Duty Feed Forward Modulation for PWM Loop Stability
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Solution Overview
Problem
Existing PWM power converters face challenges in improving stability and response speed without monitoring the supply voltage, as previous solutions require additional circuit complexity and pins to manage non-linear ramp signals and supply voltage monitoring.
Innovation Solution
A method and apparatus that extract duty information from the PWM signal to modulate the slope or voltage level of a linear oscillating ramp signal, allowing for improved stability and response speed without monitoring the supply voltage, by using a duty information circuit and a feed forward circuit to adjust the modulation gain dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If supply voltage monitoring is implemented to improve PWM loop stability, then stability is improved, but device complexity increases due to additional monitoring circuits and pins
Solution Approach 1:
The patent extracts the essential information needed for stability control (duty cycle information) from the PWM signal itself, rather than monitoring the supply voltage. This is achieved by using the PWM signal's inherent characteristics (duty cycle variations) to generate a compensation signal that stabilizes the PWM loop, eliminating the need for separate voltage monitoring circuits and reducing device complexity while maintaining stability.
2Speed
If traditional PWM control is used, then device complexity is low, but transient response speed is slow
Solution Approach 1:
The patent implements preliminary action by proactively adjusting the PWM duty cycle in response to detected voltage drops before the system becomes unstable. The compensation circuit continuously monitors the PWM signal and pre-adjusts the duty cycle based on duty cycle information, enabling faster transient response without requiring complex additional control circuits.
Solution Approach 2:
The patent employs feedback by using the duty cycle information extracted from the PWM signal itself to generate a compensation signal that is fed back to the PWM controller. This self-feedback mechanism enables rapid transient response by continuously adjusting the duty cycle based on real-time PWM signal characteristics, improving speed without significantly increasing device complexity.
Data Source
AI summary
The duty of a PWM signal in a power converter is extracted to feed forward to modulate the slope of a linear oscillating ramp signal or the voltage level of an error signal, so as to modulate the duty of the PWM signal, by which the transient response of the power converter and the stability of the PWM loop both are improved.