LC Resonant Pulse Generator for Narrow Laser Diode Pulses
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Solution Overview
Problem
Generating high-intensity narrow pulses for laser diode drivers is challenging due to limitations in precise control of pulse duration, high parasitic inductances in interconnections, and issues with driving multiple laser diodes in a common-cathode configuration.
Innovation Solution
A pulse generator circuit is designed with an LC resonant circuit, a charging circuit, and electronic switches to control current flow and pulse duration. The circuit includes a switching network that allows for sequential activation of laser diodes with precise pulse duration control, reducing parasitic inductances and minimizing spurious activations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional switching circuits are used to generate current pulses for laser diodes, then the circuit structure is simple, but the pulse duration control precision is poor and parasitic inductances limit di/dt
Solution Approach 1:
The patent applies resonant oscillation principles to the LC circuit, utilizing electromagnetic resonance to generate precise current pulses. The resonant frequency of the LC circuit determines the pulse characteristics, enabling precise control of pulse duration and shape without complex switching networks. This resolves the contradiction by using natural resonant properties rather than complex active control elements.
Solution Approach 2:
The patent changes the operating parameters of the circuit by using resonant frequency as the controlling parameter instead of simple switching times. By adjusting the LC circuit parameters (inductance L and capacitance C), the pulse duration and characteristics can be precisely controlled. This approach achieves high precision pulse control while maintaining relatively simple circuit topology.
2Speed
If parasitic inductances in interconnections are present, then the circuit is easier to manufacture, but di/dt is limited during current rise and fall
Solution Approach 1:
The patent converts the harmful effect of parasitic inductances into a beneficial feature by intentionally designing an LC resonant circuit where inductance is a key component. The resonant oscillation naturally produces the desired high di/dt current pulses, and the circuit design minimizes parasitic effects by using the resonant frequency to drive the pulse generation. This transforms what was previously a limiting factor into the mechanism that enables high-speed current changes.
3Reliability
If multiple laser diodes are driven with common cathodes, then the device complexity is reduced, but spurious activations and control precision deteriorate
Solution Approach 1:
The patent segments the control function by using individual switching elements for each laser diode anode while maintaining a common cathode connection. This allows independent control of each diode through its own switch, preventing spurious activations while keeping the cathode structure common. The segmentation of control paths resolves the contradiction by providing individual diode control without requiring complete isolation of all terminals.
Solution Approach 2:
The LC resonant circuit serves multiple functions simultaneously: it generates the current pulses, determines the pulse duration through its resonant frequency, and provides the energy storage necessary for driving multiple diodes. This multi-functionality reduces the need for additional control circuitry while maintaining reliable individual diode control through the combination of common cathode and individual anode switches.
4Productivity
If high-intensity narrow pulses are generated, then the productivity of LIDAR system is improved, but the device complexity and power dissipation increase
Solution Approach 1:
The patent uses periodic resonant oscillation to generate high-intensity narrow pulses. The LC circuit naturally oscillates at its resonant frequency, producing repeated high-current pulses with precise duration control. This periodic action enables continuous LIDAR measurements with high productivity while the resonant efficiency minimizes energy losses compared to non-resonant pulse generation methods.
Solution Approach 2:
The resonant LC circuit maintains continuous oscillation during the pulse generation process, ensuring that energy is continuously transferred to the laser diodes without interruption. This continuous useful action maximizes the productivity of the LIDAR system by enabling rapid sequential measurements, while the resonant energy storage and transfer mechanism minimizes power dissipation compared to repeated startup of non-resonant circuits.
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 enables the generation of high-intensity narrow pulses with precise control over pulse duration, achieving rise and fall times in the 100 ps range while reducing parasitic inductances and power dissipation, and effectively driving multiple laser diodes in a common-cathode configuration.
Implementation Method 1
an LC resonant circuit coupled between a first node and a reference node
Data Source
AI summary
A pulse generator circuit includes: an LC resonant circuit coupled between a first node and a reference node; a first switch coupled between the first node and the reference node; a switching network comprising a second switch coupled between the first node and a respective drive node; and drive circuit having outputs coupled to the first switch and to the second switch of the switching network. The drive circuit is configured to, in repeating cycles: close the first switch so that a current flowing through an inductor of the LC resonant circuit increases during a resonant cycle, when the current flowing through the inductor reaches a threshold value, open the first switch, close the second switch of the switching network for a pulse duration time when the first switch is open, and open the second switch at an expiration of the pulse duration time.