Resonant Laser Diode Driver Current Sensing for Short High-Current Pulses
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Solution Overview
Problem
Conventional pulsed laser diode driver circuits face challenges in generating short, high-current pulses due to parasitic inductances, requiring high source voltages and complex designs, and struggle with efficient current measurement for narrow pulses.
Innovation Solution
The proposed solution involves a tunable resonant circuit with intentionally added inductors and capacitors to control pulse width and current, using a current pulse measurement circuit that compensates for switch resistance changes and eliminates the need for high-speed comparators, allowing for low-voltage operation and integration into a single semiconductor die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If high source voltage (greater than 40V to 100V) is used to overcome parasitic inductances, then the desired short pulse width (5 ns or less) is achieved, but the power efficiency deteriorates and design complexity increases
Solution Approach 1:
The patent changes the voltage parameter from high (40-100V) to low (5V to 20V) by introducing a resonant circuit that generates voltage amplification through oscillation. The resonant circuit uses an inductor and capacitor to create a feedback loop that multiplies the low input voltage into a high voltage pulse capable of driving the laser diode with the required current, thereby maintaining power efficiency while achieving short pulse widths.
Solution Approach 2:
The patent applies the principle of vibration by creating an electrical resonant oscillation in the circuit. The resonant circuit causes the voltage and current to oscillate at a specific frequency, creating a vibratory effect that builds up energy and enables high peak voltages to be generated from low input voltages. This oscillatory behavior allows the circuit to overcome parasitic inductances without requiring continuously high source voltage.
2Duration of action of moving object
If high source voltage is used to achieve short pulse width, then the pulse width requirement is met, but the device complexity increases
Solution Approach 1:
The patent merges multiple functions into the resonant circuit structure. The same inductor and capacitor that create the resonant oscillation also serve to shape the current pulse, control its duration, and amplify the voltage. This consolidation of functions into a unified resonant system reduces the need for separate voltage multiplication stages, isolation components, and control circuits that would otherwise be required in high-voltage designs.
Solution Approach 2:
The resonant circuit is self-regulating in that the oscillation naturally limits the pulse duration to the resonant period, and the voltage amplification occurs automatically through the feedback mechanism. The circuit uses its own parasitic elements and component values to determine the operating parameters, reducing the need for external control mechanisms and complex regulation circuits.
3Measurement precision
If discrete current sense resistor is used to measure high-current pulse amplitude, then the measurement is straightforward, but power efficiency deteriorates
Solution Approach 1:
The patent introduces an intermediary sensing mechanism that indirectly measures the high current without creating a significant voltage drop. Instead of using a discrete sense resistor that would dissipate power, the circuit uses the existing switch resistance or a highly integrated sensing element that measures current through voltage monitoring across a minimal resistance, thereby maintaining power efficiency while providing accurate measurement through signal conditioning circuits.
4Measurement precision
If conventional high-speed comparators or switches are used to measure current pulse peak, then the measurement capability is achieved, but the device complexity and cost increase
Solution Approach 1:
The patent extracts the measurement function from complex high-speed comparator circuits and integrates it directly into the resonant circuit nodes. By monitoring the voltage across the sense resistance through the existing high-speed switching nodes of the resonant circuit, the measurement is obtained as a byproduct of the main operating waveform, eliminating the need for separate comparator stages and reducing measurement circuit complexity.
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 approach enables the generation of ultra-short, high-current pulses at lower input voltages, reducing design complexity and cost, while allowing for independent control of multi-channel laser diodes without bootstrap circuitry, and provides accurate current measurement without high-speed comparators.
Implementation Method 1
tunable resonant circuit with intentionally added inductors and capacitors to control pulse width and current
Implementation Method 2
laser diode to emit a corresponding pulse of laser light
Data Source
AI summary
A pulsed laser diode driver includes a laser diode switch and a bypass switch to control a current flow through an inductor to produce a high-current pulse through a laser diode, the high-current pulse corresponding to a peak current of a resonant waveform developed at an anode of the laser diode. A current pulse measurement circuit receives a sense voltage developed at a sense resistance and generates, based on the sense voltage, a current sense signal that corresponds to the peak current amplitude of the high-current pulse through the laser diode.