One-Cycle PFC Circuit Reduces Line Current Distortion
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Solution Overview
Problem
Non-linear loads connected to AC power sources cause power wastage and damage due to out-of-phase current and voltage, leading to low Power Factor (PF), and existing PFC circuits suffer from line current distortion and complexity.
Innovation Solution
A PFC circuit with a control circuit comprising a current conduction duration determining circuit, integrator circuit, feedback circuit, divider circuit, oscillator circuit, and gate control circuit, which reduces line current distortion and complexity by using one-cycle average-current-mode control and eliminating the need for complex math components like multipliers and dividers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a PFC circuit is designed to minimize line current distortion, then Power Factor improves, but device complexity increases due to requiring complex math components like multipliers and dividers
Solution Approach 1:
The patent extracts and eliminates the complex math components (multipliers and dividers) from the PFC circuit while retaining the essential Power Factor correction functionality through a simplified control architecture that uses basic operational amplifiers and integrators
Solution Approach 2:
The control circuit is segmented into distinct functional blocks (error amplifier, integrator, comparator, oscillator) that operate independently but coordinate to achieve Power Factor correction, allowing each block to be simple while the overall system remains effective
2Loss of energy
If existing PFC circuits use complex control mechanisms, then Power Factor is improved, but line current distortion increases
Solution Approach 1:
The patent implements a feedback mechanism where the control circuit continuously monitors the AC line current and voltage phases, and automatically adjusts the switching duty cycle to maintain current in-phase with voltage, thereby improving Power Factor while minimizing current distortion through closed-loop control
Solution Approach 2:
The integrator circuit serves as an intermediary element that smooths the error signal from the phase detector and generates a clean control voltage for the PWM modulator, filtering out high-frequency switching noise and preventing current distortion while maintaining accurate Power Factor correction
Data Source
AI summary
A control circuit for controlling a Switch-Mode Power Supply (SMPS) includes a current conduction duration determining circuit, an integrator circuit, a feedback circuit, a sawtooth generator circuit, and a gate control circuit. The current conduction duration determining circuit produces a duration signal according to a duration of a current of the SMPS. The integrator circuit produces an integrator output corresponding to an integral over time of a magnitude of the current. The feedback circuit produces a comparison voltage according to an output voltage of the SMPS. The sawtooth generator circuit produces a sawtooth signal using the comparison voltage and duration signal, such as by dividing the comparison voltage by the duration signal. The gate control circuit generates a gate signal for controlling a power switch of the SMPS according to a comparison of the sawtooth signal to the integrator output. The SMPS may be a Power Factor Correction circuit.