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LT4320 based active rectifier
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Old 14th January 2021, 03:34 PM   #1041
prasi is offline prasi  India
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LT4320 based active rectifier
on the tht rectifier pcb its still there on bottom as smd foot print. ,
on the smd rectifier pcb, its removed.
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Old 15th January 2021, 01:32 AM   #1042
prasi is offline prasi  India
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LT4320 based active rectifier
Quote:
Originally Posted by metal View Post
In this post, I thought you were offering ICs, when I read your previous answer today I figured these were the PCBs. Anyway, do you also offer these chips as well? If not can you or anyone plz direct me where to find the cheapest prices yet reliable source for these ICs.


Kindly find below my order:
1. CRC PCB: x1 pcs
2. THT PCB: x1 pair
3. SMD PCB: x1 pair
pl pm me your paypal email, complete postal address.
regards
prasi
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Old 16th January 2021, 12:13 PM   #1043
wgh52 is offline wgh52  Germany
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Default Will this CT rectifier work or burn??

I have read many many postings, lots of words, but did not find a final answer to my specific question: Will the following configuration work with the 4320 or will it fail?

LT4320 based active rectifier-agr-mit-trafomittelanzapfung-png

Please note that the two winding sections are indicated to be wound in sequence (i.e. they are in phase), so my conclusion from previous discussions is that the configuration should work.

So I'm just simply requesting a yes/no answer, as the transformer is what I have (part of a purchased item) and if the answer is no, the diodes rectifier will just stay in place and two secondary winding snubbers will be implemented.

Thanks and Regards,
Winfried
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File Type: png AGR mit Trafomittelanzapfung.png (2.3 KB, 218 views)
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Old 17th January 2021, 06:10 PM   #1044
DaveFred is offline DaveFred  Canada
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LT4320 based active rectifier
Quote:
Originally Posted by prasi View Post
Hi Dave somehow i missed your post.
here are answers.
Use either R1-R6 or RP1/RP2. effective resistance about 0.1 ohm to 0.33 ohm is a good value for crc type supply.
for 35v secondaries, PB3506 OR PB3508/PB3510 are good. but will need heatsink depending on current demanded from your amp. e.g. for 5 amps, voltage drop in rectifier is ~1.0v , so power dissipated is approx 5W.
for class ab amp and normal listening, you could do away without heatsink.
Blocked

chassis discoonect network ... Power Supply for Power Amplifiers or some use a cl-60 between psu ground and chassis.

RB and RB- you can use 3300ohm also, its not critical. it determines how fast your caps are discharged when powered down.

For the chassis disconnect,

If using dual mono PSU boards, should each board get its own "ground disconnect network" each attached to a common star ground,

Or can one "ground disconnect network" be connected to both boards?

ground loop board.jpg

Thank you,

David.
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Old 18th January 2021, 01:39 AM   #1045
prasi is offline prasi  India
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Something like this.. there is no best single solution. depends on how you build it. are they single mono blocks? or everything in same case?

example understanding star grounding

read this excellent article by hifisonix
http://hifisonix.com/wordpress/wp-co...ound-Loops.pdf
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Old 18th January 2021, 01:52 AM   #1046
DaveFred is offline DaveFred  Canada
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LT4320 based active rectifier
Quote:
Originally Posted by prasi View Post
Something like this.. there is no best single solution. depends on how you build it. are they single mono blocks? or everything in same case?

example understanding star grounding

read this excellent article by hifisonix
http://hifisonix.com/wordpress/wp-co...ound-Loops.pdf
Everything in one case.

Thanks for the links, will read up!
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Old 19th January 2021, 07:27 AM   #1047
ghitus is offline ghitus  Italy
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Hi guys, given a transformer AC output, how can I calculate the DC voltage output for a PSU with this rectifier? For normal diode rectifiers the formula is DCV = 1.414 x ACV - 1.414. Can I apply the same formula with lt4320 based rectifiers or is it different?

Thank you very much,
Gaetano.
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Old 19th January 2021, 07:34 AM   #1048
jean-paul is offline jean-paul  Netherlands
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Yes it is exactly the same. However normally the calculation distracts 2 x Vf of the diodes (the last part 1.414 is normally 2 x 0.7V) which we practically don't have with ideal rectifiers.

The very low Vf like a few tens of mV makes that in practice the theoretical voltage is the result. It would be like DCV = 1.414 x ACV - 0.12. Don't underestimate this as for instance with low power DC power applies one can often choose a lower transformer voltage and reduce losses/heat.
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Last edited by jean-paul; 19th January 2021 at 07:41 AM.
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Old 19th January 2021, 08:31 AM   #1049
ghitus is offline ghitus  Italy
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Ok, then if I use these rectifiers for an amp PSU (e.g. 40VAC input) I can also not consider these few tens mV. Is it right?

Gaetano.
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Old 19th January 2021, 08:32 AM   #1050
tvicol is offline tvicol  Europe
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LT4320 based active rectifier
Quote:
Originally Posted by ghitus View Post
Hi guys, given a transformer AC output, how can I calculate the DC voltage output for a PSU with this rectifier? For normal diode rectifiers the formula is DCV = 1.414 x ACV - 1.414. Can I apply the same formula with lt4320 based rectifiers or is it different?

Thank you very much,
Gaetano.
You need to take in account the loss over your secondary trafo as well.

Correct formula is Vdc=(1,4142 x Vac) - 2(Rdson x Iload) - (Rsecondary X Iload)

Where:
Vdc - voltage after LT4320 rectifier
Vac - voltage at the secondary trafo with no load connected
Rdson - is the mosfet drain to source resistance at saturation. Usually at Vds > 10V
Rsecondary - Series trafo secondary resistence. In many cases this is higher than mosfet Rdson
Iload - current trough your load

Example:
A trafo that have 9Vac in secondary and able to deliver 5A.
A mosfet with Rdson 6mohm at Vds>6V
A trafo with 300mohm secondary at full load will have after synchronous rectifier:
Vdc = (1.4142 x 9Vac) - 2(0.006ohm x 5A) - (0,3ohm x 5A) = 11,16V

while with a normal bridge you have:
Vdc = (1.4142 x 9Vac) - (2 x 0,7V) - (0,3ohm x 5A) = 9,82V


Regards,
Tibi
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