Split Feedback Divider for Stable Low-Noise Power Conversion
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Solution Overview
Problem
Switched mode power supplies (SMPS) face challenges in maintaining a stable output voltage due to noise interference, particularly in noise-sensitive applications, as traditional filtering methods can reduce the output voltage and introduce impedance issues.
Innovation Solution
A circuit with a split feedback divider and capacitive and resistive dividers is used to compensate for the effects of filtering, ensuring the output voltage remains stable by providing a feedback signal that adjusts the power converter's operation to maintain the desired voltage level despite impedance from filtering components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional filtering methods are used to reduce noise in output voltage, then noise variance is reduced, but output voltage stability deteriorates due to impedance issues
Solution Approach 1:
The feedback path is segmented into two separate dividers: a resistive feedback divider that provides accurate DC voltage feedback, and a capacitive feedback divider that provides AC noise feedback. This segmentation allows each divider to be optimized for its specific function without compromising the other, resolving the contradiction between noise reduction and voltage stability.
Solution Approach 2:
The capacitive feedback divider acts as an intermediary that selectively extracts the AC noise component from the output voltage and feeds it back to the controller. This intermediary approach allows noise cancellation without requiring the entire feedback path to have low impedance, thus maintaining output voltage stability while reducing noise variance.
2Object-affected harmful factors
If filtering components are added to reduce noise, then noise variance is reduced, but device complexity increases
Solution Approach 1:
The feedback circuit uses standard electronic components (resistors and capacitors) that serve multiple functions: the resistive divider provides both voltage division and low-pass filtering, while the capacitive divider provides both AC coupling and noise extraction. This multi-functionality reduces the need for additional dedicated noise-filtering components, thereby limiting the increase in device complexity.
3Measurement precision
If feedback signal is taken directly from output voltage, then voltage accuracy is maintained, but noise interference increases
Solution Approach 1:
Different parts of the feedback signal are treated with different quality characteristics: the DC component is extracted through the resistive divider for accurate voltage measurement, while the AC noise component is extracted through the capacitive divider for noise cancellation. This local quality differentiation allows simultaneous achievement of voltage accuracy and noise reduction.
Data Source
AI summary
A circuit comprises a controller configured to receive an input voltage and control a power converter to provide an output voltage based on the input voltage. The controller is also configured to receive a feedback voltage from a split feedback divider, the feedback voltage based on the output voltage and control the power converter to provide the output voltage based on the input voltage and the feedback voltage.