Integrated Gate Drive Architecture for High Step-down Multiphase Buck Converter

Point of load DC-DC multiphase buck converters operating with high step-down conversion ratios work with narrow duty cycles. So-called "high step-down multiphase buck" topologies present advantages in terms of extended duty cycle, reduced passive components' size and reduced switches' breakdown voltages. However, these topologies require a more complex gate drive structure for their high side switches which are working each on a different voltage domain. A common approach is based on a cascade of bootstrap drivers. This solution requires a dedicated voltage source usually working at a voltage lower than the input one. The proposed drive architecture eliminates the need of this additional voltage source being directly supplied on fractions of the input voltage. It also provides a recycling of the gate charge at the turn-off of the switches. Its behaviour is demonstrated by an integrated implementation together with the power stage switches of a high step-down four phases buck converter switching at 10 MHz. Power stage measured waveforms show the correct operation of the proposed design of the drive architecture.