A class D system with optimal THD for automotive applications

A class D system consists of a class D amplifier and an LC filter. To guarantee the best THD performance, both the class D amplifier and the LC filter must obtain optimal THD. State-of-the-art class D amplifiers can obtain up to -90 dB THD. However, the LC filter exhibits orders of magnitude lower THD due to the LC components linearity. As a result, the THD performance of such a class D system will be bottle necked by the LC filter. One way to mitigate the issue is to include the LC filter in the feedback loop of the class D amplifier. However this complicates the loop stability. Another way to mitigate the problem, is to use a so-called “feed-forward” LC non-linearity compensation can be performed. The LC filter characteristics will first be measured during start-up, and then dynamically compensated by the class D amplifier during the normal operation. The student will build a complete class D system with an existing class D amplifier and different types of the LC filters, to optimize the system THD performance.

Contact

dr. (EI group) Qinwen Fan

Electronic Instrumentation Group

Department of Microelectronics

Last modified: 2019-10-02