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LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)
LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)
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Old 3rd July 2018, 11:03 AM   #1
doctormord is offline doctormord  Germany
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Default LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)

Anyone in for a testrun of a LTC3784 2/4 phase boost converter?

LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-polyphaseboost-1-jpg

The converter ist meant to power a class-d amplifier from different sources and is intended for use with the TPA3151 or TPA3255 but not restricted to this.

LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-59_ltc3787_schematic-png

LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-169_compensation-png

Design is made for either 2 or 4 phase operation at ~250kHz.

Input Voltage is 10V minimum up to the desired output voltage with pass through if the input voltage is higher than the output. This is especially usefull when using a 10s lithium pack to power an amp at 36V native voltage. As long as the pack voltage is higher than 36V (42V max for 10 cells) it is passed through the converter for best efficiency. When the input drops below 36V the converter starts boosting. Efficiency is in the range 90-98%.

Simulations are done for 1000W cont. load:

2 phase:
LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-5_bsz067n06ls-png

4 phase:
LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-14_bsz067n06ls_4ph-png

Initial design parameters:

600W cont. output
1200W peak output (thermally limited)

regulation loop bandwidth > 10kHz

4 phase operation for 12V SLA battery input with up to 30A per phase
2/4 phase operation for voltages greater than 24V like SLA in series or lithium battery packs
100*100mm in size


The PCB is a 4 layer board with 100*100mm in dimension. The design is finished and several use cases are available for simulation in LTSpice and LTpowerCAD.

Motivation:
Even if there are boost converters available for "cheap" from Aliexpress/TaoBao/Ebay, these are mainly limited to about 30A cont. input current and single phase (hard switching) with lots of radiated EMI (by design). With 10V input voltage under load, these run out of "ompf" at about 300W input power. The 2/4 phase concept shown here is able to push 30A per phase so 1200W from 10V input should be possible.

Groupbuy intent:

This groupbuy is for a bare PCB with schematics, BOM and assembly instructions. I want to order a minimum of 10pcbs but actually need less so thats where you can jump in.

For the first run i'd order standard 1.6mm, 4 layer, 1oz, green silk board with HASL. The price for one PCB is roughly 7€ then. If there's enough interest, we may order ENIG (2oz.) boards with Red or Blue silkscreen.

International shipping is 4€ untracked or 6.20€ tracked with "Deutsche Post" from Germany.

Risks:

The design is practically untested (as usual for the first run), so their is a small risk that some things need manual patches. Having said that, the implementation is working in simulation (LTSpice, LTpowerCAD), so the chances are high it works out of the box. Things need tweaking are regulation bandwidth and compensation.

I've done several designs for class-D, dsp, audio, etc. in the past, so this is not my first project. You may check on 360customs.de which is my uncommercial build blog.

Best regards,

Christian
Attached Images
File Type: jpg PolyphaseBoost - 1.jpg (185.7 KB, 299 views)
File Type: png 59_LTC3787_schematic.png (86.2 KB, 306 views)
File Type: png 169_compensation.png (67.6 KB, 289 views)
File Type: png 5_BSZ067N06LS.png (129.1 KB, 277 views)
File Type: png 14_BSZ067N06LS_4ph.png (128.6 KB, 273 views)

Last edited by doctormord; 3rd July 2018 at 11:08 AM.
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Old 31st July 2018, 04:33 PM   #2
doctormord is offline doctormord  Germany
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Actual digikey BOM cost is at 100€+tax. Simulations do look fine for 50V output voltage at 23A load current stepped up from 10V input voltage. (draining ~123A from the battery)
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Old 31st July 2018, 06:56 PM   #3
xrk971 is online now xrk971  United States
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LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)
Nice project Dr Mord! Can this be a dual rail supply?

In any event, you can out me down for a pair of boards.

---

I recently have been working with JPS64 to make a simple way to get really clean +/-18v at 1amp to 2amps for smaller amps and preamps. All powered from 8v to 18v wallwart without need for dealing with mains AC voltages and dangers associated with linear transformers.

Here is a design for a 1amp supply with TPS7Axxx low noise LDO's (it's the middle rectangular board):
Click the image to open in full size.

Simple High Performance DC Coupled Class A HPA with sub PPM THD

Here is a 2amp version with some different parts (the rectangular board on left):
Click the image to open in full size.
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Old 13th August 2018, 05:12 PM   #4
doctormord is offline doctormord  Germany
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Thanks, what are all those VIAs do in your layout? Does this have any benefitical effect to the signals when not done in multistrip-configuration?


The LTC3784/87 is single supply only, i built up one prototype for measurements and tuning.


LTC3784 2/4-Phase Boost Converter for up to 55V Output 600/1200W (TPA3251, TPA3255)-img_2359_1280-jpg
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File Type: jpg IMG_2359_1280.jpg (364.9 KB, 139 views)
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Old 30th August 2018, 08:37 AM   #5
irs20957 is offline irs20957  Russian Federation
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Very Nice!
I build full isolation DC/DC 10-14>36/48V, for car and other using, may be LLC
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Old 2nd September 2018, 02:18 AM   #6
doityourselfamp is offline doityourselfamp
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any shared doc here ?
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