COT Buck Converter Control for Smooth 100% Duty Transition
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Solution Overview
Problem
COT Buck DC-to-DC converters experience significant output voltage fluctuations during transitions between normal operation mode and 100% duty operation mode, failing to meet accuracy specifications due to input voltage drops close to output voltage.
Innovation Solution
A power converter design incorporating a switching circuit with a high side switch, low side switch, and a mode control circuit that generates a switch control signal to extend the on-time of the high side switch in the second operation mode, allowing seamless transition and minimizing output voltage fluctuations by determining the end of on-time based on feedback and ramp voltage signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter operates in normal operation mode with periodic switching, then the output voltage is lower than input voltage with regular switching cycles, but during transition to 100% duty mode the output voltage experiences large fluctuations exceeding accuracy specifications
Solution Approach 1:
The patent implements dynamic switching between two control modes (first operation mode with periodic switching and second operation mode with extended on-time) based on the ratio of output voltage to input voltage. The mode control circuit dynamically selects the appropriate control strategy, allowing the converter to adapt to different operating conditions and avoid voltage fluctuations during transitions.
Solution Approach 2:
The patent changes the control parameter from fixed periodic switching to variable extended on-time switching when the input voltage approaches the output voltage. The logic circuit extends the on-time of the high side switch based on the first comparing signal, fundamentally changing the switching behavior to maintain output voltage accuracy during critical transitions.
2Stability of the object's composition
If the high side switch on-time is extended in the second operation mode, then the output voltage remains stable when input voltage drops close to output voltage, but the switching circuit complexity increases with mode control and logic circuit requirements
Solution Approach 1:
The patent segments the control function into distinct modules: a mode control circuit that determines operating mode based on voltage ratio, a logic circuit that generates control signals, and comparator circuits that provide feedback. This segmentation allows each module to perform a specific function, making the complex control strategy manageable and implementable.
Solution Approach 2:
The patent introduces a mode control circuit and logic circuit as intermediary components between the switching circuit and the control signals. These intermediary circuits translate the complex control requirements into simple, actionable signals for the high side and low side switches, managing the complexity through intermediate control layers.
Data Source
AI summary
The present disclosure relates to a power converter and to a buck DC-to-DC power converter, such as a constant-on-time (COT) Buck DC-to-DC power converter. Additionally, a COT Buck DC-to-DC converter is provided which has a seamless transition between the normal operation mode and the 100% duty operation mode.