Variable off time current-mode floating buck controller - A different approach

Switch-mode power supplies have become the premier choice for LED backlighting applications. This paper introduces a new current-mode floating buck controller architecture, used for driving constant current through a string of LEDs. Unlike state-of-the-art controllers, this architecture is based on fixed peak current and variable OFF time as the current control method. An innovative time modulator is added to provide a constant feedback loop response regardless of external components. The proposed controller architecture is designed, implemented in a 0.5μm CMOS process and its performances are validated by simulations and measurements.