Continuous Conduction Mode PFC Circuit with Reduced Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power supply circuits with continuous conduction mode power factor correction require line sensing, inductor current sensing, and multipliers, which complicates the design and stability of the current control loop.
Innovation Solution
A power supply circuit that generates a carrier signal voltage and a sampling voltage indicative of the drain current of a drive transistor, with the ON time of the drive transistor set to twice the intersection time when the carrier signal voltage equals the sampling voltage, allowing for continuous conduction mode power factor correction without the need for line sensing or inductor current sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional power factor correction is implemented with line sensing, inductor current sensing, and multipliers, then power factor correction capability is achieved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the need for line sensing, inductor current sensing, and multiplier circuits from the power factor correction system. By using a simplified control mechanism that compares carrier signal with a reference voltage to generate PWM signals, the invention removes complex sensing and calculation components while maintaining power factor correction functionality.
Solution Approach 2:
The system uses the carrier signal itself and a simple reference voltage comparison to automatically generate the PWM control signals needed for power factor correction. The control circuit self-regulates the switching transistor based on the intersection detection between carrier signal and reference voltage, eliminating the need for external sensing circuits and complex control logic.
2Measurement precision
If line sensing and inductor current sensing are used, then accurate power factor correction is achieved, but ease of manufacture decreases
Solution Approach 1:
The patent removes the requirement for line sensing circuits and inductor current sensing circuits. Instead of measuring actual line voltage and inductor current, the system uses a simplified approach where the carrier signal intersection with a reference voltage determines the PWM duty cycle, greatly simplifying manufacturing.
Solution Approach 2:
The invention replaces expensive and complex sensing circuits with simple, inexpensive voltage comparison logic. The reference voltage and carrier signal intersection method requires minimal components, making the system much easier and cheaper to manufacture while maintaining adequate control precision for power factor correction.
3Reliability
If multiplier and sensing circuits are included, then power factor correction performance is improved, but ease of operation worsens
Solution Approach 1:
The patent removes the multiplier circuit and complex sensing systems that complicate the control loop. The simplified control mechanism using carrier signal intersection with reference voltage creates a more stable and easier-to-operate system while maintaining power factor correction performance.
Data Source
AI summary
A power supply circuit includes continuous conduction mode power factor correction (PFC). The PFC may be performed by generating a carrier signal voltage at a beginning of a switching cycle of the power supply, generating a sampling voltage indicative of drain current of a drive transistor, and detecting when the carrier signal voltage has decreased to the same level as the sampling voltage at an intersection time. The ON time of the drive transistor may be set to twice the intersection time.