Adaptive On-Time Switching Converter Frequency Control
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Solution Overview
Problem
Constant-on-time switching converters experience frequency variations and large output voltage variations when transitioning between high and low load conditions, and existing adaptive-on-time techniques are noise-sensitive and may reduce efficiency.
Innovation Solution
A switching converter with a pulse generator, ramp generator, and controller that adjusts the switching frequency by detecting parameters of the ramp signal, such as amplitude or on-width, and generating control signals to modify the on-time or slope of the pulsed signal, thereby maintaining a stable switching frequency without increasing noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If adaptive-on-time techniques use signals from supply voltage pins, output voltage pin and switching SW pin to adjust frequency, then frequency stability is improved, but noise sensitivity increases
Solution Approach 1:
The patent introduces an intermediary mechanism that detects switching frequency indirectly through ramp signal parameters (amplitude or on-width) rather than directly measuring noisy voltage pins. The ramp signal serves as a mediator that carries frequency information in a noise-immune form, allowing the controller to adjust the switching frequency without being sensitive to electrical noise from supply voltage, output voltage, or switching node measurements.
2Speed
If COT converters control switching cycle based on load demand, then transient response speed is improved, but switching frequency variation increases
Solution Approach 1:
The patent implements a feedback mechanism where the controller detects ramp signal parameters that reflect the actual switching frequency, compares them against reference values, and adjusts the on-time accordingly. This closed-loop feedback maintains a stable switching frequency while preserving the fast transient response capability of COT converters by dynamically adjusting the on-time based on detected frequency deviations caused by load changes.
3Stability of the object's composition
If AOT techniques adjust on-time using adaptive current based on voltage differences, then frequency stability is improved, but converter efficiency decreases
Solution Approach 1:
The patent extracts the frequency detection function from noisy voltage signal measurements and implements it through ramp signal parameter detection instead. By taking out the dependency on voltage pin measurements and using ramp signal characteristics (amplitude or on-width) as the detection basis, the system achieves frequency stability without the energy losses associated with adaptive current generation based on voltage differences.
Data Source
AI summary
Adaptive-on-time techniques to improve the frequency variations inherent in constant-on-time COT converters are presented. A switching converter contains a power switch; a pulse generator adapted to generate a pulsed signal to switch the power switch on with a switching frequency; a ramp generator adapted to generate a ramp signal; and a controller adapted to detect a parameter of the ramp signal, compare the parameter with a reference value, and to generate a control signal based on the comparison to control the switching frequency. This allows controlling a switching frequency of the converter without increasing a noise level of the converter.