With almost every project/design I work on there is a switch-mode PSU that needs testing. In order to quantify the switch-mode PSU's performance you have to load it down to typical and worst case load conditions. This will allow you to make sure the Inductor is properly sized, the ripple current is acceptable, and just to make sure the supply is stable. In the past I would either grab a variable power resistor box or buy some 25Watt resistors and just make a load brick for the project.
The down side with using resistors as loads is you have to buy new values of resistors for every supply voltage you are testing. There has to be an easier way.... and there is!
I got the idea to make a variable Current (Sink) Load from watching one of Dave Jone's EEVBlogs.
This Variable Current Load takes out all the "Ohm's Law" guess work when applying loads. If I need a 0.5Amp load, I just adjust the pot to set 0.5V across my 1 Ohm Current Sense Resistor and I have a 0.5Amp load irregardless of the Load Voltage. The Load voltage could be +3.3V, +5V, +12V, +24V and I still have a 0.5Amp Load...GREAT!
This was a fun project and the current sink works really well. The 10 turn pot allows some pretty precision current settings. I am pretty pumped to use my new Variable Current Load on Monday to test my new project at work.
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