Reference Voltage Generator for LED Brightness Control
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Solution Overview
Problem
Existing LED string brightness control systems face difficulties in precisely controlling brightness below a predetermined ratio due to limitations in reference voltage generation, where the upper limit reference voltage does not reach zero while the lower limit reference does, making it challenging to adjust LED string brightness effectively.
Innovation Solution
A reference voltage generator is designed with an amplifier, transistors, and resistors to generate high and low limit dimming signals based on a dimming signal, allowing for precise control of LED string brightness by varying the reference currents and voltages, even when the dimming signal is below a threshold value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upper limit reference voltage is set to a level higher by a predetermined margin based on the dimming signal, then the reference voltage can provide a safety margin for brightness control, but the upper limit reference does not reach zero voltage even when the dimming signal reaches zero, making it difficult to control LED string brightness below a predetermined ratio
Solution Approach 1:
The patent applies dynamics by making the reference voltage variable rather than fixed. The reference voltage generator dynamically adjusts the reference voltage based on the dimming signal level, allowing the upper limit reference to reach zero when the dimming signal reaches zero. This enables full-range brightness control from 0% to 100% while maintaining reliability through adaptive margin adjustment.
Solution Approach 2:
The patent changes the parameter of reference voltage from a fixed offset to a variable parameter that scales with the dimming signal. By using a reference voltage generator that produces a reference voltage proportional to the dimming signal, the system achieves both reliability (through maintained margins) and full brightness control range (by allowing the reference to reach zero).
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
This solution enables precise control of LED string brightness by generating varying high and low limit dimming signals, ensuring the LED string can be accurately adjusted to desired brightness levels, including low brightness settings, by differentiating the changing rates of reference voltages.
Implementation Method 1
an amplifier including two input terminals connected to a dimming signal and a first node, respectively, and an output terminal
Implementation Method 2
second and third transistors configured to form a current mirror
Implementation Method 3
two resistors connected between one electrode of the second transistor and the one electrode of the first transistor
Data Source
AI summary
A reference voltage generator disclosed herein includes an amplifier including two input terminals connected to a dimming signal and a first node, respectively, and an output terminal, a first transistor including a gate connected to the output terminal of the amplifier and one electrode connected to the first node, second and third transistors configured to form a current mirror, and two resistors connected between one electrode of the second transistor and one electrode of the first transistor.