12VDC 5Amp Low Cost Power supply Using LM338...

In this, i am going to make a 12V 5A Low Cost very Effective Power Supply Using LM338.

A power supply is an integral part of any electronic circuit or device, they are used to supply electric power to an electric load.

The power supply is an electronic device that is usually referred to as an electric power converter because it converts one form of electrical energy into another form (AC to DC)

The Heart of This Circuit is LM338 Adjustable Regulator IC and the Second important thing is the Step-Down AC Transformer that should have a Primary Rating of 230V or 110V and Secondary coil should be rated about 15V and 5Ampere.

The it comes with a lot of built-in features like constant with temperature, short circuit protection, thermal regulation, etc. Its voltage is adjustable between 1.2 to 37 volts and you can use it on any desired fixed voltage between its range. This circuit is built to take 12 volts and 5 amperes fixed output from this IC. This is exceptionally easy to use and require only 2 resistors to set the output voltage. Careful circuit design has resulted in outstanding load and line regulation comparable to many commercial power supplies.

LM338 Electronic Components

A unique feature of the LM338 family is time-dependent current limiting. The current limit circuitry allows peak currents of up to 12 A to be drawn from the regulator for short periods of time. This allows the LM138 to be used with heavy transient loads and speeds start-up under full-load conditions. Under sustained loading conditions, the current limit decreases to a safe value protecting the regulator. Also included on the chip are thermal overload protection and safe area protection for the power transistor.

Circuit Explanation

The transformer is stepping down the voltage from 230V AC to 15V and then it is passed through a 10 Amp 50 PIV bridge rectifier where it’s converted into a DC ripple. This signal is now sent to a noise filtering capacitor before being fed into the IC.

LM338 has three terminals, pin 2 is an input pin where we are sending our DC signal. Adjust pin is Pin 1 which is used to adjust or set the desired voltage, here we have connected it with 1.9K ohms resistor you can use any other resistor according to your desired output voltage. The output is generating from Pin 3 which is then filtered and sent to the output of this circuit. Its necessary to use a suitable heatsink because this IC will get hot during the operation.

Bill Of Materials

1. Step-Down Transformer (230V/15V, 5A).

2. IC LM338K

3.10A 50 PIV Bridge rectifier

4. 2X1N4007 Diode

5. Heat Sink (Suitable for LM338K)

6. Resistor 1X 220Ω, 1X1.9KΩ

7. Capacitors (1X3300μF, 1X0.33μF, 1X0μF/25V, 1X100μF)