Switched-Capacitor Laser Circuit for Fast Current Modulation
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Solution Overview
Problem
Laser circuits face challenges in rapidly changing laser current due to inherent characteristics, limiting the control of radiation intensity, particularly in applications requiring fast adjustments.
Innovation Solution
Incorporating a switched-capacitor circuit with capacitors and switches to provide a charge package at predetermined times, allowing precise control of laser current through digital-to-analog converters, including video, bias, and threshold converters, and utilizing supply voltages relative to ground potential to reduce signal level shifting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional laser current control is used, then the laser circuit is simple, but the laser current cannot change rapidly
Solution Approach 1:
The laser current control is segmented into multiple independent components: a switched-capacitor circuit for rapid current changes, a video DAC for continuous control, and a bias DAC for baseline adjustment. Each component handles a specific aspect of current control, enabling fast response without requiring the entire circuit to be complex.
Solution Approach 2:
The switched-capacitor circuit pre-charges capacitors to specific voltage levels before they are switched into the laser circuit. This preliminary charging action allows the circuit to instantly provide the required current step change without waiting for gradual charging, achieving rapid laser current modulation.
2Measurement precision
If multiple digital-to-analog converters are used, then the laser current control precision is improved, but the device complexity increases
Solution Approach 1:
The current control function is segmented across three separate DACs: the bias DAC sets the baseline current level, the video DAC provides continuous modulation, and the switched-capacitor circuit handles rapid step changes. This segmentation allows each DAC to operate within its optimal range with appropriate resolution, achieving high overall precision without requiring a single extremely high-resolution converter.
Solution Approach 2:
The system dynamically selects which DAC or circuit component to use based on the required control precision and speed. For slow, precise adjustments, the video DAC is used. For rapid changes, the switched-capacitor circuit takes over. This dynamic allocation optimizes both precision and response time while managing complexity.
3Ease of operation
If supply voltages are used relative to ground potential, then signal level shifting is reduced, but the power consumption increases
Solution Approach 1:
The switched-capacitor circuit uses supply voltages referenced to ground potential, creating equipotential regions that eliminate the need for additional level-shifting circuitry. By designing the circuit to operate directly from ground-referenced supplies, the patent avoids the power losses associated with level translation while maintaining ease of operation and signal integrity.
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 rapid and precise control of laser current, reducing fluctuations due to temperature shifts and enhancing flexibility in generating laser current, thereby improving the control of radiation intensity.
Implementation Method 1
the switched-capacitor circuit comprises a capacitor and a first switch that is coupled to a first electrode of the capacitor and is coupled to the first terminal of the laser
Data Source
AI summary
A laser circuit (10) comprises a switched-capacitor circuit (110), a video digital-to-analog converter (23) and a laser (20) with a first and a second terminal (21, 22). The first terminal (21) of the laser (20) is coupled to the switched-capacitor circuit (110) and to the video digital-to-analog converter (23). Moreover, a method for operating a laser circuit (10) is described.