Laser Drive Circuit Timing for Faster Emission Fall Time
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current laser drive circuits for light-emitting diodes in distance-measuring sensors face challenges in accelerating the fall time of the emission waveform, which affects ranging accuracy.
Innovation Solution
A laser drive circuit and sensor apparatus that utilize a first drive current unit with series-connected MOSFETs, a voltage drop unit to lower the gate-source voltage of the MOSFET, and a timing generating unit to control the drive current and voltage drop, specifically accelerating the fall time by temporarily increasing and then reducing the current through the light-emitting diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional drive circuits are used for light-emitting diodes, then the circuit structure is simple, but the fall time of the emission waveform cannot be sufficiently accelerated
Solution Approach 1:
The drive circuit is segmented into multiple functional units: a drive current unit with series-connected first and second MOSFETs for current control, a voltage drop unit with third MOSFET for gate-source voltage control, and a timing generating unit for coordinated switching. This segmentation allows independent optimization of each unit's function to achieve fast fall time while maintaining manageable circuit complexity.
Solution Approach 2:
The voltage drop unit is activated in advance before the light-emitting element is extinguished. By dropping the gate-source voltage of the first MOSFET beforehand, the circuit prepares for rapid current termination, enabling the light-emitting element to be extinguished quickly when the timing generating unit activates the extinction sequence.
2Measurement precision
If the light-emitting element is extinguished quickly, then ranging accuracy is improved, but control precision of the drive current becomes more difficult
Solution Approach 1:
The timing generating unit coordinates the switching of the first, second, and third MOSFETs based on precise timing signals. The control unit monitors the states of all MOSFETs and adjusts the drive current waveform accordingly, providing feedback control that ensures both rapid extinction and precise current management for accurate ranging measurements.
Solution Approach 2:
The circuit dynamically changes multiple parameters: the drive current magnitude is adjusted by the first and second MOSFETs, the gate-source voltage is dropped by the third MOSFET, and the timing of these changes is precisely controlled. By coordinating these parameter changes, the circuit achieves both fast extinction and precise current control.
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
The solution effectively accelerates the fall time of the emission waveform, improving ranging accuracy in distance-measuring sensors by efficiently controlling the light emission and extinction of the light-emitting diode.
Implementation Method 1
a light-emitting element that emits light in accordance with a current amount
Data Source
AI summary
A laser drive circuit is provided which includes: a first drive current unit (240) configured to adjust, by a first MOSFET (MN2) and a second MOSFET (MN3) being connected in series, an inflow of a current to a light-emitting element (LD11) that emits light in accordance with a current amount when the light-emitting element emits light and when the light-emitting element is extinguished; a voltage drop unit (MN4) configured to cause a gate-source voltage of the first MOSFET to drop when the light-emitting element is extinguished; and a timing generating unit (220) configured to generate a signal for controlling driving of the first drive current unit and the voltage drop unit.