Bridgeless PFC Power Converter With Inverted Slope Compensation
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Solution Overview
Problem
Existing AC/DC converters with bridgeless PFC circuits face challenges in implementing peak current mode control due to the need for negative slope compensation, which is not supported by commercially-available slope compensation components designed for DC/DC converters, leading to instability and larger reactor sizes.
Innovation Solution
The AC/DC converter employs a controller with a peak current mode control system that includes a first slope compensation circuit for positive polarity and a second slope compensation circuit with an inverting circuit for negative polarity, using commercially-available components to enable stable operation with a smaller reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If peak current mode control is adopted to reduce reactor size, then the reactor can be made smaller, but negative slope compensation is required which is not supported by commercially-available components
Solution Approach 1:
The patent inverts the approach by detecting voltage polarity and selecting between positive and negative slope compensation circuits, rather than trying to create a universal slope compensation circuit. This allows the use of commercially-available positive slope compensation components while handling negative polarity through circuit inversion selection.
Solution Approach 2:
The patent changes the parameter of slope compensation type based on voltage polarity. By detecting whether the input voltage is positive or negative, the system dynamically selects the appropriate slope compensation circuit (positive or negative), enabling peak current mode control with smaller reactors while maintaining stability.
2Device complexity
If average current mode control is used, then the control is simpler, but the reactor becomes large in size and switching frequency cannot be increased
Solution Approach 1:
The patent introduces dynamic polarity detection and switching between different slope compensation modes, transforming the static average current mode control into a dynamic peak current mode control system that adapts to voltage polarity, thereby reducing reactor size while maintaining control simplicity.
3Ease of manufacture
If commercially-available slope compensation components are used directly, then the cost is reduced, but they cannot process negative slope compensation signals required for AC/DC converters
Solution Approach 1:
The patent segments the slope compensation function into separate positive and negative polarity circuits. By dividing the functionality, the system can use commercially-available positive slope compensation components for positive polarity while implementing a separate negative slope compensation path, thereby maintaining component availability while achieving polarity versatility.
Solution Approach 2:
The patent introduces a polarity detection circuit as an intermediary that determines which slope compensation circuit to activate. This mediator enables the system to use standard commercial components while adapting to AC power's bidirectional polarity through intelligent circuit selection.
Data Source
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AI summary
An alternating current/direct current (AC/DC) power converter including a bridgeless power factor correction (PFC) circuit and a controller is provided. The bridgeless PFC circuit includes input-side wirings, output-side wirings, an input-side capacitor, a reactor, and a pair of switching elements disposed between the input-side wirings and the output-side wirings, and on which a switching operation is performed by the controller. The controller includes a peak current control unit which executes a peak current mode control by using a first slope compensation circuit corresponding to a positive polarity of AC input voltage, and a second slope compensation circuit corresponding to a negative polarity of the AC input voltage. The second slope compensation circuit has an inverting circuit which inverts the polarity of the AC input voltage, and is structured using a same slope compensation circuit as the first slope compensation circuit.