استرجاع المركبة المستمرة dc واسطة ثنائي .. كتاب التلفزيون الملون والعادي

10-3 Continuous Vehicle Recovery DC Dual Mode:

It is a common way to retrieve the continuous component - and the circuit consists of Figure (10-4) of the capacitor C, the resistance, and the diode: D - if we assume that the diode is not present in the circuit, then the vibrating pulses are not in one level as in Figure B, as the capacitor prevents the continuous component of the signal visible from entry.

And when adding the binary D: it leads to making the level of the pulses in one value as in Figure C. The working principle of the circuit is that the capacitor C is charged to its maximum at the peak of each synchronization pulse. This value at its peak amplifies the voltage from zero to the top of the negative value of the synchronous pulse - and it is this part of the signal that causes the diode to connect. Di

It is noted that the voltage of the pulses in the figure is (10) (8) (4) volts for the white, gray and black lines. At the white line, the capacitor C is charged to its end (+10 volts) at the tip of the diode - and it appears as if this voltage is in series with the signal and works to raise the signal (10) volts to the positive direction - this puts the synchronization pulse in the zero voltage level (form /C/) and similarly, the (8) volt gray signal charges the capacitor and raises the signal by (8 volts) in the positive direction - thus placing the synchronization pulse in the zero voltage level also. Finally, the dark signal charges the capacitor to +4V, setting the synch pulse to zero as well. In fact, continuous composite recovery is not very effective in maintaining the level of the vibrating pulses correctly - and the lighting control switch may misalign the vibrating pulses Therefore, additional circuits are placed in many TV sets to erase the horizontal and vertical return lines, in order to ensure that the return lines do not appear in any condition.

The recovery of the continuous component in the case of the positive polarity of the synchronization pulses: In the previous figure, the image signal was fed to the screen valve network - because the polarity of the oscillation and synchronization pulses is negative - but in the case of its feeding to the cathode of the monitor valve, the visual signal and pulses must be reversed, so they are of positive polarity, and in this case The case will not change in the circuit unless the diode is connected, and the peak of the pulses must be made in the zero line and the image signal must be kept in the negative direction.
10-4 TV sets that do not have a continuous vehicle recovery system:

Since the cost of the device plays a major role when designing its circuits, that is why many companies shorten the circuits as long as this does not affect a significant and clear effect on the quality of the image. There are devices that do not have DC recovery circuits - and it is known that the image will become darker, but the viewer can then increase the light switch - and this makes the vertical lines of return appear on the screen, which is disturbing to the viewer - and to rid the image of it, the designer usually resorts to the application of pulses Additional negative pulses on the screen valve network during the vertical erasure period, or positive pulses can also be applied to the cathode of the screen, giving the same result. These pulses are usually connected to a pole that the image signal does not reach. These extra pulses cut off the electronic beam in the screen, and the vertical return lines do not appear in any position of the lighting or contrast switch. In fact, canceling the continuous component leads to a decrease in the degree of contrast in the image, but this gap has been filled by developing the phosphorescent layer of the screen and making it better in the degree of contrast, so the viewer cannot notice any loss in the continuous component of the image signal.

Direct connection method and the continuous vehicle stay with the signal: The application of the direct link method between all stages of the image amplifiers, including the link between the image detector and the image primary amplifier, and between the final image amplifier and the screen valve, will keep the continuous vehicle with the signal. There is no need for a recovery process, but this requires higher feeding efforts, better voltage regulation, and high-quality filters, and the matter is more simple when using direct connection in transistor amplifiers, and the required voltage does not exceed (100) volts. Figure (10) - (5) shows a transistor amplifier circuit by direct connection