Encyclopedia of radio electronics and electrical engineering / Civil radio communications
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The output voltage of the proposed simple power supply is -13 ... 14 V. It is capable of delivering a current of 1 ... 1.5 A. The ripple level is no more than 10 mV. and the output resistance is -0.04 ... 0.07 Ohm. Figure 1 shows a stabilized rectifier circuit. The source of alternating voltage 12.6 V is a mains transformer that provides the necessary current in the secondary winding.
A feature of a stabilized rectifier is that. that even with a breakdown of the transistor VT1, it will not create a dangerous voltage for the radio station at the output. If this happens, then when transmitting, the radio station will not even leave the operating mode - only AC hum will appear in the signal. There is no need for any additional measures to protect against short circuits in the load circuit. In this case, the transistor VT1 will be closed and the current in the load will decrease to almost zero.
In the one shown in Fig. 2 diagram Ui, - the minimum collector-emitter voltage of the transistor VT1. at which it still retains its functions. In the formula for calculating the ripple voltage, the current is in amperes, the capacitance is in microfarads, and the voltage is in volts.
The transformer can be used unified, with a power of at least 30 watts. for example, TN36, TN46, etc. TN type transformers have two. three or four 6,3-volt windings, allowing both series and parallel connection. A possible circuit for switching on a four-winding transformer, designed to be powered from a 220/127 network, is shown in fig. 3.
Transistor VT1 must be installed on a heat sink with an area of at least 70 cm2. For better thermal contact, it is recommended to introduce a heat-conducting paste under the transistor, for example, KPT-8.
Establishing the device comes down to setting the required output voltage with resistor R5.
The unit can also be used to power a radio station that consumes much more current in transmission mode. In this case, you should replace the transistor VT1 with KT825D. With an increase in the current consumption, it will, of course, be necessary to use a larger capacitor C1. Otherwise, the ripple on it will be excessive and the transistor VT1 will exit the stabilization mode.
With a significant increase in current, it will be necessary to apply a heat sink with a larger dissipation area and use a more powerful step-down transformer, for example. TN10 (load current up to 6 A) or TN11 (7.8 A). It may be necessary to replace silicon diodes VD1-VD4 with their rather large forward voltage drop Unp = 1 ... 1,2 V with germanium D3O3 (current up to 3 A), D304 (5 A) or D305 (10 A), in which Unppr \u0,25d 0,3 ... 2 V. or for diodes with a Schottky barrier: 2998D2 with indices B or C, 219D0,4G or others with Unp<XNUMX V.
Author: Yu.Vinogradov, Moscow
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