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Post Info TOPIC: Ideal diode LTC4357 as a 3-phase rectifier or a buck/boost diode
definitionofis


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Posts: 42
Date: January 26th
Ideal diode LTC4357 as a 3-phase rectifier or a buck/boost diode
 

Here is the schematic if anyone wants to try 3-phase synchronous rectification. I have not built this circuit. I have no idea if it will work. I have no experience with LTC4357 ideal diodes and the specifications do not show them used for switching at 6Hz or faster, like my generator will produce. I added a battery-full voltage threshold for doing a dump through some SCRs, which I have kicking around. I'll likely add infrared flood light sockets or toaster oven outlets for the dump loads.

I'll report results if I build the circuit.

Maybe someone will comment if this is not workable, and they have experience, or if I made an error.

edit: I chose FDB3632 MOSFETs. IRF3205 MOSFETs look good, too. CR6CM SCRs.

Those are KiCAD files.



-- Edited by definitionofis on Thursday 26th of January 2012 06:57:55 PM



-- Edited by definitionofis on Thursday 26th of January 2012 07:25:27 PM

Attachments
myParts2.lib (0.4 kb)
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definitionofis


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Posts: 42
Date: January 16th
RE: Ideal diode LTC4357 as a 3-phase rectifier or a buck/boost diode
 

I found a discussion of that here.

http://forum.allaboutcircuits.com/showthread.php?t=31906

excerpt:

As SgtWookie says, synchronous rectification will be "the icing on the cake" and can be done with the basic circuit as drawn if you use MOSFETS. It's a little known fact that with current flowing through the body diode (the MOSFET reversed polarity) the device will still function. So you can reduce the diode losses by switching on the MOSFET while rectifying. However, you will need to monitor the voltage and the current flowing through the devices to know when to switch them on and off.



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sjh7132


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Date: January 16th
RE: Ideal diode LTC4357 as a 3-phase rectifier or a buck/boost diode
 

I think synchronous rectification is close to the same thing.  A lot of controllers can control a low side FET for that purpose.



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Steve
definitionofis


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Posts: 42
Date: January 16th
Ideal diode LTC4357 as a 3-phase rectifier or a buck/boost diode
 

http://cds.linear.com/docs/Datasheet/4357fd.pdf

Has anyone tried to use this ideal diode for 3-phase rectification, or in a buck/boost converter at high speed, like 40Khz?

The application notes say it is used for ORing power supplies. Power supplies do not switch polarity often. So my guess is that it wastes power when you switch it fast.

I just wondered if anybody tried it.

Apparently, the IC is attached to a N-Channel MOSFET in the reverse of normal direction of a MOSFET in a circuit.  It runs in unison with the body diode and enhances its conduction and then shuts off in time, to act like a diode.

I thought all the current would only flow through the body diode. They say they can turn on the mosfet such that the low resistance flow of electrons is from drain to source, which is the same direction as the body diode.

A dual version: LTC4355



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