SLAA898 September 2022 TAS3251 , TPA3255
For a step-up transformer, it is hard to test the efficiency directly. By connecting the 1,2 (20 V) primary side with the TPA3255 device, and a 50-Ω resistor load with 70-V secondary side (based on Figure 3-7), an equivalent 4-Ω load is obtained according to Table 3-1. For this system, see the efficiency result from the red curve in Figure 4-1. Since system efficiency is a product of the TPA3255 device and the 18737, the transformer efficiency is represented by the red curve data over the blue curve data, resulting in the green curve.