For the power transistor receivers from the network is usually used consoles, consisting of a step-down transformer and rectifier with stabilizer voltage. However, the use of them as separate designs it is convenient. For portable receivers can make a prefix (Fig. 1.30), which will fit in the compartment.
The console is designed to power handheld radios or other devices that use battery "Crown", from 220 V. the Output voltage of the console 9, maximum current load 30 mA. At load currents up to 25 mA voltage consistently, and at a current of 30 mA is reduced to 7 V.
The prefix is insensitive to short circuits in the load (current short circuit 35 mA). The main parts of transformerless consoles rectifier diode VD6…VD9 with damping resistors R3 R7…, Converter voltage (VT1, VT2 and T1 and the rectifier diode VD2, VD3 with parametric the stabilizer. AC line voltage is rectified, the DC voltage converted to AC high frequency, and finally, the last again straightens up. Due to the presence of the transformer, the input and output console galvanically isolated, high enough frequency Converter allows to perform the transformer, and means. and the whole console is small.
One of the circuit features of this console is that the role of ballast the resistance of the stabilizer output voltage perform the quenching resistors R3 R7.... This occurs as follows. When increasing the output voltage the current flowing through the Zener diode VD1 increases, causing an increase of current, consumed by the Converter. The voltage of the quenching resistors increases, the voltage of the power Converter falls, reducing the output the tension. The stabilization factor of such a stabilizer is very high (about 1000 load current up to 20 mA). Zener VD4 and VD5 do not participate in the consoles and only need to limit the voltage on the Converter and on the diodes D6 D9…in case of failure of generation.
The transformer T1 is wound on the annular ferrite core 700NM (size CHH). Winding 1-2 and 2-3 contain 85 turns, 4-5 and 9-10 25 turns 6-7 and 7-8 - 100 turns the PEV-2 is 0.2. As VD1, you can use any Zener voltage stabilization 8…10 V Instead of diodes DV you can use any diodes, series VD9 (except DB), CD, CD. In the console you can use transistors CTB, KT315 with any letter index, CTA…CTG. Zener XA can be replaced by DA. The establishment of consoles comes down to the correct connection of the transformer windings and the selection of the resistor R1, which a current of the Zener diode VD1 maximum.
Author: A. P. Seman