Approximate 2-Degree-Of-Freedom control of a class-D amplifier using FPGA

In recent years, it is desired that the bandwidth of a class-D amplifier is widened using sampling frequencies as low as possible. For example, it is expected in the application of the power amplifier of vibration generator that the bandwidth is kept 5[kHz] within the load impedance ∞~2 [Ω]. In this paper, it is shown that this demand to the class-D amplifier can be attained by an A2DOF (Approximate 2-Degree-Of-Freedom) digital controller with 200[kHz] switching and sampling frequencies. The controller is implemented by a FPGA and it is shown from experiments that this demand is attained enough.