Calculations on the spectral performance of discrete pulse modulation strategies

Discrete pulse modulation strategies such as delta modulation and sigma-delta modulation have been used in power electronics for more than a decade. They have gained more interest recently because they perfectly match the requirement of resonant link converters to restrict switchings to discrete points in time. The spectral performance of a sigma-delta modulator is calculated analytically without requiring complex mathematics. For the case of a DC input, the spectral components of the modulator output are given as closed-form expressions. For rectangular voltage pulses, the harmonic content of the output current in an inductive load is derived in closed form for both DC and sinusoidal inputs. The results are compared with similar expressions for PWM