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Each phase of a multiphase buck converter (interleaved converter) has at least one set of switching transistors and one inductor. To benefit from the multiphase properties, the on-times for the phases are shifted against each other. In high-load steady-state operation, all stages should be active and equally shifted against each other with the supply current balanced between stages. As a result, the inductor currents are also phase shifted to minimize ripple in both the supply current and the supply voltage. At high current levels, conduction losses dominate. So, multiphase buck converters have a superior efficiency and a lower heat dissipation than single converters, because the total current is distributed over multiple stages rather than a single stage.
Controller based multiphase buck converters have even greater efficiency since they can dynamically activate stages during high-load periods and remove stages during low-load periods.
Multiphase buck converters also have superb response to load steps. Since on-times for the phases are shifted against each other, a multiphase buck converter can quickly react to a load step by adjusting the pulse width modulation (PWM) signal for the phase immediately following the load step. In stacked designs, the primary controller provides the PWM signal for all phases. The design keeps a predefined phase shift between stages. Controller based multiphase designs can dynamically phase-align or activate/deactivate PWM signals for the corresponding stages to further minimize undershoots and overshoots from these load transients.
Even though they are a powerful tool for improving performance and efficiency of high-speed SoC power design, multiphase buck converters can make validation and debugging tests more challenging when analyzing phase management under various static load conditions or under dynamic load step scenarios.