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MCB type
Rating (A)
Relative number of LED drivers (%)
B
4
25
B
6
40
B
10
63
B
13
81
B
16
100 (reference)
B
20
125
B
25
156
B
32
200
B
40
250
C
4
42
C
6
63
C
10
104
C
13
135
C
16
170
C
20
208
C
25
260
C
32
340
C
40
415
L, I
16
108
L, I
10
65
G, U, II
16
212
G, U, II
10
127
K, III
16
254
K, III
10
154
The max. recommended amount of drivers in the table above only serves as
guidance. The actual maximum amount in the application may differ; it is dependent
on MCB brand/type and inherent MCB tolerances.
Design-in Guide - Philips Xitanium LED Xtreme SR driver
How to Determine the Number of Drivers on a MCB
The maximum recommended amount of drivers connected to a
Miniature Circuit Breaker (MCB) can be calculated with the help of
the conversion table shown on the left. In this table the stated
amount for a 16A B type MCB is used as reference (100%). The
maximum recommended amount of drivers for different types of
MCB can be calculated by this formula:
Max. amount of drivers = reference x relative number in %
Example:
If the datasheet states a max. amount of 20 drivers on a 16A B type
then for a 13A C type the max. amount is 20 x 135% = 27 drivers.
How to determine the Number of Drivers on a melting fuse
The maximum recommended amount of drivers on a melting fuse is
defined either by the aggregate inrush current or the aggregate
steady-state input current.
The amount of drivers can be calculated, using the specified values in
the datasheet of the maximum input current and inrush current (I
and T
) as well as the melting integral I
width
as specified by the fuse manufacturer.
The melting integral value I
t of the aggregate inrush current must
2
be 50% below the specified melting integral value I
order to prevent melting of the fuse when the drivers are
connected to mains voltage simultaneously. And the aggregate
steady-state input current shall remain below 80% of the fuse
rating to prevent overheating of the fuse.
The following formula can be applied to calculate the I
driver inrush current:
I
t = (I
)
x (0.8 x T
)
2
2
peak
width
Example:
A group of drivers is connected to a 16A gG melting fuse with a
melting integral value of 350A
and width is 53A and 300µs. Steady-state input current is 0.9A per
driver.
Question: what is the recommended maximum amount of drivers in
this group connected to this fuse from inrush current and steady-
state input current perspective?
Answer: the corresponding I
(0.8 x 300 x 10
-6
) = 0.68A
2
s per driver. The aggregate value of the
driver inrush current must remain below 0.5 x 350A
translates in a maximum of √(175A
The corresponding steady-state input current is 16 x 0.9 = 14.4A.
This is above the 80% rating of the 16A fuse. Therefore, the
maximum recommended amount of drivers is (16A x 0.8) /0.9 = 14
drivers.
In this example, the maximum recommended number of drivers is
defined by the steady-state input current.
2
t value of the applied fuse
t of the fuse in
2
t value of the
2
2
s. Specified driver inrush current peak
2
t value of the inrush current is (53)
2
s = 175A
2
s/0.68A
2
s) = 16 drivers.
peak
2
x
2
s. This
21
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