Totem-Pole PFC Current Sensing for Fast Cycle-by-Cycle OCP
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Solution Overview
Problem
Current totem-pole bridgeless PFC circuits face complexity and cost issues with cycle-by-cycle overcurrent protection (OCP) and synchronous rectifier (SR) mode detection and control.
Innovation Solution
A power factor correction (PFC) circuit with integrated bidirectional current sensing and overcurrent protection circuits for each switch, enabling rapid response to overcurrent conditions and SR mode detection, using a controller to manage switch states and thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cycle-by-cycle overcurrent protection and synchronous rectifier mode detection are implemented in totem-pole bridgeless PFC circuits, then protection reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines overcurrent protection and synchronous rectifier mode detection functions into a unified control architecture. The current sense circuit serves dual purposes: detecting overcurrent conditions and determining SR mode operation. The controller integrates multiple control functions (OCP, SR mode detection, PWM generation) into a single device, reducing the number of separate components and interconnections while maintaining comprehensive protection and control capabilities.
Solution Approach 2:
The controller is designed to perform multiple functions simultaneously: it generates PWM signals for switch control, monitors current through the sense circuit for overcurrent protection, and detects synchronous rectifier mode conditions. This multi-functional approach eliminates the need for separate dedicated circuits for each function, thereby reducing overall device complexity while improving reliability through integrated protection mechanisms.
2Measurement precision
If integrated bidirectional current sensing circuits are added to each switch, then overcurrent detection precision is improved, but device complexity increases
Solution Approach 1:
The bidirectional current sensing capability is integrated directly into the switch structure, allowing a single sensing circuit to measure current in both directions during different switching phases. This eliminates the need for separate sensing circuits for each current direction and reduces the overall component count while maintaining precise bidirectional current measurement capability for both OCP and SR mode detection.
3Speed
If rapid response overcurrent protection is implemented, then protection speed is improved, but device complexity increases
Solution Approach 1:
The overcurrent protection mechanism is designed to detect and respond to overcurrent conditions within the same switching cycle in which they occur. The current sense circuit continuously monitors switch current and immediately triggers protective action when thresholds are exceeded, without requiring complex multi-cycle analysis or external intervention. This same-cycle response achieves rapid protection while using straightforward comparison logic rather than complex control algorithms.
Data Source
AI summary
A PFC circuit is disclosed. The circuit includes a first switch having a first power switch, a first current sense circuit and a first overcurrent protection circuit, a second switch having a second power switch, a second current sense circuit and a second overcurrent protection circuit, the first switch coupled to the second switch at a switch node, an inductor coupled between the switch node and an AC input terminal, and a controller arranged to transmit control signals to the first and second switches, where the first current sense circuit is arranged to transmit a first signal including at least one of a magnitude and a polarity of a first current through the first power switch, and the first overcurrent protection circuit is arranged to receive the first signal and transition the first power switch to a first off-state in response to the first signal exceeding a first predetermined threshold.