Multi-phase Switching Converter Phase Shedding Control
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Solution Overview
Problem
Current switched-mode power converter circuits face inefficiencies due to switching loss and DC loss, particularly at lower load currents, where the number of active phases should be minimized to reduce switching loss and improve efficiency, while maintaining dynamic load operation without transient voltage changes.
Innovation Solution
A multi-phase switched-mode power converter circuit with a control circuit that dynamically adjusts operational signals across multiple power stages, using phase shedding and adding mechanisms to optimize efficiency by activating or deactivating phases based on current thresholds and voltage feedback, ensuring equal current distribution and minimizing output voltage undershoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the number of active phases is reduced for lower load currents, then switching loss is reduced and efficiency is improved, but the system's ability to handle dynamic load changes is compromised
Solution Approach 1:
The control circuit continuously monitors output current and uses this feedback to determine when to activate or deactivate phases. This closed-loop control ensures that phase configuration automatically adapts to dynamic load changes, maintaining optimal efficiency while preserving the system's ability to respond to varying load conditions
Solution Approach 2:
The control circuit proactively activates additional phases before the load current increases to a level that would cause excessive voltage undershoot, and deactivates phases before load current decreases to a level where switching loss would dominate. This anticipatory control maintains both efficiency and dynamic response capability
2Loss of energy
If phases are deactivated to reduce switching loss, then efficiency is improved for lower load currents, but transient voltage changes occur
Solution Approach 1:
The control circuit gradually reduces the output current of phases before deactivating them, rather than sudden complete shutdown. This preliminary current reduction allows the load to transition smoothly to remaining phases, minimizing transient voltage changes while still achieving the efficiency benefits of phase deactivation at lower load currents
Solution Approach 2:
The system prepares for phase deactivation by pre-adjusting current distribution and ensuring adequate headroom in remaining active phases. This cushioning approach prevents severe voltage undershoot by ensuring that when phases are deactivated, the remaining phases can immediately absorb the increased current demand without causing significant voltage transient
Data Source
AI summary
A multi-phase switched-mode converter has a control circuit configured to receive a shed threshold signal indicating that the total output current has fallen below a total current threshold level. The control circuit further includes slave phase shedding switches that have a common switching pole connected to a current share amplifier of each slave power stage, a first select pole is connected to a phase target current level, and a second select pole is connected to a phase zero target current level. A control terminal is connects the phase zero target current signal to each slave power stage to decreases their output currents to approximately a zero level. When the output current approaches the zero level, the slave power stages are deactivated. A panic circuit activates the slave power stages when the load current increases precipitously.