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Mosfet high voltage AC switch

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bobcat1

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mosfet ac switch

HI

Any one can guid me on how to design a mosfet high voltage AC swtich - or AC mosfet soild state relay

Any ideas,application note,ref design are wellcom.

Thanks

Bobi
 

phildog

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fet ac switch

~should using a gate drive circuit like opto-coupler to drive the gate of mosfet.
~make sure the opto-coupler can stand for high voltage such as H11D1.
~using a 15Amp fuse at the power supply.
~AC switch can be using 4 n-channel mosfet or 2 p-channel mosfet and 2 n-channel mosfet to drive the AC switch.
 

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ac mosfet

A basic solid state relay is made from two MOSFET in an anti-series circuit (source and gate terminals connected) and a photovoltaic optocoupler.
 

bobcat1

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ac switch fet

Hi

Thank you for your help

Can you provide a schematic diagram with part number please?

All the best

Bobi
 

max0412

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high voltage mosfet switch

I've used the LH1262CAC and the VO1263. The VO1263 has higher drive capability,both are available at Newark.

Code:
http://canada.newark.com/93K1107/electromechanical-industrial-control/product.us0?sku=vishay-semiconductor-vo1263aac

Hmm they went up almost a buck since the last time I bought some.

There all out of the LH1262CAC but the VO1263 is better anyways.

Anyways here is a good appnote from Vishay for getting the most out of the VO1263.

Code:
http://www.vishay.com/docs/81225/ssrvo126.pdf

If this is for your 250VAC @ 20A application that you also posted here.

Code:

You may want to use either a triac or electromechanical relay. You will need some large beefy expensive (400 to 600V) mosfets with single digit or low double digit miliohm Rdson.These FETS have large efffective input capacitance,meaning with the limited drive capability of a any photovoltaic driver your FET will be in the linear region for miliseconds.

They show the VO1263 driving a mosfet with a Qg of 56nC in a little over 1mS in the appnote above.Thats a 40V FET,a comparable 400 to 600V FET will have a Qg easily over 100nC if not several hundred Qg.

You can also browse through Vishays other notes here.

Code:
http://www.vishay.com/solid-state-relays/related#appnot

This is why I think for your 250VAC 20A app a FET ssr is not practical.

A typical mosfet you would be looking at

Code:
http://www.microsemi.com/datasheets/60N60B_SCS(G)_B.PDF

Note this is $44 device at digicrap you need two; normalize RDSON to 125C and each mosfet will be dropping about 3V @ 20Arms thats 60W!!This is just rough approximations but you get the idea.
 

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