Boost Converter Feedback Control for Stable PFM-PWM Transitions
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Solution Overview
Problem
Conventional boost converters face issues with operation stability in high load current regions and mode switching, leading to deteriorated load transient characteristics and variable switching frequencies due to input or output voltage changes.
Innovation Solution
A voltage converter with a converting circuit and a switching control circuit that adjusts a feedback voltage based on the inductor current state, generates switching control signals, and includes a ripple injection circuit to stabilize mode switching and maintain a fixed switching frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the boost converter operates in PFM mode in low load current region and switches to PWM mode in high load current region, then efficiency is improved, but load transient characteristic deteriorates due to mode switching
Solution Approach 1:
The patent implements dynamic mode switching between PFM and PWM based on operating conditions, and dynamically adjusts the on-time parameter to smooth transitions. The control circuit monitors load conditions and adaptively changes operating mode and timing parameters to maintain stability during transitions, resolving the contradiction between efficiency improvement and transient response degradation.
2Reliability
If the boost converter limits inductor charging time on an on-time basis, then load transition characteristic improves, but operation stability deteriorates in high load current region
Solution Approach 1:
The patent dynamically adjusts the on-time parameter based on operating conditions, particularly extending on-time in high load current regions to maintain stability. The control circuit modifies timing parameters adaptively, increasing on-time when needed to prevent instability while maintaining fast transient response, thus resolving the contradiction between transient performance and operational stability.
3Adaptability or versatility
If the boost converter operates with variable switching frequency, then adaptability to input voltage changes is improved, but switching frequency stability deteriorates
Solution Approach 1:
The patent implements periodic switching with controlled on-time and off-time intervals, creating a more stable switching frequency pattern. By regulating the on-time parameter and using periodic timing control, the system maintains more consistent switching frequency while still adapting to voltage changes through duty cycle adjustment, resolving the contradiction between adaptability and frequency stability.
Data Source
AI summary
A voltage converter includes a converting circuit having an inductor connected to a switching node, a first switch element connected between the switching node and a ground voltage, and a second switch element connected between the switching node and an output node; and a switching control circuit configured to adjust a feedback voltage divided from an output voltage of the output node based on a current state of the inductor, and configured to generate switching control signals for charging the inductor with an input voltage and discharging a voltage charged in the inductor, based on a sensing signal based on a current of the inductor and the adjusted feedback voltage.