8 Frequency Selection

Raising the frequency of a switched-mode power supply results in a size reduction of many of the reactive components. The transformer is typically the largest single component in the DC/DC converter, and its physical size is highly dependent on operating frequency. The high efficiency of a GaN switch at elevated frequencies is the fundamental tool for reducing solution size.

Figure 8-1 shows how the operating frequency affects the transformer volume in a CLLLC converter. The transformer volume is normalized to the volume at 100 kHz, which means that at 500 kHz, the volume of the transformer should be about 35% of what a 100-kHz design would be. This enormous volumetric reduction means that designers will need to consider a few other factors before deciding on the exact switching frequency.