An Analytical Methodology to Evaluate the THD of High Power Class D Amplifiers

Compared to their analog counterparts, class D amplifiers (CDAs) have the advantages of high efficiency and are preferred for high frequency and high power applications. However, the main drawback of the CDA is its low fidelity. To improve the fidelity of the CDAs, wide-bandgap (WBG) semiconductor devices are used and the number of semiconductor devices is also increased to further increase the equivalent switching frequency. THD is an important index to evaluate the fidelity of the CDAs. The works on this issue have focused on low power CDAs. While for high frequency and high power application with Silicon Carbide (SiC) MOSFETs, some other issues become significant such as the delay, switching transition process and the voltage oscillations. These issues, which are neglected for low power CDAs, will impact the frequency spectrum of the output PWM signals and therefore influence the THD. This paper proposes an analytical method to evaluate the THD of the high power CDAs, using Silicon Carbide (SiC) MOSFETs. The evaluation method is efficient and verified by simulation results.