LED Backlight Driving Circuit With Parallel Voltage Clamp

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Solution Overview

Problem

Existing LED driving circuits require large switching elements and expensive processes due to the high voltage applied to control LED strings, which are formed by connecting multiple LEDs in series.

Innovation Solution

Incorporating a withstanding-voltage reducing circuit in parallel with the switching element, which allows a leakage current to flow when the voltage exceeds a predetermined level, reducing the voltage applied to the switching element and using a field effect transistor to adjust current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If multiple LEDs are connected in series to form an LED string for backlight, then the brightness control capability is improved, but the voltage applied to the switching element increases

Engineering Contradiction:

Improvebacklight brightness controlVSAvoidvoltage applied to switching element

Core Design Contradiction:

Illumination intensityVSStress or pressure

Solution Approach 1:

The patent divides the LED string control into multiple segments by introducing a withstanding-voltage reducing circuit that operates in conjunction with the switching element. This circuit segments the voltage stress, allowing the switching element to handle only a portion of the total voltage while the other portion is managed by the voltage-reducing circuitry, thereby enabling series-connected LEDs for brightness control without exposing the switching element to the full high voltage

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The withstanding-voltage reducing circuit acts as an intermediary between the high-voltage LED string and the switching element. This intermediary circuit includes components that limit or reduce the voltage reaching the switching element, protecting it from excessive voltage stress while still enabling effective control of the LED string for backlight brightness adjustment

Inventive Principle:

Principle #24Intermediary (Mediator)

2Stress or pressure

If a switching element with high withstand voltage is used to control the LED string, then the voltage handling capability is improved, but the size of the switching element increases

Engineering Contradiction:

Improvevoltage withstand capabilityVSAvoidsize of switching element

Core Design Contradiction:

Stress or pressureVSArea of moving object

Solution Approach 1:

The voltage handling function is segmented between two components: the switching element and the withstanding-voltage reducing circuit. The switching element only needs to withstand a reduced portion of the total voltage, allowing it to be smaller in size, while the voltage-reducing circuit handles the remaining voltage requirements, achieving the needed voltage capability without increasing switching element size

Inventive Principle:

Principle #1Segmentation

3Stress or pressure

If a switching element with high withstand voltage is used to control the LED string, then the voltage handling capability is improved, but the manufacturing cost increases

Engineering Contradiction:

Improvevoltage withstand capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

Stress or pressureVSEase of manufacture

Solution Approach 1:

The patent segments the voltage handling requirements between cost-effective components. Instead of using an expensive high-voltage switching element, the solution uses a lower-cost switching element combined with a withstanding-voltage reducing circuit that can be implemented using standard, inexpensive electronic components, thereby reducing overall manufacturing cost while maintaining the required voltage handling capability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs inexpensive components in the withstanding-voltage reducing circuit to replace the need for expensive high-voltage switching elements. By using multiple lower-cost components that collectively achieve the voltage reduction function, the overall manufacturing cost is reduced while maintaining adequate voltage handling capability for the LED string control

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 approach reduces the size of the LED driving circuit and lowers manufacturing costs by enabling the use of less expensive switching elements with lower withstand voltages.

Implementation Method 1

a withstanding-voltage reducing circuit connected in parallel with the switching element and configured to allow a leakage current to flow when a voltage at a point connected in parallel with the switching element exceeds a predetermined voltage

Methodology Applied

Scientific EffectZener breakdown: Avalanche Breakdown

Data Source

PatentUS12550240B2Light emitting diode driving circuit and backlight apparatus of display

Publication Date: 2026.02.10 LX SEMICON CO LTD

AI summary

An LED driving circuit can include a switching element connected to one end of an LED string and configured to adjust current flowing through the LED string, and a withstanding-voltage reducing circuit connected in parallel with the switching element and configured to allow a leakage current to flow when a voltage at a point connected in parallel with the switching element exceeds a predetermined voltage.