US2153655A - Cathode ray tube control circuits - Google Patents

Description

April 1'1, 1939. Y R. URTEL ET AL 2,153,655

CATHODE RAY TUBE CONTROL CIRCUITS Filed July l5, '1956 DEFLEGTING Con.

DFLEcrma con.

ATTORN EY Patented Apr. 11, 1939 UNIED STATES TENT OFFECE CATHODE RAY TUBE CONTROL CIRCUITS Application July 15, 1936, Serial No. 90,706 In Germany July 8, 1935 1 Claim.

The invention relates broadly to control circuits for cathode ray tubes and more specifically to a circuit arrangement whereby the production of the cathode ray beam in the tube may be blocked or diminished when the deflecting means for the tube are being energized in such fashion as to return the beam to some initial or base point from a position towhich it has been previously denected.

This is particularly important Where the cathode ray tube is employed as a television receiving element and where the beam has swept across one line of the picture and must be returned to the beginning of the line without alecting the picture detail. If the beam is allowed to sweep back across the fluorescing screen with any intensity, the iiuorescent screen is brightened for thatline and hence picture detail is affected as well as a flicker effect being produc-ed.

According to the invention, a portion of the energy used to return the beam to the initial point, or an energy operating synchronously therewith, is joined in seiies to a rectiiier, in this instance, a dry rectifier, which is triggered by a biasing arrangement, as for instance, a steady voltage, so that the rectified energy produces a voltage in excess of the triggering voltage and the excess is used as a blocking voltage in the control circuit for the cathode ray beam.

The invention will best be understood by reference to the accompanying drawing in which:

Figure 1 shows a schematic embodiment of our invention.

Figure 2 shows a modified arrangement according to Figure 1, and

Figure `3 shows still another embodiment of our invention.

Referring to Fig. l, I0 represents a coil connected in the deflection energy circuit of the cathode ray tube, and may be the magnetic deflection coil of the tube itself. Inductively coupled thereto is a coil I I across which is connected a loading resistor I2. Joined in series with this parallel arrangement is a rectifier I3, a resistance I5 and a biasing voltage I4. The direction of the induced Voltage in the -coil II when the beam is being returned to its initial position is indicated by the positive and negative signs thereon. Joined in series with the resistor I5 is the secondary of a transformer I9 whose primary is energized by the picture signals with which th-e cathode ray beam is modulated, the control electrode of the tube I6, said control electrode being indicated as 20, a biasing voltage I8 and the cathode of the tube Il.

(Cl. Z50-27) The circuit arrangement shown in Fig. 1 functions in such a fashion that during the energizing of the deiiecting members of the tube I6 in such manner as to return the beam to its initial position, there appears in the coil II a voltage, the 5 direction of said voltage being indicated by the positive and negative signs on the diagram. The direction of this voltage is such as to oppose that of the biasing battery I4 and hence, if it is greater than the Value of the voltage I 4, it will cause a l0 current to flow through the series circuit comprising the coil II, rectifier I3 and resistor I5. The resistor I5 being connected in series with the cathode I'I of the tube I6, the secondary of transformer I9 and a control electrode 20 of the tube, 16 the control electrode 20 will be biased with respect to the cathode of the tube by an amount equal to the voltage drop across resistor I5, and hence if the value of this voltage be suiiicient, the cathode ray beam would be blocked. 20

When the dellecting members of the tube have returned to a state wherein the cathode ray beam, if produced, would impinge at the initial point, the dir-ection of the deecting voltage changes so as to sweep the beam back again linearly across 25 the screen. During this time the voltage induced in coil I I would be in a'direction opposite to that indicated by the signs, hence coil II would tend to oscillate at its natural frequency due to the collapse of current through the rectifier. The re- 30 sistor I2 acts as a damping member to suppress the production of' a voltage o-n the positive half of the oscillation which might exceed the Value of the biasing battery I4 and hence cause a rectified current whose Voltage drop across the re- 35 sistor I 5 would tend to either substantially reduce or entirely block the production of the cathode ray beam.

The arrangement shown in Fig. 2, substitutes an auto-transformer arrangement for the two 40 coils I0 and Il of Fig. 1. In this case the potentials opposite to that in the arrangement shown in Fig. 1 and therefore the rectifier connections and biasing member are changed accordingly, that is to say reversed. The voltage drop through 45 resistor I5 is opposite to that in Fig. 2 and therefore the control electrode and the cathode are suitably connected thereto or, in other words, the connections to the resistor I5 are, in Fig. 2, reversed in position from those shown in Fig. 1. 50 The operation of the circuit is the same.

Referring to Fig. 3, the resistor I5 has been supplanted in position by the rectier I3 and it is the potential across the rectifier and not across the resistor which serves the control elements of 55 the tube. In this case, in order to limit the current passing through the rectifier, it is advisable to provide a resistor element 2| connected as shown in the diagram. The direction of the potential source I4 and the rectier in Fig. 3 correspond to those in Fig. 1. However, it is obvious that the circuit may be modified in the manner suggested in Fig. 2.

What We claim is:

An apparatus for controlling the production of a cathode ray beam, a cathode ray tube having an electromagnetic beam deection coil for deflecting the cathode ray beam comprising a deflection voltage circuit, a deection coil energized from said circuit, electrical means coupled to the coil connected to the deection Voltage circuit so that the coupled coil forms a transformer secondary and derives energy from the deflecting coil, a first series electrical circuit comprising said coupled electrical means, a rectifier and a resistor, a second series circuit comprising a control electrode of the cathode ray tube, the aforementioned resistor, the cathode of the cathode ray tube and 10 a source of modulating potential.

RUDOLF URTEL. ROBERT ANDRIEU.

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