High-power boost converter with CC/CV modes for a tight industrial enclosure. Off-the-shelf modules were either too large or couldn't do the firmware-selectable current/voltage profiles the application needed.
The Solution
Custom switching design with a bent aluminum heatsink that doubles as an EMI shield. The thermal path was the critical constraint; the heatsink geometry keeps junction temps under 85°C at full load in a sealed enclosure. CC/CV crossover handled in firmware with a smooth transition region to avoid oscillation at the mode boundary.
Results
Roughly a third the footprint of the commercial module it replaced. The client controls power profiles through a serial interface instead of external pots and comparators.
How the control works
The profile lives in firmware. The switching stage and its bent aluminium heatsink handle the power, while the firmware handles the CC/CV crossover with a smooth transition region so the loop never hunts at the mode boundary, and the client sets profiles over a serial link instead of with pots and comparators.The thermal path set the design. In a sealed enclosure at 50°C, the losses of a converter this size have nowhere to go. With board copper alone the switch reaches its 85°C limit at about 51% of rated power, and a flat plate only gets to about 90%. Bending the aluminium so it touches the enclosure wall and covers the switching node lowers the thermal resistance enough to run at full power under the limit, and the same part shields the noisiest node.
