Voltage Converter Frequency Control for Low-Load Noise and Ripple
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Solution Overview
Problem
Voltage converters operating in Discontinuous Conduction Mode face challenges in maintaining high efficiency over a wide range of output load currents due to switching frequency being proportional to output current, leading to unpredictable output voltage ripple and increased switching noise, especially at low load conditions.
Innovation Solution
A voltage converter with a primary control loop that varies switching frequency based on an on-time value code and a secondary control loop that adjusts the on-time value or peak output current code to keep the switching frequency within predetermined thresholds, avoiding forbidden frequency bands and optimizing energy output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If switching frequency is increased to maintain high efficiency, then power efficiency is improved, but switching noise and output voltage ripple increase
Solution Approach 1:
The patent implements dynamic switching frequency adjustment through a secondary control loop that continuously monitors and modifies the switching frequency based on operating conditions. The controller dynamically selects from multiple frequency options to optimize the balance between efficiency and noise, rather than using a fixed frequency approach.
Solution Approach 2:
The patent changes the switching frequency parameter adaptively based on load conditions and operational requirements. By varying the frequency within a defined range and avoiding forbidden bands, the system optimizes efficiency while minimizing noise and ripple generation under different operating scenarios.
2Object-generated harmful factors
If switching frequency is varied to reduce noise, then switching noise is reduced, but output voltage ripple becomes unpredictable
Solution Approach 1:
The patent employs a secondary control loop that provides feedback on switching frequency and adjusts the frequency accordingly. This feedback mechanism ensures that frequency variations are controlled and compensated, maintaining predictable output voltage ripple characteristics even as the frequency is adjusted to reduce noise.
Solution Approach 2:
The system uses dynamic frequency adjustment with controlled variations rather than static frequency. The controller adaptively modifies switching frequency within acceptable ranges while maintaining stability through regulated control, allowing noise reduction without sacrificing voltage ripple predictability.
3Loss of energy
If on-time value is increased to improve efficiency at low load, then power efficiency is improved, but switching frequency decreases below optimal range
Solution Approach 1:
The patent implements dynamic coupling between on-time value and switching frequency control. When on-time is increased to improve efficiency, the secondary control loop simultaneously adjusts the switching frequency to maintain it within the optimal range, preventing frequency from dropping too low while still achieving efficiency improvements.
Solution Approach 2:
The system coordinates changes in multiple parameters (on-time value and switching frequency) together. By adjusting both parameters in a coordinated manner, the patent achieves efficiency improvement at low load while maintaining switching frequency within acceptable operational boundaries.
4Object-generated harmful factors
If secondary control loop is added to regulate switching frequency, then switching noise and ripple are reduced, but device complexity increases
Solution Approach 1:
The secondary control loop is designed to perform multiple functions: regulating switching frequency, avoiding forbidden frequency bands, and coordinating with the primary control loop. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The secondary control loop acts as an intermediary between the power stage and the control system, mediating frequency adjustments to achieve noise reduction without requiring complex direct control of individual switching elements. This intermediary approach simplifies the overall control architecture compared to direct complex control methods.
Data Source
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AI summary
One example discloses a voltage converter, including: a power stage configured to generate an output voltage (Vo) and an output current (Io) based on a switching frequency (fs); a primary control loop configured to vary the switching frequency (fs) in response to an on-time value code (Ton_code) and/or a peak output current code (iLpeak_code); and a secondary control loop configured to generate the Ton_code and/or the iLpeak code.