Can oversampling improve the dynamics of PWM controls?

Abstract

Regular Sampling is the state of the art when employing digital discrete-time control to pulse width-modulated systems. However, the fact that the dynamics of discrete-time control is below that of an analog continuous-time control is often not being aware. The paper shows that digital control dynamics can be improved with oversampling, i.e. employing a higher rate for sampling and controller updating as with Regular Sampling without increasing the pulse frequency. As a result, it is shown that already an oversampling rate of about 8 to 16 provides approximately the same dynamics of a continuous-time control. The benefits of even higher oversampling rates are of minor significance, which can be understood as a clear design recommendation. Though the consideration is carried out with a simplified circuitry, the results are of general meaning and can be transferred easily to application in the area of drive control or switched-mode power supplies.