Bridge rectifier from a controller chip - Page 1
Forum section: electronics / projects

author: Frederico Acardi
author_rank: Contributor
timestamp: August 13, 2021, 11:16:19 am
content: Hello I am trying to find a solution to make an ideal bridge rectifier (MOSFET) to make a DC output.I need to be able to feed it 300VAC 60Hz and get 450VDC 120Hz at 1A Max.(I need to add that I would like a solution which dont need to add too big caps after the bridge to get a stable DC)I saw this solution from LThttps://www.analog.com/en/products/lt4320.html, but it only support up to 72VDC output.I saw NXP TEA2208 solution but it seems it will not be able to produce DC after the bridge rectifier. Even if I use capacitors after.see here (https://community.nxp.com/t5/Power-Management/TEA2208-Switch-Speed-Waveform/m-p/1153992/highlight/true#M1163)Is there any way to achieve it ?Do you know any chip controller that would allow me to do it ?Do you know what I should look for in a mosfet specs for the best design ?Thank you.

author: Terry Bites
author_rank: Super Contributor
timestamp: August 13, 2021, 12:07:12 pm
content: have a look at thishttps://www.farnell.com/datasheets/1801529.pdfor thishttps://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwi8iqPUiq7yAhWHfMAKHQwbCroQFnoECAYQAQ&url=https%3A%2F%2Fwww.analog.com%2Fen%2Fabout-adi%2Fnews-room%2Fpress-releases%2F2015%2Fpower-factor-correction-boost-controller.html&usg=AOvVaw3JZBIl2ekvu2-0JGHLO6J-Itsa PFC bost converter. You dont need to worry about bridge losses or massive caps. The design process is not so complex.There are many PFC boost controllers out there. eg LT8312What is wrong with a using bridge rectifier? Your current is low so no great losses, about 0.5%. If you rectify 300V AC with ideal diodes you can only get 424V (300*sqrt 2) peak even with monster caps, so some form of boost is required. In what context do you want to achieve this conversion?

author: Frederico Acardi
author_rank: Contributor
timestamp: August 13, 2021, 12:16:32 pm
content: Hello thanks. But I still need a bridge rectifier to convert AC to DC before the PCF boost converter.I wanted to have an active bridge rectifier made with mosfets like this,

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 12:23:09 pm
content: It will be hard to get any efficiency advantage compared to regular diode rectifier. Losses already are less than 1% when rectifying 300VAC with regular diode rectifier, good luck doing better than that with MOSFETs. So there is no point using that.QuoteAnd how synchronous MOSFET rectifier is supposed to help you with that? It's for lower loss at when rectifying lower voltages. Nothing to do with your intention of reducing smoothing capacitor whatsoever.QuoteThen the question is for what the small capacitance requirement is for? PFC does not have smoothing cap on it's input, it accepts rectified pulsed DC voltage.

author: TimNJ
author_rank: Super Contributor
timestamp: August 13, 2021, 02:58:02 pm
content: I checked out those new NXP bridge rectifier controllers a few weeks ago. I have no clue what their intended market is...someone with a lot of money I think.Look at the User Manual for TEA2208T:https://www.nxp.com/docs/en/user-guide/UM11348.pdfFor a 500W nominal application, they show you can get ~0.7% improvement over a diode bridge. First off, not that much, and secondly, the cost difference is absurd! You need four 600V rated MOSFETs with RDSON < 30mΩ! The recommended MOSFET is IPT60R028G7, which costs $15USD each at 100pcs quantity! And the TEA2208T controller is like $5. So, that's $65 BOM cost for 0.7% improvement for their nominal application. The cost of the GSIB15A60 bridge they compare against is...$1.50!!Perhaps as time goes on, the cost of the MOSFETs will go down. But for today, the value proposition is pretty abysmal. Maybe a super space constrained military application (see: deep pockets) will pony up for this, but otherwise, I don't think so.

author: David Hess
author_rank: Super Contributor
timestamp: August 13, 2021, 04:54:38 pm
content: I have seen it done using a comparator for each MOSFET to hold the MOSFET on when the body diode would otherwise conduct. The tricks then become supplying power to the comparator circuits and making them handle the high reverse voltage.As Terry Bites points out, only a very small improvement in efficiency at high voltage is available over just using diode rectifiers.

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 05:16:22 pm
content: At 1A max current quite likely that controller and driving MOSFETs will consume more power than any power savings from improved voltage drop.

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 05:24:43 pm
content: Quote from: TimNJ on August 13, 2021, 02:58:02 pmWith 115V mains voltage. With 230V Probably there will be no improvement at all.

author: Frederico Acardi
author_rank: Contributor
timestamp: August 13, 2021, 05:37:24 pm
content: So its pointless for efficiency ? It is not worth it, thank you all for the help.But can it help with noise compared to schottky bridge ? And how they compare with transformer secondary ringing ?

author: TimNJ
author_rank: Super Contributor
timestamp: August 13, 2021, 06:20:33 pm
content: Quote from: Frederico Acardi on August 13, 2021, 05:37:24 pmYes, it's pointless in 99% of applications. Schottky bridge rated at mains voltage doesn't really exist. There are some high voltage Schottky diodes out there, but I think their forward voltage is even higher than a standard silicon rectifier.Just use something like a GSIB15A60 or GSIB25A60. No active bridge controller is going to give you steady DC...It's just meant to replace a bridge, that's all. If you need steady DC, use a PFC stage. At 500W, try UCC28180. You can probably get a demo board for reference.Also, if you are not experienced in this...please be careful. Remember to take precaution when working with mains as to not kill yourself.

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 06:34:16 pm
content: Quote from: TimNJ on August 13, 2021, 06:20:33 pmI don't think that using 15-25A rectifier for 1A current is appropriate. You will probably have something like 0.2-0.3V less voltage drop compared to much smaller rectifier.

author: TimNJ
author_rank: Super Contributor
timestamp: August 13, 2021, 06:53:42 pm
content: My bad, I was thinking about a ~500W project I am tangentially working on, where the current is more like 5-6A @ 90Vac. OP is talking about ~1A @ 300Vac.That said, if the OP was considering spending all that money on an active bridge circuit, then spending a $1.50 on the 25A bridge doesn't seem too bad.

author: Frederico Acardi
author_rank: Contributor
timestamp: August 13, 2021, 07:24:33 pm
content: Thank you guys.I don't care about the price, because its just a one off build, and i wanted to test these bridges, I don't have a production in mind so you can give me pricey solutionsBut I think wraper wanted to say that if I use less current handling parts, the voltage drop will be smaller than with high current parts.

author: wraper
author_rank: Unknown
timestamp: August 13, 2021, 07:31:49 pm
content: Quote from: Frederico Acardi on August 13, 2021, 07:24:33 pmVoltage drop will be smaller with diode rectifier rated for higher current, but look at actual forward voltage numbers at given current for particular rectifier. But the difference will not be large enough to make any significant difference. FWIW there are many other places where to optimize power consumption before even looking at mains rectifier since there is only a tiny efficiency improvement possible.

author: David Hess
author_rank: Super Contributor
timestamp: August 13, 2021, 08:02:33 pm
content: Quote from: Frederico Acardi on August 13, 2021, 07:24:33 pmThat is true, but power lost due to reverse leakage and charge transferred through the increased junction capacitance will be greater. So increasing the size of the rectifier eventually results in higher losses.