A state-observer based controller for CCM flyback converters with constant power loads

This paper proposes a controller for a continuous conduction mode (CCM) flyback converter supplying constant power loads (CPL)s. The controller is implemented in two stages and is based on sensing only the output voltage of the converter. The inner loop implements active damping by performing feedback of core/air-gap flux in order to damp limit cycle oscillations due to CPL. To overcome the challenge of sensing and feedback of a magnetic quantity, a state observer is implemented. To compensate for voltage deviation due to active damping and to perform voltage regulation, an integral controller is added in the outer loop. Reasonable assumptions are made to the system to derive the state observer while also maintaining model accuracy. The controller achieves exponential stability and the stability conditions are derived. Simulation results show that the proposed observer tracks the state variables accurately and also verifies the validity of the control approach.