PFC Control Circuit Simplifies Peak Current Detection
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Solution Overview
Problem
Existing PFC circuits have complex peak current detecting circuits and inefficient average input current waveform control, especially in Discontinuous Current Mode, affecting power factor correction efficiency.
Innovation Solution
A control method for PFC circuits that generates compensation signals based on output voltage and input voltage, producing on-time and on-time delay signals to control power switches, ensuring high power factor and efficiency by fixing on-time signal values at specific power modes, and using analog-to-digital conversion and comparing circuits to manage inductor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If peak current detecting circuit is used to generate control signal, then PFC control can be realized, but the detecting circuit becomes very complicated
Solution Approach 1:
The patent extracts the peak current detection function from a separate complex detecting circuit and integrates it into the control circuit through voltage sampling and processing. The control circuit directly obtains peak current information by sampling the voltage across the inductor and processing it through operational amplifiers and reference voltage comparisons, eliminating the need for a dedicated complex peak current detecting circuit.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it generates the control signal for the power switch, processes the peak current information, regulates the output voltage, and manages the switching timing. This multi-functional control circuit replaces what would otherwise require separate dedicated circuits for each function, simplifying the overall system architecture.
2Reliability
If prior art method is used to generate average input current waveform, then PFC control is achieved, but the waveform is not a perfect rectified sine wave, thus efficiency is affected
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the output voltage and compares it with a reference voltage. Based on this feedback, the control circuit adjusts the duty cycle of the power switch to maintain a perfect rectified sine wave input current waveform, ensuring high power factor and efficiency especially in DCM operation.
Solution Approach 2:
The control circuit dynamically adjusts the switching parameters (on-time, off-time, duty cycle) based on real-time operating conditions including input voltage, output voltage, and load requirements. This dynamic adjustment ensures the input current waveform perfectly follows the rectified sine wave shape across different operating modes (CCM, CRM, DCM), maximizing efficiency.
Data Source
AI summary
A control method of a PFC (Power Factor Correction) circuit having at least one power switch, the control method having: producing an effective value of an input voltage; generating a compensation signal based on an output voltage and an output voltage reference signal; generating an on time signal based on the compensation signal, the effective value of the input voltage, a first on time period value and a second on time period value; generating an on time delay signal based on the input voltage, the output voltage, the first on time period value, the effective value of the input voltage and the compensation signal; and generating a current valley signal based on the input voltage, the effective value of the input voltage, the compensation signal, the second on time period value, and an inductance value of the inductor adopted by the PFC circuit.