Voltage Converter Adapter Current Feedback Loop Stability
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Solution Overview
Problem
Voltage converters, such as NVDC battery chargers, face challenges in stabilizing the adapter current feedback loop due to complex double poles, making it difficult to design a compensator for stable regulation in adapter current limit mode.
Innovation Solution
Incorporating a high pass filter and a gain factor in the adapter current feedback loop to split the complex double pole, improving dynamic performance and simplifying compensator design, while maintaining DC operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage converter operates in adapter current limit mode, then the adapter current can be regulated, but the feedback loop becomes unstable due to complex double poles
Solution Approach 1:
The patent applies segmentation by dividing the complex double pole into two separate real poles through the high pass filter. This transforms the difficult-to-compensate complex pole pair into two simpler real poles that can be handled independently, significantly reducing compensator design complexity while maintaining loop stability.
Solution Approach 2:
The high pass filter acts as an intermediary element in the feedback loop. It modifies the feedback signal to cancel out the effect of the complex double pole, effectively mediating between the unstable feedback loop and the compensator to achieve stable operation without requiring a complex compensator design.
2Object-generated harmful factors
If the complex double pole is not split, then the circuit structure remains simple, but undesirable peaking and phase change occur
Solution Approach 1:
The high pass filter serves as an intermediary that eliminates the harmful peaking and phase change effects caused by the complex double pole. By positioning this filter in the feedback path, it modifies the feedback characteristics to remove the undesirable effects without requiring major structural changes to the overall circuit.
Solution Approach 2:
The patent changes the parameter characteristics of the feedback loop by introducing the high pass filter, which alters the pole locations from complex to real. This parameter transformation eliminates the peaking and phase change issues while maintaining a relatively simple circuit structure through minimal additional components.
Data Source
AI summary
A voltage error signal is provided to a PWM controller of a voltage regular and used to produce a PWM signal that drives a power stage of the regulator. When operating in an adapter current limit regulation mode, an adapter current sense voltage, indicative of an adapter current, is compared to an adapter current reference voltage to produce an adapter current error signal. A compensator receives the adapter current error signal and outputs a compensated adapter current error signal. The adapter current sense voltage, or a high pass filtered version thereof, is subtracted from the compensated adapter current error signal to produce the voltage error signal provided to the PWM controller. Alternatively, an input voltage, or a high pass filtered version thereof, is added to the compensated adapter current error signal to produce the voltage error signal.