Backlight Unit Vibration Damping via PCB Holes and Shield Flanges
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Solution Overview
Problem
The vibration of lamps in direct type backlight units causes noise due to resonation with balance PCBs, and the existing shielding mechanism is not effectively secured against these vibrations, leading to increased noise levels in large-sized LCDs.
Innovation Solution
The design incorporates vibration absorbing holes in the bottom cover where the balance PCBs are mounted and integrates shield covers with flanges that have a greater inner angle before fastening to reduce vibration transfer, enhancing adhesion and preventing shield cover vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If lamps are parallel-driven using high voltage AC signal to reduce backlight unit volume, then the volume of backlight unit is reduced, but the lamps vibrate due to rapid energy changes in electrodes, causing noise through resonation with balance PCBs
Solution Approach 1:
A vibration absorbing member is introduced as an intermediary component between the lamps and balance PCBs. This member absorbs the vibration generated by the lamps and prevents it from being transmitted to the balance PCBs, thereby eliminating the resonation noise while maintaining the parallel-driven configuration
Solution Approach 2:
The vibration absorbing member converts the harmful vibration energy from the lamps into a beneficial damping effect. By absorbing the vibration, the harmful resonation noise is eliminated, and the system benefits from reduced noise without sacrificing the volume reduction achieved through parallel-driven operation
2Ease of operation
If shield cover is fastened to bottom cover using L-shaped flanges, then the shield cover is positioned, but the flanges are not firmly attached due to same bending angle before and after fastening, causing shield cover vibration
Solution Approach 1:
The flange is designed with asymmetric bending angles: a first bending angle before fastening that is greater than a second bending angle after fastening. This asymmetric design creates a mechanical interference fit that firmly attaches the shield cover to the bottom cover, preventing vibration while maintaining ease of assembly
Solution Approach 2:
The flange incorporates curved bending surfaces with specific angles instead of sharp corners. The first bending surface has a greater angle than the second bending surface, creating a gradual transition that facilitates assembly while ensuring firm attachment and vibration prevention
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 solution effectively reduces the vibration of components and associated noise by absorbing lamp vibrations and securing the shield covers firmly, improving the operational stability of the backlight unit and liquid crystal display.
Implementation Method 1
a bottom cover that receives the lamps and the first and second balance PCBs and has a plurality of vibration absorbing holes formed in an area where the first and second balance PCBs are formed
Implementation Method 2
integrates shield covers with flanges that have a greater inner angle before fastening to reduce vibration transfer, enhancing adhesion and preventing shield cover vibration
Data Source
AI summary
A backlight unit and a liquid crystal display using the same are provided. The backlight unit includes a plurality of lamps, a first balance printed circuit board (PCB) that commonly supplies a high voltage AC signal to electrodes at one side of each of the lamps, a second balance PCB that commonly supplies the high voltage AC signal to electrodes at the other side of each of the lamps, and a bottom cover that receives the lamps and the first and second balance PCBs. A plurality of vibration absorbing holes are formed in an area where the first and second balance PCBs are formed.