Improved simple power supply. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Improved simple power supply. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power Supplies

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The stabilized power supply for digital devices described in [1] certainly deserves the attention of radio amateurs. And for all its advantages (a fixed voltage of 5 V for TTL circuits and an adjustable voltage of 3-15 V for CMOS circuits), it has disadvantages: the absence of a voltmeter and the need to control and adjust the voltage when connecting electronic devices designed for different voltages.

To eliminate these shortcomings, an improved simple power supply is proposed (Fig. 1).

(click to enlarge)

Low alternating voltage 12-13 V from power transformer T1 is supplied to the bridge rectifier VD1-VD4, the HL1 light indicates its presence. The output DC voltage of the rectifier is smoothed by capacitor C1.

Capacitors C2 and C3 ensure the stability of the power supply at high frequencies, and capacitor C4 serves for additional output decoupling. The unregulated direct voltage acting on capacitor C1 is supplied to the inputs of voltage stabilizers DA1-DA3 (Fig. 2), which are connected at points A, B, O (see Fig. 1, where Dai is the location where the stabilizers are connected).

Switches S1, S2 (Fig. 2) can connect one of the three stabilizers, which give voltages of 5, respectively; 9; 12 V (main standard voltages for powering electrical circuits) with a maximum stabilization current Istab = 1,5 A. They switch the stabilizers DA1-DA3 at points A and B, and all stabilizers can be connected to point "0". The VD1-VD3 LEDs, connected through the limiting resistors R1, R2, R3, indicate the presence of an output voltage of 5, 9 or 12 V.

Advanced simple power supply

All components of the power supply (Fig. 1), with the exception of the power transformer and controls, are mounted on a printed circuit board. Diodes VD1, VD2 are installed on one aluminum heat sink with an area of 140 cm2, and diodes VD3, VD4 are installed separately on aluminum heat sinks with an area of 70 cm2. Voltage stabilizers DA1-DA3 are installed on one aluminum heat sink with an area of 60 cm2. The overall dimensions of the power supply 200x100x90 mm are selected depending on the materials used.

Details. Resistors (carbon, film, 0,25 W), capacitors C1, C4 electrolytic, C2 and C3 metal-paper or polystyrene, 25 V, rectifier diodes VD1-VD4 type KD202B; voltage stabilizers DA1 - 142EN5A (KREN5A), DA2 - 142EN8A (KREN8A), DA3 - 142EN8B (KREN8B); LEDs VD1-VD3 type AL307 in red, green and yellow colors; light bulb HL1 -12 V, 0,1 A; switches S1, S2 type P2KL; FU1 - 1 A fast fuse.

Power transformer T1 for 20 W with a primary winding of 220 V and a secondary winding of 12 V and a current of 1,6 A. The author made a transformer on a toroidal magnetic core with an internal diameter of 52 mm, an outer diameter of 82 mm and a height of 20 mm (from a failed autotransformer). The primary winding has 3190 turns of copper winding wire with a diameter of 0,23 mm, the secondary winding has 174 turns of copper winding wire with a diameter of 0,9 mm.

References:

1. Tuli M. Reference manual on digital electronics. - M.: Energoatomizdat, 1990

Author: V.M. Bosenko

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