Electric lamp and discharge devices: systems – Cathode ray tube circuits – Power supply from deflection circuit source
Reexamination Certificate
2002-08-29
2003-12-09
Wong, Don (Department: 2835)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Power supply from deflection circuit source
C336S145000, C336S183000
Reexamination Certificate
active
06661187
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Related Art
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.
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 HV 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
.
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
.
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.
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.
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
.
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.
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.
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
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.
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.
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 o
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