A new project for 2017, the dual channel 300 W
programmable DC electronic load.
I just finished testing the prototype DC Load Module for the project, and except for a few small issues with hole diameters all went well. The initial test was at 25 volts and a load current of 3 amps, for a total dissipation of 75 watts.
The goal of the project is a programmable, dual channel DC electronic load capable of 300 watts and a maximum of 30 volts and 13 amps.
The microprocessor I plan on using for the project is the Teensy 3.2, and the current plan is to mount everything in a reused HP 6200‑B power supply enclosure.
What makes this load module different than many of the past MOSFET based electronic loads, is the IXYS IXTX110N20L2 Linear MOSFET. This MOSFET was designed to operate in the linear operational region with an extended FBSOA.
The MOSFET has a maximum rating of 200 volts and 110 amps. So a single MOSFET should meet and exceed my design requirements.
I included a Maxim Integrated 44284AUT current sense amplifier with a gain of 50, on the load module close to the 4‑wire sense pins of an Ohmite 0.005 ohm current shunt resistor.
The heatsink is a Wakefield-Vette OMNI-UNI-41–75, which can be mounted as a pair with a 60 mm fan cooling the main fin channel. The fan is rated at 40 cfm at 1 ” H2O pressure. It will be interesting to see how well the fan / heatsink combo keeps the MOSFET at a safe temperature under a full load. I may need to add a second MOSFET just to spread the heat more evenly across the heatsink.
I still need to make some voltage drop measurements of the circuit board under full load to verify that the prototype circuit board with 1 oz copper traces will handle a continuous load, or if I will need to change to 2 oz copper traces.
I have already completed some initial testing of the current sense Op-amp with the Teensy 3.2 microprocessor, but still need to finish the MOSFET control design.
More to come…
I am very interested in seeing how you are progressing with this project. I just ordered a pair of heatsinks, a handful of the MOSFETS, and the 4 wire current sense resistors in preparation for making my own 🙂
Have you shared the latest version of the PCB for this? I saw your March 2016 update and am looking to build this version, with or without the uC control… I have a real need for a DC load and I love this design so far.
Thanks!
SH
Hi Sonny,
I am making slow but sure progress on the DC Load project. The L2-MOSFET boards are mostly done with the exception of some minor spacing issues with the 0.5 ohm balance resistors.
The MOSFET boards do need to be made using 2oz 0.8mm copper. I am also in the process of changing the MAX44284F (50V/V) to the MAX44284H (100V/V) to match the current range on the control board.
Heat-sink components must be mounted before installing the 4 terminal current shunt resistor otherwise it interferes with the clamps.
Link to the Eagle CAD V7.7 Rev 0.2 ZIP file is below. Use at your own risk as there have been small changes since the last tested version.
https://www.barbouri.com/assets/ThermalSingle02.zip
Greg (Barbouri)
Hello.
Is there any progress with the project?
Hi Krong,
Currently no progress on the DC Load project, as I am using all my free time on test equipment repairs.
Basically the MOSFET DC Load section is finished only requiring a control section.
The control section can be as simple as an op-amp and potentiometer to set the current.
Greg (Barbouri)
Is ThermalSingle02 the latest version of files?
Could you share it if it isn’t?