Totem-Pole PFC Phase-Angle Control for Bidirectional Power Flow
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Solution Overview
Problem
The conventional Totem Pole power factor correction circuit is not suitable for bidirectional operation, particularly in discharging modes, due to current cut-off issues and inability to handle phase shifts caused by inductive or capacitive loads, leading to power quality impacts and system shutdowns.
Innovation Solution
A Totem Pole power factor correction circuit with a control unit that includes current and voltage detection loops and a control loop to dynamically adjust the duty cycle of the slow-switching leg switches, allowing them to follow the phase angle of the AC voltage and maintain continuous energy transmission during phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional Totem Pole circuit uses fixed slow-switching control, then the circuit operates normally in charging mode, but the current cuts off and the system shuts down in discharging mode with phase shifts
Solution Approach 1:
The patent implements dynamic adjustment of the slow-switching leg duty cycle based on phase angle detection. The control unit dynamically modifies the duty cycle of slow-switching switches QA and QB according to the detected phase angle of AC voltage, enabling the circuit to adapt to different operating conditions (charging/discharging modes) and prevent current cut-off in discharging mode
Solution Approach 2:
The patent introduces a phase angle detection mechanism that provides feedback to the control unit. The control unit receives phase angle information from the detection mechanism and uses this feedback to adjust the duty cycle of slow-switching switches, ensuring continuous current flow and preventing system shutdown during discharging operation
2Ease of manufacture
If the slow-switching transistor switch QB is turned on later due to voltage offset, then the circuit structure remains simple, but the current cuts off causing power quality impact
Solution Approach 1:
The patent implements preliminary phase angle detection and proactive duty cycle adjustment before current cut-off occurs. The control unit detects the phase angle in advance and adjusts the duty cycle of slow-switching switches proactively to ensure they turn on at the correct timing, preventing current cut-off and maintaining power quality
Solution Approach 2:
The patent changes the duty cycle parameter of slow-switching switches based on detected phase angle conditions. By dynamically adjusting this parameter, the circuit maintains proper switching timing and prevents current cut-off without requiring complex circuit structural modifications
Data Source
AI summary
A Totem Pole PFC circuit includes at least one fast-switching leg, a slow-switching leg, and a control unit. Each fast-switching leg includes a fast-switching upper switch and a fast-switching lower switch. The slow-switching leg is coupled in parallel to the at least one fast-switching leg, and the slow-switching leg includes a slow-switching upper switch and a slow-switching lower switch. The control unit receives an AC voltage with a phase angle, and the control unit includes a current detection loop, a voltage detection loop, and a control loop. The control loop generates a second control signal assembly to respectively control the slow-switching upper switch and the slow-switching lower switch. The control loop controls the second control signal assembly to follow the phase angle, and dynamically adjusts a duty cycle of the second control signal assembly to turn on or turn off the slow-switching upper switch and the slow-switching lower switch.