Interleaved PFC Control Circuit for Stable Phase Difference
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Solution Overview
Problem
Existing power factor correction circuits in critical mode experience a decrease in power factor due to rapid phase changes in interleaved operations, which disrupt the waveform of the input current.
Innovation Solution
A control circuit that restricts the phase adjustment of the second current relative to the first current by controlling the ON width of the second switching element, maintaining a predetermined phase difference and minimizing waveform disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase adjustment is performed rapidly to maintain predetermined phase difference in interleaved operation, then power factor improvement is achieved, but waveform disturbance occurs and power factor decreases
Solution Approach 1:
The patent implements dynamic phase adjustment by detecting the actual phase difference between first and second currents and adjusting the ON width of the second switching element accordingly. This dynamic adjustment maintains the predetermined phase difference under varying operating conditions while avoiding excessive adjustment that would cause waveform disturbance. The control circuit continuously adapts the phase relationship based on real-time current measurements, resolving the contradiction between maintaining power factor and preventing waveform distortion.
Solution Approach 2:
The patent employs feedback control by detecting the phase difference between the first current and second current, comparing it with the predetermined phase difference, and adjusting the ON width of the second switching element based on the detection result. This closed-loop feedback mechanism ensures that phase adjustment is performed only when necessary and within appropriate limits, thereby maintaining power factor improvement while preventing harmful waveform disturbances that would otherwise occur with rapid or excessive adjustment.
2Stability of the object's composition
If ON width of second switching element is adjusted to control phase difference, then phase stability is improved, but switching losses increase
Solution Approach 1:
The patent applies partial action by adjusting the ON width of the second switching element only to the extent necessary to maintain the predetermined phase difference, rather than performing excessive or continuous adjustment. The control circuit detects the actual phase difference and applies minimal correction needed to maintain stability, thereby achieving phase control while minimizing unnecessary switching operations and associated energy losses.
3Reliability
If phase detection and adjustment are performed continuously, then power factor is maintained, but device complexity increases
Solution Approach 1:
The control circuit is designed to perform multiple functions: detecting the phase difference between currents, comparing it with the predetermined phase difference, determining the appropriate ON width adjustment, and controlling the second switching element. By integrating these functions into a single multi-functional control circuit, the patent maintains power factor improvement while avoiding the need for separate dedicated circuits for each function, thereby limiting the increase in device complexity.
Data Source
AI summary
A control circuit is provided, which controls, for a power supply circuit, a switching operation of a first switching element which controls a first current and a second switching element which controls a second current, the power supply circuit including the first switching element and the second switching element, the control circuit including a phase detection circuit which generates a phase difference signal which indicates a phase difference between the first current and the second current and a phase compensation circuit which adjusts a second phase, at which the second switching element operates, relative to a first phase, at which the first switching element operate, based on the phase difference signal and the duration of the ON period of the second switching element.