LED Backlight Driver Headroom Control for Lower Heat Dissipation
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Solution Overview
Problem
Existing LED backlight modules face imprecise power and heat reduction due to varying transistor characteristics and high manufacturing costs from increased pin counts when estimating headroom voltage using gate or drain voltages.
Innovation Solution
A backlight driver system with a current regulator and headroom detection circuit that controls the driving current and supply voltage based on feedback voltage, reducing heat loss and manufacturing costs by precise regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If gate voltage monitoring is used to estimate headroom voltage, then power consumption is reduced, but measurement precision deteriorates due to transistor characteristic variations
Solution Approach 1:
The patent introduces an intermediary resistor connected in series with the LED string. This resistor converts the headroom voltage into a measurable voltage drop that can be directly monitored without relying on transistor characteristic estimates. The intermediary element provides a reliable reference that is independent of transistor variations, resolving the contradiction between power reduction and measurement precision.
Solution Approach 2:
The patent replaces the electrical estimation method (monitoring gate voltage to infer headroom voltage) with a direct electrical measurement method (measuring voltage drop across the intermediary resistor). This substitution eliminates the need for complex estimation algorithms and improves measurement accuracy while maintaining power efficiency.
2Manufacturing precision
If drain voltage regulation is used to control supply voltage, then headroom voltage control is improved, but device complexity increases due to increased pin count
Solution Approach 1:
The patent combines the headroom detection function with the existing voltage regulation circuit by using the same intermediary resistor for both current sensing and headroom voltage measurement. This merging of functions eliminates the need for additional dedicated pins and circuitry, achieving precise headroom control without increasing device complexity.
Solution Approach 2:
The intermediary resistor serves multiple functions: it acts as a current sensing element, a headroom voltage reference, and a protection element. This multi-functionality reduces the overall component count and pin requirements while maintaining precise voltage control capability.
Data Source
AI summary
According to an embodiment of the invention, a backlight driver of driving a light-emitting diode (LED) string via a driving transistor in a load path is provided. The LED string, the driving transistor, and an electrical load are coupled to form the load path. The backlight driver includes a current regulator and a headroom detection circuit. The current regulator is coupled to the driving transistor and the first terminal of the electrical load to control a driving current flowing through the load path according to at least a feedback voltage from a first terminal of the electrical load. The headroom detection circuit is coupled to the first terminal of the electrical load and a voltage regulator to control the voltage regulator to regulate a supply voltage to a first terminal of the LED string according to at least the feedback voltage.