Switching Converter Control Circuit for Power Factor Correction
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Solution Overview
Problem
Switching converters face limitations in power factor (PF) and total harmonic distortion (THD) due to error currents generated during mode transitions, such as from continuous to discontinuous conduction modes, which disrupt the sinusoidal nature of input current and reduce PF and increase THD.
Innovation Solution
The implementation of a control circuit with a current compensation signal generating circuit and control signal generating circuit that adjusts the conduction time of the main power switch based on current compensation signals, ensuring the inductor current follows the input voltage by compensating for error currents, thereby improving PF and reducing THD.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional switching converter operation is used, then the converter can operate in different conduction modes, but error currents are generated during mode transitions that distort input current and reduce power factor
Solution Approach 1:
The patent detects error currents generated during conduction mode transitions and uses feedback control to compensate for their harmful effects. By measuring the distorted input current and comparing it with a reference sinusoidal waveform, the system generates a compensation signal that cancels out the error currents, thereby converting the harmful distortion into an opportunity for active correction and achieving sinusoidal input current despite mode transitions.
2Power
If conventional switching converter operation is used, then the converter can process power, but total harmonic distortion increases due to non-sinusoidal input current
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the input current waveform, compares it with a reference sinusoidal signal, and adjusts the switching control signals accordingly. The feedback loop detects deviations caused by harmonic distortion and generates corrective actions to minimize THD, allowing the converter to maintain low harmonic distortion while processing power effectively.
3Power
If conventional switching converter operation is used, then the converter can regulate output voltage, but input current does not follow input voltage waveform due to error currents
Solution Approach 1:
The patent employs dual feedback loops: one for output voltage regulation and another for input current waveform control. The input current feedback loop ensures that the current follows the voltage waveform by detecting deviations and adjusting the switching duty cycle accordingly, while the output voltage loop maintains proper voltage regulation. This coordinated feedback control achieves both voltage regulation and current waveform stability simultaneously.
Data Source
AI summary
A control circuit for a switching converter, can include: a current compensation signal generating circuit configured to generate a current compensation signal based on a current sampling signal representing an inductor current; and a control signal generating circuit configured to adjust a current control parameter of a current control loop in the switching converter according to the current compensation signal, in order to increase power factor (PF) and reduce total harmonic distortion (THD).