In the daily practice of Amateur radio (and not only!) there is a need for compact voltage source 3…5 V. To have such a source, it is necessary to carry several batteries or AA batteries. The appearance of a miniature integrated converters allows you to easily solve this the problem. Managed to get a small (55x30x10 mm) device powered on just one (!) penlight batteries or battery size. AA or AAA.
Output voltage 3.3 V at currents up to 200 mA or 5 V at currents up to 100 mA.
Converter circuit depicted in Fig. 7.1.
Fig. 7.1
The Converter is built based on the domestic circuit CRP included according to the standard scheme. Consider the operation of the Converter in detail.
The Converter contains a simple charger allows to charge the battery.
HL1 led is designed to indicate the battery charging mode and at the same time is a voltage regulator. Resistor R1 is used to limitation of the charging current and is selected depending on the capacity used of the battery.
Switching modes of OPERATION-CHARGE is performed by the switch SA1 ( the layout of the lower position of the engine - CHARGE, the upper position), and the choice of the output voltage - switch SA2 (in the diagram layout bottom the position of the slider - selection voltage +5 V, the upper position of the voltage selection +3.3 V).
The Converter is assembled on a single-sided PCB size mm 46x17 unilateral foiled fiberglass thickness 0,5…1 mm.
The device incorporates resistors MLT-0,125, polar capacitors type K50-35 (a), non-polar capacitors - type K10-7 or imported counterpart. Led HL1 any type. AL307 or similar. Choke L1 - finished miniature type. ES or improvised. Diode VD1 Converter - 1 N581 7 or 1 N5819. Diode VD2 - conventional silicon, type - KD521 (KD522) with any letter index.
Switches - any slide on two provisions of the appropriate size.
The Converter chip can be replaced with imported analogue MAH. Thus will significantly increase output currents up to 300 mA at a voltage of 3.3 V and 200 mA at a voltage of 5 V) and increase efficiency. It should, however, note that the imported significantly (several times!) more expensive chips CRP.
The printed circuit Board of the device shown in Fig. 7.2, and the arrangement of elements on Board - in Fig. 7.3.
Fig. 7.2
Fig. 7.3
Authors: S. R. Bashirov Bashirov A. S.