PFC Switching Control for Stable Output and Lower THD
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Solution Overview
Problem
Power factor correction circuits in power adapters face challenges in achieving Energy Star 6.0 specifications due to power loss, particularly when operating in critical mode, which affects total harmonic distortion (THD) and efficiency.
Innovation Solution
A control device for a power factor correction circuit that includes a detection unit, holding unit, determining unit, and condition specifying unit to manage the number of free vibrations of the switching element's drain-source voltage, adjusting the switching frequency based on load conditions to stabilize output and reduce THD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a power factor correction circuit operates in critical mode to reduce cost and improve efficiency, then switching control becomes simpler and cost decreases, but power loss increases making it difficult to achieve Energy Star 6.0 specifications
Solution Approach 1:
The patent applies dynamics by transitioning the power factor correction circuit from static critical mode operation to dynamic control that adapts between critical mode and discontinuous conduction mode. The control device dynamically adjusts the switching element's on-time based on operating conditions, allowing the circuit to optimize between cost-efficiency (critical mode) and low-power-loss (discontinuous mode) scenarios, thereby achieving Energy Star 6.0 specifications while maintaining manufacturing simplicity.
Solution Approach 2:
The patent employs parameter changes by modifying the switching element's on-time parameter based on the operating state. The control device changes the duty cycle parameter dynamically - using longer on-times in discontinuous mode for low power loss and shorter on-times in critical mode for cost efficiency. This parameter adaptation allows the circuit to meet Energy Star 6.0 requirements across different operating conditions.
2Stability of the object's composition
If switching frequency is increased to improve output stability, then output voltage stabilization improves, but total harmonic distortion increases affecting Energy Star compliance
Solution Approach 1:
The patent applies periodic action by utilizing the natural periodicity of the AC input voltage and implementing synchronized switching control. The control device adjusts the switching frequency to be synchronized with the line frequency, creating periodic switching patterns that reduce harmonic distortion. This periodic synchronization allows output voltage stabilization while minimizing THD to meet Energy Star 6.0 specifications.
3Loss of energy
If the number of free vibrations is reduced to lower switching frequency, then power loss decreases, but output stability deteriorates
Solution Approach 1:
The patent applies dynamics by making the number of free vibrations a dynamic parameter rather than a fixed value. The control device dynamically adjusts the switching element's on-time to maintain appropriate vibration counts during different phases of the AC cycle. This dynamic adjustment allows the circuit to reduce switching frequency and power loss during certain conditions while maintaining output stability during others, achieving Energy Star 6.0 compliance across varying loads.
Data Source
AI summary
The present disclosure provides a control device for a power factor correction circuit. The power factor correction circuit is disposed in a power supply device configured to generate a direct current output voltage from an alternating current voltage applied to a pair of power supply terminals. The power factor correction circuit is disposed between a full-wave rectifier circuit configured to generate a full-wave rectified voltage by full-wave rectifying the AC voltage and an output wiring configured to apply the output voltage. The power factor correction circuit includes an inductor inserted between the full-wave rectifier circuit and the output wiring, and a switching element configured to switch between an on state and an off state to control a current flowing through the inductor.