LED Driving Circuit With Dual-Mode Dimming for Flickerless Low Brightness

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing LED lighting systems often suffer from flicker issues, especially at lower brightness levels, which can be visually bothersome and cause physiological effects in users.

Innovation Solution

A LED driving circuit controlled by a microcontroller that utilizes feedback parameters from both logical operations within the circuit and operational conditions to maintain flickerless operation down to 0.5% of maximum brightness. This involves controlling a voltage converter and a power factor correction circuit in transition or discontinuous modes based on user-desired brightness levels and threshold brightness.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If LED dimming control is implemented, then brightness can be adjusted to lower levels, but perceptible and imperceptible flicker occurs in the light output

Engineering Contradiction:

Improvebrightness levelVSAvoidflicker

Core Design Contradiction:

Illumination intensityVSObject-affected harmful factors

Solution Approach 1:

The patent implements dynamic switching between transition mode and discontinuous mode operation based on the desired brightness level. At higher brightness levels, the circuit operates in transition mode, while at lower brightness levels (below threshold), it switches to discontinuous mode. This dynamic adaptation eliminates flicker across the entire dimming range by optimizing the operating mode for each brightness level.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the operational parameters of the power factor correction circuit by switching between two distinct operating modes (transition mode and discontinuous mode). This parameter change is triggered by comparing the desired brightness level against a threshold, allowing the circuit to maintain flickerless operation across different brightness conditions by adjusting its fundamental operating characteristics.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If conventional dimming techniques are used, then brightness control is achieved, but the lowest achievable brightness level is not sufficiently low

Engineering Contradiction:

Improveminimum brightness levelVSAvoidflickerless operation

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent enables the circuit to dynamically adapt its operating mode based on the desired brightness level. By switching to discontinuous mode when the desired brightness falls below a threshold level, the circuit achieves reliable flickerless operation at extremely low brightness levels (down to 0.5% of maximum), which conventional techniques cannot achieve.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If the power factor correction circuit operates in transition mode, then efficiency is maintained at higher brightness levels, but flicker occurs at lower brightness levels

Engineering Contradiction:

Improveoperational efficiencyVSAvoidflicker at low brightness

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent implements a dynamic operating mode selection mechanism that transitions the power factor correction circuit between transition mode and discontinuous mode based on the desired brightness level. This dynamic switching ensures that the circuit operates in the most appropriate mode for each brightness condition, maintaining efficiency at high brightness levels while eliminating flicker at low brightness levels.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the fundamental operating parameters of the power factor correction circuit by switching between two distinct modes. This parameter change allows the circuit to maintain optimal efficiency characteristics at higher brightness levels while achieving flickerless operation at lower brightness levels, resolving the trade-off between efficiency and flicker elimination.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12212228B2LED control and driving circuit capable of both analog and digital dimming

Publication Date: 2025.01.28 STMICROELECTRONICS INT NV

AI summary

A method includes receiving a plurality of digital feedback signals from a voltage converter, controlling the voltage converter based upon a user desired brightness level and the plurality of digital feedback signals, the voltage converter receiving input from a DC voltage bus and providing output to drive a lighting load, and receiving a plurality of feedback signals from a power factor correction circuit that receives a rectified mains voltage and provides output to the DC voltage bus, and based thereupon operating the power factor correction circuit in transition mode or discontinuous mode based upon the user desired brightness level and a threshold brightness. The plurality of feedback signals include an input sense signal that is a function of the rectified mains voltage as drawn by the power factor correction circuit and an output sense signal that is a function of the output provided to the DC voltage bus.