This article will focus on a simple practical circuit of an adjustable voltage regulator for a car, garage or home. The article is suitable for radio amateurs of any level.
The voltage of the electrical on-board network of the car is, as a rule, 12.6 volts. However, this value is not very stable and may fluctuate within certain limits, depending on the condition of the battery, operating modes of the generator and some other factors.
In addition, many modern consumers (electronic devices) require a supply voltage below this value for their operation, for example - 5 or 9 volts. This article shows a fairly simple circuit of an adjustable voltage regulator that allows you to get the stable value you need at the output.
With the ratings of radioelements shown in the diagram, the circuit provides an output current up to 300 mA. This regulator also has overload and short circuit protection in the load. The load current is limited to the maximum allowable value
300 mA. This value (maximum permissible current) is determined by the rating resistor R2.The lower its resistance, the greater the permissible current in the load. However, when choosing the maximum current during the tuning process, it is necessary to control the current through Zener diode VD1 (D814A) and, if necessary, choose a zener diode with a high permissible operating current. In addition, for a more powerful load, the power transistor should be replaced with a more powerful one. As transistor VT2 in most cases, the type KT315 with any letter.
The desired value of the output voltage is set using a variable (trimmer) resistor R4. In some cases, it may also be necessary to select constant voltage divider resistors - R3 and R5.
All resistors can be installed power from 0.125 watts (MLT-0.125, MLT-0.25). Powerful transistor VT1 (KT814B) should be installed on a radiator with an area of the order of 30 cm sq (or more, depending on the required output power and the type of power transistor used).
Can be used transistors such as KT816, KT818 and others, the required power. Resistor R1 * is selected to ensure the most stable operation of the stabilizer when the load is connected and its reliable "restart" after an overload or short circuit at the output.
Naturally, at the present time it is easier to assemble such a stabilizer on one specialized microcircuit - voltage regulator (series KREN or imported, type LM317 or similar).
But many radio amateurs often have some "reserves" of such transistors and other radio components, which are currently difficult to find practical use. Therefore, such a transistor version may well be used with benefit.
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