Backlight Dimming Circuit Using Gamma Voltage for Real-Time PWM Control
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Solution Overview
Problem
Current backlight dimming methods for liquid crystal displays are either costly, require complex hardware, or have slow response times, failing to achieve real-time energy savings effectively.
Innovation Solution
A backlight dimming circuit utilizing a precision resistor, operational amplifier, and comparator to convert and amplify voltage differential signals into pulse width modulation dimming signals, allowing real-time adjustment of backlight brightness without increasing costs or complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If ambient light sensor dimming is used to automatically adjust backlight brightness, then energy saving is improved, but response time becomes slow and hardware cost increases
Solution Approach 1:
The patent replaces the mechanical/optical sensing system (ambient light sensor) with an electrical signal-based system. The gamma voltage signal, which already exists in the display system, is directly utilized to control backlight brightness through PWM modulation, eliminating the need for physical light sensors and their associated response delays.
Solution Approach 2:
The patent introduces a voltage conversion circuit and PWM control circuit as intermediaries between the gamma voltage signal and the backlight control. These circuits convert the gamma voltage into PWM duty cycle signals that directly control backlight LED brightness, enabling real-time response without additional sensing hardware.
2Illumination intensity
If local dimming with multiple LED drivers is implemented to control brightness of each region, then display quality is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent makes the single PWM control circuit serve multiple functions: it processes gamma voltage signals, generates PWM dimming signals, and controls overall backlight brightness. This multi-functionality eliminates the need for separate control circuits for each backlight region, maintaining simplicity while achieving effective dimming.
Solution Approach 2:
The patent combines the gamma voltage processing function with the PWM dimming control function into a single integrated circuit system. By merging these functions, the patent avoids the complexity of multiple independent LED driver circuits while still achieving effective backlight brightness control.
3Ease of operation
If manual dimming through operation menu is used to adjust backlight brightness, then user control is improved, but operation complexity increases and real-time adjustment is lost
Solution Approach 1:
The system performs automatic self-adjustment of backlight brightness based on the gamma voltage signal from the display controller. The PWM control circuit automatically converts gamma voltage to appropriate dimming levels without requiring user intervention, making the system self-regulating while maintaining simple operation.
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
The solution enables real-time backlight dimming with reduced power consumption and costs, maintaining a simple circuit structure that aligns brightness with screen conditions, thereby promoting energy conservation.
Implementation Method 1
converting and amplifying the voltage differential signal across the precision resistor R to a DC voltage signal by the operational amplifier Q
Implementation Method 2
compare the DC voltage signal with the sawtooth signal of the boost IC and then outputting a pulse width modulation dimming signal according the comparison results
Implementation Method 3
a precision resistor R, which is connected between the noninverting input terminal and the inverting input terminal of the operational amplifier Q, the voltage differential signal across the precision resistor R
Data Source
AI summary
The present invention provides a backlight dimming circuit, a dimming method of the same and a liquid crystal display thereof. The backlight dimming circuit comprises a power supply voltage terminal VCC, which is used to provide supply voltage; an operational amplifier Q, the noninverting input terminal of which connected with the power supply voltage terminal VCC, and the inverting input terminal of which connected with a load terminal; a precision resistor R, which is connected between the noninverting input terminal and the inverting input terminal of the operational amplifier Q, the voltage differential signal across the precision resistor R being converted and amplified to a DC voltage signal by the operational amplifier Q and outputting; and a comparator C, the noninverting input terminal of which receiving the DC voltage signal output from the operational amplifier Q, and the inverting input terminal of which receiving a sawtooth signal from a boost IC in a boost converter, which is used to compare the DC voltage signal with the sawtooth signal of the boost IC and then outputting a pulse width modulation dimming signal according the comparison results. The structure of the present invention is simple, and the costs are low. The backlight brightness is associated with the screen in real-time, which reduces the backlight power consumption and promotes the energy conservation of the products.