FI74569B - KOPPLINGSANORDNING FOER VERTIKALAVLAENKNING AV ELEKTRONSTRAOLAR I ETT TELEVISIONSBILDROER. - Google Patents

Abstract

1. A circuit arrangement for the vertical deflection of electron beams in a television picture tube, wherein the deflection current is obtained by actuating, with line-frequency, pulse-width-modulated signals, a bipolar switch (2, 3), one contact of which is directly at reference potential and the other contact of which is connected to reference potential through a series connection consisting of a winding (8) of the line transformer, of an integrating coil (4) and of an integrating capacitor (5), one connection of the deflection winding (6) of the television picture tube being connected to a positive supply voltage (+) through a precision resistor (7), characterised in that an inductive component (4', 9) is connected in series with the integrating capacitor (5) and that the other connection of the deflection winding (6) of the television picture tube is connected to the reference potential through the series connection of the inductive component (4', 9) and the integrating capacitor (5), the inductive component being so dimensioned that it at least compensates the current through the deflection winding (6) resulting from the line-frequency residual voltage at the integrating capacitor (5).

Description

74569

SWITCHING ARRANGEMENT FOR VERTICAL DEVIATION OF ELECTRONIC BEAMS IN A TELEVISION IMAGE TUBE

The invention is based on a switching arrangement for the vertical deflection of electronic beams in a television picture tube, in which the deflection current is generated by controlling line frequency pulse width modulated signals from a bipolar switch connected to a series and a second terminal to the capacitor of the integrating member. Such a coupling is described in EP patent application 000 8263. This coupling has great advantages over the hitherto known vertical deflection coupling arrangements Ib of a television picture tube, which are manifested, for example, in the good efficiency and high reliability of the coupling. However, said switching arrangement has the disadvantage that a line frequency interference voltage occurs in the integration capacitor, which causes geometric distortions in the image. In this case, it may happen that the always-existing tolerances of the picture tube increase the geometric error so that it becomes disturbing. The error occurs so that the raster reproduced on the picture tube has an angle error that increases as you move from the top to the bottom of the image. The deviations of the horizontal line from the left edge of the image to the right edge can be up to 1 mm at the top of the image and increase up to ** · mm at the bottom of the image. This error is caused by the line frequency residual voltage in the integration capacitor, which causes a corresponding line-30 current to pass through the vertical deflection coil. This error could be reduced by enlarging the inte-groove capacitor, but this solution must be ruled out, because due to the multiple phase-shifting components in the output stage of the deflection circuit, such as the inte-35 groove coil, the integration capacitor and the vertical deflection coil, ... ..... I ! _ 2 74569 would be required when the loop gain would have to be reduced as the phase shift increases. In addition, an oversized integration capacitor would be an obstacle to a required vertical scan sweep of less than 1 ms.

The invention is based on the object of providing a solution to avoid the described geometrical error, which does not cause disadvantages to the coupling principle shown.

In the following, in connection with an exemplary embodiment, the essential features of the invention will be explained by means of a drawing.

Figure 1 shows the essential features of a vertical deflection circuit;

Fig. 2 and Fig. 3 show the signals present at the switching points drawn in the block switch diagram, and

Figure * 4 shows another switching variant.

In Fig. 1, in the control circuit 1, line-frequency vertically modulated pulses are formed, which are applied to a gate electrode of a thyristor 2, a diode 3 is connected in opposite directions in parallel with this thyristor. An integrating coil 4 is connected in series with this combination 2 and 3. as a vertical frequency triangular current passing through a vertical deflection coil 6 and a measuring resistor 7 connected in series therewith, one end of which is in the supply voltage. The integrator-25 with the coil 4 and the integration capacitor 5 is in series with the coil 8 of the line transformer of the television receiver.

Figure 2 shows the voltages and currents as they appear at the beginning of the figure. Fig. 2a shows the line frequency voltage variation U 1 of the integration coil 4.

After the return scan t ^, the diode 3 is conductive in the discharge direction for the time t ^. After this time, thyristor 2 is in the closed state. The conductivity time of the thyristor is continuously increased 74569 3 during the vertical deflection time, so that the thyristor is switched on at the bottom of the figure for a very long time, as shown in Fig. 3a. The voltage UL generates a line frequency current 1 ^ 5 through the integration coil 4 which is approximately equal to the charge current 1 ^ of the integration capacitor 5 (Fig. 2b, Fig. 3b). This current causes a parabolic voltage in the capacitor 5 according to Figures 2c, 3c. Without the operation according to the invention, this voltage would cause an additional deflection current 10 1 ^ 'to pass through the deflection coil 6, as shown in Figures 2d and 3d. This line frequency interference current causes the geometric distortions described in the introduction. This interference current can be compensated by the addition of an inductive component. A rectangular line frequency sub-voltage 15 is generated in the sub-inductance 4 'of the integration coil 4, which causes the compensating deflection current 1 ^ "according to Figs. 2e, 3e to pass through the vertical deflection coil 6. The result is the total deflection current 1 ^.

When the inductive component 4 'is formed in Fig. 1 by means of a tap Z in the integration coil 4, Fig. 4 shows another switching transformation in the case where the integration coil 4 is between the thyristor-diode combination 2 and 3 and the line transformer winding 8. In this case, an appropriately dimensioned additional inductance 9 is connected in series with the in-25 integration capacitor 5.

Claims (2)

74569 4 A switching arrangement for vertically deflecting electron beams in a television picture tube, wherein the deflection current is generated by controlling bipolar switch (2,3) connected by line frequency tree width modulated signals connected to a line transformer winding (8) and a coil (4) and a capacitor with the element in series, wherein one pole of the deflection coil (6) is connected to the measuring resistor (7) and the other terminal to the capacitor integrating, i.e. an inductive component (41.9) is connected in series with the integrating capacitor n (5). ) connected to the deflection coil (6) and that the inductive component is dimensioned so as to at least partially compensate for the current caused by the residual voltage of the line frequency of the capacitor (5) to the deflection coil (6). Coupling arrangement according to Claim 1, characterized in that the inductive component (4 ') is formed by a part of the integration coil (4) via a tap (Z) to which the deflection coil (6) is connected.