Boost Converter Variable Frequency Oscillator EMI Reduction
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Solution Overview
Problem
Conventional liquid crystal display boost converters generate electromagnetic interference due to concentrated energy spectra, and using variable frequency switching pulses to mitigate this results in unstable panel driving voltages and image display issues.
Innovation Solution
A boost converter system that employs an oscillator generating a variable frequency oscillation signal, either in a predetermined pattern or randomly, synchronized with frame start, to control the switching pulse for the transistor driving the reactor, ensuring a stable panel driving voltage without interfering with image stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed frequency switching pulse is used to drive the reactor, then the boosting operation is stable, but electromagnetic interference occurs due to concentrated energy spectrum
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed frequency switching pulse to a variable frequency switching pulse. The oscillation signal generator produces signals with frequencies that vary over time, causing the reactor to operate at different frequencies dynamically. This dynamic frequency variation spreads the energy spectrum, reducing electromagnetic interference while maintaining boosting functionality through continuous adaptation of the switching characteristics.
2Object-generated harmful factors
If a variable frequency switching pulse is used to reduce electromagnetic interference, then the energy spectrum is spread, but the panel driving voltage becomes unstable
Solution Approach 1:
The patent implements feedback by introducing a voltage detector that continuously monitors the panel driving voltage and feeds this information back to the oscillation signal generator. The oscillation signal generator adjusts the switching frequency based on the detected voltage levels, creating a closed-loop control system. This feedback mechanism ensures that even with variable frequency operation, the panel driving voltage remains stable by dynamically compensating for any deviations.
3Object-generated harmful factors
If variable frequency switching is implemented, then electromagnetic interference is reduced, but image stability is affected
Solution Approach 1:
The feedback mechanism monitors not only the panel driving voltage but also ensures proper synchronization with the image display timing. By adjusting the variable frequency switching based on real-time voltage detection, the system maintains consistent voltage levels during critical image display periods, preventing image instability while still achieving electromagnetic interference reduction through overall frequency variation.
Solution Approach 2:
The patent employs periodic action by synchronizing the variable frequency switching with the display refresh cycle. The oscillation signal generator coordinates the frequency variations with the periodic nature of image display, ensuring that voltage stability is maintained during each frame period. This periodic coordination allows frequency variation for EMI reduction while preserving image stability through rhythmic synchronization.
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 system effectively reduces electromagnetic interference by spreading the energy spectrum, maintaining stable boosting operations and consistent panel driving voltages across frames, thus preventing image instability.
Implementation Method 1
a boosting voltage loaded from the reactor L1 by a switching operation of the field-effect transistor FET1 is stored in the condenser Cout
Implementation Method 2
a condenser Cout for storing a voltage which is loaded through a blocking diode D1 from the reactor L1
Data Source
Figure 1
Figure 2
Figure 3(a)~4
AI summary
In order that a boost converter of an LDI can reduce electromagnetic interference by generating a panel driving voltage through the use of a variable frequency, while achieving a stable boosting operation using the same frequency whenever each frame begins, an oscillator generates an oscillation signal having a frequency, which varies in a predetermined pattern or hops in a random pattern around a center frequency, and generates an oscillation signal having a preset fixed frequency whenever each frame begins.