JPS6122846B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flyback transformer used for supplying high DC voltage to a cathode ray tube in a TV receiver or the like, and more particularly to a flyback transformer improved so that its ringing ratio is reduced. In general, a flyback transformer consists of a primary winding that is an input winding, a secondary winding that is a high voltage output winding, and a tertiary winding that takes out signals such as AFC, AGC and secondary B power. The windings are magnetically coupled to each other and wound, and in particular, the primary winding and the tertiary winding are tightly coupled. A flyback transformer constructed in this manner is required to have a ringing ratio as small as possible in order to operate efficiently. This ringing ratio is, as shown in Fig. 1, which shows a high voltage pulse when fifth-order tuning induced on the secondary side of a flyback transformer is taken as an example.
This is the ratio between the first ringing peak value B and the sum A of the shot pulse peak value and the ringing peak value B. In other words, the ringing ratio is Rr
It refers to the value expressed as =B/A×100 (%). In conventional flyback transformers, the ringing ratio is reduced by appropriately tuning the resonance circuit between the leakage inductance and stray capacitance of the secondary winding. However, with this method, the ringing and the shot pulse change in relation to each other, making it very difficult to adjust them.Moreover, even if the peak value of the ringing is reduced below a certain value, the peak value of the shot pulse will also decrease at the same time. In addition, there was a natural limit to the improvement of the ringing ratio. The present invention has been made in view of these points, and provides a flyback transformer in which the ringing ratio can be adjusted extremely easily by completely new means, and the value can be made smaller than before. The purpose is to The specific structure is that the magnetic coupling with the primary winding is weak at both ends of the primary winding or the secondary winding, and the leakage magnetic flux of the secondary winding with respect to the primary winding is chained. At least a part of the tertiary winding is wound at the crossing position, and the tertiary winding is used so as to be rectified during the scanning period. is designed to reduce only the peak value of the ringing regardless of the relationship. An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 2, reference numeral 11 indicates a low voltage coil bobbin having a plurality of winding grooves inserted into the core 12, 13 indicates a primary winding which is dividedly wound into each of the winding grooves of this low voltage coil bobbin 11, and 14 indicates this primary winding 13. This is a tertiary winding for taking out the secondary B power source wound at both ends of the upper part, and has a loose magnetic coupling with the primary winding 13 and is placed close to the secondary winding described later. Therefore, they are wound with a thick insulating material 15 such as a resin film interposed therebetween and connected in series. Note that the winding direction of these tertiary windings 14 is arbitrary, but these tertiary windings 14
is used so that when a load is connected through the rectifier circuit, rectification is performed only during the scan period, so-called scan period rectification. The circuit that performs this scanning period rectification can have several configurations depending on the combination of the winding direction of the tertiary winding 14 and the connection direction of the rectifier elements of the rectifier circuit connected thereto. In short, the circuit configuration may be such that a rectifying element such as a diode constituting a rectifying circuit connected to the tertiary winding is not conductive during the retrace period but conductive only during the scanning period. 16 is a high voltage coil bobbin having a plurality of winding grooves fitted into the low voltage coil bobbin 11; 17 is a secondary winding that is dividedly wound in each winding groove of this high voltage coil bobbin 16; It covers the secondary winding 14 and is formed close to the tertiary winding 14. In other words, the secondary winding 17 is formed such that both ends thereof correspond to the positions where the tertiary winding 14 is wound. The flyback transformer of the present invention is basically constructed as described above. In other words, in a conventional flyback transformer, all of its tertiary windings are formed to be closely magnetically coupled to the primary winding, and its rectification method is either blanking period rectification or scanning period rectification. However, in the present invention, the tertiary winding is at both ends of the primary winding or the secondary winding,
The point where the magnetic coupling with the primary winding is loose and the leakage flux of the secondary winding with respect to the primary winding interlinks with the winding, and the tertiary winding is rectified during the scanning period and used. It has a major feature in that it has been made as follows. Next, the functions and effects of the flyback transformer configured as described above will be explained. Now, as shown in the circuit diagram of FIG. 3, the flyback transformer of the present invention has a horizontal deflection circuit 18 on the primary winding 13 side, a rectifier circuit 19 on the secondary winding 17 side, and a rectifier circuit on the tertiary winding 14 side. The circuits 20 are connected respectively.
Here, the tertiary winding 14 is connected so that its rectification method is scanning period rectification, as described above. A 15.75KHz square wave pulse signal is applied to the input side of the primary side horizontal output transistor configured in this way, and a load is connected to the tertiary winding 14 to obtain 5th order tuning. The pulse waveform induced in the next winding 17 was observed using a synchroscope. As a result, a waveform as shown in FIG. 4a was obtained, and the value of the ringing ratio determined from this waveform was 11.5%. In order to compare the flyback transformer of the present invention with the conventional one, the tertiary winding 14 in FIG. 2 is wound directly on the primary winding 13 with the insulating material 15 removed. A flyback transformer was constructed whose structure was exactly the same as that of the embodiment shown in FIG. 2, and the pulse waveform induced in its secondary winding was observed in the same manner as described above. As a result, a waveform as shown in Figure 4b is obtained, and the value of the ringing ratio determined from this waveform is
It was 17.0%. This fact shows that the flyback transformer of the present invention has a significantly improved ringing ratio compared to the conventional one.
The reason why the ringing ratio was greatly improved in this way is that only the amplitude of the ringing was reduced without any change in the shot pulse waveform, as is clear from comparing both waveforms in Figure 4 a and b. . The reason why the amplitude of this ringing has become smaller is because its frequency has become higher. The reason why only the ringing waveform has changed without any change in the shot pulse waveform is as follows. In other words, the rectification method of the tertiary winding 14 is scanning period rectification, and since the load is connected to the tertiary winding, the tertiary winding 14 is only active during the scanning period, that is, during the period when ringing occurs. This results in an alternating current short-circuit via the capacitor in the rectifier circuit. Since the tertiary winding 14 that acts in this way is placed close to both ends of the secondary winding 17, the secondary winding 14 that acts in this way is The leakage magnetic flux at both ends of the coil 17 interlinks with the tertiary winding 14. However, as described above, this tertiary winding 14 is AC-short-circuited only during the scanning period, so a current that cancels the interlinked magnetic flux flows through the tertiary winding 14 only during the scanning period, and the secondary winding 14 The leakage magnetic flux that is unavoidably generated at both ends of the winding 17 is substantially reduced only during the scanning period. On the other hand, the frequency of ringing during the scanning period is the resonant frequency of the series resonant circuit of the leakage inductance L _l of the secondary winding 17 and the stray capacitance C _S , and as is well known,

Since it is determined by the following formula, as described above, as the leakage magnetic flux of the secondary winding 17 decreases, its resonance frequency, that is, the ringing frequency increases. As above, 3
Since the secondary winding 14 is AC short-circuited only during the scanning period, the amplitude of the ringing can be reduced without any effect on the shot pulse waveform. Although the structure of the flyback transformer of the present invention and its effects have been described above, the structure of the flyback transformer of the present invention is not limited to that shown in the second figure. Rather, it is not limited to what is shown in the second figure. Rather, what is shown in the second figure is a principle embodiment for explaining the present invention, and the ringing ratio is actually designed in balance with other characteristics of the flyback transformer. The structures shown in FIGS. 7 to 7 are more practical. That is, in the case shown in FIG. 5, the tertiary winding 14 is formed in the winding grooves at both ends of the low voltage coil bobbin 11 in parallel with the primary winding 13, and the secondary winding 17 is formed in the winding grooves at both ends of the low voltage coil bobbin 11. and the tertiary winding 14.
In the case shown in FIG. 6, by raising the bottom of the winding groove in which the tertiary winding 14 shown in FIG. The one shown in FIG. 7, which improves the linkage with the leakage magnetic flux, has the tertiary winding 14 formed in the winding grooves at both ends of the high-voltage coil bobbin 16 in parallel with the secondary winding 17. . In all of these, the ringing ratio can be reduced for the same reason as the one shown in the second figure, although there are some differences in degree. In the above embodiments, each winding has been described as having a split winding, but the present invention is not limited to this, and an appropriate winding such as a solenoid winding can be applied. In addition, as in the above embodiment, all of the tertiary windings are provided at positions where the magnetic coupling with the primary winding is weak and where the secondary windings interlink with the leakage magnetic flux with respect to the primary winding. Instead, as shown in Figure 8,
It is also possible to have a structure in which the primary winding is closely magnetically coupled to the primary winding, and the windings are dispersed and connected in series. In this way, when the tertiary winding is distributed between the primary winding and the one closely magnetically coupled,
Even when the load power connected to the tertiary winding is large, the high voltage regulation does not deteriorate. In other words, all of the tertiary windings have loose magnetic coupling with the primary winding,
If the secondary winding is installed in a position that intersects with the leakage magnetic flux with respect to the primary winding, as the load power increases and the current flowing to the tertiary winding increases, the induced waveform of the secondary winding will change. Of these, 5 are for the shot pulse waveform.
As shown in Figure 9, which shows an example of the case of next-order tuning, a distortion occurs in which the right shoulder drops, which has a negative effect on high voltage regulation. In the case of dispersion between closely magnetically coupled sources, distortion of the shot pulse waveform as shown in FIG. 9 does not occur even if the load power is large. Further, the tertiary winding of the flyback transformer of the present invention is provided at both ends of the primary winding or the secondary winding, where the leakage magnetic flux with respect to the primary winding of the secondary winding is greatest. When connecting the tertiary windings provided at both ends in series as explained in the embodiment shown in the second figure, connect the connecting wires to the primary windings excluding both ends where the tertiary windings are provided. It is more effective if the magnetic flux is wound around the winding several times, since it interlinks with the leakage magnetic flux other than both ends of the secondary winding where the leakage magnetic flux is the largest. Furthermore, the tertiary windings provided at both ends of the primary winding or the secondary winding do not necessarily have to be connected in series. You can connect two loads and use each as an independent tertiary winding, or
It is also possible to use tertiary windings provided at both ends of the primary winding or the secondary winding, connected in parallel. The point is that each of the tertiary windings may be used so as to be rectified during the scanning period. The load to which the rectifier circuit is connected to the tertiary winding may be an external electric circuit or may be only an impedance element such as a resistor.
In this way, when the load connected to the tertiary winding is an impedance element, the tertiary winding is connected to the secondary B
It can also be used not for the purpose of extracting power but merely for the purpose of improving the ringing ratio. In this way, if the tertiary winding is not used for the purpose of taking out the secondary B power supply to be supplied to an external electric circuit, but is used only to improve the ringing ratio, the tertiary winding should be connected to the A rectifier circuit and a load such as an impedance element can be integrated with a flyback transformer. Furthermore, when an impedance element such as a resistor is connected as a load, a tertiary winding that extracts signals such as AFC and AGC can also be used. Various embodiments of the flyback transformer of the present invention have been described above, but the point is that the magnetic coupling with the primary winding is weak and the primary At least a part of the tertiary winding may be wound at a position interlinked with the leakage magnetic flux of the secondary winding with respect to the winding, and the tertiary winding may be used in a manner that rectifies the tertiary winding during the scanning period. There are various configurations that satisfy this requirement in addition to the embodiments described above, and the present invention includes all of them. By having the flyback transformer of the present invention configured as described above, it is possible to reduce only the amplitude of the ringing without affecting the shot pulse in any way, and the adjustment is extremely easy, thereby reducing the value of the ringing ratio. This has the excellent effect of making it much smaller than before. Furthermore, when such a flyback transformer is incorporated into a TV receiver, it is possible to suppress unnecessary radiation to an extremely low level.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a pulse waveform for explaining the ringing ratio, Fig. 2 is a cross-sectional view of a main part of a flyback transformer according to an embodiment of the present invention, and Fig. 3 is a diagram showing the effects of the flyback transformer of the present invention. FIG. 4 is a diagram showing the induced waveform of the secondary winding of the flyback transformer in the mounted circuit diagram of FIG. 3, where a is the one according to the present invention and b is the conventional example. FIGS. 5 to 8 are partial sectional views of main parts showing other embodiments of the flyback transformer according to the present invention, and FIG. 9 is a diagram showing pulse waveforms for explaining high pressure regulation. 11...Low voltage coil bobbin, 12...Core, 1
3... Primary winding, 14... Tertiary winding, 15... Insulating material, 16... High voltage coil bobbin, 17... Secondary winding, 18... Horizontal deflection circuit, 19, 20... Rectifier circuit .

Claims (1)

[Claims] 1 At both ends of the primary winding or secondary winding, the tertiary At least a part of the winding is wound, and these three
A flyback transformer characterized in that the secondary winding is used so as to be rectified during a scanning period.