Romano Torres
9th January 2013
DC/DC Converters
 To convert a dc input voltage Vs into a dc output voltage
Vo;
 To regulate the dc output voltage against load and line
variations;
 To reduce the ac voltage ripple on the dc output voltage
below the required level;
 To provide isolation between the input source and the
load;
From reference [10]
Applications
 Electronic devices:
 Internal sub-circuits require different voltage levels;
 Low battery voltage level needed.
 Photovoltaic panels:
 Increase the voltage level of electric current produced.
Step-Down Buck Converter
Image from reference [10]
Step-Up Boost Converter
Image from reference [10]
Buck-Boost Converter
Image from reference [10]
Cuk Converter
Image from reference [10]
Transparency
Resistors
Images from reference [5]
Capacitors
Transparent thin-film transistors
 In 2003 appear the first successful reports of TTFT
using ZnO as channel layer material [1] [3] [8].
 In 2004, K. Nomura et al. report the successful
fabrication of TTFT with a-GIZO (amorphous galliumindium-zinc-oxide) [9].
TTFT device structure
Staggered bottom-gate
Image from reference [10]
TFT operation modes
Cut-off:
Pre-saturation:
Saturation:
No current flow.
Vgs<Vt
Vgs>Vt
Vds>Vgs-Von
&
Vds<Vgs-Vt
a-GIZO TFT limitations
 p-type devices with poor semi-conductor
characteristics;
 Threshold voltage shift due DC-bias;
 Source and drain contacts’ resistance influence the
TFT characteristics;
a-GIZO TFT limitations
• Temperature:
• Oxygen vacancy.
Image from reference [6]
a-GIZO TFT limitations
• Light:
Image from reference [7]
Transparency
 Problems with inductors:
 Poor conductance;
 High parasitic resistance;
 Low quality factor.
Voltage multipliers
 Due the various problems with transparent inductors,
we propose use voltage multipliers;
 How does it work?
Proposed positive DC/DC Converter
Images from reference [4]
Proposed negative DC/DC Converter
Images from reference [4]
Transparent photovoltaic panels
Image from reference [2]
References
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[1] P. F. Carcia, R. S. McLean, M. H. Reilly and G. Nunes, "Transparent ZnO thin-film transistor
fabricated by RF magnetron sputtering", Applied Physics Letters, vol.82, no.7, pp. 1117-1119, Feb
2003.
[2] C. Chen, L. Dou, R. Zhu, C. Chung, T. Song, Y. Zheng, S. Hawks, G. Li, P. Weiss, and Y. Yang,
“Visibly transparent polymer solar cells produced by solution processing,” in American Chemical
Society vol. 6 no.8, 2012, pp. 7185-7190.
[3] R. L. Hoffman, B. J. Norris and J. F. Wager, "ZnO-based transparent thin-film transistors", Applied
Physics Letters, vol.82, no.5, pp. 733-735, Feb 2003.
[4] S. Hong, “DC-DC Converters using Indium Gallium Zinc Oxide thin film transistors for mobile
display applications,” in Japanese Journal of Applied Physics, 2010.
[5] D. Keszler, R. Presley and J. Wager, Transparent Electronics. New York, USA: Springer, 2008.
[6] S. Kuk, S. Lee, S. Kim, B. Kim, S. Park, J. Kwon, and M. Han, “Light-induced hysteresis of In–
Ga–Zn–O thin-film transistors with various temperatures,” in IEEE Electron Device Letters vol. 33 no.
9, 2012, pp. 1279-1281.
[7] S. Lee, S. Kim, Y. Lee, W. Lee, K. Yoon, J. Kwon, and M. Han, “The effect of the photo-induced
carriers on the reliability of Oxide TFTs under various intensities of light,” in IEEE Electron Device
Letters vol. 33 no. 2, 2012, pp. 218-220.
[8] S. Masuda, K. Kitamura, Y. Okumura, S. Miyatake, H. Tabata and T. Kawai, "Transparent thin film
transistors using ZnO as an active channel layer and their electrical properties", Journal of Applied
Physics, vol.93, no.3, pp. 1624-1630, Feb 2003.
[9] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, “Room-temperature
fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors,” in
Nature vol. 432, 2004, pp.488–492.
[10] M. Rashid, “DC DC Converters,” in Power Electronics Handbook. San Diego, USA: Academic
Press, 2001, pp. 211-224.