Quantum Cascade Laser Driver Active Voltage Pulldown

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Solution Overview

Problem

Quantum cascade devices used in infrared laser assemblies face significant heat generation and power consumption issues, leading to decreased efficiency as temperature increases, despite pulsed drive voltage techniques, due to slow voltage decay when nominally off.

Innovation Solution

A laser assembly design that incorporates a pulsed drive profile with spaced on-time and off-time segments, utilizing highside and lowside FET drivers or MOSFET drivers to actively pull down voltage to approximately zero volts during off-time segments, reducing thermal load and power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If pulsed drive voltage is used to reduce thermal load and power consumption, then power consumption is reduced, but voltage decay is slow when nominally off leading to residual power consumption

Engineering Contradiction:

Improvepower consumptionVSAvoidresidual power consumption

Core Design Contradiction:

Use of energy by stationary objectVSLoss of energy

Solution Approach 1:

The patent applies periodic pulsed drive voltage to the quantum cascade device, switching between on-state and off-state periodically. During off-state, a pull-down circuit actively discharges residual voltage to achieve complete voltage decay, preventing residual power consumption while maintaining the benefits of pulsed operation for reducing average thermal load and power consumption.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent introduces a pull-down circuit as an intermediary component that actively discharges residual voltage from the quantum cascade device during off-state periods. This intermediary circuit ensures complete voltage decay by providing a dedicated discharge path, eliminating the slow natural decay and associated residual power consumption.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Duration of action of moving object

If continuous voltage is applied to maintain quantum cascade device operation, then laser output is continuous, but thermal load and power consumption increase significantly

Engineering Contradiction:

Improvelaser output continuityVSAvoidthermal load

Core Design Contradiction:

Duration of action of moving objectVSTemperature

Solution Approach 1:

The patent uses periodic pulsed voltage drive instead of continuous voltage application. The quantum cascade device receives voltage in discrete pulses with off-periods in between, during which the pull-down circuit actively discharges residual voltage. This periodic operation maintains laser output during on-periods while significantly reducing average thermal load and power consumption compared to continuous operation.

Inventive Principle:

Principle #19Periodic action

3Use of energy by stationary object

If pulsed drive profile with active voltage pull-down is used, then power consumption is reduced and device is cooled, but device complexity increases due to additional circuitry

Engineering Contradiction:

Improvepower consumptionVSAvoidcircuit complexity

Core Design Contradiction:

Use of energy by stationary objectVSDevice complexity

Solution Approach 1:

The patent introduces a pull-down circuit as an intermediary component that actively discharges residual voltage from the quantum cascade device during off-state periods. This additional circuitry, while increasing device complexity, enables complete voltage decay and eliminates residual power consumption, achieving significant net power savings that outweigh the added circuit complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 design significantly reduces power consumption and enhances laser efficiency by maintaining a cooler quantum cascade device, with simulations indicating a potential 40% improvement in light production efficiency.

Implementation Method 1

These quantum cascade devices generate photons through the injection of electrons into designed quantum wells by the laser driver

Methodology Applied

Scientific EffectQuantum cascade:

Implementation Method 2

the laser driver includes a highside field-effect transistor (FET) driver that is used to control a highside switch for directing voltage to the quantum cascade device during each on-time segment, and a lowside field-effect transistor (FET) driver that is used to control a lowside switch when pulling down the voltage in the quantum cascade device during each off-time segment

Methodology Applied

Scientific EffectField-effect transistor operation:

Implementation Method 3

the laser driver directs voltage to the quantum cascade device in a pulsed fashion to reduce thermal load and power consumption of the quantum cascade device

Methodology Applied

Scientific EffectThermal management through pulsed operation:

Data Source

PatentUS11189992B2Pulsed quantum cascade device assembly with active voltage pulldown

Publication Date: 2021.11.30 DAYLIGHT SOLUTIONS INC

AI summary

A laser assembly (10) for generating a pulsed output beam (16) includes a quantum cascade device (12); and a laser driver (14A) that controls the voltage to the quantum cascade device (12) in a pulsed drive profile (950) to generate the pulsed output beam (16). The pulsed drive profile (950) includes a plurality of spaced on-time segments (952) in which the laser driver (14A) directs voltage to the quantum cascade device (12), and at least one off-time segment (954) in which the laser driver (14A) pulls down the voltage from the quantum cascade device (12). The off-time segment (954) occurs between two on-time segments (952).