LT4320 based active rectifier

[prasi]

1 jonboylaw 2 nos?
2 tombo56 2 nos.
3 prasi 4 nos.

 

[nautibuoy]

Hi prasi, apologies in advance if I've not been keeping up but a couple of questions if I may.

Referencing the schematic in post #165;

1. I have soldered up my boards with a 10uF ceramic cap in position C1 so I'm assuming I don't need the electrolytic in C2?

2. I have a couple of the odler HASL boards and they have pads for CS, RS and CX but on the newer boards these aren't present?

3. I omitted the LED because I ordered parts that were too small - I misjudged the pad size for the LED and RLED - I managed to solder the resistor across the pads but not the LED - can you confirm the smd part sizes for future reference. I couldn't find an smd BOM?

 

[jonboylaw]

1 jonboylaw 4 nos.
2 tombo56 2 nos.
3 prasi 4 nos.

 

[prasi]

Hi Nautibuoy,
here are the answers
1. yes, electro not required.
2. yes, snubbers were removed as it might be convenient to have tht snubbers on the main psu boards where this daughter board fits. e.g. my (now out of stock) CRCRC PSU PCB
3. the LED is 1206 size and its corresponding resistor is also 1206 with slightly bigger pads. the three dots indicate the cathode side,,

 

[nautibuoy]

Thanks prasi.

That's a shame about the snubber disappearing as I will be using these with ZM's Cap Bank PCBs as part of my SissySIT project so I have no convenient way of implementing them. Maybe I'll make a small sub-board to plug into the AC connector pads - worth the effort?

I'll get some 1206 LEDs next time I place an order for some parts.

Cheers

 

[prasi]

I think many guys have posted that lt4320 doesn't need snubbers ... so I do not think it worth the effort.

 

[nautibuoy]

Thanks prasi, I'm all for avoiding unnecessary work!

 

[danishdart]

I have a question for Prasi. Is the irfz24npbf MOSFET Suitable for the LT4320?

The only of the four crucial parameters that I don't understand in its Datasheet
is for the Gate charge(Qg). It says 20 nC . Is that Nanofarad and is it low enough?
I think it refers to capacitance.
Any help would be appreciated.

 

[prasi]

the four parameters that you can consider are
Vdss >> your intended output voltage.
Rdson< 10mOhm
Vgsth between 2-3 V or slightly more
Qg: < 50nC
refer to tvicol post below
LT4320 based active rectifier

 

[danishdart]

Well it looks like it's all within spec. Thanks prasi for condensing all that information for me. Even the internal diode is good.

 

[prasi]

hello dani,
only that the Rdson seems to be 70mOhm, which is a bit high..

 

[danishdart]

Ooh yes! You're right.
In my head I was off by one decimal point.
Thanks for saving me there.
I've already ordered from digikey some MOSFETS
from your list in an earlier post.
I'm at work so I can't elaborate But I'm sure they will be fine.
I'll just have to wait.

 

[triode_al]

the four parameters that you can consider are
Vdss >> your intended output voltage.
Rdson< 10mOhm
Vgsth between 2-3 V or slightly more
Qg: < 50nC
refer to tvicol post below
LT4320 based active rectifier

My Mosfets are 0,035 Ω (VNP28N04) and 0,022 Ω (RFG50N06) respectively.
tvicol says :

Selecting the right mosfet is a challenge. You can end with a good ideal bridge or a poor one. -- At very first start internal diodes are conducting till output voltage reach operation level for LT4320. Internal diodes must be able to sustain entire capacitive load for a very short time. An low esr 10000uF capacitor will surge up to 10A in a very short time.

I'll go ahead but am a bit scared 😱
I don't even understand how it works, because the internal diodes conduct in a different direction than the mosfet . . .

I bought a finished ideal bridge but somewhere it disappeared after delivery . Now my wife says I should be a good boy and clean everything up, then I'll find it. Makes me cry.​

 

[danishdart]

Hi Prasi. I sent you a PM. Is it possible for me to order
10 * LT4320 THT boards?

 

[SHC14]

Hi Prasi, I sent you a PM about an order for 20 * SMD LT4320 boards.
Is it always possible to get this board ?
Thanks.

 

[danishdart]

I had a more thorough reading of this thread and found that prasi had already posted the gerber files for the THT boards and
after uploading them at PCBway I received 20 boards today. Thanks prasi.

Whilst on their site I noticed that under their "shared projects"
there is already a design for SMD LT4320 boards there ready to be made by PCBway.
Here is the link: LT4320 - "diode bridge" - Share Project - PCBWay

 

[triode_al]

I finally installed the Ideal Bridge in a separate house. I have CLC: 2.200uF - 22mH/0.25 ohm - 10.000 uF. I have 5x7.1 volt winding; No load 49.5Volt; at 2.7 Amps it is 44.3 before and 43.5 V after the choke. The residue is about 12-15mV pure sine.

So incredible.

- Well worth the time. [I could not find the chips; only Mouser has them but my basket said € 20 shipping. So I Aliexpress-ed it that took 6 weeks. Not an expres service]

 

[triode_al]

Does this work with center tapped transformers (say 18-0-18V), or do we need two separate winding for this to create symmetric power supply?

Bridges are getting super hot (upwards of 75C) in my Aleph J build, and I need to figure out a way to lower the temperature inside the chassis!

Each polarity needs its own rectifier. Center tapped will blow the ideal bridge. And yes, my standard big metal 25A bridges used in my a Pass SIT got hot too, and performance was bad.

 

[xrk971]

You cannot use center tapped topology for the LT4320.

 

[prasi]

I finally installed the Ideal Bridge in a separate house. I have CLC: 2.200uF - 22mH/0.25 ohm - 10.000 uF. I have 5x7.1 volt winding; No load 49.5Volt; at 2.7 Amps it is 44.3 before and 43.5 V after the choke. The residue is about 12-15mV pure sine.

So incredible.

- Well worth the time. [I could not find the chips; only Mouser has them but my basket said € 20 shipping. So I Aliexpress-ed it that took 6 weeks. Not an expres service]

Hello triode,
congratulations on the build. lucky you got goodones from aliexpress.