DIY PARAMETRIC STABILIZER ON TRANSISTOR AND ZENER DIODE

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As you know, not a single electronic device works without a suitable power source. In the simplest case, a conventional transformer and a diode bridge (rectifier) with a smoothing capacitor can act as a power source. However, it is not always at hand to have a transformer for the desired voltage. And even more so, such a power source cannot be called stabilized, because the voltage at its output will depend on the voltage in the network.
An option to solve these two problems is to use off-the-shelf stabilizers, for example, 78L05, 78L12. They are convenient to use, but again, they are not always at hand. Another option is to use a parametric stabilizer on a zener diode and transistor. Its circuit is shown below.

Stabilizer circuit

VD1-VD4 in this diagram is a conventional diode bridge that converts alternating voltage from a transformer to direct. Capacitor C1 smoothes the voltage ripple, turning the voltage from pulsating to constant. In parallel with this capacitor, it is worthwhile to put a film or ceramic capacitor of small capacity to filter high-frequency pulsations, because At a high frequency, the electrolytic capacitor does a poor job. The electrolytic capacitors C2 and C3 in this circuit are for the same purpose - smoothing out any ripples. The chain R1 - VD5 serves to form a stabilized voltage, the resistor R1 in it sets the stabilization current of the zener diode. Resistor R2 load. The transistor in this circuit absorbs the entire difference between the input and output voltage, therefore a decent amount of heat is dissipated on it. This circuit is not intended to connect a powerful load, but, nevertheless, the transistor should be screwed to the radiator using heat-conducting paste.
The voltage at the output of the circuit depends on the choice of the zener diode and the value of the resistors. The table below shows the ratings of the elements for receiving 5, 6, 9, 12, 15 volts at the output.

Instead of the KT829A transistor, you can use imported analogs, for example, TIP41 or BDX53. It is permissible to install a diode bridge any one that is suitable for current and voltage. In addition, you can assemble it from separate diodes. Thus, when using a minimum of parts, a workable voltage stabilizer is obtained, from which other electronic devices that consume a small current can be powered.