Totem Pole PFC Skip-Mode Control for Output Overvoltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Totem pole power factor correction circuits experience over-voltage issues in low-power modes due to EMI circuitry responses, leading to unregulated output voltages exceeding device ratings, which is a challenge in adapting these circuits for lower power consumer applications while meeting EMI and power consumption reduction requirements.
Innovation Solution
A method for controlling the PFC circuit by detecting polarity changes in the input voltage and applying a pulse sequence to EMI capacitors to manage voltage transitions during skip mode, using open-loop control to charge or discharge the capacitors incrementally, thereby preventing overcharging and maintaining regulated output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If totem pole PFC circuit uses EMI circuitry for electromagnetic interference filtering, then EMI compliance is improved, but output voltage becomes unregulated and exceeds device ratings in low-power modes
Solution Approach 1:
The controller detects polarity changes of the AC line voltage and proactively applies pulse sequences to the EMI capacitors before over-voltage conditions can develop. This preliminary action charges or discharges the capacitors incrementally, preventing unregulated output voltage excursions before they exceed device ratings, while maintaining EMI filtering functionality.
Solution Approach 2:
The controller continuously monitors the state of the EMI capacitors and the AC line voltage polarity, using this feedback information to determine when to apply pulse sequences. This closed-loop control ensures the EMI capacitors are managed appropriately to maintain both EMI compliance and output voltage regulation, preventing the harmful effect of unregulated voltage.
2Use of energy by moving object
If totem pole PFC circuit operates in low-power modes to reduce power consumption, then energy efficiency is improved, but over-voltage issues occur due to EMI circuitry responses
Solution Approach 1:
In low-power skip mode operation, the controller proactively manages the EMI capacitors by detecting polarity changes and applying pulse sequences to charge or discharge them incrementally. This preliminary management prevents over-voltage conditions from developing, allowing the circuit to operate safely in low-power modes without the harmful effect of over-voltage exceeding device ratings.
3Reliability
If pulse sequence is applied to EMI capacitors to prevent overcharging, then output voltage regulation is improved, but additional control complexity is introduced
Solution Approach 1:
The EMI capacitors are managed autonomously through open-loop control based on AC line voltage polarity detection. The controller automatically detects polarity changes and applies appropriate pulse sequences to charge or discharge the capacitors without requiring complex closed-loop voltage regulation, allowing the circuit to self-regulate and reducing the need for additional complex control circuitry.
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
The solution effectively reduces power consumption and prevents over-voltage in low-power modes, ensuring compliance with EMI standards and device safety by stabilizing the output voltage within rated limits.
Implementation Method 1
applying a pulse sequence to a second transistor of the fast-leg portion of the PFC circuit to change a voltage on an EMI capacitor from a first voltage corresponding to the first half cycle to a second voltage corresponding to a second half cycle
Data Source
AI summary
During a light load (or no-load) operation of a totem pole power factor correction circuit (i.e., PFC), a pulse width modulation (PWM) controller can operate in a skip mode. Further, the PWM controller may disable portions of the PFC to reduce standby power consumption. In this mode, and in this disabled configuration, the output of the PFC may be peak charged over time to a voltage that could be damaging or destructive. This peak charging results from the PFC circuit's inability to fully charge/discharge EMI capacitors between half cycles of the input line voltage. The present disclosure provides circuits and methods to fully charge/discharge the EMI capacitors to prevent peak charging the output.