Multi-Channel LED Backlight Driving Circuit with Per-Channel Feedback Detection
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Solution Overview
Problem
The use of a single-channel type driving circuit for multi-channel LED backlights in liquid crystal display devices makes it difficult to detect and protect defective channels, leading to potential damage of LEDs due to overcurrent issues.
Innovation Solution
A liquid crystal display device with a backlight driving circuit that includes a light emitting diode controlling portion, a light emitting diode driving portion, and a detecting element on each channel to monitor feedback voltages, convert them into feedback signals, and adjust driving voltages to prevent overcurrent, along with a method to detect defects and perform protection operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-channel type driving circuit is used for multi-channel LED backlight, then production cost is reduced, but the ability to detect and protect defective channels is lost
Solution Approach 1:
The patent divides the feedback detection function into separate detecting elements for each channel. Each channel has its own detecting element connected to the feedback terminal, allowing independent detection of each channel's status while using a single shared driving circuit. This segmentation enables defect detection at channel level without requiring a separate driving circuit for each channel.
Solution Approach 2:
The patent introduces a current set resistor as an intermediary component between the single-channel driving circuit and the multi-channel LED backlight. This resistor, combined with the feedback terminal, creates a feedback mechanism that allows the single-channel circuit to indirectly monitor and detect defects in individual channels through the feedback voltage changes caused by each channel's current consumption.
2Device complexity
If a single-channel type driving circuit is used for multi-channel LED backlight, then device complexity is reduced, but overcurrent protection capability is lost
Solution Approach 1:
The patent implements a feedback mechanism where each channel's current consumption is monitored through a feedback terminal connected to a detecting element. The feedback voltage, which reflects the current status of each channel, is used to detect defects. When a defect is detected, the system can adjust or stop driving the affected channel, preventing overcurrent damage while maintaining a simple single-channel driving circuit structure.
Data Source
AI summary
A backlight driving circuit for a liquid crystal display device including a light emitting diode controlling portion for outputting a brightness control signal, a light emitting diode driving portion that amplifies an input voltage to produce the first driving voltage and that uses the brightness control signal to adjust a second driving voltage, a backlight unit including a plurality of channels, each of the plurality of channels including a light emitting diode array supplied in common with the first and second driving voltages from the light emitting diode driving portion, a feedback voltage terminal on each of the plurality of channels that outputs a feedback voltage to the light emitting diode controlling portion, a detecting element on each of the plurality of channels that detects the feedback voltage, and a current set resistor disposed between the plurality of channels and a ground terminal of the light emitting diode driving portion.