DE1062348B - Arrangement to protect cathode ray tubes, preferably vidicon tubes, in the event of failure of the deflection devices - Google Patents

Description

GERMAN

In the case of cathode ray tubes, there is known to be the risk that if the deflection devices fail, for example due to tube damage, the cathode ray stops at one point on the screen and passes through Overload damage to this point occurs. To protect against such damage is already a large number of solutions are known. However, there are cathode ray tubes in which the from Cathode ray swept area is already impaired when the ray remains in one place for a short time can be. It is therefore in contrast to the usual picture recording tubes with these arrangements effective protection is only possible through immediate beam suppression. The task at hand consists in creating an arrangement with which, in the event of failure of the deflection devices, the opposite Overloading of very sensitive signal plates of vidicon tubes with only a small amount of components let protect.

The invention consists in that two transistors acting as switches are provided, which the Horizontal and vertical deflection voltages supplied in this way are that they only allow the beam current to flow during the working period of the cathode ray tube allow. In one embodiment of the invention are in the cathode circuit to be protected Tube two n-p-n transistors are provided, those on the base electrode from the horizontal and vertical deflection device Voltages obtained are supplied in such a way that during the working period of the cathode ray tubes a negative rest bias voltage is compensated, which a blocking of the beam current causes. When using p-n-p transistors, these are between the cathode of the one to be protected Cathode ray tube and a positive voltage source turned on, and their control electrodes are voltages obtained from the deflection device supplied in such a way that during the working period of the Cathode ray tube a positive reverse voltage is switched off from the cathode. The present arrangement 4 <> tion has the advantage that it enables the beam current to flow simultaneously during the return of the scanning beam blanking / in order to obtain a reference value: of the signal for image black and disturbances of the To prevent signal build-up during the return.

The arrangement allows immediate protection of the Pick-up tube in the event of failure of a tilting device.

Exemplary embodiments of the invention are explained with reference to the figures. ■

The embodiment shown in Fig. 1 allows the protection of a Vidicon-Bildabtaströhrc, which is labeled V. The npn transistors Tr ₁ arrangement for protection

of cathode ray tubes,

preferably vidicon tubes,

if the deflection devices fail

Applicant:
Siemens & Halske Aktiengesellschaft,

Berlin and Munich,
Munich 2, Wittelsbacherplatz 2

Dipl.-Ing. Hans Breunig, Karlsruhe-Hagsfeld,

and Dipl.-Ing. Heinz-Günther Walter, Karlsruhe,

have been named as inventors

and Tr ₂ are in series between the cathode K of the tube V and ground parallel to the resistor R ₁ . Via the voltage divider R _3i R ₄ , a positive voltage is applied to the cathode K of the tube V as soon as the transistors Tr ₁ and Tr _{2 are} connected to the negative, negative bias voltage U ₂ , which in the idle state via the resistors R ₁ and R ₂ the basis is laid are locked. Via the capacitors C ₁ and C ₂ , the transistors are supplied with voltages taken from the horizontal and vertical deflection devices, which during the operating period of the deflection devices open the transistors to such an extent that they are operated on the saturation characteristic. The resistor R _{3 also} serves to limit the current. The diodes D ₁ and D _{2 have the} effect that the pulse voltage is superimposed on the quiescent bias voltage U _2. The relationships occurring here are shown in FIG

The protective effect in the event of a control pulse failure is _{not delayed by the time constants of the capacitors C 1} and C ₂ , the resistors R ₁ and R ₂ and the corresponding input resistances of the transistors, since with a suitable circuit arrangement a negative pulse is created in the event of a sudden failure of the deflection current, which causes the locks the respective transistor immediately.

In. Fig. 3 shows a simpler circuit arrangement with pnp transistors Tr ₃ and Tr ₁ . The designations of the other switching elements correspond to those in Fig. 1. During the operating period, however, the transistors are blocked by a positive pulse, which has the effect that none

909 579/337

positive voltage can reach the cathode K. It is also possible to control the Wehnelt cylinder instead of the cathode in a similar manner.

Claims (3)

Patent claims: 1. Arrangement to protect cathode ray tubes, preferably vidicon tubes, in the event of failure of the deflection devices, characterized in that two transistors acting as switches are provided are to which the horizontal and vertical deflection voltages are applied in such a way that they only allow the jet current to flow during the cathode ray tube operating period. 2. Arrangement according to claim 1, characterized in that two n-p-n transistors in the Cathode circuit of the tube to be protected are provided, those on the base electrode from the Horizontal and vertical deflection obtained voltages are supplied so that during a negative rest bias voltage is compensated for during the working period of the cathode ray tube, which causes a blockage of the jet stream. 3. Arrangement according to claim 1, characterized in that that two p-n-p transistors between the cathode of the cathode ray tube to be protected and a positive voltage source are switched on, the S expensive electrodes from the Deflection device obtained voltages are supplied so that during the working period of Cathode ray tube a positive reverse voltage is switched off from the cathode. 1 sheet of drawings ÄS QiK) 57Q / 337 7.