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Solar Cell Bypass and String Blocking Diode Development


TECHNOLOGY AREA(S): Space Platforms 

OBJECTIVE: Develop space solar cell bypass and solar cell string blocking diodes for next generation of cell and array technologies. 

DESCRIPTION: Advancements in spacecraft solar array technologies are impacting the ability to use conventional discrete diodes for cell bypass protection and string blocking diodes. For example, the move to larger solar cells (>30cm2) and the development of flex blankets means that bypass diodes may experience temperatures beyond which they were designed to reliably operate. In addition, these diodes are likely to experience significantly higher radiation environments when incorporated into flex blankets. As always, low-cost and ease of integration are important considerations. State of the art blocking diodes are axial lead type that are connected to the electrical system via a diode board on the rear of the rigid solar array. These blocking diodes are not rated to the temperatures typically seen in spacecraft operation. In addition, they are mechanically large, thus cannot be easily integrated into rolled or z-folded flexible array blankets. Ideally, a new blocking diode will be suitable for incorporation at the end of the string of cells, thereby avoiding the need for excessive array wiring and separate diode boards, be in a flat format (i.e. flat pack) to permit simplified integration in flexible array blankets and be tested and qualified for the temperatures, radiation environments and voltages (>150V) expected on future solar arrays. The solar array diodes should be capable of operation in a Low Earth Orbit (LEO) for 5 years and in a Geosynchronous Earth Orbit (GEO) or Medium Earth Orbit (MEO) for 15 years after storage on the ground for 5 years. 

PHASE I: Perform preliminary analysis and conduct trade studies to determine possible alternate bypass or blocking diode technologies and/or packaging. Perform initial experiments to reduce risk or select from several potential approaches. 

PHASE II: Fabricate and test new diode hardware in simulated operational environments appropriate for a wide range of satellite missions (LEO, MEO, HEO). 

PHASE III: Technology developed will be applicable to all military and commercial space platforms and suitable for inclusion in solar array qualification activities (AIAA S-111 and S-112). 


1: Hiroyuki Toyota, Mitsuru Imaizumi, Hironori Maejima and Hajime Hayakawa, Behavior of silicon bypass diodes in proton and high temperature environments for Mercury probe MMO, Proc. 42nd IEEE Photovoltaic Specialist Conference (2015)

2:  T. W. Woike

3:  S. C. Stotlar

4:  L. Woods, The bypass diode assembly: solar cell protection for Space Station Freedom, Proc. IEEE Photovoltaic Specialists Conference, pp.1288 - 1293 (1990)

5:  R. L. Mueller

6:  D. R. Burger, Solar array passive functional tests, Proc. 25th IEEE Photovoltaic Specialists Conference, pp. 313 – 316 (1996)

7:  Standard: Qualification and Quality Requirements for Space Solar Cells (AIAA S-111A-2014)

KEYWORDS: Satellite, Power, Solar Array, Bypass Diode, Blocking Diode 


jaqueline Cromer 

(505) 846-3962 

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