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Confusion about transformers, specifically planar ones and how they work? Answered

I'm trying to eliminate the need for a large coil transformer (120V, 60hz, AC to AC). Now I know very little about transformers but I've been researching planar transformers (for their low profile nature and weight savings) however they only seem to come in AC to DC variants. All of the reading I do about transformers state that all they do is change voltage through inductance. Why and how does a planar transformer change incoming AC to DC with out a separate rectifier?

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mpilchfamily (author)2012-08-02

If you find a Planar Transformer that has a DC output then it does have a rectifier built into it. Since the coil windings are replaced by traces on a PCB it is easy to have an SMD rectifier tucked next to or under the ferrite core.

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tofunater (author)mpilchfamily2012-08-02

Any chance you guys can find a manufacturer that doesn't have a rectifier built in? I can't find any that aren't classed as ac to dc

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steveastrouk (author)tofunater2012-08-02

Need a spec ! What VA rating, what volts ?

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tofunater (author)steveastrouk2012-08-02

I need a manufacturer who builds them to handle up to 1.2kw at 120V at 60 hz input with an 120 volt and a 20 volt output.

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steveastrouk (author)tofunater2012-08-02

Can't be done. Planar's are used at very high frequencies, which is why they can be very small.

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steveastrouk (author)tofunater2012-08-02

Also, what about toroidal types ?

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steveastrouk (author)2012-08-02

They can't: like any transformer, they're AC in, AC out, but they ARE used in AC/DC converters.

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