DC/DC Converters with transparent electronics for application on photovoltaic

panels

Romano Torres9th January 2013

DC/DC ConvertersTo 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

Capacitors

Resistors

Images from reference [5]

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 gallium-indium-zinc-oxide) [9].

TTFT device structure

Staggered bottom-gateImage from reference [10]

TFT operation modes

Pre-saturation: Vgs>Vt & Vds<Vgs-Vt

Saturation: Vds>Vgs-Von

Cut-off: Vgs<Vt No current flow.

a-GIZO TFT limitationsp-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]

TransparencyProblems with inductors:

Poor conductance;High parasitic resistance;Low quality factor.

Voltage multipliersDue 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 [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.