Preface

Fig.1 – The switching PSU

This is the PCB I used to test all my projects.

When I drew it, I took the cue from the project published on electroniq.net (I hope the attribution is made to the right author because I found many clones on the internet). I changed something on that schematic making the improvements I thought were right also in order to try to use the components I already had available.

To be honest, what makes the project so good is not this specific schematic. That is nothing more than an elaboration of some “typical applications” suggested on the L296‘s data sheet, but the IC itself.

The l296 switching regulator requires very few external components and the current limiter is already inside it (make sure to use the L296P to take the advantage of this function).

A compact switching regulator with the L296

With an efficiency up to 90%, the minimum voltage regulation of 5.1V seems to be the only disadvantage of using this IC but the issue has been solved thanks to the circuit around the zener diode (have a look on the schematic in figure 2).

Fig.2 – The compact 2A 0-30V variable switching power supply with current control’s schematic

If I had to change something now, I would remove the trimmer R7 because it is useless. Nothing changes if you turn it and the voltage regulation by the potentiometer R6 is perfectly fine even without it.

I’m sure the PCB would support more than 2A as declared in the title (the L296 arrives up to 4A), but I’ve never tried it with a higher current than that.

Building and testing the PCB

Fig.3 – The PCB Layout

Building the PCB is quite easy. Before starting soldering the components, make the jumper using a piece of unipolar wire. Solder it first and then all the other components.

Fig.4 – The PCB bottom-mask

After that, you are ready to test the PCB. Connect a transformer to the X1 terminal (from 24V to 30V AC) and a multimeter to the X2 one. If you don’t apply any load, you don’t need to install a heat sink because the L296 will take some minutes before getting too hot. Now, if turning the potentiometer R6 the voltage output changes from 0V to 30V and goes to 0V by turning anti-clockwise the potentiometer R3, it will mean that your PCB is working properly.

Before testing it with a load, you must install a heat sink on the L296 and the diode D1. Insulate them electrically by a mica insulator as explained here. Notice that the L296’s tab is connected to the pin 8, that is the ground. So, you might insulate only the diode: in that way the heat sink will be connected directly to GND.

Download the project

Pressing the button below you can download a compressed file with all the necessary material to build this project:

• the L296 data sheet;
• the pictures of the final project, the schematic, the PCB mask and the PCB layout as shown in this post;
• the schematic and the board files in Eagle format.

If you need some help please do not hesitate to contact me or leave your comments below. Enjoy it!

I have decided to share my knowledge and my projects for free, so I have not inserted any annoying ads on andy-progetti.com. Despite this, if you like my website, please help me in developing it by leaving comments and suggestions, or by making a small donation pressing the button below.

Grazie di cuore, Andrea Dal Maso

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