Power Factor Corrector Circuit Using Dynamic Switching Frequency Control
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Solution Overview
Problem
Traditional power factor corrector (PFC) circuits face inefficiencies near the main zero-crossing due to mode changes from Boundary Conduction Mode (BCM) to Discontinuous-Conduction Mode (DCM), leading to lower efficiency, especially in AC/DC power converters for power management systems.
Innovation Solution
A power factor corrector circuit operates within a defined frequency range using a measured variable k1, which sets the relation between peak currents and stroke intervals to maintain optimal switching frequency, allowing for seamless transitions between Continuous-Conduction Mode (CCM) and DCM, ensuring efficient power factor correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If fixed frequency operation is used in CCM applications, then the PFC circuit can operate at a stable frequency, but efficiency deteriorates close to the main zero-crossing due to mode changes from BCM to DCM
Solution Approach 1:
The patent implements dynamic switching frequency adjustment by transitioning from fixed frequency CCM operation to a variable frequency system that adapts between CCM and DCM modes. The control circuit dynamically modifies the switching frequency based on the operating point, particularly near the main zero-crossing, to maintain optimal efficiency by preventing unwanted mode transitions and associated losses.
2Volume of moving object
If CCM operation is used at higher power levels, then EMI filter size can be reduced, but mode transition to DCM occurs near zero-crossing causing efficiency loss
Solution Approach 1:
The system dynamically adjusts operating parameters to maintain CCM mode at higher power levels where it provides benefits (smaller EMI filters) while preventing unwanted transitions to DCM near the main zero-crossing. The control circuit monitors power levels and switching mode, adjusting frequency and duty cycle to maintain optimal operation in each region.
Solution Approach 2:
The patent changes key operating parameters (switching frequency, duty cycle) based on the operating conditions. Near the main zero-crossing, the control circuit modifies these parameters to prevent mode transition to DCM, thereby maintaining efficiency while still allowing CCM operation at higher power levels for reduced EMI filter size.
3Ease of operation
If Ton control is used in DCM applications, then automatic correction of mains current shape for high power factor is achieved, but this control method cannot be employed in CCM operations
Solution Approach 1:
The patent develops a universal control method that can operate in both CCM and DCM modes, replacing the Ton control method that is only suitable for DCM. The new control circuitry adapts its behavior based on the operating mode, providing automatic current shape correction in DCM while using alternative control strategies in CCM, thereby achieving versatility across different operating conditions.
Solution Approach 2:
The control method changes its parameters and control strategy based on the operating mode. In DCM, it uses Ton control for automatic current shape correction, while in CCM it employs different control parameters (such as duty cycle control) to achieve similar power factor correction objectives, making the system adaptable to both modes.
Data Source
AI summary
A power factor corrector circuit and a method of operating the power factor corrector circuit include a power factor corrector operable in a conduction mode within an operating frequency between a minimum value and a maximum value. A measured variable k1 can define a relation between a predetermined level set for a current ripple of a peak current Ipeakh minus a peak current Ipeakl in combination with a variable a that sets a ratio between a primary and secondary stroke interval and a resulting time period.