FR2698480A1 - High-voltage transformer and lighting circuit using this high-voltage transformer. - Google Patents

Abstract

a) The invention relates to a high-voltage transformer and a lighting circuit using this transformer. b) High-voltage transformer and lighting circuit characterized in that the transformer comprises primary windings and a secondary winding wound on a bar form (2) of core or coil, the lighting circuit comprising a device (4 ) controlled by a high-frequency signal, the high-voltage transformer and a discharge lamp (FL1) connected to the secondary winding (SW2) of the transformer. c) The invention is applicable to liquid crystal display panels.

Description

i "High-voltage transformer and lighting circuit using this

high-voltage transformer "

BACKGROUND OF THE INVENTION

  FIELD OF THE INVENTION The present invention relates to a high-voltage transformer and a lighting circuit used

  This high-voltage transformer is used to light discharge lamps such as fluorescent lamps. More particularly, the invention relates to a high-voltage transformer and a lighting circuit used

  reading this high-voltage transformer suitable for

  use on a portable type of small device

  LCD displays (hereinafter referred to as

after DCL).

  PRIOR ART One of the conventional lighting circuits widely used to light discharge lamps such as fluorescent lamps, is a circuit of

  induction coil for lighting tube Except

  start-up circuit (eg a lighting tube) using an alternating

  Such a lighting circuit basically consists of three circuits, a phase circuit whose resistance is connected in series with a discharge lamp, a delay circuit connected in series with an inductor, and a circuit of

  phase connected in series with a capacitor.

  However, a lighting circuit or an ignition transformer of a fluorescent lamp used in background lighting of a DCL mounted on portable television sets or on equipment

  portable electronic devices such as computers,

  usually reads as a primary power source batteries such as dry batteries, or rechargeable secondary batteries In this case, a DC voltage + VDC is switched to turn on a

  FL fluorescent lamp, as shown in Figure 6.

  In the conventional arrangement shown in Fig. 6, DC voltage + Vcc is supplied to terminal TE by a primary or secondary power source. For example, one end of a 200 p F CH induction coil is connected to this terminal

  TE, while the other end of the induction coil

  CH is connected to the central CT jack of the first

  primary winding PW, of a high-voltage transformer

Tl voltage.

  The terminal TE is connected to the bases of a pre-

  transistor Q 1 and a second transistor Q 2 by

  resistors R 1 and R 2, as well as at the second winding

  primary PW 2 of the high-voltage transformer T 1.

  The first transistor Q 1 and the second

  transistor Q 2 are grounded by their transmitters

  their collectors are connected to the two terminal windings of the first primary winding PW 1 of the high-voltage transformer T 1 A capacitor C 1 is connected in parallel between the

two windings of terminals.

  The secondary winding SW 1 of the transforma-

  high-voltage transformer T1 is connected to the cathode filament

  than and to the anode filament of a FL fluorescence lamp via a capacitor ballast C 2

(from about 33 pF to 100 pF).

  The above arrangement is a kind of DC-DC converter in which the first transistor Q 1 is biased by the second primary winding PW 2 of the high-voltage transformer T 2 to

  turn on the first transistor Q1, and the voltage

  naked + Vcc applied to the central tap CT induces a current i 1, thus inducing a given voltage in

  secondary winding SW, of the high-voltage transformer

Tl voltage.

  When the second transistor Q 2 is turned on, a

  current i 2 is induced by the DC + Vcc voltage

  plotted at the central CT tap, so that a

  given dimension can be induced in the winding

  secondary SW 1 of the high-voltage transformer T 1.

  For the high-voltage transformer mounted

  in the conventional ignition circuit indicated below.

  above, one can use an EI type core, a UI type core, a pot type core, a type core

  EE, or the like Typically referring to the trans-

  high-voltage trainer shown in Figure 7A, the

  core 1, if it is small in size, has a high

  The other typical transformer, shown in FIG. 7B, comprises a large core 1 having a height H of about 20 mm, a width of about 20 mm and a diameter OD of about 1 mm.

  W about 25 mm and a length L of about 30 mm.

  It is possible to make the fluorescent lamp

  smaller FL, for example of essentially

  similar to that of the image frame of a DCL

  tative, and to give this lamp a diameter of about

  7 to 8 mm However, the ballast capacitor C 2

  necessary for secondary winding SW, trans-

355 Wdutas

  high-voltage trainer T 1, must be capable of

  carry a high voltage of about 2 kV, and so

  make the transformer high-voltage large-size

the and cheap.

  When the high voltage transformer T 1 above and the capacitor C 2 are built on a printed substrate, the substrate is made under a

  very large size corresponding to a width of about

  20 mm, a length of about 100 mm and a

  However, there are many difficulties in achieving the overall layout.

  comprising a high-voltage transformer and a circuit

baked compact lighting.

  The object of the present invention is to create a high-voltage transformer which is freed from

  problems mentioned above, ie, in other

  term, which is made in a small size and that provides a lighting circuit to dispense with any capacitor ballast that would be

  otherwise responsible for size increases.

SUMMARY OF THE INVENTION

  According to one aspect of the present invention,

  this concerns a high-voltage transformer, which is

  characterized in that it comprises primary coils and a secondary coil wound on a

  core or coil bar, and a support element

  port disposed at one end or at both ends of said core or coil bar shape to hold it, said support member being provided with input and output terminals of the primary coils

or the secondary coil.

  According to a second aspect of the invention, this

  this concerns a high-voltage transformer, which is

  characterized in that it comprises primary coils and a secondary coil wound on a core or coil bar form, a C-shaped support member for holding both ends of this form as a core or coil bar, and a discharge lamp mounted in a bridge on both legs of said C-shaped support member. According to a third aspect of the invention, the present invention relates to a lighting circuit for

  transform a continuous voltage from a source

  this direct current, in a high-frequency signal for igniting a discharge lamp, characterized in that it comprises a control device controlled by

  the high-frequency signal, a high-voltage transformer

  voltage consisting of primary coils and a secondary coil wound on a core bar form

  or coil, this transformer being connected to the ex-

  output end of the control device, and a

  discharge lamp connected directly to the coil se-

  Condenser of the high-voltage transformer.

  According to the first aspect of the invention,

  It is possible to make a transformer

  sufficiently small so that it can be

  along the side edge of a guide plate of

  background lighting light of a DCL.

  According to the third aspect of the invention,

  It is still possible to make a transformer

  te-tension small enough that it can be placed along the side edge of a guide plate

  background lighting light of a DCL.

  Finally, according to the third aspect of the invention,

  the lighting circuit is characterized in that

  that a support element intended to support a trans-

  high-voltage trainer including the lightning circuit

  rage, is placed on the side edge of a bottom lighting light guide plate of a panel of

liquid crystal.

  In the lighting circuit according to the third

  In the second aspect of the invention, the control circuit for controlling the high-voltage bar-structured transformer is connected to the primary side of the high-voltage transformer so that it can be excited by a high-frequency signal from the high-voltage transformer. a high-frequency oscillator via a switching circuit, thereby permitting

  connect the discharge lamp directly to the winding

  of the high-voltage transformer Ain-

  if, this high-voltage transformer can operate as a transformer of leak-flow type that can be

  to dispense with any high-voltage capacitors

  directly to the discharge lamp, and allows the

  lighting circuit to be built in integrated circuits.

  so that it can be very compact.

BRIEF DESCRIPTION OF THE DRAWINGS

  The present invention will now be described

  by way of example but not limited to

  tif, with reference to the accompanying drawings in

  which: Figure 1 represents a transformer

  high voltage according to the invention and the lighting circuit

rabies using this one;

  Figure 2 represents another transformation

  high-voltage generator according to the invention and the lighting circuit using the latter; Figure 3 is a diagram of an embodiment of the high-voltage transformer according to the invention; FIG. 4 is a diagram of an embodiment of the lighting circuit in which is

  mounted the high-voltage transformer according to the invention.

  FIG. 5 is an exploded perspective view of a liquid crystal TV set incorporating the lighting circuit using the high-voltage transformer according to the invention; Figure 6 is a circuit diagram of a lighting circuit in which is incorporated a conventional high-voltage transformer; and Fig. 7 is a perspective view

  of a conventional high-voltage transformer.

  DETAILED DESCRIPTION OF THE INVENTION

  Before describing the high-voltage transformer

  voltage of the invention with reference to FIGS. 1 to 3, the general structure of the lighting circuit of the invention will be explained with reference to FIG. 4.

  In Figure 4, a high frequency oscillator

  this 3 oscillates a high-frequency wave signal

rectangular at about 110 kHz.

  The signals from the oscillator 3 are respectively applied to a first circuit

  "no" IN 1, and to a circuit constituted by the branch-

  series of a second "no" circuit IN 2 and a

third circuit "no" IN 3.

  The output of the first "no" circuit IN 1 is

  applied to the base of a first communication transistor

  Q 3 via a base resistor R 3, and the output of the third "no" circuit IN 3 is

  applied to the base of a second switching transistor

  Q 4 through a basic resistor

  R 4 The normal waveform part of the os signal

  cillation is applied to the base of the second transistor

  4, because the second circuit and the third

  second "no" circuit IN 2 and IN 3 are connected in cascades

  from this base, while the inverted waveform portion of the oscillation signal is applied to the

  base of the first switching transistor Q 3.

  Transmitters of the first transistor

  mutation Q 3 and second switching transistor Q 4

  are each connected to the mass, while their

  The readers are respectively respectively connected to the base of a first control transistor Q 5 and to the base of a second control transistor Q 6. The collector of the first switching transistor Q 3 is connected to the collector of the second control transistor Q 6. by a resistor R 6, while the collector of the second switching transistor Q 4 is connected to the collector

  of the first control transistor Q 5 by a resistor

this R 5.

  Transmitters of the first transistor

  Mande Q 5 and the second control transistor Q 6 are each connected to the ground, while their collectors are respectively connected respectively to the cathodes of diodes CD 1 and CD 2 The anodes of the diodes CD 1 and CD 2 are each connected to ground The collectors are each connected to one of the terminals of the primary windings PW 3 and PW 4 of a high-voltage transformer

  T 2 which will be described below, while the other former

  tremities of the primary windings PW 3 and PW 4 are connected in series with one another at a point from where the central tap CT: In addition to this central tap CT 1 a DC voltage + Wcc = + 6 is applied. V. The high voltage transformer T 2 comprises a core 2 consisting of a ferrite core bar of the manganese type. The primary and secondary windings PW 3, PW 4 and the winding SW 2 are wound on this core bar. 2 through

  of a given insulation material A fluorescent lamp

  FL 1 is connected directly in series with the winding

  Secondary winding SW 2, while the primary and secondary windings are roughly connected to each other Thus, the secondary winding SW 2 is connected to the ground by one end and connected by the other end to an electrode. the fluorescent lamp FL 1, while one end of the other secondary winding is connected to the other electrode of the lamp.

fluorescent pe FL 1.

  The fluorescent lamp FL 1 serving as a discharge lamp is a small fluorescent lamp for the background illumination of a DCL, and has, for example, an ignition voltage of approximately 700 V, a discharge voltage of 360 V and a tube current of about 7 m A. The high-voltage transformer T 2 used with the circuit indicated above, can be constructed in a form of coil such as that shown in Figure 3 The coil 6 shown in Figure 3

  which has a substantially cylindrical configuration

  drique, is made of a synthetic resin such

  diazoterephthalate, polycarbonate or

  lyester, or glass Both ends of the coil 6 serve as support members 7 and 8 and are provided with pins 9 and 10 for connection to the terminals of the primary windings PW 3, PW 4, and the winding

secondary SW 2-

  The coil 6 is provided on its outer surface with

  of a number of necklaces between

  which primary and secondary windings PW 3,

  PW 4, as well as the secondary winding SW 2, are

  rolled onto the spool 6 In this form of

  the number of turns of the primary windings PW 3 and PW 4 in 0.2 mm diameter wire is 20,

  while the number of turns of the secondary winding

  SW 2 wire diameter of 0.05 mm in diameter, is 3000.

  It will be noted that the coil 6 has a diameter of 3.5 mm It will also be noted that the total length L of the coil 6 is 30 mm, that the maximum diameter

  Coil coil 6 is 5 mm, and that

  at the bar of a ferrite core 2 of 1.5 mm

  diameter and 30 mm in length is introduced

  fixed hole in the central cylindrical bore of the

6.

  The high-voltage transformer T 2 has

  as the structure indicated above can form a leakage transformer structure so simple that it must presumably give rise to a flow of leaks, because the magnetic coupling is coarse of the

  primary windings PW 3, PW 4 and the

  secondary bearing SW 2, are wound on both

  ends of the bar coil 6 A transformation

  leaker is too large to be used in a high-voltage transformer

  intended in particular for the background lighting of a

  The reason is that when the primary windings and the secondary winding are wound on an ET type core,

  must use a longer magnetic path to

the coarse coupling.

  The use of a leakage transformer

  as a high-voltage transformer leads to an increase

  secondary current with a corresponding increase in the leak flow giving rise to a drop in the voltage across the secondary, and thus reducing the current increase. Thus, the secondary current can be kept constant in

  a given range of charges, which makes it possible

  the large capacitor C 2 connected to the secondary side and designed to withstand the high voltage This effect contributes greatly to make the circuit

compact lighting.

  We will now describe in more detail the

  the way in which the lighting circuit operates

rabies shown in Figure 4.

  The high-frequency signal of 110 kHz supplied by the high-frequency oscillator 3 is inverted by the output of the first "no" circuit IN 1, and applied to the base of the first switching transistor Q 3 by the base resistor R 3, in order to polarize this base.

  In the same way, the high signal

  frequency appearing at the exit of the third cir-

  cured "no" IN 3 through the second circuit and the third "no" circuit IN 2 and IN 3, is applied to the base of the second switching transistor Q 4 by the base resistor R 4, so as to bias this

based.

  Thus, the first switching transistor Q 3 and the second switching transistor Q 4 are switched on and off according to the positive pulses and

  negative of the high-frequency signal.

  When the first switching transistor Q 3 is turned on, the first control transistor Q 5 is controlled so that the current i 2 coming from the voltage source + Vcc can pass through the central tap CT 1 of the primary winding of the transformer T 2, and can flow through the primary winding PW 3 as well as through the collector and the emitter of the Q control transistor 6. When the second switching transistor Q 4 is turned on, the second control transistor Q 6 is controlled so that the current i 3 from the

  source of voltage + Vcc can pass through the

  center CT 1 of the primary winding of the transformer

  high-voltage generator T 2, and can then flow through the primary winding PW 4 as well as through the collector and the emitter of the control transistor Q 6

  It will be noted that the diodes CD, and CD 2 ab-

Sorbent overcurrent.

  When a switching excitation voltage

  corresponding to the frequency of the

  frequency, is applied to the primary windings PW 3 and PW 4 of such a high-voltage transformer T 2,

  a secondary voltage is induced on the coil side

  Secondly, SW 2 is roughly coupled with

  primary elements PW 3 and PW 4 Although the fluorescent lamp

  Resident FL 1 is connected directly to the winding

  secondary SW 2, the secondary current can remain con-

  stant because of the great inductance of leakage,

  so that the fluorescent lamp FL: can be controlled

  directly without the use of any capacitor.

  To constitute the high voltage transformer

  With the arrangement shown above, the primary windings and the secondary winding are wound on the coil bar form 6 provided at both ends with support elements 7 and 8 forming an end portion. In the following, another arrangement of the high-voltage transformer T 2 that can still be effectively used according to the invention will be described in detail with reference to the

Figures 1 and 2.

  Figures LA to E show a device

  in which the lighting circuit above

  is integrated into the high-voltage transformer

  res l A to l C respectively represent a plan view, a front view and a view of the right side of the

  disposition; FIG. 1D is a sectional view of

  the line C-C 'of Figure 1B; and Figure 1E is a sectional view along the line A-A 'or B-B' of

  FIG. 1B In all FIGS. 1A to 1E, the same

  my parts as those in Figure 3 are designated

by the same references.

  A pin 10 of substantially anatomical shape

  3, is placed at the right end of a spool 6, and a cylindrical support element 8 is fitted on the spool 6, this support element comprising a network of grooves 12 from which son We will obviously notice that

  the support element 8 can receive a core 2.

  The coil 6 is of similar construction to that described with reference to FIG.

  that it is divided by five necklaces 11

  primary and secondary windings are

  These portions are more precisely rolled over. Support element 8 comprises two grooves from which wires are removed, as illustrated in FIG. 1E, and this support element is disposed at the right end of

  the coil 6 As shown in FIG.

* Seen a sectional view along the line C-C 'of Figure 1 B, the collar li A is provided on its upper part, six grooves 12 which are removed son.

  A support element 13 made of synthetic resin

  that or other similar material

  sufficiently high insulation properties, is adapted on the left end of the coil 6 As can be seen in Figures 1 B and E which show a sectional view along the line A-A 'or B-B' of the figure

  1B, the support element 13 is constituted by a

  column 13 A comprising at its upper end

  six grooves 12 from which wires are removed.

  part 13 A is further provided with a cavity 13 B

  both a diameter substantially equal to that of the core

  3 A portion of column portion 13A, with the exception of

  grooves 12, is made in a flat form.

  te to constitute a terminal block 13 C on which pins 14 are mounted to form terminals of

  connection to the winding wires of the transforma-

  This terminal block 13 C is pierced with a female screw thread 15 which is screwed onto a

core adjustment screw 2.

  The primary windings or coils PW 3 and PW 4 of the high-voltage transformer T 2 are wound on the coil 6 between the support element 13 and the first collar li A, while the given number of turns of wire is formed on the coil 6 between each of the remaining collars II and the support member 8 to thereby form the secondary winding or coil

  SW 2 Typically, this high-voltage transformer pre-

  feels a total length L: of about 37 mm, and a

maximum diameter D of 5 mm.

  Next, an 18A printed circuit board about 6 mm wide, about 50 mm long and about 1 mm thick, receives a pattern on the support member 13 of the high voltage transformer T 2, and connects to an integrated circuit 18 B forming a lighting circuit 18, by the pins 14 mounted on the block

  13 C is thus obtained a length L 2 of approx.

  40 mm, and the high-voltage transformer with its lighting circuit has a width of 5 mm or

  less, and a length of 100 mm or less.

  that reference 18 D designates an assembly.

  An example of a liquid crystal TV receiver

  compacts using such a high-voltage transformer

  voltage T 2 and an integrated lighting circuit, is shown in Figure 5 Figure 5 shows the TV receiver in an assembled state Reference 22 designates a rear frame of the TV receiver, this frame being integrated with a cover 16 to form a portable TV receiver frame Reference 17 designates batteries used as a power source for powering the TV receiver, these batteries also supplying a FL 1 downlight fluorescent lamp, as well as an integrated lighting circuit 18 and the

  high-voltage transformer T 2 The control circuit

  TV is integrated on a printed circuit board (not shown).

  felt) and is housed in the rear frame 22.

  Reference 19 designates a DCL panel mounted in a window 20 of the cover 16 A light guide plate 21 is disposed on the rear surface of the panel 19 The light guide plate

  21 is provided on its upper end with a lamp

  fluorescent background lighting FL 1, and on its lower end, the high-voltage transformer T 2 and the integrated lighting circuit 18, both

  being shown in one piece in Figure 1 A-

  if, the overall device has a diameter

  about 5 mm and a length of about 77 mm.

  According to this example, the transformer

  voltage and lighting circuit can be reduced from the standard size of 20 mm (width) x

  mm (length) x 20 mm (height), up to a

  5 mm (diameter) x 77 mm (length), which allows

  so puts them into the guide plate of

light 21.

  Referring next to FIG.

  represents another structure of mounting the trans-

  trainer high voltage T 2 used on the circuit of

  lighting in this example As illustrated, the trans-

  high-voltage trainer T 2 and the FL 1 bottom-field fluorescent lamp are bridged on two

  feet 24 A and 24 B of a support element 22 essential-

  C-shaped, and an integrated circuit 18 B

  the lighting circuit is mounted on the bottom of the support element 22 The two legs 24 A and 24 B are respectively provided with grooves 23 A and 23 B in

  which the light guide plate is

  As can be seen in FIG. 5, the fluorescent lamp FL:, the high-voltage transformer and the lighting circuit are placed below the

light guiding plate 21.

  Although the invention has been described with reference to several preferred embodiments,

  it is obvious that many changes can be made

  material, shape, structure, size, layout and application without leaving

  of the scope of the invention indicated above.

Claims (4)

R E V E N D I C A T IO N S   1) High-voltage transformer, characterized   in that it comprises primary coils and a booster   a secondary member wound on a core or coil bar form (2), and a support member (8) disposed at one or both ends of said core or reel bar shape to hold the same, this support element being provided with input and output terminals of the primary coils or the secondary coil.   2) High-voltage transformer, characterized   in that it comprises primary coils and a booster   secondary belt rolled up on a bar form   core or coil, a support element (22) in form   Me de C to maintain both ends of this form as a core or coil bar, and a discharge lamp (FL 1) bridged on both legs of this C-shaped support member.   3) High-voltage transformer according to the   claim 1 or 2, characterized in that this transformation   high-voltage meter is placed on the side edge of a light guide plate (21) of   background of a liquid crystal panel.   4) Lighting circuit for transforming a DC voltage from a DC source into a high frequency signal for igniting a discharge lamp, characterized in that it comprises a   control device (4) controlled by the high signal   te-frequency, a high-voltage transformer (T 2)   consisting of primary coils and a secondary coil   rolled onto a core bar (2)   or coil, this transformer being connected to the ex-   output end of the control device, and a discharge lamp connected directly to the coil   secondary (Sw 2) of the high-voltage transformer.   Lighting circuit according to claim 4, characterized in that a support element for supporting a high voltage transformer comprising the lighting circuit is placed on the side edge of a light guide plate.   background lighting of a liquid crystal panel.