Two-Stage Multi-Phase Buck Converter Transient Response
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Solution Overview
Problem
Conventional multi-phase buck converters face inefficiencies and limited response speed due to high voltage components and phase shedding, which leads to transient changes in output voltage and current deviations.
Innovation Solution
A phase-shedding scheme with a duty cycle compensation circuit that adjusts the pulse width modulation by temporarily changing the DC voltage offset for active phases during transitions, allowing for quicker settling of inductor currents and improved response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If phase shedding is used to reduce the number of active phases, then power consumption is reduced, but transient response speed deteriorates due to current deviations
Solution Approach 1:
The patent applies preliminary action by pre-charging the output capacitor during the off-period before the switch turns on again. This ensures that the capacitor is ready to immediately supply current during the next on-period, eliminating the transient current deviation that occurs in conventional phase shedding. The capacitor is charged in advance to the required voltage level, so when the phase is reactivated, the current transitions smoothly without deviation, thus improving transient response speed while maintaining the power savings of phase shedding.
2Power
If high voltage components are used in single stage multi-phase buck converters, then voltage step-down capability is improved, but die space requirement increases
Solution Approach 1:
The patent applies segmentation by dividing the single-stage voltage conversion into two separate stages: a first stage multi-phase buck converter that handles the initial voltage step-down from high battery voltage to an intermediate voltage, and a second stage multi-phase buck converter that handles the final voltage step-down from intermediate voltage to the low internal power supply voltage. This segmentation allows each stage to use components optimized for its specific voltage range, reducing the need for high voltage components with large die space in the second stage while maintaining the overall voltage step-down capability.
3Power
If high voltage components are used to achieve suitable drain-to-source resistances, then voltage regulation capability is improved, but gate drive losses increase
Solution Approach 1:
The two-stage architecture segments the voltage regulation function across different voltage levels. The first stage operates at high voltage with components sized for that voltage range, while the second stage operates at lower intermediate voltage with components optimized for reduced gate drive requirements. This segmentation allows the second stage to use lower voltage components that have smaller gate capacitances, thereby reducing gate drive losses while maintaining effective voltage regulation capability through the combined action of both stages.
4Loss of energy
If conventional two-stage multi-phase DC/DC power converters are used, then efficiency is improved, but response speed is limited due to phase shedding transitions
Solution Approach 1:
The patent resolves the contradiction between efficiency and response speed by applying preliminary action through pre-charging the output capacitor during the off-period. This allows the converter to maintain the efficiency benefits of phase shedding (by keeping some phases inactive during light load) while eliminating the slow transient response caused by current deviations. The pre-charged capacitor immediately supplies current when phases are reactivated, enabling fast response without sacrificing the efficiency gains from reduced conduction losses in inactive phases.
Data Source
AI summary
A multi-phase switching power converter is disclosed in which the duty cycle of active phases following a phase shedding transition is temporarily adjusted to increase the operating speed of the multi-phase switching power converter.