Interleaved Hybrid DC-DC converter for the 5V-to-1V conversion
Theres is an increasing interest in DC-DC conversion from 5V to the low core voltage (0.9-1.2V) of today’s CMOS technology employed in highly dense digital cores such as CPU, GPU, DSP. At high conversion ratios, however, it is challenging for inductive-based DC-DC converters to achieve high power densities since the inductor remains the largest component. In addition, large device voltage stress (relative to the output voltage) limits the conversion efficiency. Switched Capacitors (SC) and Resonant converters are instead affected by poor efficiency under output voltage regulation. Hybrid converters, combining advantages of traditional topologies, are well suited for high conversion ratios application, as they achieve high efficiency, high power density and output voltage regulation. However, these performances are still ultimately limited by the presence of a discrete inductor which carries a DC current equal to the load current. In addition, these converters need complicated control strategies (e.g., more than two phases) to regulate the output voltage. The proposed hybrid converter merges 2 resonant converters with a buck converter, allowing for the scaling of the discrete inductor dimensions thanks to its limited voltage swing and reduced DC current. The resonant tank is implemented to exploit Zero Current Switching (ZCS) and its inductor is realized exploiting the parasitic inductance of PCB traces and VIAs. In this way, the charging/discharging current of the filter capacitors is shaped either by the inductor current or by the resonant tank, minimizing the charge redistribution losses. The interleaved structure of the proposed converter provides a quasi-DC input current, allowing for the reduction of the input capacitance. Moreover, the high voltage rated MOS, carry half of the current compared to the non-interleaved topology, enhancing the power density of the proposed converter.
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