Integrators in pulse width modulation [switching circuits]

Abstract

Many control methods for power convertor switching circuits employ an integrator to realize PWM. Depending how the integrator is used, the dynamic performance differs greatly. This paper presents a systematic evaluation of the function of integrators in some representative integrator related PWM methods, such as ASDTIC control, delta/delta-sigma modulation, modulated integral control and one-cycle control. In general, zero steady-state error is granted for all methods. Further, the variable frequency control methods are able to achieve one-cycle dynamic response. In the constant frequency category, however, only the one-cycle control method achieves one-cycle dynamic response, i.e., it realizes zero dynamic tracking error in the cycle average sense. In this paper, performance enhancement rules were explored for variable frequency control method in order to reduce the frequency variation. For the one-cycle control method, a pulse position modulation effect is identified which deteriorates the perturbation rejection ability of the single-side modulated one-cycle control method in the high frequency range. As a result, a double-side modulation is proposed that effectively reduces this effect. In addition, a fast reset mechanism is suggested that improves the switching error correction. This paper also provides a general approach to use integrators in PWM to realize arbitrary function.