Backlight Control Circuit for Display Electromagnetic Noise Reduction
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Solution Overview
Problem
Liquid crystal display devices face challenges in managing electromagnetic noise, particularly due to the inductor current fluctuations during voltage conversion, which affect the display's performance and efficiency.
Innovation Solution
A display device and driving method that incorporate a backlight control circuit with a pulse generator and voltage drop circuit, where the pulse generator outputs control pulse signals based on voltage levels and the voltage drop circuit applies a second, lower voltage during the off section, reducing electromagnetic noise by stabilizing the inductor current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a voltage converter is used to generate driving voltage for light sources, then the display device can efficiently control light output, but electromagnetic noise increases due to inductor current fluctuations
Solution Approach 1:
The voltage drop circuit applies a second voltage to the control input terminal before the off section begins, preliminarily preparing the voltage level to prevent abrupt current changes in the inductor. This preliminary voltage adjustment reduces the severity of current fluctuations and associated electromagnetic noise when the light sources are turned off.
Solution Approach 2:
The patent changes the voltage parameter at the control input terminal from a first voltage during the on section to a second voltage during the off section. This parameter change smooths the inductor current transitions by adjusting the control voltage level, thereby reducing electromagnetic noise while maintaining efficient power conversion.
2Speed
If the light sources are rapidly turned off during the off section, then the display can quickly switch between bright and dark states, but inductor current fluctuations increase causing electromagnetic noise
Solution Approach 1:
The voltage drop circuit preliminarily adjusts the control input terminal voltage before the off section begins, preparing the system for the upcoming switch-off event. This preliminary action allows the light sources to be rapidly turned off while the voltage transition is already initiated, reducing the shock to the inductor current and minimizing electromagnetic noise.
Solution Approach 2:
The patent dynamically adjusts the voltage at the control input terminal based on the operating section (on or off). By making the voltage dynamic rather than static, the system can respond quickly to switching requirements while simultaneously managing inductor current transitions to reduce electromagnetic noise.
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 electromagnetic noise by stabilizing the inductor current, improving the display device's performance and efficiency by maintaining a constant peak value during the maintenance section.
Implementation Method 1
the voltage drop circuit applies the second voltage to the control input terminal during the off section. The second voltage is smaller than the first voltage... effectively reduces electromagnetic noise by stabilizing the inductor current
Data Source
AI summary
Provided is a display device including a plurality of light sources configured to be driven by a driving voltage, turned on during an on section, and turned off during an off section, a display panel configured to display an image by using light outputted from the light sources, a voltage converter connected to the light sources and configured to generate the driving voltage, and a backlight control circuit including a light source driving circuit and a voltage drop circuit. The light source driving circuit includes a pulse generator including a control input terminal configured to receive a first voltage during the on section and receive a second voltage during the off section and output a control pulse signal to control a level of the driving voltage based on a voltage applied to the control input terminal. The voltage drop circuit applies the second voltage to the control input terminal during the off section. The second voltage is smaller than the first voltage.