Electronics > Beginners

A niche chip (LT4320) for mains powered AC -> low volt DC "linear" based psu ?

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tszaboo:
I'm guessing that gate driving is what is the limit here. There are no external capacitors, so the internal charge pump only can supply so much current into the mosfet gate. So at higher frequency, it cannot close/open fast enough (especially at voltages like 72V) and efficiency drops. Now if only we would use MOSFETs with small gate capacitance and lower voltages...

danifel:
This is a chip built for PoE, to replace the 70V diode bridge present at every PoE Powered Device. But it is really not the best alternative around for this purpose. There is an Ideal Diode Bridge by Microsemi, PD70224, which is a lot more integrated.

tszaboo:

--- Quote from: danifel on January 22, 2014, 03:02:42 pm ---This is a chip built for PoE, to replace the 70V diode bridge present at every PoE Powered Device. But it is really not the best alternative around for this purpose. There is an Ideal Diode Bridge by Microsemi, PD70224, which is a lot more integrated.

--- End quote ---
And also a future product. From a company which is not one of the few companies I would buy stuff from.

digsys:

--- Quote from: danifel ---  This is a chip built for PoE, to replace the 70V diode bridge present at every PoE Powered Device.... 
--- End quote ---
I disagree with you here .. I don't see many PoEs needing to supply 20A without needing a heatsink.
It's exactly what it says it is - a POWER Supply bridge rectifier replacement, and they are working out perfect in our products.
Your PD70244 is NOT in the same ballpark. It's 1A (not 20A+), has 160mR inbuilt FETs (I'm using 0.9mR !!) AND it drives these
10,000pF NFETs absolutely fine to 600Hz (and beyond IF I limit the current under 20A !!).. which is ALL I (we) need for DC rectification.
I have no idea why you think it's for PoE ???

BravoV:

--- Quote from: danifel on January 22, 2014, 03:02:42 pm ---This is a chip built for PoE, to replace the 70V diode bridge present at every PoE Powered Device. But it is really not the best alternative around for this purpose.
--- End quote ---

Curious why you claim you know better than Linear Technology that designed it ?  Reading the wrong datasheet maybe ? :-//

Fyi, Linear Technology made a lot of varieties of PoE ics, try visit their website once in a while. Not an expert, but I'm pretty sure they know what they're doing.

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