Sidac
Data Sheets
(a) Circuit
VBO
R
SIDAC
VDC(IN)
≥
VB0
VC
t
RL
IL
VC
(b) Waveforms
C
IL
Rmax
≤
Rmin
≥
V
-V
IN
BO
IBO
t
VIN - VTM
IH (MIN)
Figure E9.15 Relaxation Oscillator Using a Sidac
V
CE
Monitor
(See Note B)
R
BB1
=
150
Ω
TIP-47
100 mH
Input
Voltage
0V
5V
Collector
Current
0.63 A
0
t
w
≈
3 ms
(See Note A)
t
w
100 ms
Input
50
Ω
2N6127
(or equivalent)
50
Ω
R
BB2
=
100
Ω
+ V
BB2
=0
+
V
CC
= 20 V
-
R
S
= 0.1
Ω
I
C
Monitor
Sidac V
BO
Collector
Voltage
10 V
V
CE(sat)
V
BB1
=10 V
-
Test Circuit
Voltage and Current Waveforms
Note A: Input pulse width is increased until I
CM
= 0.63 A.
Note B: Sidac (or Diac or series of Diacs) chosen so that V
BO
is just below V
CEO
rating of transistor to be protected.
The Sidac (or Diac) eliminates a reverse breakdown of the transistor in inductive switching circuits where otherwise the
transistor could be destroyed.
Figure E9.16 Sidac Added to Protect Transistor for Typical Transistor Inductive Load Switching Requirements
Ballast
H.V.
Step-up
Transformer
0.1 – 0.15 µF
220 V / 240 V
50 / 60 Hz
K2401F1
5 – 6µH
Metal
Halide
Lamp
0.22 – 0.33µF
5.6K – 8.2K
5W
Figure E9.17 Typical Metal Halide Ignitor Circuit
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E9 - 6
©2004 Littelfuse, Inc.
Thyristor Product Catalog
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