Dilshan R Jayakody’s Web Log

13.8V power supplies are commonly used in amateur radio experiments. Most of the portable amateur radio transceivers are designed to work with a 13.8V power source. We mainly build this power supply unit to power some of our amateur radio circuits and modules. This design is based on the popular LM338 5A voltage regulator. We choose this regulator because of to it’s higher current rating, short-circuit protection feature and higher availability. The prototype version of 13.8V - 5A power supply unit. Apart from that, we include MC3423 based crowbar sensing circuit to preventing an over-voltage condition of a power supply unit. We design this circuit by using commonly available 18V×2 (5A) + 12V (1A) transformer. This transformer is available in the market because it’s commonly used with some AF power amplifier systems/kits. We use its 12V terminal to drive 120mm - 12V cooling fan.

This is a high current 5V bench power supply for digital (and analog) electronic experiments. This power supply is based around National Semiconductor's LM338K positive voltage regulator. Virtually this is an indestructible power supply unit with short-circuit protection and thermal overload protection. 5V 5A Power Supply in ATX Power Supply Casing In our prototype we assemble entire power supply (including step-down transformer) in an ATX power supply casing. When assembling this power supply take extra care about wirings and mountings. LM338K need proper heat-sink and make sure to mount it closer to the main PCB. While assembling makes sure that all the wirings are in correct order. Improper wiring and/or shot-circuits may leads to critical component failures (including voltage regulator IC and step-down transformer ).  Schematic diagram of this power supply unit is available to download at google drive