LED Driver Circuit for Optical Communication

Solution Overview

Problem

Existing LED driver circuits using pulse-width modulation (PWM) consume unnecessary power and cause interference with other electronics due to rapid switching and frequency issues, which limits effective information transmission via light emitted by LEDs.

Innovation Solution

Implementing a system that drives LEDs with variable currents or voltages derived from continuous-time data signals, where light intensity is proportional to the current, and using a power-balancer circuit to adjust output power and a dimmer controller to manage phase chopping, thereby reducing interference by operating at baseband frequencies or high frequencies above the optical scanner's cutoff.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of information

If PWM-based LED driver circuits use rapid switching to encode information, then information transmission capability is improved, but power consumption increases and interference with other electronics occurs

Engineering Contradiction:

Improveinformation transmission capabilityVSAvoidpower consumption

Core Design Contradiction:

Loss of informationVSUse of energy by moving object

Solution Approach 1:

The patent applies periodic action by using pulse-width modulation (PWM) to dim the LED periodically, encoding information in the duty cycle of the pulses. This allows information transmission through light intensity variations while maintaining efficient power consumption by switching the LED on and off rather than using analog dimming

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent changes the frequency parameter of the PWM signal to encode information. By varying the frequency or duty cycle of the PWM pulses, different information can be transmitted without increasing power consumption, as the LED operates at full brightness during on-pulses

Inventive Principle:

Principle #35Parameter changes

2Productivity

If PWM-based LED driver circuits use high-frequency switching to transmit information, then data transmission speed is improved, but electromagnetic interference with other electronics worsens

Engineering Contradiction:

Improvedata transmission speedVSAvoidelectromagnetic interference

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent changes the frequency parameter of the PWM signal to encode information. By varying the frequency or duty cycle of the PWM pulses, different information can be transmitted without increasing power consumption, as the LED operates at full brightness during on-pulses

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses an optical intermediary (the LED light output) to transmit information electrically encoded data. The information is modulated onto the light output through PWM, allowing wireless optical communication without direct electrical connections, thus reducing electromagnetic interference

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If LED driver circuits use constant-amplitude current pulses to maintain color temperature stability, then light color consistency is improved, but information encoding capability is limited

Engineering Contradiction:

Improvecolor temperature stabilityVSAvoidinformation encoding capability

Core Design Contradiction:

Stability of the object's compositionVSLoss of information

Solution Approach 1:

The patent applies periodic action by using pulse-width modulation (PWM) to dim the LED periodically, encoding information in the duty cycle of the pulses. This allows information transmission through light intensity variations while maintaining efficient power consumption by switching the LED on and off rather than using analog dimming

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent applies preliminary action by pre-establishing a constant current drive mode for the LED, then overlaying PWM dimming signals on top of this stable baseline. This ensures the LED operates at consistent color temperature when fully on, while allowing information encoding through periodic dimming

Inventive Principle:

Principle #10Preliminary action

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 power consumption and interference, enabling efficient information transmission through light intensity variations while avoiding high-frequency components that could interfere with optical scanners, thus enhancing the reliability of data transmission and compatibility with other electronic systems.

Implementation Method 1

LEDs that emit light when driven by the constant current

Methodology Applied

Scientific EffectLight emission from LED: Light Emitting Diode

Implementation Method 2

The driver circuitry may dim the LED by periodically and repeatedly 'chopping' portions of the drive current down to zero amps

Methodology Applied

Scientific EffectPulse-width modulation:

Data Source

PatentUS9935711B2Method and system for optical communication

Publication Date: 2018.04.03 ABL IP HLDG LLC

AI summary

In various embodiments of the present invention data is transmitted in light emitted by a light source by generating a continuous-time data signal and generating, based thereon, a drive signal that provides power to the light source, thereby causing the light source to emit light; variations in the amplitude of the drive signal represent information in the continuous-time data signal. A change in average power delivered to the light source as a result of the variations in the amplitude of the drive signal is detected and power to the light source is adjusted to compensate.