Laser Diode Driver Circuit with Bypass Inductance Magnetization
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Solution Overview
Problem
LIDAR systems require high radiant power laser pulses for long-range measurement, but to ensure safety, these pulses must be short, necessitating driver electronics that can switch laser diode load current with extremely short rise and fall times, which is challenging due to the high voltages needed, increasing complexity and cost.
Innovation Solution
A driver circuit and method that utilize a first electronic switch and a bypass circuit to magnetize inductance effectively, with a transistor half-bridge configuration and clamping circuits to manage current ramps and voltage drops, allowing for steep current transients with a low supply voltage, reducing inductance and voltage requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high radiant power laser pulses are used for long-range measurement, then measurement range is improved, but pulse width must be reduced to ensure safety, which increases driver circuit complexity and cost
Solution Approach 1:
The patent applies preliminary action by pre-magnetizing the inductance in the driver circuit before the actual laser pulse is generated. During a pre-charging phase, current is directed through the inductance to establish a magnetic field, which is then rapidly collapsed during the pulse phase to generate the required steep current transient. This pre-preparation allows the circuit to achieve high peak currents with short rise times without requiring excessively high supply voltages or complex circuit topologies.
Solution Approach 2:
The driver circuit operates in periodic cycles consisting of a pre-charging phase followed by a pulse phase. During the pre-charging phase, the inductance is magnetized; during the pulse phase, the magnetic field collapses to drive the laser diode. This periodic operation allows the circuit to reset and prepare for the next pulse, enabling repeated generation of high-power short pulses while maintaining manageable voltage and current levels throughout the cycle.
2Speed
If high supply voltage is used to achieve steep current transients, then rise time is reduced, but voltage requirements and circuit complexity increase
Solution Approach 1:
The patent changes the operational parameters of the inductance from a static component to a dynamically utilized energy storage element. By controlling the current through the inductance during a pre-charging phase and then rapidly collapsing the magnetic field, the circuit generates high dI/dt without requiring proportionally high supply voltages. The key parameter change is utilizing the inductance's energy storage capability rather than relying solely on voltage magnitude to drive current rise.
Solution Approach 2:
The circuit employs dynamic switching control to transition between pre-charging and pulse phases. The electronic switches rapidly change state to first build up current in the inductance, then abruptly interrupt it to generate the laser drive pulse. This dynamic operation allows the circuit to achieve steep current transients through controlled energy release rather than sustained high voltage, reducing the required supply voltage level and simplifying the overall circuit design.
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
Enables the generation of short, high-power laser pulses with reduced inductance and voltage demands, simplifying the driver circuit design and reducing costs while maintaining the necessary current ramps for LIDAR applications.
Implementation Method 1
a bypass circuit that is coupled to the output node and configured to take over, when activated, the current supplied to the output node via the first electronic switch, thus magnetizing the first inductance
Data Source
AI summary
A driver circuit for driving a laser diode is described herein. In accordance with a first exemplary embodiment the driver circuit includes a first electronic switch connected to an output node that is configured to be operably connected to a laser diode. The electric connection between the first electronic switch and the output node has a first inductance. The driver circuit further includes a bypass circuit that is coupled to the output node and configured to take over, when activated, the current supplied to the output node via the first electronic switch, thus magnetizing the first inductance.