Maintaining current flow through solar cells with open connection using shunting diod

Shattuck, R. D.

English

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
REPLY TO 
ATTN OF: GP 
MEMORANDUM 
ril 5, 197 
0 :  KSI/Scientific & Technical Information Division 
A t t n :  M i s s  Winnie M, Morgan 
FROM : GP/Office of A s s i s t a n t  General 
Counsel f o r  Patent Matters 
SUBJECT : Announcement of NASA-Owned 
U.S. Patents i n  STAR 
I n  accordance with t h e  procedures contained i n  t h e  Code G P  
t o  Code U S 1  memorandum on t h i s  subjec t ,  dated June 8, 1970, 
t h e  at tached NASA-owned U.S. patent is being forwarded fo r  
abs t r ac t ing  and announcement i n  NASA STAR. 
The following information is provided: 
U . S ,  Patent  No.  
Corporate Source e w i s  Researc 
Supplementary 
Corporate Source 
NASA Patent C a s e  No. :  E004535 
Gayle Parker 
Enclosure : 
copy of Patent 
u- 
. 
https://ntrs.nasa.gov/search.jsp?R=19710013878 2020-03-17T03:04:00+00:00Z
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April 8, 1969 R. D. SHATTUCK 3,437,8 18 
P R O T E C T I O N  OF SERIALLY CONNECTED SOLAR C E L L S  AGAINST 
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INVENTOR 
RUSSELL D. SHATTUCK 
3,431,818 tates Patent Office Patented Apr. 8, 196g 
1 
3,437,818 
PROTECTION OF SERIALLY CONNECTED SOLAR 
CELLS AGAINST OPEN CIRCUITS BY THE USE 
OF SHUNTING DIODE 
Russell D. Shattuck, Bay Village, Ohio, assignor to 
the United States of America as represented by the 
Administrator of the National Aeronautics and 
Space Administration 
5 
Filed Oct. 19, 1966, Ser. No. 588,671 
U.S. CI. 250-212 5 Claims Int. CI. HOlj 39/12 10 
ABSTRACT OF THE DISCLOSURE 
Maintaining current flow through an array of serially 
connected solar cells even though the array has some 
open connections. All junctions are shunted by at least 
one protecting diode, and each connection has at least 
one completely redundant shunting diode. 
The invention described herein was made by an em- 
ployee of the United States Government and may be 
manufactured and used by or for the Government for 
governmental purposes without the payment of any 
royalties thereon or therefor. 
This invention relates to an improved serial COM~C- 
tion for solar cells in an array. The invention is par- 
ticularly concerned with maintaining current flow through 
the solar cells even though some open connections are 
in the array. 
A power supply for equipment which is used in space 
frequently utilizes an array in which a number of solar 
cells are connected in series. Such an array presents a 
problem of open connections occurring between some of 
the cells. 
Some protection may be obtained by connecting a 
diode across a cell-to-cell connection. The diode pro- 
vides an alternate path for culrent flow to insure the 
operation of the series string when an open connection 
occurs between the cells. The difficulty resulting from 
such a connection is that because the most common solar 
cell failure is a contact break the protecting diode 
contacts may open at the same time a cell-to-cell con- 
tact fails. 
These problems and difficulties have been solved by 
the present invention In which the diodes are staggered 
in such a manner that each diode is protecting more 
than one solair cell junction. This  is accomplished by 
having each diade connected as a shunt across two, 
three, or more cells. In this manner every connection 
is shunted by at least one protecting diode, and the num- 
ber of protecting diodes per solar cell connection may 
be increased. The number of protecting diodes is limited 
only by the magnitude of the allowable output degrada- 
tion in the system because the failure of any one series 
cell connection would lead to a loss of output from all 
the cells being shunted by the particular diode involved. 
It is, therefore, an object of the present invention to 
provide a solar cell array having improved electrical 
connections which maintain current flow even though 
some of the electrical contacts are broken. 
Another object of the invention is to provide improved 
connections through, which current flaw is maintained 
in a series string of solar cells with a minimum loss of 
power where there are open connections between some 
of the cells in the series. 
Still another object of the invention is to provide a 
solar cell array in which every connection between the 
cells is shunted by at least one protecting diode. 
These and other objects of the invention will be ap- 
15 
20 
25 
2 
parent from the specification which follows and from 
the drawing in which ligke numerals are used throughout 
to identify like parts. 
In the drawing: 
FIG. 1 is a plan view of an array of solar cells con- 
nected in accordance with the present invention. 
FIG. 2 is an elevation view of the array shown in 
FIG. 1. 
(Referring now to the drawing, there is shown in FIGS. 
1 and 2 a group of solar cells 10-27 which may be of 
the P on N type. Each cell as a grid 30 which is secured 
to one of its faces. The grid 30 terminates at a P con- 
tact 32 across one end as best seen in FIG. 2. An N 
contact 34 covers the entire surface of each solar cell 
opposite the grid 36. 
The cells 10-27 are mounted in a straight line array 
by placing each P contact 32 in engagement with the N 
contact 34 of an adjacent cell and soldering the resulting 
joint. ;In this manner the cells 1047 are connected in 
series at junctions 4W56 rsespectively. The array is used 
to supply current to a load 86' such as a battery which is 
charged by the array. 
,An open connection between any adjacent cells 60-27 
at a junction 40-56 of the P and N contacts prevents 
passage of current directly through the array shown in 
FICGS. 1 and 2 because the cells are connected in series. 
If a diode is connected across each cell-to-cell connec- 
tion the series strip is maintained in operation at a re- 
duced power level because the diode provides an alternate 
30- path for the current. However, the protecting diode may 
35 
40 
45 
50 
65 
60 
65 
70 
not operate in its intended fashion because $he most 
common solar cell failure is a contact failure, and the 
protecting diode contact fails at the same time the: cell- 
to-cell contact is broken. By way of illustration, a diode 
connected between junctions 43 and 44 would form a 
shunt around the solar cell 14. A break in either of these 
junctions would probably cause an interruption in this 
shunt. This is likewise true far any diode that forms a 
shunt between adjacent junctions around one of the solar 
cells in the array. 
According to the present invention, diodes 6b69 are 
used to protect the junctions 40-56. As seen in FIG. 1, 
each diode protects more than one junction. By way of 
example, the diode '60 forms a shunt across the junctions 
40 and 44. An open connection at any or all of junctions 
41, 42 and 43 woulid cause current to flow through the 
diode 601 between the solar cells 10 and 15. 
In a like manner, the diode 64 protects junctions 47, 
48, 49 and 50 because an open connection at any af 
these junctions causes current to flow through thss diode. 
The diode 68 forms a shunt between the junction 53 and 
the P contact 32 at the end of the strip. 
As shown in FIG. 1 all the junctions 40 to 56 are 
shunted by at least one protecting diode. There is no cell- 
to-cell connection which does not have at least one com- 
pletely redundant shunting diode, and some junctions have 
two spares. For example, an open connection at junction 
43 would cause current to flow through diodes 60, 61 and 
62. In a similar manner, an open connection at junction 
54 would cause current to flow through diodes 66, 67 and 
68. The diode 69 is connected between junctions 47 and 50 
to form a second shunt with diode 64 for protecting the 
center junctions 48 and 49. 
While a preferred embodiment of the invention has 
been shown and described, it will be appreciated that 
various modifications may be made to the disclosed strud 
ture without departing from the spirit of the invention or 
the scope of the subjoined claims. For example, the im- 
proved connection can be used with a number of different 
types of solar cells as well as semiconductors where reli- 
ability is of paramount consideration. 
3,437,818 
with a plurality of solar cells elec- 
trically connected in series at junctions between adjacent 
cells, the improvement comprising 
a plurality of diodes for protecting the solar cells 
against open connections at the junctions, and 
means for connecting each of said diodes as a shunt 
across at least two of the junctions between the cells 
thereby enabling current to flow through said diodes 
around an open connection at said two junctions. 
2. Apparatus as claimed in claim 1 wherein the diodes 
are connected to the junctions in an overlapping manner 
so that each cell i s  protected by at least two diodes. 
3. A space electrical power source comprising 
a plurality of solar cells, each having a grid secured 
to one of its faces terminating at a first contact across 
one end thereof and a second contact on the other 
face, 
said solar cells being mounted in a straight line array 
with each of said first contacts being in engagement 
with the second contact of an adjacent cell thereby 
forming a plurality of junctions between said solar 
cells, 
6 
10 
16 
20 
means for forming a shunt around each of said junc- 
tions SO that an open connection at said junction 
causes current to 11.0~ through said shunt thereby 
maintaining current flow through said array, and 
a diode mounted in each of said shunts to prevent 
current flowing in the opposite direction through said 
junction. 
4. A space power source as claimed in claim 3 where- 
in each diode shunts at least two junctions. 
5. A space power source as claimed in claim 4 wherein 
the shunts are connected in an overlapping manner so that 
each cell is shunted by at least two diodes. 
References Cited 
UNITED STATES PATENTS 
3,310,679 3/1967 Babish _-_-..___-____ 250-209 
RALPH 0. NILSON, Primary Examiner. 
MARTIN ABRAMSON, Assistant Examiner. 
250-211 
U.S. C1. X.R. 


Protection of serially connected solar cells against open circuits by the use of shunting diode Patent

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