Sigma Delta Modulation 2.0

Bitstream Control is a pioneering control strategy for three-phase synchronous motors enhancing dynamics and accuracy while reducing switching losses in the inverter.

Bitstream Control

Energy efficiency becomes increasingly important. Motor drives provide an extensive area for improvement. Electrical power losses in servo drives occur in the power stage and motor coils. Reduction of these losses is extremely relevant for energy efficiency but also for general systems, which also need to achieve high dynamics in challenging applications.

Trinamic implemented a new bitstream based control structure, which reduces switching actions to a minimum in order to minimize losses. This fundamental change of electrical drives’ control systems is achieved by modifying a common space vector modulator to perform as a phase voltage controller. This control block is only applying the voltage when it is demanded by the current controllers.

The A/D-conversion for this control scheme is realized by Delta-Sigma modulators, which are converting an analog signal to a high-frequency bitstream. The analog value’s digital counterpart is hidden in the mean value of the bitstream. State-of-the-art servo controllers use Delta-Sigma modulators combined with digital filters as A/D converters (ADC) for current measurement. Thereby typical distortions in these applications are successfully suppressed, a feature hard to achieve by sampling ADCs.

Bitstream-based control is the natural evolution of this development and acts directly on the bitstream and thereby supersedes the digital filter-based control strategy. The control scheme is superior in performance and accuracy in comparison with state of the art control strategies and voltage modulators.