Design and Simulation of Current Mode Controlled Synchronous Buck Converter under Light Load Condition

This paper is dealing with discrete modelling and the detailed working of closed loop current mode controlled synchronous buck under light load condition with the TYPE-3 and TYPE-2 compensation. TYPE-2 is used to decrease the settling time for output voltage or make the transient response fast. This paper will make the clear difference between TYPE-3 and TYPE-2 compensation through the performance of buck converter under light load condition. The current of High Side MOSFET is sensed using a current sense amplifier via return path to avoid the offset which will occur if the sensing of High Side MOSFET current is done directly using the resistor in series with MOSFET. In Synchronous buck converter, when the High Side MOSFET is ON the inductor current will be in positive direction, but when the Low Side MOSFET is turned ON the negative current flow through the MOSFET from source to drain. That negative current will be from source to drain because the Low Side MOSFET will be conducting in both direction and the synchronous buck converter is running in Forced Continuous Conduction Mode (FCCM). For a small dead-time, the diode across the MOSFETs will be in conduction mode to avoid the heavy shoot through the MOSFETs.