Power Factor Correction Circuit Single-Pin Voltage Detection
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Solution Overview
Problem
Existing power factor correction circuits face inefficiencies due to high harmonic content in current profiles, leading to low power factors, and struggle to accurately detect low input voltages, especially in single-pin control scenarios, which can indicate power failures.
Innovation Solution
A method and circuit that utilize a controller to monitor the voltage across a switch and the ratio of on and off periods to detect low input voltages, allowing for precise adjustment of output voltage and detection of abnormal input conditions using a single input pin, enabling effective power factor correction and emergency lighting scenarios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single input pin is used for power factor correction control, then device complexity is reduced, but the ability to accurately detect low input voltage is compromised
Solution Approach 1:
The single input pin is designed to perform multiple functions: it monitors both the voltage across the switch and detects low input voltage conditions. By making this single component multi-functional, the patent reduces the number of pins required while maintaining the necessary detection capabilities, thus resolving the contradiction between device complexity and measurement precision.
Solution Approach 2:
The patent uses the voltage across the switch as an intermediary signal that contains information about both switch state and input voltage level. By monitoring this intermediary parameter, the system can infer input voltage conditions without requiring a separate detection mechanism, thereby maintaining detection accuracy while reducing pin count.
2Productivity
If the switch on period is extended to adjust output voltage towards target value, then power factor correction is improved, but the risk of over-current conditions increases
Solution Approach 1:
The patent implements feedback monitoring of the voltage across the switch during its on period. This feedback mechanism allows the system to detect abnormal voltage conditions that may indicate over-current situations, enabling real-time adjustment of the on period duration to maintain power factor correction effectiveness while preventing over-current damage.
Solution Approach 2:
The switch on period is made dynamic rather than fixed. The controller continuously adjusts the on period duration based on real-time monitoring of switch voltage and output voltage conditions. This dynamic adjustment allows the system to optimize power factor correction while automatically adapting to prevent over-current conditions, resolving the contradiction between productivity and reliability.
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 improves power factor correction by efficiently adjusting output voltage and detecting low input voltages, ensuring reliable operation and emergency lighting functionality even during power failures, while reducing circuit complexity and cost.
Implementation Method 1
By rapidly switching the switch on and off, the inductor is repeatedly first connected directly to ground via the switch and then connected to the output capacitor (via the diode) when the switch is turned off. When the switch is on the current flow through the inductor increases and, during the subsequent time period in which the switch is off, the current decreases, effectively pushing current through the diode to charge the output capacitor.
Implementation Method 2
A PFC circuit essentially comprises an inductor followed by a diode, with a switch (typically an FET) connected between the inductor and the diode to ground.
Implementation Method 3
By rapidly switching the switch on and off, the inductor is repeatedly first connected directly to ground via the switch and then connected to the output capacitor (via the diode) when the switch is turned off.
Implementation Method 4
A PFC circuit essentially comprises an inductor followed by a diode, with a switch (typically an FET) connected between the inductor and the diode to ground.
Data Source
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AI summary
A power factor correction circuit includes an inductor L1, a diode D1, a switch Q3 and a controller 24. An input voltage Vin is applied to the inductor L1 which is cyclically discharged through the diode D1 by the operation of the switch Q3. The method of operation includes: operating a controller 24 to obtain an indication of the voltage across the switch Q3, monitoring the indication of the voltage across the switch Q3 to determine when the inductor L1 reaches a discharged state in response to the switch being in an off state, and the switch Q3 being controlled by the controller 24 to vary the on period of the switch Q3, during which the inductor is charged, for adjusting an output voltage Vbus towards a target value Vbus _target. The controller 24 monitors at least one of the indication of the voltage across the switch Q3 and the ratio of the switch on period Ton to the switch off period Toff for detecting that the input voltage Vin has a low value.