Warm LM2596S-5 PWM regulator

I have made a DC-DC converter using a LM2596S-5 regulator. The input is 12 V DC.

I thought PWM converters should have high degree of efficiency (hence low power dissipation), but even with 10mA load the regulator is a bit warm. I can touch it without big problems, but a few degrees warmer and I cannot touch it any more. Estimated somewhere between 50 and 60 deg C.

I have mounted a heat sink to the regulator.

Is this normal?

Diagram of the converter:

Shouldn't the inductor be 33uH, not 33mH?

MK1888:
Shouldn't the inductor be 33uH, not 33mH?

Ah yes it is 33 uH, not mH.

Hi,
Have you layed your circuit out as suggested by the datasheet?
Layout on SMPS is very important due to the high frequency nature of the regulators operation.

NOTE; The wide tracks and large ground plane area?

Can you post an image of your project please?

Thanks.. Tom.... :slight_smile:

Yes, I have. At least when it come to the components close to it. My modification is the fuse, a red led indicating blown fuse and a constant current driving a green led indicating that the fuse is OK and that the regulator have input power.

The regulator is on a prototype board and the I use AWG22 wires for the ground and VCC (from 12 V input to the output).

Here is an image (sorry about the size, my PhotoShop PC died yesterday).

PhotoShop? Really?

For simple dealing with images, IrfanView is the app on Windoze.

I have yet to get to grips with the Gimp. :astonished:

Look at section 9.2.1 of the datasheet here: http://www.ti.com/lit/ds/symlink/lm2596.pdf?&ts=1589290175216

Paul__B:
PhotoShop? Really?

For simple dealing with images, IrfanView is the app on Windoze.

I have yet to get to grips with the Gimp. :astonished:

Paint is even easier.
Tom... :slight_smile:

Paul__B:
PhotoShop? Really?

For simple dealing with images, IrfanView is the app on Windoze.

I have yet to get to grips with the Gimp. :astonished:

Because I'm used to it :wink:

MarkT:
Look at section 9.2.1 of the datasheet here: http://www.ti.com/lit/ds/symlink/lm2596.pdf?&ts=1589290175216

I know about that. The connections between those components should be kept as low as possible. But it doe not say how short they should be.

But I assume that this may be the problem - the connections are too long?

Hi,
I think there is a mass of info in the application data sheet about layout, this one emphasizing the conductors that need to be big and close to the 2596 pins.


Tom... :slight_smile:

I'll experiment with this a bit and see what happens if I try to get the components closer than they are today.

Loop area is key, and low-inductance traces (ie wide).