Backlight Driver Board Standby Dimming Control
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Solution Overview
Problem
Current backlight driver circuits in LCD TVs suffer from dim lighting when in standby mode due to uncontrolled current flow through the backlight LED strip, leading to LED decay and suboptimal display effects.
Innovation Solution
A backlight constant current driver board incorporating a boost circuit, switchover switch circuit, and constant current control circuit that manages the current flow to the backlight LED strip via a light strip socket, using PWM and ENA signals to control the switchover switch and maintain constant current, preventing current flow to ground during standby.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a small package chip (SOP-8 or TSOP-6) is used for backlight driver circuit, then the price is reduced, but the operating frequency cannot be adjusted and no soft start function is available
Solution Approach 1:
The patent divides the backlight driver circuit into separate functional modules: a constant current drive control chip (U1) in a small package (SOP-8) for cost-effective current control, and a separate voltage control chip (U2) in a larger package (SOP-32) for voltage regulation and soft start functionality. This segmentation allows each chip to be optimized for its specific function while maintaining overall system versatility and adjusting operating parameters.
2Productivity
If the input voltage Vin is close to the output voltage Vout, then the duty ratio in the boost circuit is smaller, but when the system is in standby or the constant current drive control chip is not working, a loop is formed between the output voltage and ground causing small currents to pass through the backlight LED light strip
Solution Approach 1:
The patent introduces a new voltage control chip (U2) as an intermediary component between the boost circuit and the constant current drive control chip. This voltage control chip actively monitors and adjusts the input voltage to the boost circuit, ensuring that when the system is in standby mode, the voltage is reduced to prevent current flow through the LED strip, thereby eliminating the dim light problem while maintaining efficient operation during normal use.
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
Prevents dim lighting by ensuring the backlight LED strip turns off completely during standby, extending its lifespan and improving display quality by synchronizing the switchover switch with the PWM signal and boost circuit.
Implementation Method 1
a boost circuit, configured to increase an input voltage to a first output voltage
Implementation Method 2
suppose there are 8 LED lights, and a VF value to each LED light is 3.3V
Data Source
AI summary
Backlight constant current driver board comprises boost circuit, constant current control circuit, switchover switch circuit, and light strip socket, connects to backlight light strip via light strip socket. Boost circuit boosts input voltage before outputting output voltage and transmits via light strip socket as power supply to backlight light strip. Switchover switch circuit controls, according to PWM signal and power supply voltage, connection or disconnection of current loop between backlight light strip and ground. Constant current control circuit monitors and keeps constant current magnitude of backlight light strip in switchover switch circuit. By switchover switch circuit, during system standby, formation of current loop between backlight light strip and ground is prevented so backlight light strip does not emit light, thus solving problems of screen emitting dim lights when existing LCD television standby or constant current drive control chip not working.