High-Voltage LED Backlight Circuit Topology for Heat Reduction

Solution Overview

Problem

Current backlighting configurations for displays, which use strings of light emitting diodes, are inefficient due to the use of high-voltage boost circuits, low-frequency inductors, and linear regulators that generate heat, are expensive, and require large components to withstand high-voltage conditions, leading to limited regulation loop bandwidth and increased costs.

Innovation Solution

A backlighting system utilizing a high-voltage source at one polarity and a low-voltage regulator at the opposite polarity, eliminating the need for high-voltage transistors and diodes, and employing a low-voltage regulator to control LED string illumination, allowing for smaller, less expensive components and higher frequency operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If high-voltage boost circuits are used to power LED strings, then sufficient voltage is achieved, but heat generation increases and component size increases

Engineering Contradiction:

Improveheat generationVSAvoidvoltage output

Core Design Contradiction:

TemperatureVSPower

Solution Approach 1:

The circuit is divided into two separate power supply paths: a high-voltage source for the top of LED strings and a low-voltage regulator for the bottom of LED strings. This segmentation allows each part to operate at its optimal voltage level, reducing the need for high-voltage components throughout the entire circuit and thereby reducing heat generation and component size.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of using a traditional single-ended high-voltage power supply architecture, the patent inverts the approach by using a dual-ended architecture where the low-voltage regulator is placed at the bottom of the LED strings. This inversion allows the majority of the circuit to operate at low voltage, with only the necessary high-voltage path existing at the top of the LED strings.

Inventive Principle:

Principle #13The other way round (Inversion)

2Reliability

If high-voltage components are used to withstand high-voltage conditions, then reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvewithstand high-voltage conditionsVSAvoidcomponent specifications

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The circuit is divided into two separate power supply paths: a high-voltage source for the top of LED strings and a low-voltage regulator for the bottom of LED strings. This segmentation allows each part to operate at its optimal voltage level, reducing the need for high-voltage components throughout the entire circuit and thereby reducing heat generation and component size.

Inventive Principle:

Principle #1Segmentation

3Speed

If low-frequency inductors are used in boost circuits, then voltage boosting is achieved, but switching losses increase and frequency operation is limited

Engineering Contradiction:

Improveoperating frequencyVSAvoidswitching losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

Instead of using a traditional single-ended high-voltage power supply architecture, the patent inverts the approach by using a dual-ended architecture where the low-voltage regulator is placed at the bottom of the LED strings. This inversion allows the majority of the circuit to operate at low voltage, with only the necessary high-voltage path existing at the top of the LED strings.

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration reduces heat generation, component size, and cost, while enabling higher frequency operation and more efficient illumination control, as the low-voltage regulator operates at higher frequencies with smaller components, reducing switching losses and electromagnetic interference.

Implementation Method 1

Some current backlighting configurations use strings of light emitting diodes

Methodology Applied

Scientific EffectLight emitting diode effect: Light Emitting Diode

Data Source

PatentUS9860946B2Circuit topology for driving high-voltage LED series connected strings

Publication Date: 2018.01.02 MAXIM INTEGRATED PROD INC

AI summary

A system for backlighting a display uses an open or closed loop and small components that are well suited to high-frequency applications. The system includes multiple LED strings, a high-voltage source, and a low-voltage regulator that has a polarity opposite to that of the high-voltage source. The high-voltage source and the low-voltage regulator provide voltage differences across the LED strings to illuminate them. In one embodiment, the high-voltage source is about 200 VDC, and the low-voltage regulator produces voltages between −2 VDC and −30 VDC. Many types of displays, such as those used on LCD televisions and LCD personal computers, can be backlit in accordance with the embodiments.