Silicon Carbide (SiC) and Gallium Nitride (GaN) power devices promise significant energy and cost savings for power electronics converters than feasible with silicon power devices. Low-voltage GaN power diodes and HEMTs rated up to 650V volts are now commercially available; and GaN power devices rated up to 3.5kV are expected soon. This half-day short course will present the physics, technology, application engineering of low-voltage (< 650V) GaN power switch modules for increased energy efficiency in a wide range of DC-DC power converter applications including computing, communication, transportation, and renewable energy integration. The design and performance of GaN power switch modules for prototype point-of-load (POL) DC-DC power converters will be discussed and tradeoffs in performance vs. cost will be critically assessed.