# difference between isolated and non-isolated circuit

#### hackers99

Joined Nov 18, 2009
36
can anyone please tell me the difference between the isolated and non-isolated circuit...

#### Ghar

Joined Mar 8, 2010
655
Isolated generally refers to having a physical separation that prevents a DC connection.
The level of isolation is usually hundreds of volts or even more, so that even if that high voltage exists across your isolating device it won't break.

The most common way is to have a transformer - the wires aren't physically connected but signals and even power can move through it.
Another is to have an optocoupler, where you have an LED shining onto a light sensitive diode. The signal goes through but it's not physically connected.

There's a few other methods too.

#### hackers99

Joined Nov 18, 2009
36
but to undertake a paper based design and component for light -weight efficiency DC-DC converter for an electric vehicle application we can select isolated circuit topology for a single converter or modular interleaved converter.......

#### retched

Joined Dec 5, 2009
5,207
Ok. That is part of the assignment problem, but what is the question?

Do you want to know how to draw isolation on paper?

Here is a transformer circuit diagram. Notice how there is no PHYSICAL conductor that connects the two. The power is transfered from one side to the other via magnetic fields.

Isolation Transformer:

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#### hackers99

Joined Nov 18, 2009
36
the question is dc-dc converter is required to operate from a voltage source that may vary over the range of 150-300V (Vin) and maintains an o/p voltage of 600V and the voltage ripple should be less than 1% pk-pk the power throughout may be 100kw. the convester must hav a light weight and efficient of 95%....

#### retched

Joined Dec 5, 2009
5,207
The '....' are getting old. Is the question to DESIGN it?

You original question was about isolation, now its a dc-dc converter?

#### hackers99

Joined Nov 18, 2009
36
my design decision is to ue non-lsolated ckt and use a interleaved converter....any suggestions plz...

#### hackers99

Joined Nov 18, 2009
36
yes design of electric vehice dc-dc converter...

#### retched

Joined Dec 5, 2009
5,207
What do you have so far?

#### mik3

Joined Feb 4, 2008
4,843
Because the input voltage is over 50V, you may need to design an isolated converter due to electrical regulations. I am not sure about that so you need to ask.

It would be good to use an interleaved converter for low voltage high current applications because they offer higher efficiency and better thermal profile than normal converters.

Using an isolating transformer offers another advantage to isolation. If the output voltage of the converter will be constant, you can choose a proper transformer's ratio so that the duty cycles is such that the output voltage ripple is eliminated (almost) due to the interleaved action.

#### hackers99

Joined Nov 18, 2009
36
could u please tell how to calculate the inductor value in the interleaved boost converter...

#### mik3

Joined Feb 4, 2008
4,843
could u please tell how to calculate the inductor value in the interleaved boost converter...
Define the maximum ripple current per leg and calculate it like a single leg converter.