12v, 5V, 3A dual power supply based on the LM2596

[hrishib]

Hello, I'm trying to design a 12v, 5V, 3A dual power supply based on the LM2596 voltage regulator. Now I need about 2A on both the 12V and the 5V rails. This is supposed to power a SATA HDD and a raspberry pi board. I've attached a schematic here and I was hoping you folks could tell me if it would work? Also can I use the 5V rail to power a raspberry pi along with the HDD in parallel? Feel free to dismantle this circuit completely if necessary.

Any help would be really appreciated. Thanks.

 

[(*steve*)]

When you say "unrectified 40V", I assume you mean "unfiltered 40V"

The input voltage of 40V is at the extreme upper end of the input voltage range for this chip. If you allow 10% variation for changes in line voltage, you will exceed it by some margin.

I haven't looked at the actual circuit you've used for the regulators, I presume you got it from the datasheet and that the component values (especially the value of the inductor and the rating of the diode) are correct.

The way you've wired the two regulators to the common supply is correct.

Individual input capacitors is probabyly a good idea given the application.

When wiring this, take note of the requirements to keep certain connections either short or star connected to a single point (this will be in the datasheet). Actually, on my copy of the datasheet it shows this on page 9 -- it shows which wiring needs to be kept short and recommends a ground plane.

 

[hrishib]

When you say "unrectified 40V", I assume you mean "unfiltered 40V"

The input voltage of 40V is at the extreme upper end of the input voltage range for this chip. If you allow 10% variation for changes in line voltage, you will exceed it by some margin.

I haven't looked at the actual circuit you've used for the regulators, I presume you got it from the datasheet and that the component values (especially the value of the inductor and the rating of the diode) are correct.

The way you've wired the two regulators to the common supply is correct.

Individual input capacitors is probabyly a good idea given the application.

When wiring this, take note of the requirements to keep certain connections either short or star connected to a single point (this will be in the datasheet). Actually, on my copy of the datasheet it shows this on page 9 -- it shows which wiring needs to be kept short and recommends a ground plane.

Thanks *steve*! This was really helpful. Yes, I realized the input need not be 40V. It'll be from a toroid transformer with 15V-0-15V windings and a current rating of 5A. Yes I saw the datasheets and the precautions about the PCB that you've mentioned. Very much to be noted indeed.