AN 5950
Understanding
i
2
Phase
Control Thyristor Datasheets
Application Note
AN5950-1 Sept 2009 LN26885
Authors: Dinesh Chamund, Colin Rout
INTRODUCTION
This note will guide you through the Dynex
i
2
Phase Control Thyristor data sheet format and
explain its contents. For the purpose of
discussion and illustration, Dynex datasheet
for the DCR3030V42 has been chosen and its
contents explained in sequence starting from
the first page.
The
i
2
Phase Control Thyristor datasheet
includes tables and graphs of data regarding
device ratings and characteristics. In order to
use the datasheet properly it is important that
the user has a good understanding of the
information presented in the datasheet. Also
when benchmarking with similar product from
a different supplier, allowance should be
made for any difference in the way the
parameters are defined, specified and
measured. Hopefully this will promote an
efficient and reliable use of the device and
also help the user to make a correct choice of
device for the intended application.
The datasheet is organised in the following
sections:
PART NUMBER
FEATURES
APPLICATIONS
TABLE OF VOLTAGE RATINGS
ORDERING INFORMATION
KEY PARAMETERS/PACKAGE OUTLINE
TABLES OF RATINGS
o
CURRENT RATINGS
o
SURGE RATINGS
o
THERMAL AND MECHANICAL
RATINGS
TABLES OF CHARACTERISTICS
o
DYNAMIC CHARACTERISTICS
o
GATE CHARACTERISTICS
CURVES
PACKAGE DETAILS
PART NUMBER
DCR3030V42
The part numbering scheme for the Dynex i
2
Phase Control Thyristor is as follows:
DCR
3030
V
42
=
Dynex Control Rectifier
=
Headline average current rating (A)
=
Package code
=
Maximum
repetitive
voltage
rating (V)/100
A Dynex datasheet is a controlled document
with a specific document number, issue
number, and date. This information appears
below the device type in the header on the
right hand side of the first page . Dynex
reserves the right to change the data without
notice and so the users are advised to refer to
the latest version by visiting Dynex web site:
http://www.dynexsemi.com
KEY PARAMETERS/PACKAGE OUTLINE
This is a summary of main parameters unique
to the part number. The full description of
these parameters is found with appropriate
test conditions in the main body of the
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AN 5950
datasheet. It is important that when
comparing the key parameters with other
similar product a full description of the
parameters should be considered as
manufacturers often specify different test
conditions.
Fig.1 gives the package outline and its code
(V).
TABLE OF VOLTAGE RATINGS
This table provides the repetitive peak voltage
ratings of the device given under specified
conditions.
Fig. 1 Package outline
FEATURES
The features section provides a list of specific
key attributes of the device design and
technologies.
APPLICATIONS
A few examples of possible application are
indicated here. It should be noted that
inclusion in this section does not imply that
Dynex has fully tested the device under all
application conditions. The suitability of a
device for a given application rests solely with
the user.
V
DRM
, V
RRM
are the peak repetitive voltages in
the (direct) forward and reverse directions.
The rating is for 50Hz half sine waves of
voltage and assumes that the device is
maintained at the maximum rated junction
temperature of 125°C by suitable heatsinking,
if required. V
DRM
& V
RRM
are the voltages that
the device reaches when the leakage currents
I
RDM
&I
RRM
reach their test limits as given in the
datasheet, or the maximum rated voltage
whichever is reached first. The device may
well be capable of reaching a higher voltage
but excessively large leakage currents will
make temperature control difficult and failure
through thermal run-away may occur for all
but the shortest pulses.
As the temperature of the device is reduced,
the natural avalanche voltage of the silicon
wafer reduces. In some cases, at very low
temperatures and at the lower limit of the
tolerance on the silicon specification the full
voltage rating of the device may not be
achieved. Where this is the case, this is
annotated on the datasheet.
Because of transient voltage spikes generated
by switching devices on the supply, thyristors
are usually operated at nominal peak line
voltages of V
DRM
divided by a safety factor of
1.5 to 2.5, depending on the transient
voltages. A low safety factor is used when the
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AN 5950
transients are largely determined, usually in
the case of self commutated converters with
large energy storage elements. If the
transients on the mains supply are unknown
then a safety factor of 2 to 2.5 should be
used.
V
DSM
& V
RSM
are the peak non-repetitive
voltages in the forward and reverse directions
and are the voltages that can be applied
occasionally and non-repetitively and should
not be exceeded under any circumstances.
ORDERING INFORMATION
This specifies the correct part number for
ordering the device, for example:
DCR3030V42 (4200V part)
Other voltage grades can be selected as given
in the table of voltage ratings.
TABLES OF RATINGS
CURRENT RATINGS
very difficult. Even if all manufacturers quoted
at the same case temperature this would still
not resolve the problem because, in reality,
what is really important in the application is
how the device performs on the heatsink.
Some manufacturers quote low values of
thermal resistance junction to case with
correspondingly higher values for thermal
resistance case to heatsink but with similar
thermals junction to heatsink. Therefore their
headline I
T(AV)
at a given case temperature may
be quoted as being higher than competitors’
devices but when rated on the same heatsink
there is no appreciable difference in
performance.
Dynex quotes a headline I
T(AV)
at 60°C case
temperature but gives full de-rating curves for
both half sine and rectangular waves to
enable the user to make direct and
meaningful comparisons.
I
T(RMS)
– RMS current rating
For today’s capsule devices I
T(RMS)
= π. I
T(AV)
/2.
Historically I
T(RMS)
could have been different
because, for single sided devices with a
flexible lead for the load current terminal, the
current carrying capability of the connections
could be less than the capability of the silicon.
For capsule (puk) devices, the cross sectional
area of the electrodes is the same as the
silicon so no allowance needs to be made. The
limitation is now the equipment busbars.
I
T
– Continuous (direct) on-state current
I
T
is the maximum continuous current that the
thyristor can conduct while maintaining the
junction temperature to its maximum rated
value of 125°C. Note that, like I
T(AV)
, this figure
depends upon the stated reference case
temperature.
I
T(AV)
– Mean on-state current
I
T(AV)
is the average value of a half sine wave
current flowing in a thyristor such that the
peak junction temperature is limited to the
rated temperature of 125°C with the case
temperature specified. The average current
rating of the device is related to the thermal
rating of the device package and thus by
equating the power generated within the
device to the power dissipated in the package,
the average current rating can be calculated.
A more thorough analysis of the current rating
derivation is given in the Appendix 1.
There is no industry standard definition for
I
T(AV)
, manufacturers quote I
T(AV)
with case
temperatures of 60°C, 65°C, 70°C and 85°C .
Others quote with respect to a heatsink
temperature of 55°C (see Fig.17 Appendix 1).
Thus direct comparison of headline ratings is
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SURGE RATING
I
TSM
– Surge (non-repetitive) on-state current
I
TSM
is the maximum 10ms half sine wave of
current, following maximum load current ( i.e.
the thyristor junction temperature is at T
j max
)
that the thyristor can conduct without the
device experiencing thermal run-away and the
silicon melting. I
TSM
is determined by the
manufacturer by viewing the forward voltage
characteristic of the thyristor at high currents
and observing the onset of thermal run-away.
Exceeding this limit will damage the device
and the rating should only be used for the
selection of fuses. Because the device is so
hot following the surge current pulse it loses
its ability to block voltage, this rating is for
zero reverse re-applied voltage. Also the
temperature excursion is so high that the
device will fail due to temperature cycling
wear out if this level of current is repeated
several times in the life of the device. In
practice, Dynex derates the surge current limit
of its i
2
thyristors by 10% which means that
the device can survive about 100 occurrences
of the stated current in its life.
I
2
t – for fusing
I
2
t for fusing is
∫
i dt and is calculated for a
2
half sine wave as
I
2TSM
.base width/2
As well as the single 10 ms half sine wave
rating, Dynex gives a graph showing the
ratings for shorter and longer pulses of
current with the corresponding I
2
t values;
figure 11 of the datasheet. These are derived
by calculating the current that gives the same
peak temperature as the 10ms half sine wave
derived from the physical rating of the device.
Again 100 occurrences in the life of the device
are permissible.
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THERMAL AND MECHANICAL RATINGS
R
th(j-c)
– Thermal resistance – junction to case
The thermal resistance enables the
calculation of the temperature rise of the
silicon in the device above the external case
temperature. It has the dimensions of °C/W
or K/W. In other words, if the device is
generating DC power losses P, then the
temperature rise of the junction above the
case temperature is P x R
th(j-c)
. Values of the
thermal resistance are given for double side
cooling and cooling via either the anode or
cathode electrode.
R
th(c-h)
– Thermal resistance – case to heatsink
Of course the reference point for temperature
rise for the user is the ultimate cooling
medium air, water, oil etc. The total thermal
resistance will include the thermal resistance
of the heat sink (fin) to ambient, which is the
user’s design choice and the contact thermal
resistance between the device contact surface
and the heat sink (Fig. 17 Appendix 1). This
resistance depends upon the quality of the
interface and the value quoted is with the
inclusion of a good quality thermally and
electrically conductive compound and with
the joint clamped to the median
recommended force.
T
vj
– Virtual junction temperature
The device junction temperature cannot be
directly measured but is usually calculated
from a measured reference temperature e.g.
case or heat sink using the product of thermal
resistance value and the power dissipation.
Hence it is referred to as the virtual junction
temperature. The maximum value of T
vj
is
limited by the blocking capability of the
device. This is set at 125°C. If this limit is
exceeded then the subsequent reliability of
the device operation cannot be guaranteed.
T
stg
– Storage temperature range
During the storage of the device there are no
application stresses applied (blocking stress,
power losses etc) and hence the storage
temperature range is determined purely by
the withstand capability of the materials used
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