Dual Buck Doubles The Duty Cycle For Ultra Low-Voltage Applications

by Patrice Lethellier, It Can Be Done, Salt Lake City, Utah, How2Power Today, May 16 2018

Focus:
The large microprocessors require a high current and a low voltage. A core voltage of 0.6 V at 200 A is not uncommon. Typically the topology used to supply this voltage is a multiphase buck with 8 to 12 phases. If input is 12 V and output is 0.6 V, the buck has to work at a duty cycle close to 5% or even lower in sleep mode where the output can be 0.3 V. At a duty cycle below 5%, the on-time barely exists and efficiency is very low. This 2- page article presents an alternative multiphase buck topology that performs the same voltage transformation as the conventional multi-phase buck but without some of the drawbacks. This topology consists of two bucks ganged with paralleled and sequenced outputs. The inputs work as if they were in series and share the 12-V input voltage. Each buck works with 6 V instead of 12 V and the duty cycle is multiplied by 2, improving efficiency.

What you’ll learn:

• How to increase the duty cycle in multiphase buck converters with high stepdown ratios

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