Analysis of Instantaneous Switching Frequency of a Hysteresis Based PWM for Control of Power Electronics

Delta Sigma (LambdaSigma) analog to digital converters are usually comprised of an analog modulator and a digital low pass filter. The delta sigma signal processing (DSSP) directly handles high frequent LambdaSigma-bitstream. One of the first approaches of DSSP was presented in [1]. In the present paper, a new approach of DSSP based on [2] and [3] will be used. The advantages of using the high frequent LambdaSigma-bitstream instead of a filtered signal are a high bandwidth in the control loop and alleviated timing constraints for measurement synchronization. To fully utilize the advantages of this concept, a new PWMmodulator (LambdaSigma-PWM) was presented in [4]. As with all other schemes, where a hysteresis element generates the switching cycle, the frequency depends on the magnitude of the reference and other parameters like hysteresis width and signal delays. This paper focuses on the choice of parameters to define the mean value of the switching frequency and its spectral spread.