Totem-Pole PFC Slow-Switch Turn-Off Using L-Phase Thresholds
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Solution Overview
Problem
Conventional totem-pole PFC circuits face issues with slow transistor response times during rapid input voltage phase changes, leading to potential short circuits and component damage due to incorrect phase control.
Innovation Solution
A totem-pole PFC circuit design where only the L-phase voltage is detected, and the turn-off timing of slow switches is controlled by comparing it with threshold voltages, enhancing response speed and ensuring immediate phase change detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the microprocessor calculates the AD value through L-phase and N-phase voltage detection circuits with resistors, then the control is comprehensive, but the response time is insufficient leading to incorrect phase control
Solution Approach 1:
The patent extracts only the essential L-phase voltage detection from the conventional two-phase detection system. By removing the N-phase detection circuit and focusing solely on L-phase voltage comparison with threshold values, the system achieves faster response time while maintaining sufficient control reliability for the slow transistor switching application.
Solution Approach 2:
The patent implements preliminary action by continuously monitoring the L-phase voltage and pre-comparing it with threshold values before the rapid phase change occurs. This allows the controller to predict the upcoming phase transition and prepare the slow transistor switching state in advance, eliminating the delay associated with post-change detection and calculation.
2Measurement precision
If the microprocessor processes both L-phase and N-phase voltages, then the control precision is higher, but the device complexity increases
Solution Approach 1:
The patent removes the unnecessary N-phase voltage detection circuit and associated processing components. By keeping only the L-phase voltage detection circuit and simplifying the processing to direct threshold comparison, the system reduces device complexity while maintaining adequate measurement precision for controlling the slow transistor in totem-pole PFC applications.
Solution Approach 2:
Instead of using complex microprocessor-based AD conversion and calculation as in conventional designs, the patent inverts the approach by using simple threshold voltage comparison. This inverted methodology achieves sufficient precision with much lower complexity by directly comparing voltages rather than converting to digital values and processing them computationally.
3Stability of the object's composition
If the slow transistor response is delayed during rapid phase changes, then the control system is stable, but short circuit or component damage occurs
Solution Approach 1:
The patent applies preliminary action by continuously monitoring the L-phase voltage and comparing it with threshold values in real-time. This allows the system to detect rapid phase changes immediately and preemptively adjust the slow transistor switching state before the harmful short circuit condition can develop, thus preventing component damage while maintaining system stability.
Solution Approach 2:
The patent implements preliminary anti-action by preparing the slow transistor switching state in advance based on predicted phase changes. When a rapid phase change is detected through L-phase voltage comparison, the system immediately counteracts the potential harmful effect by adjusting the transistor state before the short circuit can occur, thereby preventing damage while preserving stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Faster response speed in detecting phase changes, preventing incorrect phase control and potential damage by immediately turning off slow switches during rapid input voltage fluctuations.
Implementation Method 1
the controller detects a L-phase voltage of the AC power source. When a potential at the first terminal is higher than a potential at the second terminal, the controller turns off the fourth switch if the L-phase voltage is lower than a first threshold voltage.
Data Source
AI summary
A totem-pole PFC circuit and a control method thereof are provided. The circuit includes an AC power source, first and second bridge arms and a controller. The first bridge arm includes first and second switches electrically connected in series with a connection node electrically connected to a first terminal of the AC power source. The second bridge arm includes third and fourth switches electrically connected in series with a connection node electrically connected to a second terminal of the AC power source. When a potential at the first terminal is higher than a potential at the second terminal, the controller turns off the fourth switch if the L-phase voltage is lower than a first threshold voltage. When the potential at the first terminal is lower than the potential at the second terminal, the controller turns off the third switch if the L-phase voltage is higher than a second threshold voltage.