mosfet driver circuit

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torpedo2k3

Joined: 19 Jul 2009
Posts: 3
Location: united kingdom

19 Jul 2009 10:52 mosfet driver

hello
i want to build a gate drive circuit( without using driver IC) for two mosfet that are to be placed at tranformer secondary winding of LLC resonant converter instead of normal pn diode.Mosfets are required to turnon and turn off alternatively (much like full bridge rectifier ) with changing polarity of center tapped transformer (24 volt secondary )...any idea or any webpage to tell how to make this driver circuit ?Thanks
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smd_lover

Joined: 19 Jul 2009
Posts: 28
Location: Netherlands

19 Jul 2009 14:03 mosfet circuit

You can make a tomem pole with a NPN on top and an PNP in the bottom.
See schematic on page 4:
http://www.irf.com/technical-info/appnotes/an-940.pdf

Why not use an IC ? That takes less components.

torpedo2k3

Joined: 19 Jul 2009
Posts: 3
Location: united kingdom

19 Jul 2009 18:15 mosfet driver circuit

thanks .will this circuit work on secondary of center tap transformer to drive mosfets where voltage is sinosidal:| ? how can i use this circuit to drive two N-Mosfet (for synchronous rectification ) instead of one NMosfet and one PMosfter combo ????...

smd_lover

Joined: 19 Jul 2009
Posts: 28
Location: Netherlands

19 Jul 2009 19:42 mosfet driver circuits

Sinusoidal? You mean to drive the mosfets 'analog' like in an audio amplifier?

Normally the 2 N-ch mosfets are connected to ground with the sources.
The centertap is connected to the positive supply.
Each mosfet willl pull the transformer winding to ground one by one.

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torpedo2k3

Joined: 19 Jul 2009
Posts: 3
Location: united kingdom

19 Jul 2009 22:02 totem pole mosfet driver

hi ...not to drive mosfets with sinosidal signal ..i attached the circuit diagram to elablorate my question. i mean with positive sine half cycle ,upper mosfet will need to be turn On ...and other half cycle ,bottom mosfet will turn On (much like full bridge rectifier )..but i need driver/control circuit which will provide synchronization between secondary sine voltage to application of gate signal to ensure right mosfet get On at the right time ..

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kumarans

Joined: 04 Aug 2007
Posts: 46

22 Jul 2009 6:41 driver circuit mosfet

the drivers are designed in compensated manner, or by a single driver. so its fully based on Spec

walkura

Joined: 22 Nov 2006
Posts: 16
Helped: 1

22 Jul 2009 18:55 driver circuit for mosfet

You can place comperators like LM393 from (output) minus to the transformer ends followed by a totempole .
The upper comperator drives the lower mosfet and vice versa .
You can do the same with transistors using a emmitercoupled schmitt trigger followed by a totempole .
When the upperside is positive you switch the lower mosfet & vice versa .
Its not that hard ,just make sure your comperator doesnt get fried ,so do use resistors to sense the transformer .

Good luck .