Laser Diode Automatic Power Control Circuit
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Solution Overview
Problem
The direct time of flight (DTOF) laser ranging method is sensitive to temperature changes, leading to unstable emission power due to variations in internal resistance, which affects the accuracy of distance measurements and requires complex and costly circuits with photodiodes for control.
Innovation Solution
An automatic power control circuit and method for a laser diode that adjusts pulse parameters, such as the number of pulses, pulse period, and duty cycle, based on the forward voltage to maintain stable emission power within a preset range without changing the drive current setting, eliminating the need for a photodiode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the drive current is adjusted to maintain constant emission power under temperature changes, then the emission power stability is improved, but the circuit complexity and cost increase due to requiring photodiodes and additional control circuits
Solution Approach 1:
The patent extracts and eliminates the photodiode component from the traditional feedback control circuit. Instead of using a photodiode to detect laser power and feed back to adjust drive current, the invention uses a voltage measurement unit to directly measure the forward voltage of the laser diode, which correlates with temperature and emission power characteristics. This extraction of the photodiode component simplifies the circuit while maintaining emission power stability through alternative voltage-based feedback.
Solution Approach 2:
The patent substitutes the optical detection mechanism (photodiode converting light to electrical signal) with an electrical measurement mechanism (voltage measurement unit directly measuring forward voltage). This replacement eliminates the need for optical-to-electrical conversion hardware and simplifies the control system while achieving the same goal of monitoring and stabilizing emission power through electrical parameter measurement.
2Stability of the object's composition
If photodiodes and additional control circuits are added to maintain emission power, then the emission power stability is improved, but the manufacturing cost increases
Solution Approach 1:
The patent replaces expensive photodiode components with a simpler, more cost-effective voltage measurement unit. The forward voltage measurement approach uses basic electrical measurement circuitry that is significantly cheaper than photodiode-based optical detection systems. This substitution maintains the ability to stabilize emission power while dramatically reducing component costs and manufacturing complexity.
3Stability of the object's composition
If the drive current setting value is changed to compensate for temperature effects, then the emission power is maintained, but the optical properties of the laser change and subsequent calculations become complicated
Solution Approach 1:
The patent implements a feedback control mechanism that continuously monitors the forward voltage of the laser diode and adjusts the drive current dynamically to maintain constant emission power. The voltage measurement unit provides real-time feedback about the laser diode's state, and the processor uses this feedback to automatically adjust operating parameters. This closed-loop feedback system maintains emission power stability without requiring manual recalibration or changing fixed setting values, thereby preserving optical property consistency.
Solution Approach 2:
The patent transitions from static drive current setting values to dynamic adjustment of drive current based on real-time voltage measurements. The system adapts its operating parameters in response to changing temperature conditions by continuously measuring forward voltage and adjusting current accordingly. This dynamic approach maintains emission power stability while avoiding the need to change fixed setting values that would alter optical properties and complicate subsequent calculations.
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 solution maintains stable laser emission power across temperature changes without adjusting the drive current setting, reducing costs and circuit complexity while ensuring accurate distance measurements.
Implementation Method 1
a voltage measurement unit configured to obtain an indicative voltage at a specific measurement point and output the indicative voltage, wherein the indicative voltage is configured to indicate a forward voltage of a laser diode in laser emitting state
Data Source
AI summary
The present disclosure provides an automatic power control circuit and method, and a laser diode circuit comprising the automatic power control circuit. The automatic power control circuit comprises: a voltage measurement unit configured to obtain an indicative voltage at a specific measurement point and output the indicative voltage to a processor, wherein the indicative voltage is configured to indicate a forward voltage of a laser diode in laser emitting state; and the processor configured to output a pulse parameter control signal in response to change in the indicative voltage, wherein the pulse parameter control signal is used to control an adjustment for a pulse parameter of laser pulses of the laser diode, such that laser emission power is within a preset range, and wherein the pulse parameter of the laser pulses of the laser diode is used to set a total duration of pulses within a preset time period.