LED Reference Voltage Generator for High Contrast Ratio
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Solution Overview
Problem
The existing LED light emitting devices face challenges in maintaining a high contrast ratio and stable operation due to varying voltage drops across LED channels, leading to inefficient current flow and increased power loss, especially when using phase shift pulse width modulation methods.
Innovation Solution
A reference voltage generating device that detects the minimum voltage drop across multiple LED channels and adjusts the reference voltage to match a predetermined minimum value, with a faster increase when below the threshold and slower decrease when above, to optimize the output voltage of the DC/DC converter and ensure consistent current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the output voltage of the DC/DC converter is increased to compensate for LED voltage drop variations, then the current flow to LED channels is improved, but power loss in the constant current source increases
Solution Approach 1:
The patent implements a feedback mechanism where the headroom controller continuously monitors the output voltage of the DC/DC converter and adjusts the reference voltage accordingly. The minimum voltage detector identifies the lowest voltage among multiple LED channels, and this information feeds back to the headroom controller, which then adjusts the reference voltage to maintain optimal current flow while minimizing power loss in the constant current source.
Solution Approach 2:
The patent dynamically changes the reference voltage parameter based on the detected minimum channel voltage. By adjusting the reference voltage level according to actual LED voltage drop variations, the system optimizes the output voltage of the DC/DC converter, ensuring sufficient current flow to all LED channels while minimizing excess voltage and corresponding power loss in the constant current source.
2Reliability
If the reference voltage is increased to ensure sufficient output voltage for all LED channels, then current flow is maintained, but the contrast ratio deteriorates at low brightness levels
Solution Approach 1:
The patent employs a dynamic reference voltage adjustment mechanism rather than a fixed reference voltage. The headroom controller continuously adapts the reference voltage level based on real-time monitoring of LED channel voltages and DC/DC converter output. This dynamic adaptation allows the system to maintain stable operation under varying conditions while preserving contrast ratio performance, particularly at low brightness levels where a fixed high reference voltage would cause deterioration.
3Power
If the output voltage of the DC/DC converter is optimized for maximum brightness, then current flow is sufficient, but voltage drops cause uneven performance across different LED channels
Solution Approach 1:
The patent applies local quality adjustment by individually compensating for voltage drops in different LED channels. The minimum voltage detector identifies which channel has the lowest voltage, and the headroom controller adjusts the reference voltage specifically to ensure that channel receives sufficient voltage. This localized compensation approach ensures that each LED channel operates at optimal brightness while maintaining overall system power efficiency and voltage uniformity across all channels.
Data Source
AI summary
A control device and an LED light emitting device using the same are provided and technology of providing a high contrast ratio to the LED light emitting device and allowing the LED light emitting device to perform a stable operation is disclosed. The LED light emitting device includes a DC/DC converter reference voltage generator that generates a DC/DC converter reference voltage so that a minimum level of a channel voltage having a largest LED voltage drop agrees with a predetermined minimum reference voltage by detecting a plurality of channel voltages corresponding to LED voltage drops of each of a plurality of LED channels LED and an output voltage controller that controls an output voltage of the DC/DC converter using a distribution voltage corresponding to an output voltage and the DC/DC converter reference voltage.