Google’s proprietary STC employs LC resonant tank to realize soft charging and soft switching. This technology enables high efficiency high density 48V bus as the first stage conversion in a two stage step down system. Two stage combined efficiency varies in various load conditions. High STC converting ratio provides lower input voltage of second stage which leads to less switching loss in 2nd stage VRs. Lower converting ratio gives less current stress of 1st STC converter in high output power range. As a result, high converting ratio is beneficial in lower output power application, while low converting ratio has advantage in higher output power. Wiwynn is proposing a dynamic converting ratio STC design to further optimize 2-stage combined efficiency by altering converting ratio based on output power.
• High converting ratio operation in lower load
• Parallel resonant legs and operates in low converting ratio in heavy load