Semiconductor Laser Driver Electronic Dimming Circuit
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Solution Overview
Problem
Conventional dimming methods for semiconductor laser drivers in portable projectors face issues such as reduced optical energy efficiency, increased power consumption, heating, size, and cost, as well as degraded image quality due to the use of optical components or reduction in image data.
Innovation Solution
A semiconductor laser driver with a configuration of three current generator circuits that adjust current values based on control signals, allowing for dimming without relying on optical components or reducing image data, thereby maintaining high optical energy efficiency and image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If optical components (such as ND filters) are used for dimming, then the brightness of projected image can be controlled, but optical energy efficiency is reduced, power consumption increases, and heating value increases
Solution Approach 1:
The patent replaces the mechanical/optical dimming system (ND filters) with an electrical control system. Instead of using optical components to attenuate light, the invention controls the current supplied to the semiconductor laser element itself, thereby controlling the light output intensity. This substitution eliminates the energy loss associated with optical filtering while maintaining dimming functionality.
Solution Approach 2:
The patent changes the operating parameter of the semiconductor laser element by varying the current supplied to it. By controlling the current magnitude, the light output intensity is directly adjusted. This parameter-based control method achieves dimming without the energy inefficiencies of optical components, as the laser element converts electrical energy to light more efficiently when controlled through current modulation rather than optical attenuation.
2Illumination intensity
If optical components are used for dimming, then brightness control is achieved, but device size increases due to need for mechanical movement space
Solution Approach 1:
The patent eliminates the mechanical movement space requirement by replacing the optical component-based dimming mechanism with an electrical current control system. The semiconductor laser element's light output is controlled by varying the supplied current, removing the need for moving parts or additional space for mechanical dimming components, thus reducing overall projector size.
3Loss of energy
If image data amount is reduced for dimming, then power consumption is reduced, but image quality degrades due to moire patterns
Solution Approach 1:
The patent changes the approach to power consumption reduction by controlling the laser element's current rather than reducing image data. This allows full-resolution image data to be maintained while adjusting the overall brightness through current modulation, thereby reducing power consumption without introducing moire patterns or degrading image quality.
4Illumination intensity
If optical components are used for dimming, then brightness control is achieved, but manufacturing cost increases
Solution Approach 1:
The patent substitutes expensive optical components (ND filters and their mechanical mounting structures) with a simpler electrical control circuit. The current control mechanism requires only basic electronic components that are more economical to manufacture and integrate, thereby reducing overall manufacturing cost while maintaining the brightness control function.
Data Source
AI summary
A first current generator circuit generates a first current having a current value variable in accordance with a first control signal. A second current generator circuit generates a second current by limiting the first current so as to have a current value variable in accordance with a second control signal. A third current generator circuit generates a third current by limiting the second current so as to have a current value variable in accordance with a third control signal, and supplies the third current to the semiconductor laser element. Rates at which the first and second control signals change are set to be lower than a rate at which the third control signal changes.