LED Dimming Circuit Using Setpoint Voltage Modification

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Solution Overview

Problem

Conventional LED driver circuits are unable to dim LEDs below 20% of their full intensity, requiring expensive and complex pulse width modulation (PWM) solutions, which are not suitable for residential or commercial lighting applications.

Innovation Solution

A dimmable driver circuit that uses a triac to clip the AC input waveform, a full-wave rectifier, power factor correction circuitry, and a compensation network to simulate an overvoltage event, allowing the LED to be dimmed beyond 20% of its full intensity by modifying the setpoint voltage and reducing energy processing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If conventional LED driver circuits are used with a conventional dimmer, then the LED can be dimmed, but the LED cannot be dimmed below 20% of its full intensity

Engineering Contradiction:

ImproveLED dimming rangeVSAvoiddimming capability

Core Design Contradiction:

Illumination intensityVSAdaptability or versatility

Solution Approach 1:

The patent modifies the setpoint voltage parameter in the power factor correction circuitry to enable dimming below 20% intensity. By dynamically adjusting this voltage parameter in response to dimmer position, the circuit achieves extended dimming range while maintaining proper LED operation and avoiding the limitations of conventional circuits.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If pulse width modulation (PWM) is used to dim LED below 20% intensity, then the LED can be dimmed to any level, but the circuit cost and complexity increase significantly

Engineering Contradiction:

ImproveLED dimming rangeVSAvoidcircuit complexity

Core Design Contradiction:

Illumination intensityVSDevice complexity

Solution Approach 1:

The patent creates a simplified control approach that copies the essential dimming function without requiring complex PWM circuitry. By leveraging the existing power factor correction infrastructure and adding simple voltage modification logic, the system achieves PWM-like dimming performance with much lower complexity and cost.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

Instead of using PWM's time-domain modulation, the patent changes the voltage domain parameter (setpoint voltage) to achieve dimming. This parameter substitution allows the same dimming effect to be achieved through a simpler, more cost-effective mechanism that avoids PWM's complex timing and switching requirements.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If pulse width modulation (PWM) is used to dim LED below 20% intensity, then the LED can be dimmed to any level, but the engineering time required to design and implement the circuit increases

Engineering Contradiction:

ImproveLED dimming rangeVSAvoidengineering time

Core Design Contradiction:

Illumination intensityVSLoss of time

Solution Approach 1:

The patent makes the power factor correction circuitry serve a dual function: both power factor correction and dimming control. By designing the circuit to perform multiple functions simultaneously, the system eliminates the need for separate PWM control circuitry, thereby reducing both component count and engineering design time while achieving full dimming capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

4Device complexity

If conventional LED driver circuits are used with a conventional dimmer, then the circuit is simple and inexpensive, but the LED cannot be dimmed below 20% of its full intensity

Engineering Contradiction:

Improvecircuit simplicityVSAvoidLED dimming range

Core Design Contradiction:

Device complexityVSIllumination intensity

Solution Approach 1:

The patent merges the dimming control function with the existing power factor correction circuitry. By combining these two functions into a single integrated control mechanism, the system maintains circuit simplicity and avoids adding separate complex dimming circuits, while still achieving the extended dimming range below 20% intensity.

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

Enables LED dimming to any intensity between 1% and 20% of full intensity, reducing engineering time and costs compared to PWM solutions, while maintaining flicker-free operation.

Implementation Method 1

a triac to clip the AC input waveform

Methodology Applied

Scientific EffectAC waveform clipping:

Implementation Method 2

a full-wave rectifier

Methodology Applied

Scientific EffectRectification:

Implementation Method 3

power factor correction circuitry

Methodology Applied

Scientific EffectPower factor correction:

Data Source

PatentUS8779691B1Dimmable driver circuits for light emitting diodes

Publication Date: 2014.07.15 SIGNIFY HOLDING BV

AI summary

A circuit for dimming a light emitting diode is provided. The circuit includes an alternating current input voltage that is delivered to a light emitting diode. The circuit also includes a correction circuit configured to monitor the input voltage, which also delivers a current to the light emitting diode, wherein the current delivered to the light emitting diode is commensurate with the input voltage. The circuit also includes a simulation circuit electrically coupled to the correction circuit and configured to deliver an additional voltage to the correction circuit to modify a setpoint voltage when the input voltage falls below a predetermined value.