Power isolation without current drop - 24 V DC

Ankur Dubey

Other Parts Discussed in Thread: TPS40210

Hello,

i have a used signal and power isolators in my rs-485 circuit before but this time a different query regarding isolation arised-

1) in above image there are 2 boards A and B. Our main board is Board A which has input power supply of 24 Vdc, 3.2 A.

along with it a Board B has also to be connected which will be powered by Board A, thus we need to isolate the power of both the boards. from the part which is circled with a question mark in it.

Current consumption of ( Power Supply - 24 Vdc, 3.2 A)

Board A - 1.5 A

Board B - 1 A

So main constraint is that even after isolating we dont want current to be dropped below 3.2 A, when the Board B is also connected ?

What will be the best method to isolate this?

over 4 years ago

0 Ed Walker over 4 years ago

Prodigy 5 points

Hello Ankur,

Thank you for your post.

Please see TI Home > TI reference designs search

In the search PARAMETER window enter; Vin min 20V, Vin max 28V, Vout 24V, Iout 1A, ISOLATED,
https://www.ti.com/reference-designs/index.html#search?vinmin=20&vinmax=28&iout=1&vout=24&isolated=Isolated

3 designs meet the criteria.

PMP30524

This reference design provides functional isolation 500 Vrms by simply using a dual inductor from stock. Overall, the design is driven by minimum cost using TPS40210 and adding discrete UVLO. Also, the input range of 1:6 exceeds industrial standard by 7 V to 42 V, which makes this reference design (...)

PMP10856

This reference design provides an isolated 24V/1A output from a 24VAC input. The supply is laid out on a small 1.1" by 2.4" circuit board, and achieves over 85% peak efficiency.

PMP11047

This reference design provides an isolated 24V/1A output from an 18V-48VDC. The supply is laid out on a small 1.1" by 2.4" circuit board, and achieves over 90% peak efficiency.

This is how you would do an isolated source for the B Board.
Will this help you?

0 Ankur Dubey over 4 years ago in reply to Ed Walker

Intellectual 385 points

Thanks for the reply,

Actually i wanted something like this, i dont want to design a full power supply

all i need is to just isolate my 24 V without any drop in current, and that current should be between 2 to 3.2A

0 Ed Walker over 4 years ago in reply to Ankur Dubey

Prodigy 5 points

Hello Ankur,

Any converter for isolation will have an efficiency loss.
That will subtract from the available total current.
The isolated converter provides a voltage to the load, the load then determines how much current is drawn.

Current will only be limited by:
1. the isolated module current limit function, your board needs 1 Amp so the isolated module should current limit above that.
2. the input source for the main board. The 24V comes from somewhere and its source will determine the total current available.

TI has Isolated DC/DC converters and Modules;
http://www.ti.com/power-management/offline-isolated-dcdc-controllers-converters/isolated-dcdc-converters-modules/overview.html

Isolated Modules may be found here:
http://www.ti.com/power-management/offline-isolated-dcdc-controllers-converters/isolated-dcdc-converters-modules/products.html

TI does not offer a 24V 1A isolated module.
We do provide the means to make your own.

Power management

Power management forum

Power isolation without current drop - 24 V DC

PMP30524

PMP10856

PMP11047