Low Complexity Digital Quadrature Oscillators for Variable Frequency Applications

Switching frequency is utilized as a degree of freedom in digital control strategies for power converters. In addition to carrier-based schemes, quadrature oscillators offer an alternative method for the generation of variable frequency switching pulses. In this article, amplitude instability in a computationally simple digital quadrature oscillator is analyzed. Algorithms for stabilizing the oscillator are developed based on this. Further implementation issues arising are addressed and a systematic comparison to carrier-based schemes is executed. It is shown that the proposed approach can be implemented with only four additions and four comparison steps without resorting to multiplication. The studies are validated in system simulation and experiments on a commercial field programmable gate array board.