LED Driver Circuit Eliminates Sense Resistor Using Hall Effect Sensor

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Solution Overview

Problem

Existing electric light systems, particularly those using constant voltage and constant current drivers for LEDs, face inefficiencies due to parasitic energy loss in sense resistors, and are sensitive to part-to-part variations and environmental changes, leading to inconsistent LED current and increased energy consumption.

Innovation Solution

The development of novel circuits incorporating a switch, comparator, and processor to modulate the LED driving circuit, utilizing a two-switch boost converter, transformer, and sensors to measure voltage and current, allowing for dynamic adjustment of current to the LED and reducing energy waste through pulse-width modulation and feedback mechanisms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a constant current driver is used with a sense resistor to control LED current, then the LED current is stable and consistent, but the energy loss in the sense resistor increases significantly

Engineering Contradiction:

ImproveLED current consistencyVSAvoidsense resistor power dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces the traditional sense resistor-based current sensing method with a magnetic field sensing approach using a Hall effect sensor. The sense resistor is eliminated entirely, and current measurement is achieved through detecting the magnetic field generated by the current-carrying trace, substituting a mechanical/electrical sensing method with a magnetic field-based method that consumes negligible power.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a magnetic field as an intermediary to transfer information about the LED current. Instead of measuring current directly through a resistive element, the current generates a magnetic field that is detected by the Hall effect sensor, allowing indirect measurement without the energy loss associated with direct resistive sensing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of energy

If a constant voltage driver is used to reduce energy loss in the sense resistor, then power efficiency improves, but LED current becomes highly sensitive to voltage variations

Engineering Contradiction:

Improvesense resistor power dissipationVSAvoidLED current stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent implements a feedback control system where the Hall effect sensor continuously monitors the LED current by detecting the magnetic field, and the processor adjusts the PWM duty cycle to maintain the desired current level. This closed-loop feedback ensures stable LED current while avoiding the energy losses of traditional sense resistors.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent transitions from a static voltage or current control approach to a dynamic PWM-based control system. The processor dynamically adjusts the PWM duty cycle based on real-time feedback from the Hall effect sensor, allowing the system to adapt to variations in LED forward voltage and maintain consistent current without the drawbacks of constant voltage or constant current approaches.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the resistance of the sense resistor is increased to reduce sensitivity to voltage variations, then LED current becomes more stable, but additional power is wasted

Engineering Contradiction:

ImproveLED current stabilityVSAvoidsense resistor power dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent extracts the current sensing function from the resistive element entirely. By removing the sense resistor from the circuit and using a Hall effect sensor to detect the magnetic field generated by the current-carrying trace, the system eliminates the need for any resistive sensing element, thereby eliminating the associated power losses while maintaining current stability through feedback control.

Inventive Principle:

Principle #2Taking out (Extraction)

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 significantly reduces energy consumption and enhances the efficiency of LED driving circuits, extending battery life and improving the stability of LED current, thereby increasing the lifespan of electric candles and reducing power loss to less than 1% in some configurations.

Implementation Method 1

the Hall effect sensor to measure a magnetic field from the trace

Methodology Applied

Scientific EffectHall effect: Hall Effect

Implementation Method 2

A light emitting diode (LED)

Methodology Applied

Scientific EffectLight emitting diode effect: Light Emitting Diode

Data Source

PatentUS10178731B2Systems and methods for reducing energy requirements of an electric light

Publication Date: 2019.01.08 L&L CANDLE CO LLC

AI summary

Systems and methods of driving a light source, such as a light emitting diode (LED), while minimizing power consumption. Different techniques can be implemented in circuits that eliminate the traditional need for a sense resistor. By eliminating the sense resistor, a LED driving circuit's efficiency can be improved by up to and exceeding 30%. A pulse-width modulator can be used to control current flow in a buck, boost, or buck-boost circuits. Many of the configurations discussed eliminate the need for a sense resistor, which needlessly dissipates power. Others use a sense resistor minimally compared to traditional LED driving circuits.