Feed-Forward PWM Controller for Voltage Transient Compensation
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Solution Overview
Problem
PWM-based switching voltage regulators face challenges in quickly responding to rapid changes in supply voltage, leading to overshoots or undershoots in the regulated output voltage due to the inherent delay in existing feed-forward compensation circuits.
Innovation Solution
A PWM controller that adjusts the error signal inversely with respect to the supply voltage using a feed-forward circuit, incorporating a voltage-controlled current source or translinear circuit to generate an adjusted error signal, allowing for rapid compensation within a half cycle or nano-seconds, thereby maintaining a constant regulated output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback loop is used to regulate output voltage, then the regulated output voltage returns to nominal level, but the response is slow and cannot prevent overshoots or undershoots during rapid supply voltage changes
Solution Approach 1:
The patent applies preliminary action by using a feed-forward circuit that anticipates supply voltage changes and adjusts the PWM duty cycle before the feedback loop can respond. The circuit directly senses supply voltage variations and proactively modifies the control signal to compensate for upcoming output voltage deviations, thereby preventing overshoots or undershoots before they occur.
2Reliability
If a feed-forward circuit changes the slope of a ramp signal to compensate for supply voltage transients, then compensation is provided, but significant delay occurs because capacitor voltage cannot change instantaneously
Solution Approach 1:
The patent replaces the mechanical capacitor-based ramp signal generation with an electronic solution that uses a voltage-controlled current source to directly adjust the PWM duty cycle. This substitution eliminates the inherent delay caused by capacitor charging dynamics, enabling instantaneous response to supply voltage transients through electronic control rather than physical energy storage mechanisms.
3Stability of the object's composition
If the duty cycle is adjusted quickly to compensate for supply voltage changes, then output voltage stability is maintained, but the control system becomes more complex
Solution Approach 1:
The patent introduces an intermediary feed-forward control circuit that sits between the supply voltage source and the PWM controller. This intermediary circuit senses supply voltage variations and translates them into appropriate duty cycle adjustments, thereby maintaining output stability without requiring complex modifications to the existing feedback loop or PWM generation architecture.
Data Source
AI summary
A feed-forward correction circuit in a PWM controller adjusts an error signal inversely with respect to a supply voltage for a switching voltage regulator to quickly compensate for changes or transients in the supply voltage. The adjusted error signal is provided to a PWM comparator to control a duty cycle of an output signal. The switching voltage regulator can be a DC-to-DC converter or a DC-to-AC converter, and the output signal is used to generate one or more driving signals to control semiconductor switches in the switching voltage regulator. The feed-forward correction circuit uses an offset compensation technique or a translinear circuit to maintain a substantially inverse product relationship between the supply voltage and the duty cycle of the output signal, thereby reducing overshoots and undershoots in a regulated output voltage of the switching voltage regulator.