Backlight Drive Circuit Current Adjustment Range Extension
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Solution Overview
Problem
Existing backlight drive circuits for LCDs have limited capacity in adjusting currents through LEDs, resulting in significant errors beyond a specific range, making it difficult to achieve a predetermined current value.
Innovation Solution
A backlight drive circuit incorporating a booster circuit, current sensing resistor, automatic current adjustment circuit, and controller to regulate the current flowing through LEDs by comparing detected voltages with reference voltages and adjusting resistors in series or parallel connection, enabling pulse width modulation for precise current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a constant-current LED driver IC is used with a simple current adjustment circuit, then the device complexity is reduced and ease of manufacture is improved, but the current adjustment range is limited and manufacturing precision deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the voltage across the current sensing resistor is fed back to the control circuit. The control circuit compares this feedback voltage with a reference voltage and automatically adjusts the duty cycle of the PWM signal to maintain the desired current through the LED string, thereby achieving precise current control without complex manual adjustment circuits
Solution Approach 2:
The control circuit automatically regulates the LED current by detecting the voltage across the sensing resistor and adjusting the PWM duty cycle accordingly. This self-regulating mechanism eliminates the need for external complex current adjustment circuits while maintaining high precision current control within the LED's adjustable range
2Adaptability or versatility
If the current adjustment range is extended beyond the LED driver IC's capacity, then the adaptability is improved, but the current precision deteriorates due to large errors
Solution Approach 1:
The patent employs dynamic PWM control where the duty cycle is continuously adjusted based on feedback from the current sensing resistor. This dynamic adjustment mechanism allows the system to adapt to different current requirements while maintaining precision through real-time feedback, rather than relying on static external resistance values
Solution Approach 2:
The feedback voltage from the current sensing resistor is continuously monitored and fed back to the control circuit. This feedback mechanism enables the system to automatically correct current deviations and maintain precise control even when operating beyond the standard LED driver IC's adjustment range, thereby extending adaptability without sacrificing precision
3Adaptability or versatility
If a complex external circuit is added to extend current adjustment range, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The control circuit is designed to perform multiple functions: it generates PWM signals, senses current through the sensing resistor, compares feedback voltage with reference voltage, and automatically adjusts the duty cycle. This multi-functional integration extends the current adjustment range without requiring separate complex external adjustment circuits, thereby maintaining device simplicity while improving adaptability
Solution Approach 2:
The control circuit autonomously manages the entire current regulation process by detecting the voltage across the sensing resistor and automatically adjusting the PWM duty cycle. This self-service capability eliminates the need for complex external adjustment circuits, extending the adjustable current range while keeping the overall device complexity low
Data Source
AI summary
Disclosed is a liquid crystal display device, a backlight module, and a backlight drive circuit. The backlight drive circuit comprises a booster circuit, a light-emitting unit, a circuit for automatic adjustment of current, and a controller. The current flowing through an LED will be altered by the circuit for automatic adjustment of current when extending an adjustable range of the controller, so as to reach the adjustable range of the controller.