LED Drive Circuit Dimming Control for Fast Response
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Solution Overview
Problem
Conventional LED drive circuits for liquid crystal display devices with white light-emitting diodes are limited in their ability to control dimming signals with pulse widths of several tens of microseconds, resulting in inadequate response times.
Innovation Solution
The implementation of a liquid crystal display device with an LED drive circuit that includes a booster circuit, a resistance circuit, a first and second stage current mirror circuit, and a dimming control circuit, allowing for precise control of the dimming signal by bypassing a reference current to control the turning on and off of the light-emitting diode column based on a dimming control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the boosting operation of the booster circuit is ON/OFF controlled with the dimming control signal PWM, then the turning on and off of the white light-emitting diode column is controlled, but the response time is insufficient for dimming control signals with pulse widths of several tens of microseconds
Solution Approach 1:
The patent divides the current control into two separate stages: a first stage current mirror circuit that maintains constant current for stable LED operation, and a second stage current mirror circuit that responds to dimming control signals. This segmentation allows each stage to optimize for its specific function, with the second stage providing fast response for dimming control while the first stage ensures stable baseline current supply.
Solution Approach 2:
The patent introduces a second stage current mirror circuit as an intermediary between the dimming control signal and the LED column. This intermediate circuit stage amplifies and accelerates the response to dimming signals, enabling fast response times for pulse widths of several tens of microseconds while maintaining proper current regulation through the first stage.
2Speed
If a conventional LED drive circuit with a single stage current mirror is used, then the circuit structure is simple, but the response time for dimming control signals is insufficient
Solution Approach 1:
The patent segments the current mirror function into two distinct stages: the first stage current mirror circuit handles constant current maintenance, while the second stage current mirror circuit handles rapid dimming response. This segmentation improves response time by dedicating specific circuit functionality to each stage, with the second stage optimized for fast switching response to dimming signals.
Solution Approach 2:
The patent implements periodic action through the two-stage current mirror architecture where the first stage provides continuous constant current operation, and the second stage provides periodic rapid response to dimming control signals. This allows the circuit to maintain stable operation while responding quickly to periodic or pulsed dimming commands with pulse widths of several tens of microseconds.
Data Source
AI summary
The present invention provides a liquid crystal display device having an LED drive circuit which can control a dimming control signal even with a pulse width of several tens μsec or less. The LED drive circuit includes a booster circuit, a first stage current mirror circuit generating a reference current, a second stage current mirror circuit generating a driving current from the reference current, a light-emitting diode column having a light-emitting diode supplied with the driving current, and a dimming control circuit controlling the turning on and off of the light-emitting diode based on a dimming control signal.