10.3 LED System Reliability
223
P(X k = 0) = exp{Q(t)} =
∞
k=0
(Q(t)
f (t) + I )
k (t)
k
k!
e
−(t)
(10.22)
where Q(t) = Q f (t),(t) =
t
0 f (s)ds, Q is the transition-strength matrix, A is a
matrix exponent in the exp{A}.
10.3.2 The Cases of Reliability Analysis in the LED Lighting
System
Case one
A simple LED lighting system includes a circuit board, three LED devices which
are soldered on it and a common drive power. By analyzing the failure modes and
interaction effects, the potential system failures mainly includes the following three
aspects.
The failure of light source: considering the aging and mutagenic failure, it causes
the luminous efficiency output less than 70% of the initial luminous efficiency; the
welding points: the welding points are out of order; the drive failure: the drive failure
is represented by aluminum electrolytic capacitor.
Figure 10.12 shows the three LED failure trees diagram of the semiconductor
lighting system. It has four main failure modes, including the LED aging, the LED
abrupt failure, the solder failure, and the drive failure.
Fig. 10.12 The three LED failure trees of the semiconductor lighting system