AC/DC Converter Control Circuit Reducing THD via Segmented Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
AC/DC converters with power factor correction often experience significant total harmonic distortion (THD) due to fluctuating compensation signals, which weakens power factor correction performance and pollutes the power grid.
Innovation Solution
A controlling circuit for AC/DC converters that generates a compensation signal following an error between the output signal and the expected output signal during a first time interval of the AC voltage supply, maintaining a constant compensation signal during the remaining time interval, thereby stabilizing the output signal and reducing THD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a compensation signal is used to regulate the output signal in AC/DC converters, then the output signal consistency is improved, but the total harmonic distortion increases and power factor correction performance weakens
Solution Approach 1:
The half period of the AC voltage supply is divided into two time intervals: a first time interval where the compensation signal follows the error between output and expected output signals, and a second time interval where the compensation signal is held constant. This segmentation allows the system to achieve output regulation while preventing harmonic distortion propagation throughout the entire cycle.
Solution Approach 2:
The controlling circuit operates periodically by updating the compensation signal only during specific time intervals corresponding to each half period of the AC voltage supply. This periodic update mechanism synchronizes with the AC input frequency, ensuring that compensation adjustments are made at appropriate moments while maintaining stability during other periods, thereby reducing harmonic distortion.
2Measurement precision
If the compensation signal follows the error continuously, then the output signal regulation is improved, but the harmonic distortion and power grid pollution increase
Solution Approach 1:
The harmful fluctuating components of the compensation signal are extracted and removed by holding the compensation signal constant during the second time interval of each half period. This extraction eliminates the source of harmonic distortion while preserving the essential regulation function achieved during the first time interval, thereby reducing power grid pollution.
3Object-generated harmful factors
If the compensation signal is held constant throughout the half period, then the harmonic distortion is reduced, but the output signal consistency deteriorates
Solution Approach 1:
The half period is segmented into two functional intervals: the first interval allows the compensation signal to track the error for output regulation, while the second interval holds the signal constant to minimize harmonics. This segmentation enables the system to achieve both output consistency and harmonic reduction by applying different control strategies at different times.
Data Source
AI summary
In one embodiment, a controlling circuit configured for an AC/DC converter that receives an AC voltage supply, can include: (i) a compensation signal generator configured to generate a compensation signal that follows an error between an output signal from the AC/DC converter and an expected converter output signal during a first time interval of a half period of the AC voltage supply, the compensation signal being substantially constant during a remaining time interval of the half period; and (ii) a controlling signal generator configured to generate a controlling signal based on the compensation signal to maintain the output signal as substantially consistent with the expected converter output signal.