Multiphase Series Capacitor Converter With Bidirectional Phase Coupling
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Solution Overview
Problem
Conventional multiphase series capacitor DC-DC converters are limited in load transient response speed due to the rising slope of inductor current, which is constrained by the switching frequency and phase interleaving, leading to increased switching losses and inefficiencies.
Innovation Solution
A multiphase series capacitor DC-DC converter with a power stage circuit featuring inductors of two or more phases with a preset phase difference, and a bidirectional switch allowing adjacent phases to charge the load simultaneously when a transient occurs, along with a load transient response circuit that controls bidirectional switches to enhance response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If switching frequency is increased to improve load transient response speed, then rising slope of inductor current increases, but switching loss of power transistors increases and conversion efficiency deteriorates
Solution Approach 1:
The patent implements dynamic control of bidirectional switches that can transition between off-state (normal operation) and on-state (transient enhancement). During transient events, the bidirectional switch connects additional inductors to increase current rising slope, while maintaining fixed phase difference for steady-state efficiency. This dynamic reconfiguration allows the system to adapt its topology based on load conditions, achieving fast transient response without permanent increase in switching frequency or losses.
2Ease of operation
If fixed phase difference of 360°/N is maintained to avoid overlapping on-time of power transistors, then control circuit design becomes simpler, but N phase inductor currents cannot charge load simultaneously and load transient response speed is limited
Solution Approach 1:
The system dynamically adjusts the phase relationship between inductor currents by controlling bidirectional switches. During transient events, the bidirectional switch enables multiple inductor phases to charge the load simultaneously by effectively reducing the phase difference to zero for selected phases. This dynamic phase adjustment allows simultaneous charging capability while maintaining simple fixed-phase control during steady-state operation.
Solution Approach 2:
The patent segments the control into two distinct modes: steady-state mode with fixed phase difference for efficiency, and transient mode with dynamic phase adjustment for fast response. The bidirectional switch acts as a segmentation enabler, allowing the system to switch between these two operational regimes. This segmentation allows each mode to be optimized independently - simple fixed-phase control for normal operation and simultaneous charging capability during transients.
Data Source
AI summary
Multiphase series capacitor DC-DC converters are provided, including: a power stage circuit configured to convert an input DC voltage into a stable DC voltage required by a load, where the power stage circuit includes inductors of two or more phases, and there is a phase difference with a preset interval between inductor currents of phases for alternately charging the load in sequence, and a bidirectional switch is provided between inductors of every two adjacent phases, where when the bidirectional switch is turned on, the inductors of the corresponding two phases charge the load simultaneously; and a load transient response circuit configured to, when a load transient positive step occurs, control one or more bidirectional switches to be turned on to make inductors of two or more corresponding phases charge the load simultaneously. Control methods of such converters are also provided, which can realize fast response to load transient changes.