Adaptive Multi-Slope Ramp Signal for PWM Converter Transient Response
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Solution Overview
Problem
Conventional PWM power converters using multi-slope piecewise ramp signals face challenges in setting the slope turning point, leading to inadequate loop gain adjustment during load transients, which can result in unstable operation or ineffective transient response improvement.
Innovation Solution
A PWM power converter that dynamically adjusts the slope turning point of a multi-slope ramp signal based on the error signal, allowing for adaptive modulation gain in response to varying input/output voltage ratios, using a ramp generator with current sources and a slope turning point determination circuit to generate the multi-slope ramp signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a multi-slope piecewise ramp signal is used to improve transient response, then the loop gain can be increased during load transient, but the setting of slope turning point becomes complex and may cause unstable operation
Solution Approach 1:
The patent applies dynamics by making the slope turning point variable rather than fixed. The slope turning point determination circuit dynamically adjusts the turning point position based on the duty cycle of the PWM signal, allowing the ramp generator to adapt to different operating conditions and maintain optimal transient response across varying load conditions.
Solution Approach 2:
The patent implements feedback by using the duty cycle information from the PWM signal to control the slope turning point position. The slope turning point determination circuit receives feedback about the current operating state and adjusts the ramp signal accordingly, creating a closed-loop system that automatically optimizes transient response without manual intervention.
2Device complexity
If a fixed slope turning point is used in multi-slope ramp signal, then the circuit structure is simplified, but the converter cannot maintain stable operation across different duty cycles and voltage ratios
Solution Approach 1:
The patent transforms the static fixed turning point into a dynamic variable turning point that adapts to different operating conditions. The slope turning point determination circuit enables the turning point position to change with duty cycle variations, providing adaptability across different voltage ratios while maintaining a relatively simple circuit structure based on existing PWM feedback signals.
Solution Approach 2:
The patent achieves multi-functionality by enabling the ramp generator to serve multiple operating conditions with a single adaptive structure. The slope turning point determination circuit allows the same ramp generator to optimize performance across various duty cycles and voltage ratios, eliminating the need for multiple fixed turning point configurations or separate circuits for different operating modes.
3Stability of the object's composition
If the slope turning point is positioned far from the error signal touch point in steady state, then steady state operation is stable, but the loop gain cannot be increased during load transient
Solution Approach 1:
The patent resolves this contradiction by making the slope turning point dynamic. In steady state, the turning point remains positioned to maintain stability, but during load transients, the turning point automatically shifts to positions that increase loop gain and improve transient response. This dynamic repositioning allows the system to have different optimal configurations for different operational phases.
Solution Approach 2:
The patent utilizes the periodic nature of PWM operation and load transients to switch between different slope turning point positions. The slope turning point determination circuit detects transient conditions and periodically adjusts the turning point position to coincide with error signal touch points during transients, thereby increasing loop gain only when needed while maintaining steady-state stability.
Data Source
AI summary
A ramp generator is provided to provide a multi-slope ramp signal for a PWM power converter. The ramp generator determines the slope turning points for the multi-slope ramp signal according to the error signal of the PWM power converter and thereby improve the transient response of the PWM power converter. Preferably, the slope turning point of the multi-slope ramp signal varies with the average of the error signal and is thus adaptive to the error signal and thereby the load condition.