comparing to a high efficiency GaN solution without lossless sensing, the power loss savings by eliminating the external resistor results in a +0.5% efficiency benefit for the overall system at the most critical thermal conditions at 90 VAC input as seen in Figure 8. The improvements over a silicon solution would be even more significant. Alternatively, designers may opt to use higher RDS(ON) power switches which offers an even more cost-effective solution while achieving the same efficiency they were achieving previously with the reduction of total series resistance in the power path. In Figure 9, you can see how removal of the RCS hotspot component and improving the efficiency ultimately affects the thermal performance of the power supply. 0.945 0.94 0.935 0.93 0.925 0.92 0.915 80 NV6125 (170 mΩ) NV6136 (170 mΩ) Efficiency + 0.5% 120 160 200 AC Line Input (Vac) 240 280 FIG 8 Efficiency improvements over series-shunt current-sensing GaN solution. Tcore = 83.4 °C 95 NV6125 RDS(ON) = 170 mΩ TGaN= 83 °C TRs = 84.7 °C RON(TOT) = 340 mΩ RCS = 170 mΩ RCS = 85 °C 25 95 NV6136 Tcore = 80.7 °C RDS(ON) = 170 mΩ TGaN = 72.2 °C RON(TOT) = 170 mΩ RCS = 0 mΩ NO RCS NO HOT-SPOT TGaN = -10 °C 23.9 FIG 9 Thermal effects of efficiency improvements with lossless current sensing. June 2022 z IEEE POWER ELECTRONICS MAGAZINE 35 Efficiency