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Park M, Baek Y, Dinare M, Lee D, Park KH, Ahn J, Kim D, Medina J, Choi WJ, Kim S, Zhou C, Heo J, Lee K. Hetero-integration enables fast switching time-of-flight sensors for light detection and ranging. Sci Rep 2020; 10:2764. [PMID: 32066791 PMCID: PMC7026395 DOI: 10.1038/s41598-020-59677-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 01/31/2020] [Indexed: 12/05/2022] Open
Abstract
The time-of-flight (ToF) principle is a method used to measure distance and construct three-dimensional (3D) images by detecting the time or the phase difference between emitted and back-reflected optical flux. The ToF principle has been employed for various applications including light ranging and detection (LiDAR), machine vision and biomedical engineering; however, bulky system size and slow switching speed have hindered the widespread application of ToF technology. To alleviate these issues, a demonstration of hetero-integration of GaN-based high electron mobility transistors (HEMTs) and GaAs-based vertical cavity surface emitting lasers (VCSELs) on a single platform via a cold-welding method was performed. The hetero-integrated ToF sensors show superior switching performance when compared to silicon-transistor-based systems, miniaturizing size and exhibiting stable ranging and high-resolution depth-imaging. This hetero-integrated system of dissimilar material-based high-performance devices suggests a new pathway towards enabling high-resolution 3D imaging and inspires broader range application of heterogeneously integrated electronics and optoelectronics.
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Affiliation(s)
- Minseong Park
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Yongmin Baek
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Mesgana Dinare
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Doeon Lee
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Kyung-Ho Park
- Devices Technology Division, Korea Advanced Nano Fab Center (KANC), Suwon, 16229, South Korea
| | - Jungho Ahn
- Department of Electrical and Computer Engineering, Ajou University, Suwon, 16499, South Korea
| | - Dahee Kim
- Department of Electrical and Computer Engineering, Ajou University, Suwon, 16499, South Korea
| | - Joseff Medina
- Department of Mechanical and Aerospace engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Won-Jin Choi
- RayIR Corporation, LTD, 156 Gwanggyo-ro, Yeongtong-gu, Suwon, 16506, South Korea
| | - Sihwan Kim
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA
| | - Changjie Zhou
- Department of Science, Jimei university, Jimei District, Xiamen, Fujian, 361021, China
| | - Junseok Heo
- Department of Electrical and Computer Engineering, Ajou University, Suwon, 16499, South Korea
| | - Kyusang Lee
- Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, VA, 22904, USA. .,Department of Material Science and Engineering, University of Virginia, Charlottesville, VA, 22904, USA.
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Abstract
Digital LED drivers capable of blending the spectrum of two LED fixtures with different Correlated Color Temperatures through the LEDs’ power supply control are widespread. However, the digital control of lighting systems is possible only after a careful study of the LED’s response, in terms of illuminance and Correlated Color Temperature. The proposed work takes advantage of the Tunable White technology for the realization of an efficient method for LED light source characterization. In order to evaluate how the light changes as a function of the electric power supplied by the LED drivers, an experimental setup to characterize LED light sources has been designed. Starting from the data acquired from the experimental setup, a model for dimming the LED driver and obtaining the desired values of quality of light has been developed. The proposed model is based on the least squares method and its accuracy is evaluated by comparing the obtained values of illuminance and Correlated Color Temperature with those measured by an illuminance spectrophotometer. Results achieved an error of 0.3% for Correlated Color Temperature and 1.5% for illuminance using the proposed approximation functions.
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Optimization of a Series Converter for Low-Frequency Ripple Cancellation of an LED Driver. ELECTRONICS 2019. [DOI: 10.3390/electronics8060664] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
In this paper, the optimization of the power and control stages of a previously proposed topology for an off-line LED electronic driver is presented. The full system avoids the use of electrolytic capacitors at the D C link, therefore increasing the lifespan and reliability of the driver. As a consequence of having a relatively small capacitance, the D C link operates with a large Low-Frequency ( L F ) voltage ripple. This work presents a design optimization for the power and control stages of a current-fed bidirectional buck converter, operating as the LED current control stage. As this block processes only the A C power arising from the L F voltage ripple, it can increase the system efficiency against the typical two-stage solution. In the original proposal, the main drawback was the high inductor losses due to the resulting large inductor currents and large inductance value. The proposed optimization ensures an enhanced design of the inductor while keeping a constant current through the LEDs. A new optimization methodology is proposed and the theoretical results have been validated in a built prototype for a 40 W LED lamp.
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