دارة مضاعف الجهد .. كتاب التلفزيون الملون والعادي

12-4 Voltage multiplier circuit:

Some large-screen devices require a continuous voltage (+B) of up to 250 volts, so a voltage multiplier (double) or triple is required, especially for the high-voltage screen elevator. There are two ways to circuit the multiplier, namely - the half-wave multiplier

(7-12) - The full-wave multiplexer and the full-wave multiplier are better from a technical point of view, filtering aliasing and voltage regulation Figure (8-12).

The half-wave multiplexer has an important advantage that one end of the AC network is grounded, as well as one side of the rectifier current, and this limits interference a lot. Figure (A) is used in many TV sets. The resistance R1 works to protect the diode D2, D1, and the theoretical output voltage without load is 120, 339, volts DC rectified current if the input voltage AC = 120 volts

The output voltage drops to 280 volts when the device is turned on.

The circuit works as follows:

When the polarity and direction of the alternating current are as shown in Figure (B-7-12), the capacitor is charged through the diode D1 to the peak voltage, i.e. 1,4120,169 volts, and the diode D2 at this moment is reverse biased and does not work. .

When the polarity and direction of the alternating current reverses, as shown in figure (C), the capacitor C2 is charged to double the AC peak voltage, i.e. 339 volts (without load), and this happens as follows:

1- The capacitor is charged in half of the advanced cycle of the alternating current - to 1697 volts. It is noted that the polarity of the AC voltage and the charging voltage via C1 are now combined in series, and this is similar to collecting two batteries in series.

2 - The resultant of the two voltages is 1697 volts AC, the peak voltage + 169.7 volts, the capacitor
C1 now charges capacitor C2 to 339 volts.
It is twice the AC voltage and the second input D2 diode D1 is now in reverse bias, and the resistance and load reduce this voltage.

The capacitor C2 charges only during the half-cycle of the AC input current, so it is a half-wave circuit with a 50 Hz zigzag if the network is 50 Hz.
Full wave voltage multiplier circuit:

The full-wave multiplier circuit has two advantages over the half-wave, namely: The aliasing frequency is multiplier, which is 100 Hz, and it is better organized. However, it does not have a common grounding point for the AC terminal and the rectifier voltage terminal B, Figure (8-12).

Half-Wave Triple Voltage Doubler Circuit:

Added to the voltage multiplier circuit described previously, a diode, D, and a capacitor C (Fig. Sequentially, the capacitor C is charged to three times the voltage of the input peak, i.e. 1,410 x 3 = 509 volts, and with the presence of the load, the voltage drops practically to about (420 volts).

It is noted that whenever the voltage is doubled, its regulation decreases, but this does not affect much on the circuits that feed it (such as the high voltage feeding the screen valve elevator). In color television, it is usually raised from 9kV to 27kV.

12-5 Voltage Regulators:

The supply voltage regulators function to maintain a constant DC voltage constant value despite changes in the AC network voltage or change in the intensity of the load current. In monochromatic TV devices, it is not entirely necessary to regulate the constant voltage + B + because this does not pose a major problem. In color devices, the regulation Effort is necessary. Especially the high voltage connected to the screen valve elevator. This is to maintain the stability of focus, congruence, and beam current (illumination), either in transistor devices or with integrated circuits, especially the colored ones. Also, the constant voltage + B + or B must be regulated - and the voltage on which the transistors operate ranges from 5 to 25 volts, so any noticeable change in the voltage feeding them causes a defect in their work and performance. The same applies to transistors that operate in high voltages - the horizontal output transistor can work with a voltage of (110 volts), so changing this voltage can cause a change in the width of the linear structure.

For the image (raster) - and is accompanied by changes in the high voltage of the screen valve elevator
In focus (Focus) and in voltages of the screen electrodes.

It is worth pointing out that most colored devices with solid elements take most of their power or horizontal output transformer coils - therefore, any noticeable change in feeding the horizontal output transistor will change the voltage values ​​​​derived from the horizontal output transformer, and accordingly, the regulation of all voltages B or - B ensures that the circuit elements work well - even if the alternating current voltage changes between (105-135 volts) in the (120) volt network or between 185-245 volts in the 220-volt network

Types of voltage regulators:

There are several types of voltage regulators:

1- Zener diode regulators

2- Transistor regulators.

3- Tripartite organizations.

4 - Organizations on the principle of categorical