how to isolate the output of a high speed buck converter?

Question

how to isolate the output of a high speed buck converter?

mageta (Electrical)

(OP)

8 Aug 11 10:28

hi, i am trying to isolate the output of a buck converter. the challange is with the current mode sensing of the output.

is there a efficient way to do this?

it is linear tech's lt3694. i am using a transformer to isolate the secondary (output) where i have a split +/- 7v outputs. i have seen some app notes using opto isolators, but they are not very good at high temp.

please help, thanks.

zappedagain (Electrical) · Answer 1 · 2011-08-08 17:00:21

current to voltage converter -> A/D -> micro -> isolated digital channel (AD1400 series) -> micro -> D/A?

A bit overcomplicated but an idea to spur other ideas...

Z

mageta (Electrical) · Answer 2 · 2011-08-08 17:09:44

actually i have to scrap this idea, as it violates one of the design requirements.

itsmoked (Electrical) · Answer 3 · 2011-08-08 23:33:07

There are now digital isolators. Setup a V to F and feed that back across.

Keith Cress
kcress - http://www.flaminsystems.com

mageta (Electrical) · Answer 4 · 2011-08-09 10:38:49

yes i have found isolated flyback regulators, but they don't come in greater than 2 mhz, or even close.

electricuwe (Electrical) · Answer 5 · 2011-08-14 03:40:20

I'd recommend to revise your approach. You should consider the following:

- there is a large number of power control ICs on the market, usually optimized for specific topologies and either non-isolated or isolated converters

- for isolated DC/DC swithing frequency for a given power rating usually tend to be lower than for non-isolated design

- the isolated version of the buck converter is not the flyback, but the forward converter

What makes you striving for more than 2 MHz ? What is the benefit you are expecting ?

My suggestion to proceed:

- List the key requirements for your application

- Choose the most suitable topology based on some general text book or a general apllication note

- then search for a specific type of power control IC

mageta (Electrical) · Answer 6 · 2011-08-15 11:17:38

because in our application we have 2mhz rf section. anything over that would not be an issue regarding noise.

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how to isolate the output of a high speed buck converter?