Discrete-Time PFC Converter Control at AC Zero Crossings
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Solution Overview
Problem
Existing power factor correction systems face challenges in achieving high gain and frequency while maintaining stability and preserving a minimally acceptable power factor.
Innovation Solution
The implementation of a digital control system for power factor correction that utilizes multi-level, nonlinear control techniques, updating values only at zero-crossings of the input signal, and employing a hybrid control system with different operation levels for small and large signal responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If continuous-time, linear time-invariant control is used, then the control system is simple to implement, but the gain and frequency are limited and cannot achieve high performance
Solution Approach 1:
The patent replaces continuous-time, linear time-invariant control with discrete-time, nonlinear control. This substitution enables the system to achieve high gain and frequency performance while maintaining stability, effectively resolving the contradiction between ease of implementation and performance capability.
Solution Approach 2:
The patent changes the control parameters from continuous-time to discrete-time operation, and from linear to nonlinear control characteristics. This parameter transformation allows the system to operate at higher gains and frequencies while preserving stability, thus improving productivity without sacrificing ease of implementation.
2Productivity
If high gain and frequency control is implemented, then performance is improved, but stability and power factor preservation deteriorate
Solution Approach 1:
The patent implements periodic sampling at zero-crossing points of the input signal. This periodic action allows the controller to update values only at these specific moments, enabling high gain and frequency operation while maintaining stability and preserving power factor through synchronized control updates.
Solution Approach 2:
The patent employs feedback control that monitors output voltage and compares it with a reference value. The error signal generated is used to adjust the on-time of the switching element, ensuring that high gain and frequency operation maintains stability and preserves power factor by continuously correcting deviations.
3Stability of the object's composition
If continuous-time control is used, then the control is smooth and stable, but the system cannot achieve high frequency response
Solution Approach 1:
The patent transitions from static continuous-time control to dynamic discrete-time control. By updating control values at zero-crossing points and using nonlinear control techniques, the system achieves high frequency response while maintaining control smoothness through periodic synchronization with the input signal.
4Speed
If discrete-time control updating is implemented, then high frequency response is achieved, but complexity of control increases
Solution Approach 1:
The patent implements discrete-time control updating only at zero-crossing points of the input signal. This periodic updating approach achieves high frequency response while minimizing control complexity by avoiding continuous updates and leveraging the natural periodicity of the AC input signal.
Data Source
AI summary
An apparatus for controlling a power converter operable to receive a cyclically varying input signal includes a discrete-time, on-time generator coupled to the power converter and configured to regulate an output voltage of the power converter and a controller configured to compare the output voltage of the power converter against a first predetermined range to: obtain a comparison result at a zero-crossing of the cyclically varying input signal and select one of a plurality of operation levels of the discrete-time, on-time generator in response to the comparison result. The plurality of operation levels includes a linear, discrete-time operation level and a nonlinear, discrete-time operation level.