@▷ LM338-Based Power Supply with 13.8V at 5A Rating | Diagram for Schematic

LM338-Based Power Supply with 13.8V at 5A Rating

Circuit Project Description

The circuit is intended to produce a power supply unit that that utilizes a single LM338 voltage regulator to provide an output voltage of 13.8 V while carrying a current of 5 A.

Terminology Power Supply – a device that provides electrical or other types of energy to an output load, and are capable of converting some other form of energy into electricity such as generators, fuel cells, and solar power LM338 – an adjustable 3-terminal positive voltage regulator capable of supplying in excess of 5A used as battery chargers, constant current regulators, and adjustable power supplies due to its features such as protected output from short circuit, product enhancement tested, current limit constant with temperature, guaranteed thermal regulation, adjustable output down to 1.2V, guaranteed 5A, and guaranteed 7A peak output current Circuit Explanation

The circuit is well known for its capability of providing continuous peak current of 5 A or 12 A from its output during the operation. One advantage of the design is that it does not require external components to function well, as long as the circuit components are carefully connected to the board to produce the required output. There are two possible types of casing that can be by the circuit. One type of casing that can be used to enclose the circuit with the IC1 is TO-220 as it is placed on the PCB while the other type of casing is TO-3 that will encase a heatsink which will be attached in the G3 connector. The heatsink will be placed above the position of IC1. To start the operation of the circuit, the dual pole single throw (DPST) switch S1 is used as it connects to the transformer T1.

Another way of providing cooling is through the bridge rectifier B1, where a piece of U-shaped aluminum can be fixed that is opposite the case. This is done if the bridge rectifier is placed apart from the main circuit as the aluminum gets settled on its chassis and the terminal are connected by a cross-section cable to the equivalent points of the main circuit. The required voltage of 13.8 V is being regulated by the presence of the trimmer TR1 which has a multiturn. A heatsink with a fan should always be placed on IC1. The connection of the circuit is done using large cross-section cables. This is because of the high current that is passing across the components which leads to the increase in temperature. Alternatively, if cross-section cables were not used, placing pins or soldering the cables in a straight line above the PCB would be enough.

Part ListR1=270R 1/4W 2%
TR1=4k7 (Multiturn)
C1=10000uF 40V
C2-3=100 nF 100V PolyesterC4-5=10uF 25V
D1-2=1N4002 (1A/100V)
B1=25A Bridge Rectifier
IC1=LM338T1=220Vac/15VAC - 8A 
S1=2 Pole Single Throw Mains Switch
F1=250mA Fuse Application

This type of power supply, having a precise voltage of 13.8 V, is being used for various equipments or appliances like the lead-acid battery chargers, auto equipment, and citizen’s band (CB) and other communications transceivers. It can also be used in car audio amplifiers for testing due to its good regulation and low noise. The design of power supplies varies with the required voltage and current rating of equipments that requires this device.

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