Adjustable Voltage-Current Conversion for Laser Stability
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Solution Overview
Problem
Existing light output devices, such as those using laser diodes, face instability in output power due to fluctuations in drive current caused by slight changes in control voltage, especially at varying temperatures, leading to inaccurate Auto Power Control (APC).
Innovation Solution
A light output device with a control unit that sets a target current value and adjusts the voltage-current conversion characteristic line to a lower inclination, allowing for stable drive current delivery even with control voltage fluctuations, thereby stabilizing laser emission and improving APC accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a large current value is required relative to the input voltage of the voltage-current conversion unit to control the laser diode, then the drive current fluctuates largely with slight fluctuation of the control voltage, but the output power becomes unstable
Solution Approach 1:
The patent applies dynamics by making the inclination of the characteristic line adjustable rather than fixed. The control unit dynamically changes the inclination based on operating conditions, allowing the system to adapt to different temperature and power requirements. This resolves the contradiction by enabling the voltage-current conversion unit to maintain stable drive current delivery across varying conditions, preventing both excessive fluctuation and insufficient current delivery.
Solution Approach 2:
The patent changes the parameter of the characteristic line's inclination to resolve the contradiction. By adjusting the inclination of the control voltage-drive current conversion characteristic line, the system can optimize the relationship between control voltage and drive current. This parameter change allows the voltage-current conversion unit to deliver the required large current value while minimizing drive current fluctuation, thus stabilizing output power.
2Temperature
If the threshold current and drive current increase with a rise in ambient temperature, then the output power control becomes more difficult, but the APC accuracy deteriorates
Solution Approach 1:
The patent uses feedback through the Auto Power Control mechanism, where the output power is detected and used to generate a control voltage signal that adjusts the drive current. The ability to change the characteristic line's inclination enhances this feedback loop, allowing the system to compensate for temperature-induced current increases. This maintains APC accuracy across varying temperatures by dynamically adjusting the conversion characteristic.
Solution Approach 2:
The patent applies dynamics by making the voltage-current conversion characteristic adaptable to temperature changes. By dynamically adjusting the inclination of the characteristic line in response to temperature variations, the system compensates for the natural increase in threshold and drive currents. This dynamic adjustment maintains precise output power control and APC accuracy despite ambient temperature rises.
3Power
If the inclination of the characteristic line is increased to deliver more current, then the drive current reaches maximum current value faster, but the drive current fluctuates more with control voltage changes
Solution Approach 1:
The patent resolves this contradiction by making the inclination dynamic rather than fixed. The control unit can adjust the inclination of the characteristic line based on the desired operating point and current requirements. This allows the system to use a steeper inclination when maximum current delivery is needed while maintaining a gentler inclination when stability is prioritized, thus resolving the trade-off between current delivery capability and drive current stability.
Solution Approach 2:
The patent changes the parameter of the characteristic line's inclination to balance current delivery and stability. By adjusting this parameter, the system can optimize the voltage-current conversion characteristics for different operating conditions. This parameter change enables the voltage-current conversion unit to deliver adequate drive current while minimizing fluctuations, thus resolving the contradiction between power delivery and current stability.
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 provides stable output power and highly accurate APC by reducing drive current fluctuations relative to control voltage changes, ensuring consistent laser emission and extended device lifespan.
Implementation Method 1
a voltage-current conversion unit configured to convert the control voltage into the drive current
Implementation Method 2
an output unit that includes a light source, the output unit configured to output light from the light source
Data Source
AI summary
A light output device includes: an output unit including a light source; a control voltage generation unit that detects output power of the light source, and generates a control voltage for controlling a drive current of the light source; a control unit that sets a target value of the output power; a voltage-current conversion unit that converts the control voltage into the drive current; a setting unit that sets an inclination of a characteristic line of control voltage-drive current conversion in the voltage-current conversion unit; and an adjustment unit that adjusts the voltage-current conversion unit such that the drive current becomes a target current value for setting the output power to the target value in a predetermined control voltage value on the characteristic line, wherein the setting unit sets the inclination of the characteristic line to a first inclination where the drive current does not reach a maximum current value.