Electronic Ballast PFC Network for Gas Discharge Lamps
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Solution Overview
Problem
Existing electronic ballasts for gas discharge lamps face inefficiencies due to high total harmonic distortion (THD) and power factor issues, leading to reduced lamp life and increased costs, with prior solutions either complicating the circuit or increasing oscillations and current crest factor.
Innovation Solution
The electronic ballast incorporates a power factor correction (PFC) network with an inductor, diode, and capacitor, along with a switched inverter circuit and control module that continuously consumes power, maintaining a constant voltage and reducing harmonics, allowing for efficient power transfer and multiple lamp handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If relatively large capacitors are used to minimize ripple on DC voltage, then ripple is reduced, but current crest factor increases and total harmonic distortion increases
Solution Approach 1:
The circuit pre-charges the capacitor during the AC voltage peaks before the main charging phase, preparing the capacitor in advance to reduce the current spike during main charging. This preliminary action allows the capacitor to be charged more gradually, reducing harmonic distortion while maintaining voltage stability.
Solution Approach 2:
The circuit dynamically adjusts the charging current based on the AC voltage phase. By detecting the AC voltage level and modulating the charging current accordingly (higher current during peaks, lower during zero crossings), the circuit achieves both low ripple and low harmonic distortion, making the charging process adaptive rather than static.
2Object-generated harmful factors
If power factor correction circuits are used to reduce total harmonic distortion, then total harmonic distortion is reduced, but device complexity and cost increase
Solution Approach 1:
The circuit combines the power factor correction function with the existing capacitor charging circuit by adding a controlled current source that operates in conjunction with the capacitor. This merging of functions achieves power factor correction without requiring separate complex correction circuits, reducing overall device complexity while maintaining low harmonic distortion.
Solution Approach 2:
The circuit uses the lamp's own operating characteristics and the AC voltage waveform to automatically regulate the charging current. The controlled current source adjusts based on the AC voltage phase and the lamp's power requirements, making the power factor correction self-regulating without complex external control circuits.
3Productivity
If the capacitor is charged only during short time in each half cycle, then charging efficiency is high, but current crest factor increases and lamp life decreases
Solution Approach 1:
The circuit implements periodic charging phases within each AC half cycle, with the controlled current source activating during specific intervals (when AC voltage is above a threshold) and deactivating during others. This periodic action distributes the charging current over multiple intervals rather than concentrating it in one short burst, reducing the current crest factor while maintaining charging efficiency, thereby extending lamp life.
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
This configuration achieves lower THD, improved power factor, and extended lamp life by maintaining stable power delivery and reducing harmonic distortion, while allowing for efficient handling of multiple lamps with reduced component complexity and cost.
Implementation Method 1
a rectifier circuit for converting an alternating current AC input voltage into a direct current DC rectified voltage
Implementation Method 2
a power factor correction (PFC) network which includes an electrolytic capacitor that is loaded through a circuit conformed by an inductor
Implementation Method 3
when the switch is closed, it does not affect the charge of the capacitor, because it is isolated by the diode which in this case is inversely polarized
Implementation Method 4
a power factor correction (PFC) network which includes an electrolytic capacitor (or other energy storage device)
Data Source
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AI summary
The present invention discloses an electronic ballast for operating a gas discharge lamp which includes (i) a rectifier bridge circuit; (ii) a power factor correction (PFC) network that includes an electrolytic capacitor that charges by means of a circuit comprised by an inductor, diode and capacitor; and (iii) a switched inverter circuit that converts rectified DC voltage to a high frequency current AC voltage. The electronic circuit has a switch that switches on the aforementioned electronic elements making the (PFC) circuit consume energy continuously from the network, while the electrolytic capacitor remains connected to the voltage of the rectifier bridge, through the inductor and the diode, even if the inductor has no energy stored. From the storage capacitor the inverter is powered by a constant voltage and noise-free, allowing the inverter to power the luminous load properly.