One Cycle Control for Discontinuous PFC Converters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power factor correction (PFC) converters with discontinuous input currents face challenges in achieving a sinusoidal average input current, which is essential for efficient power conversion and power factor correction.
Innovation Solution
A method and circuit for controlling a PFC converter by sensing the input current and output voltage and adjusting the duty cycle of at least one switch according to a predetermined control equation, ensuring the average input current is sinusoidal, using a control circuit that implements specific equations for different converter topologies such as buck, buck-boost, and flyback converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional control schemes are used for PFC converters with discontinuous input current, then the converter can operate, but the average input current cannot be made sinusoidal
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the duty cycle of the switching element based on the instantaneous values of input voltage and current. The control equation modifies the duty cycle parameter in real-time to ensure the average input current follows a sinusoidal waveform, directly resolving the waveform precision issue while maintaining relatively simple control circuitry.
Solution Approach 2:
The control scheme employs feedback by continuously sensing the input current and using it in the control equation to adjust the duty cycle. This closed-loop approach ensures that the average input current maintains a sinusoidal waveform by comparing actual current with the desired sinusoidal pattern and making real-time corrections.
2Reliability
If the duty cycle is adjusted to achieve sinusoidal average input current, then power factor correction is improved, but control precision requirements increase
Solution Approach 1:
The control equation dynamically changes the duty cycle parameter based on instantaneous input voltage and current measurements. By expressing duty cycle as a function of these measurable parameters, the system achieves reliable power factor correction without requiring excessive control precision, as the relationships are derived from fundamental electrical parameters that can be measured with standard sensors.
3Device complexity
If a single-stage power converter is used without additional stages, then system complexity is reduced, but power factor correction and efficiency are compromised
Solution Approach 1:
The patent makes the single-stage power converter universal by enabling it to perform both power conversion and power factor correction functions simultaneously. The control equation is designed to achieve sinusoidal input current (power factor correction) while maintaining efficient power transfer, allowing one converter stage to fulfill multiple functions that traditionally required separate stages.
Solution Approach 2:
By dynamically adjusting switching parameters (duty cycle) based on instantaneous conditions, the single-stage converter achieves efficient power conversion while maintaining sinusoidal input current. The parameter changes enable the converter to optimize both efficiency and power factor correction performance without requiring additional converter stages.
Data Source
AI summary
A method of controlling a power factor correction (PFC) converter that has a discontinuous input current includes sensing the input current, sensing an output voltage and controlling a duty cycle of at least one switch in the converter in response to the sensed input current and output voltage using a control equation for controlling the duty cycle of the switch such that an average input current to the converter is sinusoidal. Example circuits capable of performing the method are also disclosed.