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…