Control Scheme for Sensorless Operation and Detection of CCM and DCM Operation Modes in Synchronous Switching Power Converters

Switching power converters with synchronous rectification utilize transitioning between inductor´s current continuous and discontinuous conduction operation modes (CCM and DCM) in order to achieve improved power efficiency across wide load and input voltage ranges. The inductor current zero crossing is sensed in order to detect the operation modes transition point between CCM and DCM. The challenges associated with this include inductor current zero crossing point sensing accuracy, noise effect near the zero crossing point, and the sensing circuitry speed and power loss. Moreover, additional hardware such as analog-to-digital converter is required if the controller used is a fully digital controller. In this letter, a control scheme for sensorless operation and detection of CCM and DCM in a switching power converter is presented. The presented controller utilizes dual control loops and does not require sensing the inductor current or any current in the converter, which eliminates or reduces challenges associated with inductor current sensing for the zero point detection. The presented controller is discussed, and proof-of-concept experimental prototype results are presented.