Quantized Voltage Feed-Forward Circuit for Power Factor Correction
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Solution Overview
Problem
Conventional voltage feed-forward circuits in power factor correction controllers introduce harmonic distortion and are slow to respond to line voltage changes due to the use of RC filtering networks, which either leave low-frequency AC signals unfiltered or require heavy filtering that slows down the system.
Innovation Solution
A quantized voltage feed-forward circuit using comparators and a logic control circuit to generate discrete voltage feed-forward coefficients that represent the AC line voltage, eliminating the need for low-frequency filtering and allowing rapid response to line voltage changes without introducing ripple-induced harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If RC filtering network is used to eliminate low-frequency AC signals, then harmonic distortion is reduced, but response speed to line voltage changes decreases
Solution Approach 1:
The patent segments the voltage detection function into multiple discrete comparator circuits, each comparing the rectified voltage against a specific reference threshold. This segmentation allows the system to detect voltage levels without requiring heavy RC filtering, as each comparator independently determines when its threshold is exceeded, thereby maintaining fast response speed while eliminating the need for low-frequency filtering that would slow down the system.
Solution Approach 2:
The patent replaces the continuous RC analog filtering mechanism with a discrete digital counting mechanism. Instead of using resistors and capacitors to filter out low-frequency AC signals, the system uses digital counters to track the number of times comparator thresholds are exceeded within a half-cycle period. This substitution eliminates the trade-off between filtering and response speed, as the digital approach provides both accurate harmonic elimination and fast transient response.
2Speed
If lighter RC filtering is used, then response speed is improved, but harmonic distortion increases
Solution Approach 1:
The patent implements a feedback mechanism where the output of each comparator is fed into a digital counter that accumulates threshold exceedance events over a half-cycle period. This feedback loop allows the system to process the raw comparator signals through digital logic that inherently filters out ripple components while preserving the fundamental voltage information. The feedback-based counting approach eliminates harmonic distortion without requiring heavy RC filtering, thus maintaining fast response speed.
3Object-generated harmful factors
If heavy RC filtering is used to eliminate ripple, then harmonic distortion is reduced, but signal lag increases
Solution Approach 1:
The patent uses preliminary action by pre-establishing multiple voltage threshold levels through reference voltage circuits before the voltage detection process begins. Each comparator is pre-configured with its specific threshold, allowing immediate detection and response when the rectified voltage exceeds any threshold level. This preliminary configuration eliminates the need for gradual RC filtering charging/discharging, thereby eliminating signal lag while still preventing harmonic distortion through the structured threshold comparison approach.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a fast response to line voltage changes while eliminating third-order harmonic distortion, ensuring stable output voltage and minimizing total harmonic distortion in the input current reference signal.
Implementation Method 1
The comparators are structured and arranged to compare the magnitude of the sensed rectified AC line voltage signal with sequentially-increasing, predetermined reference voltage threshold levels
Data Source
AI summary
A quantized voltage feed-forward (QVFF) circuit and integrated circuits using this technique. The QVFF circuit includes a plurality of comparators in combination with a logic control circuit. The comparators are structured and arranged to establish various voltage threshold levels, each providing a digital state signal representative of the sensed input voltage level. The logic control circuit is structured and arranged to use the digital input signals from the comparators to output a voltage feed-forward factor (KVFF) signal that is representative of the V2rms voltage. Output from the logic control circuit is provided to an analog signal multiplier and used to shape an input current reference (IMO) waveform. This allows detection of changes in the rms level of the input voltage on the half-cycle of the AC line voltage, resulting in a rapid response to line voltage changes. Because the KVFF factor signal contains no AC ripple component, it does not contribute to THD of the input current reference, IMO.