Saturday, February 6, 2021

Adjustable Power Supply 1.25v to 33V, 3 Amps using LM350 + PCB

Fig. 1 - PCB Power Supply LM350

Nowadays it is very important and necessary to have a bench power supply to test ours; projects, electronic circuits, to maintain equipment, among others. However, this power supply must have at least a voltage adjustment control, and at least a short circuit protection.

And this is the proposal of this circuit, a simple and very effective circuit, with protection against short circuit, and that brings in its output an adjustable voltage between, 1.25v to 33 volts, with a current of 3 Amps, which is enough for most of the projects, and still, this PS has protection circuit against short circuit and over-temperature protection.

You may be interested in: 

The LM350 Integrated Circuit

The LM350 IC is an adjustable three-pin positive voltage regulator capable of delivering 3.0 Amperes in an output voltage range of 1.2 V to 33 V. This voltage regulator is exceptionally easy to use and requires only two external resistors to adjust the output voltage.

  • Internal Current Limiting
  • Thermal shutdown
  • Secure Area Compensation

What do the LM350 integrated circuit, an essentially explosion-proof component.
The LM350 serves a wide variety of applications:

  • Static Voltage Regulator for digital circuits
  • Stable Current Regulator
  • Variable Current Regulator

This device also does an especially simple adjustable switching regulator, a programmable output regulator, or connecting a fixed resistor between the setting and the output, the LM350 can be used as a precision current regulator:

  • Guaranteed 3.0 The output current
  • Adjustable output between 1.2 V and 33 V
  • Load Regulation Normally 0.1%
  • Line Regulation Normally 0.005% / V
  • Internal thermal overload protection
  • Temperature Short-Circuit Internal Current Limiting Current
  • Compensation of the safe area of the output transistor
  • Floating Operation for High Voltage Applications
  • Standard 3-way Transistor Package
  • Eliminates Socks Many Back Fix

The Circuit

The electric schematic diagram, it follows in Figure 2 below, is quite simple, first, we have the rectifier diode bridge KBL610 that is a bridge of 6 Amperes to 1000 Volts, however, you can use anyone that you have and that is above 4 Amperes over 50 Volts.

Diodes D2 and D3 are for the protection of the IC LM350, against short circuits, because when we start the Power Supply, and the capacitor C3 is totally discharged, and it becomes as a short-circuit for the IC.

The C1 capacitor is to attenuate the ripples interference and stability of the same. The C2 capacitor has the function of constancy to decrease Ripple, and stability of the power supply. 

P1, is an analog potentiometer of 5K, if you don’t have the 5K you can put a 4.7K, which is more commercial. T1 is a transformer of at least 3 Amperes, with input according to your local network, which can be 220v or 110v depending on your region, and the transformer secondary is 25 Vac for the output of 33 Vdc.

Fig. 2- Adjustable Power Supply Schematic LM350

So you want to do a more powerful adjustable power supply, for example with 6 Amps, we have this adjustable module post in the link below:

Components List

  • U1 ........... LM350T – Integrated circuit, voltage regulator
  • D1 ........... KBL610 Silicon Rectifier Diode Bridge
  • D2, D3 .... 1N4007- Silicon rectifier diodes
  • C2 ........... 4700 uF – 50V – Electrolytic capacitor
  • C3 ........... 100 uF – 50V – Electrolytic capacitor
  • R1 ........... 220 ohms – ½ W – red, red, brown
  • T1 ........... Transformer 25 V with a minimum current of 3A
  • RP1 ......... 5 K ohms or 4,7 k ohms – Linear potentiometer
  • P1, P2 ...... Kre Block Terminal Terminal 2-Way Double Connector
  • Others .... Printed Circuit Board, tin, wire, etc.

We are offering to Download the link with the printed circuit board printing files, they are; Gerber, PDF layout, PNG, all the files with a direct link to Mega.

Direct link to download

Click in the link below to download the Files: PCB Layout, PDF, GERBER

If you have any questions, suggestions or corrections, please leave them in the comments and we will answer them soon.

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