Digital current control using a switching power amplifier and sigma delta modulation

In this paper a new method for driving a switching power amplifier by use of sigma delta modulation is proposed. After an explanation of the principles of sigma delta modulation the digital control concept is presented. The conventional solution by means of both, digital to analogue conversion and pulse width modulation is replaced by a pure digital one. A digitally implemented sigma delta modulator directly drives a switching power amplifier. Experimental results show the success of this concept in controlling the current in an active magnetic bearing for the lévitation of an iron ball.