APPLICATION OF SLIDING MODE CONTROL TO SWITCH-MODE POWER-SUPPLIES

Switch-mode power supplies represent a particular class of variable structure systems (VSS). Thus, they can take advantage of non-linear control techniques developed for this class of systems. In this paper the so called sliding mode control is reviewed and its application to switch-mode power supplies is discussed. Sliding mode control extends the properties of hysteresis control to multi-variable environments, resulting in stability even for large supply and load variations, good dynamic response and simple implementation. Application to dc-dc converters, as well as rectifiers and inverters, is analyzed and provisions to overcome the inherent drawbacks of sliding mode control, i.e. variable switching frequency and possible steady-state errors, are described. Experimental results are also reported, which allow a comparison between the sliding mode approach and other standard control techniques, e.g. current-mode control, showing its effectiveness.