GB2199701A - Flyback transformer - Google Patents

Abstract

A flyback transformer for generating an anode voltage of a CRT including a low voltage bobbin 12 around which a tertiary coil 13 is wound, a high-voltage bobbin 15 around which a secondary coil 16 is wound, and a primary bobbin 20 disposed between the low voltage bobbin and the high voltage bobbin. <IMAGE>

Description

FLYBACK TRANSFORMER The present invention relates to a flyback transformer for generating an anode voltage of a CRT which may be used, for instance, as a picture tube in a television receiver.

More particularly, the present invention relates to an improvement to the structure of such a flyback transformer.

In a conventional CRT apparatus, there has been employed a flyback transformer for generating an anode voltage of a CRT by raisin the voltage level of a so-called flyback pulse hitch pears during horizontal Dla..;;ing periods. A typical structure of such a flyback trans-crmer employed in a prior art CRT apparatus is shown in tigs. 1 to 3.

Referring to tflese, a ferrite core 1 is inserted inside a low voltage bobbin 2: Around the outer surface of the low voltage bobbin 2, a tertiary coil 3 and a primary coil 4 are subsequently wound. Then, the low voltage bobbin 2 is inserted inside a high voltage bobbin . In turn secondary coil 6 is wound around the-outer surface of the high voltage bobbin 5, and several high voltage rectifying diodes 7 are coupled to the secondary coil 6. Finally, a high voltage lead wire 8 is extracted from the upper terminal of the secondary coil 5 to the outside of a case 9 and is connected to an anode cE CRT (not shown) to supply a high voltage.

However, in such a prior art flyback transformer, since the tertiary coil 3 is wound around the low voltage bobbin 2, and the primary coil 4 is then wound around the tertiary coil 3 so tut the tuning point of harmonic frequencies should be generated within a range between the fifth and thirteenth harmonics of a fundamental frequency, it is hard to match the tuning point critically, and this causes difficulties in producing the flyback transformer. Further, in the case when the primary coil 4 does not have an arrangement with the tertiary coil 3, that is, if the primary coil does wound with being biased or inclined for the tertiary coil 3, an excessive leakage resistance and distribution capacitance may be produced and, then the produced leakage resistance and distribution capacitance are irregular.This causes a high level ringing signal to be appeared after the period of a voltage raised flyback pulse signal. Such a high level ringing signal arfects the brightness of a displayed picture, so that a so called vertical pattern is appeared in the displayed picture and sorties the size of te displayed picture my be varied due to an increase of the va-a r.

rate of the voltage raised flyback pulse signal.

Therefore, it is an object of the present invention to provide a flyback transformer in which the tunning feint of harmonic frequencies can be generated at a highest harmonics, i.e., over a fifteenth harmornic, so that the production of the flyback transformer can be simplified.

Another object of the present ill;;enLion is to provide ? flyback transformer in which a leakage resistance and a distribution capacitance can be reduced and produced regularly so that a ringing signal can be surpressed to remove a so called vertical pattern in a displayed picture and, at the same time, to decrease the variation rate of a flyback pulse signal.

Still another object of the present invention is to provide a flyback transformer in which an unnecessary high frequency signal being generated from a secondary coil wound around a high voltage bobbin should not be induced to a tertiary coil.

The above and other objects of the present invention can be achived by a preferred embodiment in which a tertiary coil is wound around a lo voltage bobbin., and a friar coil is wound aground a primary bobbin wnicn is inserted between the low voltage bobbin and high voltage bobbin.

Still another objects and features cf the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings wherein-: Fig. 1 is a semi-cross sectional view of a prior art flyback transformer; Fig. 2 is a perspective view of a low voltage bobbin used in the flyback transformer of Fig. 1; Fig. 3 is a perspective view or a nign voltage bobbin used in the flyback transformer of Fig. 1; Fig. 4 is a graphical diagram of a flyback pulse signal and a ringing signal being cer.erated in the flyback transformer of Fig. 1;; Fig. 5 is a semi-cross sectional vie of a flyback transformer according to one preferred embodi-ent of the present invention; and Fig. 6 is a graphical diagram. of a flyback pulse signal and a ringing signal being generated in the flyback transformer of Fig. 5.

Referring now to Fig. 5, there is shown a structure of a flyback transformer according to one preferred embodiment 0 the present invention as a semi-cross sectional view, in which a ferrite core li is firstly inserted inside a low voltage bobbin 12. Around the low voltage bobbin 12, a tertiary coil 13 is wound. Then, the low voltage bobbin 12 is inserted inside a primary bobbin 20 around which a primary coil 14 is wound. In turn, P.c primary bobbin u is inserted inside a high voltage bobbin 5 around which a secondary coil 16 is wound. Finally, several high voltage rectifying diodes 17 are coupled to the secondary coil 16, and a high voltage lead wire 18 is extracted from the upper terminal cf the secondary coil 18 to the outsoe of a case 19, which will them be connected to an anode of a CRT (not shown).

In such a flyback transformer structured as above, since the primary bobbin 20 around which the primary ccil 14 is wound is disposed between the low voltage bobbin 12 and the high voltage bobbin 14, the tertiary coil 13 around the low voltage bobbin 12 and the secondary coil 16 around the high voltage bobbin 15 are spaced away from each other so that the unnecessary high frequency signal being generated from the secondary coil 16 and being induced to the secondary coil 13 can be prevented.

Further, since the primary, secondary and tertiary coils 14, 16 and 13 can be arranged with each other, not being biased or inclines, a leakage resistance anc a distribution capacitance being produced from the tertiary coil 13 can be maintained at a predetermined level and, hence, the induced voltage at the tertiary coil 13 can be stabilized.

Additionally, since the tertiary coil 13 and the primary coil 14 are separately wound around the low voltage bobbin 12 and the primary bobbin 20, respectively, an the space between the primary coil 14 and the secondary coil 16 is to be narrower, the leakage resistance and the distribution capacitance being produced from the tertiary coil 13 and the primary coil 14 can be reduced and be generated regularly.

And, according to the preferred embodiment of the present invention, the tuning point c. harmonic frequencies can be produced over a fifteenth harr.nic of a fundamental frequency.

This causes a ringing siena: to be suppressed and appeared only for a short time so that a difference of brightness of a displayed picture can be substantially disapreared, a so called vertical pattern does not substantially appeared in the displayed picture, and the size of the dIsplayed picture can be constantly maintained at a predetermined eve because the tiariation of the flyback pulse signal can De prevented.

As will be well known from the above detaile description the present invention has advantages that the high resolution G. ,-, displayed picture can be achieved since a difference of brightness and so called a vertical pattern are not appeared in the displayed picture, the size of the displayed picture can be maintained at a predetermined level, there is no need to critically adjust the tuning point of harmonic frequencies since it is produced over a fifteenth harmonic, and that the production of the flyback transformer can be simplified.

Claims (2)

1. A flybacktransformer fe generating an anode voltage of a CRT including a low voltage bobbin 12 around which a tertiary coil 13 and a primary coil 14 are subsequently wound, and a high voltage bobbin 15 around which a secondary coil 16 is wound, wherein a primary. bobbin 20 is disposed between said low voltage bobbin 12 and said high voltage bobbin 15, and said tertiary coil 13 and said primary coil 14 are wound around said low voltage bobbin 12 and said primary bobbin 20, respectively;

2. A flyback transformer for generating an anode voltage of a CRT substantially as herein described with reference to Figures 2 to 6.