PWM Light Source Drive Voltage Stabilization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pulse-width modulation (PWM) light source drives face challenges in maintaining stable optical power and wavelength stability, especially during PWM operation, due to high bandwidth requirements in the circuitry and instability during off-time intervals.
Innovation Solution
A PWM light source drive system comprising a microcontroller, a voltage regulator, and a light detector that generates a PWM signal and its inverse, using the light detector's optical power feedback signal during on-time intervals and the inverse PWM signal during off-time intervals to stabilize the output drive voltage, thereby maintaining stable optical power without demanding bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional PWM circuitry is used to modulate the drive signal, then the light source can be modulated, but the circuitry requires high bandwidth which increases complexity and reduces stability during off-time intervals
Solution Approach 1:
The feedback signal is segmented into two distinct components: an optical power feedback signal during on-time intervals and an inverse PWM signal during off-time intervals. This segmentation allows each component to be optimized for its specific function, reducing the overall bandwidth requirement while maintaining modulation capability
Solution Approach 2:
An inverse PWM signal is introduced as an intermediary during off-time intervals to stabilize the voltage regulator. This intermediary signal compensates for the absence of optical feedback during off periods, reducing the need for high bandwidth circuitry while maintaining system stability
2Reliability
If optical power feedback is used during on-time intervals, then optical power stability is improved, but the voltage regulator becomes unstable during off-time intervals when no feedback is available
Solution Approach 1:
The inverse PWM signal is generated in advance during off-time intervals to preemptively counteract the instability that would otherwise occur. By providing this compensating signal before the voltage regulator becomes unstable, the system maintains continuous stability without requiring high bandwidth feedback
Solution Approach 2:
Instead of using the optical power feedback signal during off-time intervals (when no light is emitted), the system uses the inverse PWM signal. This inversion approach provides the necessary feedback during periods when the conventional feedback mechanism cannot operate, maintaining voltage regulator stability throughout the entire PWM cycle
3Stability of the object's composition
If continuous feedback is required to maintain voltage regulator stability, then stability is improved, but during PWM off-time no optical feedback is available increasing bandwidth demands
Solution Approach 1:
The feedback mechanism operates periodically with two distinct modes: optical power feedback during on-time intervals and inverse PWM feedback during off-time intervals. This periodic alternation ensures continuous voltage regulator stability while avoiding the need for continuously high bandwidth, as each mode operates at relaxed bandwidth requirements for its specific time period
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 system achieves stable, relatively constant optical power during PWM operation across a wide dynamic range of modulation, maintaining voltage regulator stability during off-time intervals and providing a range of brightness control for the light source.
Implementation Method 1
a light detector configured to detect light energy emitted by the light source, to generate an optical power feedback signal based on the detected light energy
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A pulse-width modulation (PWM) light source drive (100, 200) for driving a light source (106, 206) is provided that includes a microcontroller (104, 204), a modulation element (110, 210), a voltage regulator (102, 202), and a light detector (108, 208). The microcontroller is configured to generate a PWM signal (114, 214) and an inverse PWM signal (120b, 220b). The modulation element is configured to generate a drive signal (116, 216) based on the PWM signal. The light source is configured to be driven by the drive signal. The voltage regulator is configured to generate an output drive voltage (112, 212) for the light source. The light detector is configured to detect light energy (1 18, 218) emitted by the light source, to generate an optical power feedback signal (120a, 220a) based on the detected light energy, and to provide the optical power feedback signal to the voltage regulator during a laser-on driving interval. The microcontroller is configured to provide the inverse PWM signal to the voltage regulator during a laser-off driving interval. The voltage regulator is configured to adjust the output drive voltage based on the optical power feedback signal during the laser-on driving interval and based on the inverse PWM signal during the laser-off driving interval.