Stabilized power supply 0...30 volts. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Power Supplies
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Dear radio amateurs. Now there are a lot of radio elements, including imported ones, for the development and modeling of their own designs. In amateur radio literature, on the Internet, you can find a lot of interesting amateur radio circuits and solutions. Every radio amateur knows how necessary a stabilized power supply is in a home laboratory. A lot of small-sized radioelements and designs appeared, they began to take on compactness, thereby freeing up space on the desktop. A lot of amateur radio power supply circuits can be found on the KR142EN12, KR142EN22A, KR142EN24, etc. microcircuits. But the trouble is that the lower adjustment limit of these microcircuits is 1,2-1,3 volts.
A radio amateur sometimes has to use a voltage of 0,5 ... 1 V. In this common power supply circuit (Fig. 1), a solution is proposed where the lower limit is 0 V.
The voltage at the anode zener diode VD3 KS113A must be exactly (-1,3V). It is necessary to adjust the resistor R8 and achieve a lower limit of 0.00V. The current protection resistor R3 can be calculated by the formula R(protect)=0,7/I(protect). I(protect) - the maximum current at which the protection will operate. Because there is no nominal value of 210 ohms, the resistor is made up of several. Capacitor C2 can be varied from 10 to 50 microfarads. Capacitor C3 can be used at 200 microfarads, but tantalum. Resistor R5 can be used from 10 to 36 ohms.
Rice. 1. Schematic diagram of the power supply (click to enlarge)
Prices for LM317 and KR142EN12 chips are low. This circuit is subject to any radio amateur and has current and short circuit protection.
Characteristics of this option
The output voltage is adjustable within 0...30,5 V.
Maximum load current 5 A.
The LM317 chip, without any modification, is replaced by the domestic KR142EN12. The protection system is taken from the Radio magazine. Resistor R3 can be calculated for any protection current. It is not recommended to raise the current above 5A, although it is possible. The lower limit of voltage adjustment is set by resistor R8. This resistor must be multi-turn, type SP5. The upper limit is selected by resistor R7. Plus bus 5v. you can power the digital scale of the power supply.
The printed circuit board was not developed, surface mounting was used. When using the KR142EN22A microcircuit, the VT2 transistor can be omitted. Good luck to YOU in the field of amateur radio.
Author: Anatoly Nikolaevich Patrin, Kirsanov, Tambov region, patrin@tamb.ru; Publication: evm.wallst.ru
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