Backlight Unit Protection Circuit for Over-Voltage Prevention

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Solution Overview

Problem

Backlight units face challenges in detecting and managing over-voltage conditions, particularly when a lamp or its driving circuitry fails, leading to abnormal operation and potential damage.

Innovation Solution

Incorporating a protection circuit on a printed circuit board (PCB) that detects an open-lamp-protection voltage and compares it with a reference voltage, controlling the inverter to prevent over-voltage by turning it off when the detected voltage exceeds the reference, thereby maintaining balanced electrical currents and preventing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If the operation driver boosts voltage to maintain uniform brightness when a lamp fails, then brightness uniformity is improved, but over-voltage damage to remaining lamps worsens

Engineering Contradiction:

Improvebrightness uniformityVSAvoidover-voltage damage

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The protection circuit performs preliminary detection of lamp status before over-voltage can occur. When a lamp failure is detected, the circuit preemptively prevents voltage boosting, avoiding the harmful effect before it happens while maintaining brightness uniformity through alternative control mechanisms

Inventive Principle:

Principle #10Preliminary action

2Device complexity

If voltage detection is simplified to reduce circuit complexity, then device complexity is reduced, but detection precision of open-lamp-protection voltage worsens

Engineering Contradiction:

Improvecircuit complexityVSAvoidvoltage detection precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

A voltage divider circuit acts as an intermediary that transforms the high open-lamp-protection voltage into a lower, safer detection voltage. This intermediary mechanism enables precise voltage detection without requiring complex high-voltage measurement circuits, thus maintaining detection precision while simplifying the overall circuit design

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If the inverter continues operating to maintain brightness when a lamp fails, then productivity is improved, but reliability of the system worsens

Engineering Contradiction:

Improvebrightness maintenanceVSAvoidsystem reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The protection circuit implements continuous feedback monitoring of lamp status and voltage conditions. When abnormal conditions are detected, the feedback mechanism automatically adjusts or stops inverter operation, maintaining system reliability while minimizing impact on brightness maintenance through controlled operation adjustments

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8736196B2Backlight unit, method of operating the same and liquid crystal display device having the same

Publication Date: 2014.05.27 KOERA TAIYO YUDEN

AI summary

A backlight unit includes; a light source, an inverter which provides the light source with an input voltage, and a printed circuit board (“PCB”) connected to the light source, wherein the PCB includes a protection circuit which detects an open-lamp-protection voltage which varies according to a change of the input voltage and changes a reference voltage according to the change of the input voltage, wherein the protection circuit turns off the inverter when the detected open-lamp-protection voltage is higher than the changed reference voltage.