Study of a Hybrid Fixed Frequency Current Controller Suitable for DC–DC Applications

The authors investigate a hybrid constant switching frequency current controller that uses both the turn-on and the turn-off current mode and the sliding mode control techniques. It is suitable for one-, two-, or four-quadrant operations and can be used with most topologies of dc-dc converters. It presents some advantages over the conventional peak current mode control. Indeed, it allows using low compensating slope without compromising the stability and it can work in the full range of the duty cycle values. Two methods are presented to study the characteristics of the proposed current controller. First, a high frequency small-signal average model is developed which takes into account the high switching frequency. It allows getting some basics design concerns such as overflow, time response and frequency behavior of the hybrid current controller. Second, a mathematical model derived from chaos theory is developed. It allows investigating the nature of the cycle described by the state trajectory, and determining the operating switching frequency of the current controller. Besides, it will be used to study its robustness properties according to loads parameters variations. Experimental results validate the theoretical approach and prove the effectiveness of this hybrid fixed frequency current controller.