Triple outputs 160W Lab PSU -- EPSUX3 version 2 ! - diyAudio
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Old 17th October 2014, 01:19 PM   #1
Frex is offline Frex  France
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Arrow Triple outputs 160W Lab PSU -- EPSUX3 version 2 !

Hello,

As promised in the previous thread, this is here a new
start for an "upgraded" version of the unfinished v1 lab power supply.

A big piece of the job design has already done, but many work still
to be done before to have a "ready to be build by anyone" serious project
without any malfunction.
Another important point, for this new design i've take care as possible
to choose low cost and easy to find part in order to give the better chance
to build a DIY high performance PSU without paying more than a commercial
one.

So i will post here regularly the project progress.

First, the key specifications of the EPSUX3v2 laboratory power supply:

- Small and light weight design.
- Triple isolated outputs, 160W total power available.
(2 x 0..20V 0..3A + 1 x 0..12V 0..3A).
- Wide input voltage main 85..265AC 50/60Hz.
- High-efficiency design.
- Current or voltage regulation available down to 0V.
- Voltage or current displays for each outputs.
- Mixed switching/linear outputs regulations .
- Very fast transient response and low noise.
- thermal sensor
- Symetric output mode with only one setting (master/slave mode).
- Output disable switch (no need to turn off the PSU).
- Magnetic part easy to build (DIY friendly).
- Low cost and easy to find components.
- Designed with EMC and safety considerations.

The EPSUX3 will use same enclosure and front panel design as the V1.
So, a picture of the EPXU3v1, just for remember of how does it look:
Click the image to open in full size.

Many improvements has been made in the new specs.
The input AC/DC convertion is done now by a PFC
and LLC converter, allowing more power and higher
efficiency.

The output stage use now a buck step-down converter
followed by a new linear regulator from LinearTech, the LT3081.
For this output stage, i was inspired by this article in LTmag.

The presence of a linear regulator will improve drastically the
output transient response and avoid the need of high value
filtering output capacitor that is undesirable for a lab PSU.
Linear regulator reduce also the switching noise
from step down pre-converter.

You can see bellow the Beta version of the EPSUX3v2 full synoptic :
Click the image to open in full size.

Here, a more detailled synoptic of the output stage block :
Click the image to open in full size.


Today, i have done some job on the PFC stage (based on NCP1654 IC from Onsemi).
It seem working fine from 0 to 220W and for 90 to 250Vac at input.Cool !
A small picture of the prototype "on the fly" board ;
Click the image to open in full size.

I love to build design like that...





I will come back soon.
Regards.

Frex

Last edited by Frex; 24th October 2014 at 04:33 PM.
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Old 19th October 2014, 09:05 AM   #2
Nisbeth is offline Nisbeth  Denmark
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Looks very nice as usual, Frex

/U.
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Old 19th October 2014, 09:47 PM   #3
carpin is offline carpin  Netherlands
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I am following this interesting project closely.
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Old 20th October 2014, 06:45 AM   #4
jcga is offline jcga  France
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Hi,
looks very interesting, I will folow the progress as I would like to build one of these
JC
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Old 21st October 2014, 11:58 AM   #5
Spirtos is offline Spirtos  Greece
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Looks very nice & interesting project as well as the previous version.
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Old 24th October 2014, 04:40 PM   #6
Frex is offline Frex  France
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Hello,

I had missed to give the LTmagazine Article link. It's now corrected in post #1.
This is the article that inspired the hybrid output regulator in the EPSUX3v2.
It must render unto Caesar what belongs to Caesar.

Some projects news tommorow.
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Old 26th October 2014, 12:45 PM   #7
Frex is offline Frex  France
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Hello,

Some news of the project progress.
I worked on PFC optimization, trying various inductor (home made and commercial).
Working with high efficiency is much more easy from a 230V main (EU) than 110V..
I get about 97%@200W with 230V main, but hardly 94% with 90Vac.
The PFC design is now mainly clean, just need to test others MOSFETs
for optimizing cost/efficiency (i receive parts these days).

I will work next weeks on LLC that works, but i want to do some changes.
I want to try to replace the gates drive transformer with a silicon driver.

I worked also lately on the CPLD design and all parts speaking with.
From the previous design, i replace the ADC (ADS7816) and the analog mux (DG408)
by a 8 inputs low cost ADC, the MCP3208. This solution is much less expensive and need much less space.
I also replace all digital potentiometers (AD8402) by a dual SPI DAC, the MCP4802 ( that are also less expensive).

I used a prototype board to test each new parts to test functionality and validate the CPLD code.
In the previous design, the digitals potentiometers controlled a voltage divider that giving
a non-linear output range from digital code. Now, a big improvement has been done using
a new control method. I use the control pin from the LT3081 regulator that are drive
by the dual output DAC (1 output for voltage setting and one for the current setting).
This control scheme allow a linear variation of the output with the DAC code.
The DAC work fine and the ADC is not yet functional but it's a question of days.

In parallel of that, i built a prototype board to test the output regulator section (buck+LT3081 hybrid regulator).
The design is mainly inspired from the LT journal note, but because their design use a very small
and hard to solder buck IC, i replaced it by a TPS5450 regulator in SOIC8 package, more DIY friendly.
The hybrid regulator work fine with this buck IC. The very precise voltage and current settings allow
and real square V/I regulation. Another interesting function is it's ability to regulate the output voltage down to 0V.
This require a small negative current to be sourced on the output.
A small negative voltage generator allow this (-8mA).

Currently, i don't have done serious measurements on the regulator (like noise and transient response).
The LT note describe mainly the same topology and there is no reason that i find very different results from us.
Anyway i will done some measurements these weeks.

You can see below some pictures illustrating the current work from each part.
The questions and remarks are welcomed.
I will be continue to post project news to let you informed.
Regards, and to soon.

Frex


The CPLD DAC/Display and ADC proto board :
Click the image to open in full size.

The EPM570 eval board
Click the image to open in full size.


Both connected together
Click the image to open in full size.


The output regulator board TPS5450 + LT3081
Click the image to open in full size.


The LT3081 zoom ( schottky bridge rectifier for the the 3 outputs of LLC on background).
Click the image to open in full size.
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Old 26th October 2014, 02:00 PM   #8
AR2 is offline AR2  United States
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Frex,
I love when you do projects. Your projects are so informative and interesting to follow. Not to mention, a great addition to every home lab. If there is such an award, than your projects would be in the all time DIYAudio Hall of Fame, branded as Frextronix.
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Old 26th October 2014, 03:54 PM   #9
jcga is offline jcga  France
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+1
And for sure I will build one !
Best from France
JC
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Old 26th October 2014, 10:36 PM   #10
carpin is offline carpin  Netherlands
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On the CPLD DAC/Display and ADC proto board, I see the 4 digit display, do you use this setup in the final design?
From 3 digit to 4 digit?

Thanks
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