LED Driving Circuit Current Balance Controllers

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Solution Overview

Problem

Conventional LED driving circuits face inefficiencies in power management due to heat generation and increased system cost, particularly when dealing with large LED currents and multiple LED strings, as they require multiple dedicated power converters and linear transistor control methods.

Innovation Solution

A driving circuit that utilizes a power converter and switching balance controllers to regulate currents through LED strings, adjusting duty cycles and voltage drops across buck switching regulators to maintain uniform LED currents and reduce the need for multiple dedicated converters, thereby improving power efficiency and reducing heat generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If linear LED current balance controllers are used to control transistors in linear mode, then LED current regulation is achieved, but heat generation increases and power efficiency decreases

Engineering Contradiction:

ImproveLED current regulationVSAvoidpower efficiency

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces linear transistor control with switching regulator control. Instead of using transistors in linear mode that dissipate power as heat, the invention uses switching regulators that operate in saturation/cutoff modes, substituting a more efficient switching mechanism for the inefficient linear control mechanism.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters of the control transistors from linear mode to switching mode. By changing the duty cycle of PWM signals, the switching regulators can precisely control LED current while maintaining high efficiency, avoiding the power dissipation inherent in linear mode operation.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If dedicated DC/DC converters are used for each LED string, then precise current control is achieved, but system cost increases

Engineering Contradiction:

Improvecurrent control precisionVSAvoidsystem cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges multiple dedicated DC/DC converters into a single shared power converter. Multiple switching regulators share the same power conversion stage, reducing component count and system cost while maintaining precise current control for each LED string through individual PWM control of each switching regulator.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent creates a universal power converter that serves multiple LED strings simultaneously. The single DC/DC converter provides power to multiple switching regulators, each controlling an LED string, making the power conversion system multi-functional and reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Illumination intensity

If multiple dedicated power converters are used for multiple LED strings, then uniform brightness is achieved, but system complexity and cost increase

Engineering Contradiction:

Improveuniform brightnessVSAvoidnumber of power converters

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent combines multiple power conversion functions into a single DC/DC converter that serves all LED strings. By sharing the power conversion stage and using individual switching regulators for each LED string, the system achieves uniform brightness control while reducing the number of power converters from multiple to one.

Inventive Principle:

Principle #5Merging (Combining)

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

The solution achieves improved power efficiency and uniform brightness across LED strings without the need for multiple dedicated power converters, reducing heat issues and system costs while maintaining desired light outputs.

Implementation Method 1

a power converter, which converts an input voltage to a desired output voltage for powering the LED strings

Methodology Applied

Scientific EffectElectrical Energy Conversion:

Implementation Method 2

Each buck switching regulator includes a corresponding switch coupled between the regulated voltage and a corresponding inductor

Methodology Applied

Scientific EffectElectrical Energy Conversion:

Data Source

PatentUS8253352B2Circuits and methods for powering light sources

Publication Date: 2012.08.28 O2 MICRO INT LTD

AI summary

A driving circuit for powering a plurality of light-emitting diode (LED) light sources includes a power converter and a plurality of current balance controllers. The power converter receives an input voltage and provides a regulated voltage to the LED light sources. The current balance controllers coupled to the power converter control a plurality of currents through the LED light sources respectively. The current balance controllers receive a first reference signal indicative of a target average level and a second reference signal indicative of a maximum transient level, and regulate an average current of each of the currents to the target average level and a transient level of each of the currents within the maximum transient level.