Optical Pulse Test Circuit Using Resonant Capacitor Discharge
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Solution Overview
Problem
Conventional platforms and methodologies for testing optical devices, particularly VCSEL arrays in automotive and LIDAR applications, face challenges in generating high-speed and high-current electric pulses due to parasitic inductance and impracticality for large-scale reliability testing, with existing techniques being costly and inaccurate.
Innovation Solution
A printed circuit board (PCB) with an electrical driver circuit incorporating a FET switch, resistors, capacitors, and inductors generates high-speed, high-current pulses by using a resonant capacitor discharge mechanism, minimizing parasitic inductance and enabling accurate peak current determination through normalized waveform analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional testing platforms are used to generate high-current pulses, then the optical device can be tested, but parasitic inductance degrades the pulse quality and measurement accuracy
Solution Approach 1:
The patent extracts the harmful parasitic inductance from the testing platform by using a resonant capacitor discharge mechanism that minimizes inductance. The circuit is designed to isolate and eliminate the effects of parasitic inductance through the resonant discharge path, allowing accurate peak current measurement without the degradation caused by conventional inductive elements.
Solution Approach 2:
The patent changes the operational parameters of the testing system by using normalized waveform analysis. By normalizing the current waveform to a reference waveform, the system can determine peak current values independently of parasitic inductance effects, transforming the measurement approach from direct absolute measurement to ratio-based normalized measurement that is immune to inductance variations.
2Measurement precision
If existing testing methodologies are used, then optical device testing can be performed, but the cost is high and accuracy is limited
Solution Approach 1:
The patent employs a cost-effective testing approach by using a simple resonant capacitor discharge circuit with minimal expensive components. The method uses normalized waveform analysis that does not require expensive high-bandwidth measurement equipment, replacing costly conventional testing apparatus with a simpler, more economical circuit configuration that achieves comparable or superior accuracy.
Solution Approach 2:
The patent uses normalized waveform copying where the actual current waveform is normalized to a reference waveform shape. This allows the system to determine peak current values by comparing waveform characteristics rather than requiring expensive direct high-current measurement equipment, effectively creating a virtual reference that simplifies the measurement system and reduces costs.
3Manufacturing precision
If high-current pulses with narrow width are generated, then the optical output pulse characteristics can be accurately characterized, but the challenge of generating and measuring such pulses increases
Solution Approach 1:
The patent performs preliminary normalization of the current waveform before measurement and analysis. By pre-normalizing the waveform to a reference shape and calculating normalized time values in advance, the system simplifies the measurement process for narrow pulses. This preliminary processing allows accurate characterization without requiring extremely high-bandwidth measurement equipment, as the normalization reduces the impact of measurement system limitations.
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 allows for efficient characterization and reliability testing of optical devices by generating pulses with peak currents up to 200 amps and durations less than 10 nanoseconds, while maintaining accurate measurements and reducing the impact of parasitic inductance on resonance.
Implementation Method 1
the one or more capacitors are configured to, when the switch is in the on state, discharge a current pulse to the optical device
Implementation Method 2
generates high-speed, high-current pulses by using a resonant capacitor discharge mechanism
Implementation Method 3
the optical device is configured to receive the current pulse from the one or more capacitors and to emit, based on a flow of the current pulse through the optical device, an optical output pulse
Data Source
AI summary
A characterization circuit for an optical device includes: an optical device, a switch, a switch driver, one or more resistors, and one or more capacitors. The switch driver is configured to receive a trigger pulse from an external pulse generator and to provide the trigger pulse to the switch, which causes the switch to be in an on state. The one or more capacitors are configured to, when the switch is in an off state, receive a charge current (e.g., with a greater than 50 nanoseconds rise time) from an external driver voltage source via the one or more resistors; and, when the switch is in the on state, discharge a current pulse (e.g., with a less than 10 nanosecond pulse width) to the optical device. The optical device is configured to receive the current pulse and to emit, based on the current pulse, an optical output pulse.