Power Converter Control Circuit for CCM Power Factor Correction
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Solution Overview
Problem
Some power converters with power factor correction (PFC) circuits are limited to specific operation modes, such as Discontinuous Conduction Mode (DCM) and Boundary Conduction Mode (BCM), and cannot operate in Continuous Conduction Mode (CCM), which restricts their power factor correction capabilities.
Innovation Solution
A control circuit for power converters that includes a current detection circuit and a control signal generator, which generates a switching control signal making the input current proportional to the voltage conversion function, allowing the power converter to operate as a pure resistance in various modes, including CCM, thereby maintaining a power factor close to 1.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a COT power converter is operated in DCM or BCM to realize power factor correction, then the power factor can be corrected, but the converter cannot operate in CCM mode
Solution Approach 1:
The patent changes the control parameter from fixed on-time to variable on-time that adapts to different conduction modes. The control circuit dynamically adjusts the on-time parameter based on whether the converter is operating in CCM, BCM, or DCM, enabling power factor correction across all modes through parameter adaptation
Solution Approach 2:
The control circuit is designed to universally handle multiple conduction modes (CCM, BCM, and DCM) within a single unified control framework. The circuit can automatically detect and adapt to the current operating mode, making the power converter capable of power factor correction regardless of which conduction mode is active
2Device complexity
If power converters are limited to specific operation modes, then the control circuit can be simplified, but the power factor correction capabilities are restricted
Solution Approach 1:
The control circuit employs dynamic characteristics by continuously monitoring the relationship between input voltage, output voltage, and switching frequency to automatically detect the conduction mode. The circuit dynamically adjusts control parameters in real-time based on operating conditions, enabling adaptation to different modes without requiring separate fixed control circuits for each mode
Data Source
AI summary
A control circuit for a power converter can include: a current detection circuit configured to generate a current detection signal that represents an input current; a control signal generator configured to generate a switching control signal such that the current detection signal is directly proportional to a voltage conversion function; and a power stage circuit of the power converter being controlled by the switching control signal, where the voltage conversion function is a ratio of an input voltage and an output voltage of the power converter.