Driving the PWM-Controlled System to Monostable Behavior by Periodic Modulation of a Carrier Signal

The normal (“nominal)” mode of operation of a PWM -driven power stage under several circumstances can be only one of multiple coexisting stable modes for the same set of parameters; that phenomenon is referred to as multistability. The “non-nominal” modes are most often characterized by lower efficiency and higher ripples and are undesired. That leads us to the search of the strategies to control those nonlinear phenomena. Our proposal is based on transferring the system to a monostable behavior utilizing a periodic modulation of a carrier signal. The applicability of the proposed control and the suitable ranges of the modulation strength are studied using the bifurcation diagram. In addition, if the control should provide a return to an uncontrolled state after the control goal is achieved, we demonstrate that an implementation should include smooth attenuation of the modulation strength to ensure the “nominal” operation after the control is disabled.