Electronics > Beginners
Beefing up a Won-Hung-Lo Boost Converter
unit998x:
Hi All, I recently bought a DC-DC boost converter from eBay:
http://www.ebay.co.uk/itm/10A-DC-DC-600W-10-60V-to-12-80V-Boost-Converter-Step-up-Module-Power-Supply-UK-/350975904870?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item51b7cb4c66
It claims to be able to switch 10A, however details on it are incredibly vague and although the page shows it to be UK based, its actually made in china, so I wouldn't trust it at 10A at all.
I need to make a boost converter that can switch 20A continuous 1hr+ with peak surge of 70A. The input voltage would be 22-26V and output maximum needs to be 36V. I have traced out the PCB for this 10A device and attached a schematic, I have no idea what inductance L1 is or the value of some ceramic caps as I have no LCR meter (but I have guessed some from the UC384X datasheet). For this reason I have attached some photos of the device and its heat sink (the inductor looks a lot shoddier than in it's eBay picture.
What kind of work would need to be done on this device to make it capable of the specs above?
I have so far thought of this:-
* Increase trace width on PCB
* Higher current inductor
* Replace the rectifier with a higher rating.
* Replace the caps with some of a reputable brand
* Larger input fuse
Also, would I be right in thinking that the control side of the circuitry is fine, and it is just the power side that needs beefing up?
EDIT: RV1 is the Current Adjust POT, RV2 is the Voltage Adjust POT
Thanks, if you need any more info, just ask.
LukeW:
The current capacity of the actual switching device (eg. MOSFET, either integrated into the chip or external) obviously plays a large part in determining maximum power handling too.
It might be easier to just design and build something from scratch that meets your specs.
You mean to say you need 36V out at 20A continuous, or 720W? If that's honestly what you want you're basically wasting your time trying to hack that, you'll need to engineer something that is fit for purpose from scratch.
mariush:
The MBR20100CTL diodes are 20A 100v ... for 20A continuous you'd need 30-40A diodes. That's one of the first things you'd have to change.
The UC3843 is ancient, probably more than 15 years old now. There's much better driver chips out there. Not worth the trouble imho..
T3sl4co1l:
How about a top view photo? Trace the circuit? Any other identifiable or at least important-looking components besides chip resistors and capacitors?
--- Quote from: unit998x on June 03, 2014, 01:52:28 pm ---Also, would I be right in thinking that the control side of the circuitry is fine, and it is just the power side that needs beefing up?
--- End quote ---
Not at all. The whole thing might be shit. >:D
--- Quote from: mariush on June 03, 2014, 02:25:41 pm ---The UC3843 is ancient, probably more than 15 years old now. There's much better driver chips out there. Not worth the trouble imho..
--- End quote ---
You must be f'n kidding... people still use the MC34063 for god's sakes. Now there's a terrible chip. Only complaints I have about the UC384x are, the driver output is bipolar (= weak saturation voltages; but, beefy enough for its applications) and there's no way to compensate the overall chaotic behavior of the system (which isn't so much the chip, as the fundamental concept it is based on: peak current mode operation).
Nothing wrong with UC384x in and of themselves, but you really need slope compensation and a current transformer here. Shunt resistors and DCM aren't going to cut it, not if you want something better than, well, what's pictured above let's say. :)
Tim
unit998x:
--- Quote from: T3sl4co1l on June 03, 2014, 04:40:28 pm ---How about a top view photo? Trace the circuit? Any other identifiable or at least important-looking components besides chip resistors and capacitors?
--- End quote ---
Hi Tim, I attached a Schematic of the device to the original post called ShenzenConverter.pdf, hopefully I did trace it correctly, would the current transformer be used in place of R5 in this schematic then?
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