Power Factor Correction Circuit Using Periodic Sampling
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Solution Overview
Problem
Existing power factor correction solutions face inefficiencies due to high-speed current sense loops that are power inefficient, particularly at low power demands, and require complex multiplier circuits, making it difficult to filter switching noise and electromagnetic interference, especially when dealing with low current and low voltage conditions in power grids.
Innovation Solution
An electrical circuit with adaptive current sensing and a converter using switches and inductors that generates a regulated output by subtracting reference signals from measurement signals to obtain error signals, minimizing overtones and phase errors, allowing for power factor correction while operating at a constant frequency and reducing circuit complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-speed current sense loops are used for power factor correction, then power factor correction capability is improved, but power efficiency deteriorates especially at low power demands
Solution Approach 1:
The patent employs periodic sampling of the current waveform at specific phases (e.g., zero-crossing points and peak points) rather than continuous high-speed sensing. This periodic measurement approach captures essential waveform characteristics while dramatically reducing the operational frequency of the control loop, thereby minimizing switching losses and improving power efficiency especially during low power demand conditions.
Solution Approach 2:
The system uses the existing AC waveform characteristics (zero-crossing points and peak points) as natural reference signals for control. By leveraging these inherent features of the AC waveform, the system eliminates the need for separate high-speed reference signals or complex synchronization circuits, reducing overall system complexity and power consumption while maintaining effective power factor correction.
2Measurement precision
If high-speed current sense loops operate at increased frequency to handle reduced output demand, then power factor correction accuracy is improved, but switching losses increase
Solution Approach 1:
The control loop operates periodically at the AC line frequency (50/60 Hz) by sampling at specific waveform points, rather than attempting high-speed continuous control. This approach achieves sufficient measurement precision for power factor correction by capturing zero-crossing and peak information, while keeping switching frequency low to minimize losses.
Solution Approach 2:
The system uses partial information from the current waveform (specifically zero-crossing points and peak points) rather than attempting to process the entire waveform at high speed. This selective sampling provides adequate precision for power factor correction while dramatically reducing the computational and switching burden.
3Measurement precision
If multiplier circuits are used in existing power factor correction solutions, then control accuracy is improved, but circuit complexity increases
Solution Approach 1:
The patent extracts and removes the complex multiplier circuit from the power factor correction system. By using periodic sampling at zero-crossing and peak points combined with simple comparison and pulse generation logic, the system achieves effective power factor correction without requiring multiplication operations, thereby significantly simplifying the circuit architecture.
Solution Approach 2:
The system replaces expensive and complex multiplier circuits with simple, low-cost digital logic elements such as comparators, counters, and pulse generators. These simpler components perform the necessary control functions with adequate accuracy while being much easier to implement and more reliable.
4Adaptability or versatility
If existing power factor correction circuits operate at variable frequency, then adaptability to load conditions is improved, but filtering switching noise and EMI becomes difficult
Solution Approach 1:
The control system operates at a fixed periodic frequency synchronized with the AC line frequency (50/60 Hz). By maintaining constant frequency operation and using periodic sampling at standardized intervals, the system makes it easy to filter switching noise and EMI using simple fixed-frequency filters, while still adapting to varying load conditions through the periodic nature of the control loop.
Data Source
AI summary
Provided are electrical circuits and methods for power factor correction. An example method includes receiving, by converter, an input voltage at a fundamental frequency and generating an output voltage; generating, based on the output voltage, a first measurement signal; subtracting a first reference signal from the first measurement signal to obtain a first error signal; generating an adaptive current sense signal, generating a reference voltage based on the input voltage, subtracting the reference voltage from the current sense signal thus generating a second measurement signal to control the current measurement; subtracting the second measurement signal from the input voltage to obtain a difference signal, wherein the difference signal is largely minimized by removing overtones of the fundamental frequency; generating, based on the difference signal, a second error signal; using a sum of the second error signal as a first order correction to the first error signal to regulate the converter.