRT. An anode cap supplies high voltage generated from a high-voltage terminal of the high-voltage bobbin  110  to the CRT through an anode cable  139 .  
       [0007] The number of high-voltage wires  113  are wound around the high-voltage bobbin  110  of the above configured FBT  100  as follows: As shown in FIGS. 2 and 3, the first one of insulating films  114  is wound around the outer circumference of a hollow cylindrical bobbin body  111  and the first one of the high-voltage wires  113  is wound with a coil winder (not shown) around the first insulating film  114 . The second one of the insulating films  114  is wound around the first wound high-voltage wire  113  and the second one of the high-voltage wires  113  is wound around the second insulating film  114 . The above procedures are repeated in a radial outwardly to form a plurality of high-voltage coil layers, in which the outermost one of the insulating films  114  is wound around the outside surface of the outermost high-voltage coil layer so as to insulate the outermost high-voltage coil layer. Upon applying electric power, this configuration allows the potential difference among the wound coil layers to generate a high voltage, which is transferred through the anode cable  139  to the CRT.  
       [0008] In the high-voltage coil layers laminated in multiple interposing the insulating films  114  around the high-voltage bobbin  110 , both ends of the high-voltage wires  113  each are alternately connected between an upper terminal pin  117  in any one of upper pin supporting portions  115  and a lower terminal pin  118  in any corresponding one of lower pin supporting portions  116 . The upper pin supporting portions  115  are provided in plurality in an upper portion of the bobbin body  111 , and the lower pin supporting portions  116  are provided in plurality in a lower portion of the bobbin body  111 . Lead wires extended from both ends of the diodes  119  are electrically connected in series with one another.  
       [0009] Further, the focusing pack  131  of the focusing section  130  is internally mounted with a Printed Circuit Board (PCB) where an adjustable resistor portion is printed for adjusting the plurality of focusing voltages. The bleeder resistor  132  is electrically connected with the high-voltage terminal of the high-voltage bobbin  110  to drop the high voltage therefrom to a certain level of about 18 or 32% of the initial level, and fixedly mounted to one side of the focusing pack  131  with a holder  133 .  
       [0010] The first pin terminal  137   a  and the second pin terminal  137   b  are fixedly installed in the focusing pack  131 . The first pin terminal  137   a  is electrically connected with the first long pin  117   a  by inserting the first long pin  117   a  into the first pin terminal  137   a , in which the first long pin  117   a  is an upper terminal pin of the high-voltage terminal outputting the high voltage. The second pin terminal  137   b  is electrically connected with the second long pin  117   b  by inserting the second long pin  117   b  into the second pin terminal  137   b , in which the second long pin is another upper terminal pin disposed between the high-voltage terminal and a low-voltage terminal for drawing out the focusing voltage. The first and second pin terminals  137   a  and  137   b  are connected with the bleeder resistor  132  via cables  136   a  and  136   b , and the high-voltage bobbin  110  is connected by its low-voltage terminal with an Automatic Brightness Limiter (ABL) circuit.  
       [0011] In such a conventional configuration as set forth above, however, since the focusing section  130  is necessarily provided with an additional space and holder for fixedly installing the bleeder resistor  132  in one side of the focusing pack  131 , there are restrictions in downsizing the FBT  100  or reducing manufacturing cost.  
       [0012] Further, where the first long pin  117   b  corresponding to the first long pin  117   a  fixed in position is displaced in order to adjust the position of drawing the focusing voltage, it is needed to identically displace the second pin terminal  137   b  into which the second long pin  117   b  is correspondingly inserted. This creates a very complicated and troublesome assembly process while failing to promptly coping with various design requirements from consumers as drawbacks.  
       SUMMARY OF THE INVENTION  
       [0013] The present invention has been made to solve the conventional problems as set forth above and it is therefore an object of the present invention to provide an FBT capable of readily displacing the drawing position of focusing voltage during the operation of winding high-voltage wires around a high-voltage bobbin so as to promptly correspond to various article conditions.  
       [0014] It is another object of the invention to provide an FBT capable of connecting one end of a high-voltage terminal and a drawing terminal of focusing voltage to a bleeder resistor and integrating the bleeder resistor to a high-voltage bobbin without using long pins and pin terminals so as to downsize final articles as well as reduce manufacturing cost.  
       [0015] According to an aspect of the invention to obtain the above objects, it is provided a fly back transformer for providing a DC high voltage and at least one focusing voltage to a CRT in a TV set or monitor, comprising: a horizontal output section for receiving horizontal synchronous pulse and generating sawtooth wave; a low-voltage bobbin having a low-voltage wire wound around the outside surface thereof to form a first coil; a high-voltage bobbin having a plurality of high-voltage wires wound for plural times interposing insulating films around the high-voltage bobbin to form a second coil having a number of high-voltage coil layers and a plurality of high-voltage rectifier diodes each connected in series between each of plural upper terminal pins and each of plural lower terminal pins; a focusing pack having a PCB internally mounted thereto by molding insulating resin, the PCB being printed with an adjustable resistor to adjust the at least one focusing voltage, and a focus input terminal for receiving the focusing voltage; a bleeder resistor detachably fixed in position to the high-voltage bobbin, and having an upper end electrically connected with one of the upper terminal pins corresponding to a high-voltage terminal to output the final high voltage generated from the high-voltage bobbin and a lower end electrically connected to the focus input terminal; and a focus-drawing wire disposed between the first one of the high-voltage coil layers and the last one of the high-voltage coil layers, and having one end connected with the upper terminal pin to draw a voltage generated between the high-voltage terminal and a low-voltage terminal of the high-voltage bobbin and the other end connected with the lower end of the bleeder resistor electrically connected with the focus input terminal of the focusing pack.  
       [0016] According to another aspect of the invention to obtain the above objects, fly back transformer for providing a DC high voltage and at least one focusing voltage to a CRT in a TV set or monitor, comprising: a horizontal output section for receiving horizontal synchronous pulse and generating sawtooth wave; a low-voltage bobbin having a low-voltage wire wound around the outside surface thereof to form a first coil; a high-voltage bobbin having a plurality of high-voltage wires wound for plural times interposing insulating films around the high-voltage bobbin to form a second coil having a number of high-voltage coil layers and a plurality of high-voltage rectifier diodes each connected in series between each of plural upper terminal pins and each of plural lower terminal pins; a focusing pack having a PCB internally mounted thereto by molding insulating resin, the PCB being printed with an adjustable resistor to adjust the at least one focusing voltage, and a focus input terminal for receiving the focusing voltage; a bleeder resistor detachably fixed in position to the high-voltage bobbin, and having an upper end inserted into an inserting member in an upper side of the bobbin body and a lower end inserted into a settling member in a lower side of the bobbin body, the upper end being electrically connected with one of the upper terminal pins corresponding to a high-voltage terminal and the lower end being electrically connected with the focus input terminal; and a focus-drawing wire disposed between the first one of the high-voltage coil layers and the last one of the high-voltage coil layers, and having one end connected with the upper terminal pin to draw a voltage generated between the high voltage terminal and a low-voltage terminal of the high-voltage bobbin and the other end connected with the lower end of the bleeder resistor. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0017] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
     [0018]FIG. 1 shows a high-voltage stabilizing circuit in use for a general FBT;  
     [0019]FIG. 2 is an exploded perspective view of a general FBT;  
     [0020]FIG. 3 schematically shows a bobbin section and a focusing section of a general FBT;  
     [0021]FIG. 4 is an exploded perspective view of an FBT of the invention;  
     [0022]FIG. 5 schematically shows a bobbin section and a focusing section of an FBT of the invention; and  
     [0023]FIG. 6A shows the state of winding high-voltage wires around a high-pressure bobbin of the FBT of the invention; and  
     [0024]FIG. 6B shows the state of winding a focus-drawing wire around a high-pressure bobbin of the FBT of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
     [0025] Hereinafter the present invention will be described in more detail.  
     [0026]FIG. 4 is an exploded perspective view showing a bobbin section and a focusing section in an FBT adopting a drawing method of focusing voltage according to the invention, FIG. 5 schematically shows the bobbin section and the focusing section of the FBT of the invention, and FIGS. 6A and 6B show the state of winding high-voltage wires and a focus-drawing wire around a high-pressure bobbin of the FBT of the invention.  
     [0027] As shown in FIGS.  4  to  6 B, the FBT  1  of the invention comprises a bobbin section with a high-voltage bobbin  10  and a low-voltage bobbin  10   a  disposed in a superposing manner. Around the low-voltage bobbin  10   a , a low-voltage wire is wound for plural times to constitute the first coil where an external power source is applied. The high-voltage bobbin  10  comprises a hollow cylindrical bobbin body  11  with an inner central opening into which the low-voltage bobbin  10   a  is inserted, and a plurality of high-voltage wires  13  are wound around the outside surface of the hollow cylindrical bobbin body  11  interposing insulating films  14  to form a plurality of coil layers thereby constituting the second coil.  
     [0028] The bobbin body  11  is provided with a plurality of upper pin supporting portions  15  each mounted with an upper terminal pin  17  in the upper end, a plurality of lower pin supporting portions  16  each mounted with a lower terminal pin  18  in the lower end, and diodes  19  each connected in series between the each upper terminal pin  17  and the each lower terminal pin  18 .  
     [0029] A PCB (not shown) having an adjustable resistor portion is sealed to a focusing pack  31  defining a focusing section  30  with insulating resin to adjust the focusing voltage of a CRT. The focusing pack  31  is provided with a plurality of knobs  31   b  mounted in the front, and on the other hand, a focusing connector terminal  31   a  and an anode connector terminal  39   a  each exposed from the rear for receiving the focusing voltage and a high voltage.  
     [0030] The bobbin body  11  of the high-voltage bobbin  10  is mounted with a bleeder resistor  32  printed with a resistor pattern  32   a  on one outside face. The bobbin body  11  is provided in an upper side with an inserting member  33   a  into which the bleeder resistor  32  is inserted by its upper end and in a lower side with a settling member  33   b  into which the bleeder resistor  32  is settled by its lower end. Adjacent to the inserting member  33   a  and the settling member  33   b , the bobbin body  11  is provided with upper and lower pin grooves  33   c  and  33   d  which U-shaped upper and lower terminal pins  35  and  36  are respectively inserted into and fixedly disposed in.  
     [0031] The resistor pattern  32   a  of the bleeder resistor  32  is electrically connected by its upper end via a lead wire  34   a  with the last upper terminal pin  35  corresponding to a high-voltage terminal for outputting the high voltage generated from the high-voltage bobbin  10 , and by its lower end via a lead wire  34   b  with the last lower terminal  36  corresponding to the high-voltage terminal. The last lower terminal pin  36  is electrically connected with the second end of a focus-drawing wire  2  which is connected by the first end with an intermediate one of the upper terminals  17  so as to receive the focusing voltage from the intermediate upper terminal  17  disposed between the high-voltage terminal and a low-voltage terminal in the high-voltage bobbin  10 .  
     [0032] The focus-drawing wire  2  is disposed between the first and last high-voltage coil layers during a process of forming a plurality of high-voltage coil layers by alternately winding the high-voltage wires  13  interposing the insulating films  14  around the outside surface of the bobbin body  11  with a coil winder (not shown).  
     [0033] That is to say, in the process of forming the second coil by winding one of the insulating films  14  around the outside surface of the high-voltage bobbin  10  and the first one of the high-voltage wires  13  for plural times around the first insulating film  14  to form the first coil layer, winding another one of the high-voltage wires  13  for plural times around the first coil layer interposing the second insulating film  14 , and repeating the above steps for plural times, the focus-drawing wire  2  is disposed according to the following process steps of: winding one of the insulating films  14  around any high-voltage coil layer predetermined for forming the focus-drawing coil layer, winding the focus-drawing wire  2  with the first end connected to the intermediate upper terminal pin  17  in one direction, soldering the second end of the focus-drawing wire  2  with the last lower terminal pin  36  connected with the lower end of the bleeder resistor  32 , and electrically connecting the last lower terminal pin  36  with the focus connector terminal  31   a  to feed the drawn focus voltage to the focusing pack  31 . After winding another one of the insulating films  14  around the focus-drawing wire  2  around the bobbin body  11 , the remaining high-voltage coils  13  are alternately wound to complete the process of forming the second coil.  
     [0034] The focus-drawing wire  2  like this is connected in one-to-one correspondence with one end of the at least one intermediate upper terminal pin  17  between the last upper terminal pin  35  corresponding to the high-voltage terminal of the high-voltage bobbin  11  and the first one of the upper terminal pins  17  corresponding to the low-voltage terminal. The focusing voltage drawn from the intermediate upper terminal pin  17  is smaller than the high-voltage generated from the high-voltage terminal  35 , and increases as the position of the intermediate upper terminal pin  17  approaches the high-voltage terminal  35  from the low-voltage terminal.  
     [0035] Further, the focus-drawing wire  2  is preferably wound in the same direction as the high-voltage wires  13  wound around the high-voltage bobbin  11  so as to efficiently obtain the high-voltage. Also, the focus-drawing wire  2  may be wound in the shortest distance between the intermediate upper terminal pin  17  and the last lower terminal pin  36  or around the bobbin body  11  at least once.  
     [0036] The inserting member  33   a  and the settling member  33   b  of the bobbin body  11  for fixing the bleeder resistor  32  are preferably installed in the high-voltage terminal side generating the high-voltage so as to facilitate electric connection between the bleeder resistor  32  and the upper and lower terminal pins  35  and  36  in the high-voltage terminal side.  
     [0037] The last upper terminal pin  35  is a U-shaped pin member fixed to the upper pin groove  33   c , and integrally has the first pin  35   a  connected with the lead wire  34   a  led out from the upper end of the resistor pattern  32   a  in the bleeder resistor  32  and the second pin  35   b  connected with one end of the last one of the diodes  19 . The last lower terminal pin  36  is also a U-shaped pin member fixed to the lower pin groove  33   d , and integrally has the first pin  36   a  connected with the lead wire  34   b  led out from the lower terminal of the resistor pattern  32   a  in the bleeder resistor  32  and the second pin  36   b  connected with one end of the focus-drawing wire  2 .  
     [0038] The following discussion will show the operation of the invention.  
     [0039] In the FBT  1  of the invention, applying sawtooth wave to one end of the first coil formed in the low-voltage bobbin  10   a  and electric power to the other end thereof, the sawtooth wave applied to the first coil of the low-voltage bobbin  10   a  is stepped up by the high-voltage coil layers forming the second coil of the high-voltage bobbin  10 .  
     [0040] At the same time, the sawtooth wave is rectified by the diodes  19  each connected in series between each of the upper terminal pins  17  and each of the lower terminal pins  18  to output a high voltage (e.g. about 25 kV) to the last upper terminal pin  35 . The high voltage output is inputted into a high-voltage output terminal such as an anode cap connected to the CRT through an anode cable  39  and simultaneously toward the bleeder resistor  32  electrically connected with the last upper terminal pin  35 . The high voltage inputted to the bleeder resistor  32  is stabilized owing to voltage drop up to about 18 to 32% of the original level while passing through the resistor pattern printed in the bleeder resistor  32 .  
     [0041] Further, the focus-drawing wire  2  is electrically connected via the insulating films  14  among the high-voltage coil layers between the lower end of the bleeder resistor  32  and the intermediate upper terminal pin  17  which is mounted between the first upper terminal pin  17  in the lower-voltage terminal side and the last upper terminal pin  35  in the high-voltage terminal side. The high-voltage is partially drawn out through the focus-drawing wire while being stepped up as approaching from the low-voltage terminal to the high-voltage terminal, the drawn-out focusing voltage is inputted to the PCB through the focusing connector terminal  31   a  of the focusing pack  31 , and the focusing voltage input is adjusted by the adjustable resistor portion of the PCB.  
     [0042] In the meantime, where it is desired to design the FBT  1  to input a higher focusing voltage to the focusing pack  31  at the consumer&#39;s request, the first end of the focus-drawing wire  2  is connected with the intermediate upper terminal pin  17  more adjacent to the high-voltage terminal during the process of winding the high-voltage wires  13  around the high-voltage bobbin  10 . On the other hand, for the purpose of designing the FBT  1  to input a lower focusing voltage to the focusing pack  31 , the first end of the focus-drawing wire  2  is connected with the intermediate upper terminal pin  17  more adjacent to the low-voltage terminal.  
     [0043] As set forth above, the invention provides the bleeder resistor to be integrally installed in the high-voltage terminal side of the high-voltage bobbin and connected by the upper end with the high-voltage output terminal and by the lower end with the focus-drawing wire for drawing out the focusing voltage so that the entire size of an FBT article can be significantly reduced to realize downsizing, reduce manufacturing cost and shorten manufacturing process as well.  
     [0044] Further, the invention allows the position of drawing out the focusing voltage to be simply changed during the process of winding the high-voltage wires around the high-voltage bobbin so as to promptly cope with various focusing voltage requirements from consumers thereby enhancing the productivity as an effect.  
     [0045] Although the invention has been shown and described with reference to the certain preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.