DE1272340B - Circuit arrangement for obtaining a control voltage from a television signal - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

H04n

German class: 21 al-33/50

Number: 1272 340

File number: P 12 72 340.9-31 (F 48786)

Filing date: March 26, 1966

Opening day: July 11, 1968

The invention relates to a circuit arrangement for obtaining a control voltage from a television signal carried in a main channel, from this signal itself or from its components a reference voltage is obtained and a control voltage is derived therefrom in a first secondary channel which controls an amplifier stage located in the main channel, the television signal or its - preferably obtained by peak rectification - extreme value via a second secondary channel is fed to the first secondary channel and the delay of the caused by the second secondary channel Control process is smaller than the delay caused by the first secondary channel, according to the patent 1 242 674.

In one embodiment of the circuit arrangement according to the main patent, the television signal or the voltage obtained by peak rectification is supplied to a level selector, which only lets through signal components which are greater than a predetermined threshold value. These signal components are supplied to the first secondary channel via the second secondary channel and via a condenser. It will the smoothing of the control voltage output via the first secondary channel is not impaired as long as the level selector does not let any signal components through.

The invention relates to an improved and simplified development of the proposed circuit arrangement.

In a circuit arrangement for obtaining a control voltage from one in a main channel guided television signal, in the case of this signal itself or from its components in a first secondary channel a control voltage is derived and an amplifier stage located in the main channel regulates, with the TV signal or its extreme value - preferably obtained by peak rectification is fed via a second secondary channel to the first secondary channel and that through the second The delay in the control process caused by the secondary channel is smaller than that caused by the first secondary channel Delay is, according to patent 1242,674, according to the invention, the second secondary channel contains an arrangement with threshold characteristic, which is parallel to the resistance of the time constant element in the first secondary channel is connected, and is the capacitor lying with one connection at the circuit point of the time constant member with the other terminal at a fixed potential, such that when If the threshold value is exceeded, the resistor bridges and the capacitor with less delay than is reloaded via the resistance.

Circuit arrangement for extraction

a control voltage from a television signal

Addendum to the patent: 1 242 674

Applicant:

Television G. m. B. H.,

6100 Darmstadt, Am Alten Bahnhof 6

Named as inventor:
Dipl.-Ing. Emil Sennhenn,
6100 Darmstadt-Arheilgen

In addition to the smaller number of switching elements in the second secondary channel than in the exemplary embodiment the circuit arrangement according to the invention has the circuit arrangement already proposed the advantage that it is with a suitable dimensioning of the switching elements in the second auxiliary channel can achieve that after the rapid compensation of signal jumps in the direction of white over the second Secondary channel the delayed entry via the first secondary channel into the stable one, due to the signal level after the signal jump given operating state from the black direction and therefore in the television picture is practically not discernible.

The invention will now be explained in more detail with the aid of the figure.
The television signal 2 is fed via terminal 1 and via the capacitor 6 to the base of the transistor 7 (of type 2N1613), which forms an impedance converter with the resistors (6.8 kOhm). This is connected via terminals 9 or 10 to the positive pole (+ 12VoIt) or to the negative pole (-12VoIt) of an operating voltage source. The direct current component of this video signal is kept constant by means of a clamping stage, which consists of transistor 11 (type SFT 229), resistor 12 (220 kOhm), potentiometer 13 and capacitors 14 (0.1 μΩ) and 15 (10 μΨ) is formed. Horizontal-frequency square-wave pulses 17 are supplied via terminal 16,

809 569/401

whereby the emitter-collector path of the transistor 11 during the duration of the square-wave pulses 17 becomes conductive and the circuit point 18 is connected to a constant potential. This constant Potential of z. B. 0.35 volts is set using the potentiometer 13, the ends 19 and 20 are connected to corresponding voltages.

From the emitter of transistor 7, the television signal is fed to transistor 22 (type 2 N1613), in whose emitter circuit the capacitor 23 is arranged. This capacitor 23 is thus during the Duration of the image signal components charged to the respective extreme value.

The capacitor 23 is charged to a constant potential at periodically recurring times. It is therefore connected to ground via a controllable valve 25 (transistor of the SFT 229 type) and via the resistor 26 (22 ohms). The emitter-collector path of the transistor 25 is used as a controllable valve, the base of which is fed via terminal 27 to a sequence of vertical- frequency pulses 28 via the capacitor 29 (5 μΈ) . The base of the transistor 25 is connected to ground via the resistor 31 (220 kOhm). When the capacitor 23 is recharged, a voltage drop occurs across the resistor 26, from which the control voltage is subsequently derived.

The pulse-like voltage drop across resistor 26 is amplified using transistor 32 (type 2 N 708) and resistors 33, 34 (1 kOhm each) and 35 (4.7 kOhm) and from the collector of transistor 32 to an impedance converter with the transistors 36 (type 2 N 708), 37 (type SFT 229) supplied with complementary conductivity. In this way, a signal (peak amplitude 10V _ss ) is generated at circuit point 38, the course of which is largely similar to the voltage drop taken from resistor 26.

In order to derive a control voltage from the signal in circuit point 38, this signal is via the capacitor 41 (0.1 μΡ) of the base of the transistor 42 (type BCY 80) supplied; by means of a clamping circuit 43, the potential of the pulse base kept constant. At the base of the transistor 42 there is therefore a voltage curve whose Pulse base remains permanently at the same potential, whereas the remaining part of the voltage curve shifts proportionally to the corresponding extreme values of the image signal components. the Transistors 42 and 42 'with resistors 44 and 44' are connected as impedance converters; from the emitter of the transistor 42 ', the control voltage 47 is output via the resistor 45.

The clamping pulses that take effect in node 50 must have a vertical frequency. They are generated in the clamping step 43. This clamping step 43, like the valve 25, is therefore supplied with the same vertical-frequency pulses 28. The clamping stage 43 consists of the transistors 51, 52 (both of the type OC141), of the resistors 53 (470 kOhm), 54 (2.2 kOhm) and of the capacitors 55 (30OpF), 56 (2nF) and 57 (0 , 2 μΈ). Terminals 58 and 59 are connected to voltages of +12 volts and -12 volts, respectively.

By means of the circuit arrangement described so far, depending on the Peak rectification obtained and applied to the capacitor 23 voltage derived a control voltage and via a first secondary channel I and via terminal 5 to the video amplifier (not shown) fed.

According to the invention, the capacitor 46 of the time constant element is located in the first secondary channel I on the one hand at circuit point 68 and on the other hand at a fixed potential. The output of the second secondary channel II is also connected to circuit point 68. The secondary channel II contains a condenser 71 in series with a diode 72 acting as a threshold value arrangement, which is connected by a resistor 73 (20 kOhm) is bridged. Its input is like resistor 45 to the emitter of the transistor 42 'connected.

The mode of action is as follows: occurs through a signal jump in the direction of white at the emitter resistor 44 'of transistor 42' and thus a positive voltage jump across resistor 45, which is greater than the starting voltage of the diode 72, the normally blocked diode 72 becomes conductive and transmits the voltage jump at the capacitor 23 with a small delay while bypassing the resistor 45 to the capacitor 46 and thus to the output 5 of the circuit arrangement. The control process therefore continues immediately after the occurrence of the charge reversal following the signal jump, and the control voltage reduces the gain of the regulated amplifier stage in the main channel. In the output signal of the regulated amplifier stage, only a very short white pulse occurs, which practically does not interfere. Is the The voltage difference across the resistor 45 has become smaller than the starting voltage of the diode 72, so it blocks this again the way via the second secondary channel, and the remaining voltage difference is equal slowly with the higher delay of the first secondary channel, until the capacitor 46 the dem has assumed the control voltage corresponding to the new signal level.

The point in time of the transition from control with a small time constant via the second secondary channel on the first secondary channel with a larger time constant can be determined by the dimensioning of the circuit arrangement to be influenced. In contrast to the embodiment already proposed in the main patent the circuit arrangement, it can be achieved that the running into the stable, through the first Secondary channel given operating state from the direction of black of the regulated signal takes place, which is in the television picture practically does not appear disturbing.

Claims (2)

Patent claims: 1. Circuit arrangement for obtaining a control voltage from one in a main channel guided television signal, from this signal itself or from its components in a first Secondary channel, a control voltage is derived and an amplifier stage located in the main channel regulates, the television signal or its - preferably obtained by peak rectification - Extreme value is fed to the first secondary channel via a second secondary channel and the delay of the control process caused by the second secondary channel is smaller than that caused by the delay caused by the first secondary channel is, according to patent 1242674, characterized in that that the second secondary channel (II) one Contains arrangement with threshold value, which is parallel to the resistor (45) of the time constant element is connected in the first secondary channel, and the one with a connection at the switching point (68) lying capacitor (46) of the time constant element with the other connection is at a fixed potential, such that when the threshold value is exceeded, the resistance (45) bridged and the capacitor (46) with less delay than across the resistor (45) is transhipped. 2. Circuit arrangement according to claim 1, characterized in that the arrangement with Threshold characteristic consists of a diode (72) connected in parallel with a resistor (73) and which is in series with a capacitor (71) in parallel with the resistor (45) of the time constant element lies. 1 sheet of drawings