Analysis and compensation on nonlinearity in transfer characteristics of PWM amplifier

In this study, the nonlinearity in transfer characteristics of a PWM switching bridge amplifier is analyzed, and an inverse function concept is proposed to compensate it. The nonlinearity in PWM amplifier is caused by the dead time that prevents the shorting problem of power transistors. The nonlinearity is analyzed to obtain both the analytic solution in closed form and its simplified form for the transfer characteristics between the PWM duty cycle and the load current. These solutions are verified by computer simulation and experiment on a brushless DC motor drive. In addition, a parametric study is performed to investigate the nonlinearity in PWM transfer characteristics. Furthermore, an inverse function concept based on these solutions is proposed to compensate the nonlinearity in the transfer characteristics of PWM amplifier.