Thermal Tests (with images)

November 14, 2013 in 8 Channel PDU by Joshua Oster-Morris

I received the thermal imaging camera yesterday and went about doing my first thermal survey of the Motobrain this morning. In this test, I let the Motobrain draw about 40A for an hour and then took some thermal photos of it. What I found surprised me. I assumed the warmest part of the circuit would be the switching transistors that all the current is flowing through. This is not the case however. It turns out the hottest part of the circuit are the MOSFET drivers which use a charge pump to create 20V+ and are used to turn the MOSFETs on and off. After an hour the drivers are running at about 37C as you can tell from the top photo below (the cross hair is on the driver chip). The second photo shows the bottom of the power board which is the board that has all the current flowing through it. The warmest part of it is <32C after an hour (this board is thermally coupled on both sides so the top and bottom should be roughly the same temp). That is not very exciting at all. That is hardly even warm. Great news for Motobrain! The third photo shows Motobrain against the backdrop of the test jig. It is the coolest thing in the frame essentially. I promise, all the 40A of current driving those loads in the background are running through the Motobrain but its impedance is so darn low it doesn’t break a sweat.