Electronics > Beginners

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

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BravoV:

--- Quote from: digsys on November 28, 2013, 03:12:59 pm ---Next I'll check lowest AC possible ...

--- End quote ---

Great, so eager to see if the UVLO kicks in, and how those mosfet drivers perform at quite low voltage. I guess they designed this chip with the target circuit for linear regulator with output minimum at 5V, isn't it ?

Quoting the datasheet :
"OUTP Undervoltage Lockout (UVLO) Threshold, Conditions : (INn = OUTP, Other IN = 0V) , Min 6.2V, Max at 7.0V"

digsys:
Only had time to run a few more tests, some pix later.
- With small load, min AC is app 6V. Literally just kicks in / drops out.
- Increased Caps to 60,000uF and 18A Load. Ran several mains on/off sequences rapidly - didn't bother it or confuse it. annoyed ...
- As above into a dead SHORT for 5 secs. FETs started heating up damn fast, IC still kept trying to run them, and instantly recovered
once short cct was removed. Transformer was reading AC 83A RMS !!!! at 24VAC ... it's a big transformer :-)
So far, failed to blow the sucker up. I'll try huge Inductor loads next week.

BravoV:
So far it looks pretty good eh ?  :clap:

About the upcoming destructive tests  >:D with inductor, do you put any TVS as recommended by the datasheet ?

With the inductor kick back voltage, I guess it can easily surpassed the absolute max. rating at 80V for the OUTP pin, so exciting to hear the results of this test.

Thanks for keeping us updated.  :-+

digsys:
In Version 2 I used - IRFS3004-7P : D2PAK, 0.9mR, 280A, 9200pF, 40V. The LT4320 had no problems at all driving the higher Gate capacitance,
BUT once again there was a sudden LARGE temp rise at around 16A. Turns out that the IC will operate at 6VAC, but at ~16A+ you need a
min of 12VAC to give the charge pumps sufficient drive. (even though the waveforms looked perfectly OK).
With the new layout 3oz both sides, the PCB starts to get warm after 15-20 secs at 21A. Max dropout is ~100mV for a few mS during the
capacitor charge time. Once I upgrade the E-Load (once again) to 30A+, I'll try for a destructive test. All in all - I LOVE IT
More pix at - www.pbase.com/digsys/electronics_stuffz

BravoV:
Thanks for the update !  :-+

I guess at 6VAC is barely enough power to feed the gate driver isn't it ?

Just curious, at +30A you mentioned that you are going for destructive test, at what voltage ?

PS : Seeing your photo gallery there, to be honest, I sort of lost the interest of this chip for a while, too much distractions, there are tons of cool T&M equipments you have there, just wow !!!!!!  :o

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