Light Source Drive Circuit Using Low Voltage Transistors
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Solution Overview
Problem
The existing light source drive circuits for LCD devices require high withstanding voltage transistors, leading to increased manufacturing costs and reduced price competitiveness, while also facing challenges in enhancing contrast ratio.
Innovation Solution
The proposed light source drive circuit incorporates a low withstanding voltage transistor configuration, utilizing a combination of voltage and current controllers with PWM signals, operational amplifiers, and resistors to control the voltage and current applied to the LED portion, allowing for efficient LED drive with reduced voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high withstanding voltage transistor is used in the light source drive circuit, then the circuit can handle high voltage requirements, but the manufacturing cost increases and price competitiveness deteriorates
Solution Approach 1:
The patent divides the voltage control function into two separate components: a voltage controller that manages high voltage supply to the LED portion, and a current controller that regulates current using a low withstanding voltage transistor. This segmentation allows the expensive high voltage transistor to be replaced with a cheaper low voltage transistor in the current control path, while the voltage controller handles the high voltage requirements separately.
Solution Approach 2:
The voltage controller acts as an intermediary between the high voltage power supply and the LED portion, isolating the low withstanding voltage transistor from direct exposure to high voltage. The voltage controller converts high voltage to a lower voltage level that the standard transistor can handle, thereby mediating the voltage levels to enable cost-effective component selection.
2Device complexity
If a simple current control method is used, then the circuit complexity is reduced, but the contrast ratio enhancement capability is limited
Solution Approach 1:
The patent merges voltage control and current control functions into a single integrated controller unit that manages both aspects of LED operation. This combination allows the circuit to achieve enhanced contrast ratio through coordinated voltage and current modulation while maintaining relatively simple overall circuit architecture. The PWM signal simultaneously controls both voltage and current parameters.
Solution Approach 2:
The patent employs PWM (Pulse Width Modulation) signals to control the transistor switching, enabling periodic on-off action that modulates both voltage and current to the LED portion. This periodic control method enhances contrast ratio by completely turning off the LED during off-periods (achieving true black levels) while providing full brightness during on-periods, all without requiring complex analog control circuits.
Data Source
AI summary
A light source drive circuit is disclosed which uses a low withstanding voltage transistor is discussed. The light source drive circuit can enhance price competitiveness. Also, the light source drive circuit can allow a current flowing through an LED portion to be eliminated when a PWM signal is not applied. Therefore, the light source drive circuit can enhance a contrast ratio.