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Application Specific Discretes
A.S.D.TM
FLC21 Series
September 2000 - Ed: 5D
LOW POWER
FIRE LIGHTER CIRCUIT
The FLC21 series has been especially developed
for capacitance discharge operation. The main
applications are: fuel ignitors, fuel or gas heaters,
gas ranges, cooker tops, barbecues, water
heaters, HVACs, portable ignitors, insect killers.
Based on ST's ASDTM technology, it provides a
fully integrated function, with high performance
and reliability levels, adapted to severe and hot
temperature environment.
The typical supply of the FLC21 fire lighter circuit is
a DC battery or the AC mains.
Th: Thyristor for the switching operation.
Z: Zener diode to set the igniting threshold voltage.
D: Diode for the reverse conduction.
R: 2 k
resistor.
DESCRIPTION
Z
R
D
Th
pin 3
pin 1
pin 2 not connected
FUNCTIONAL DIAGRAM
TO-92
(Plastic)
s
DEDICATED THYRISTOR STRUCTURE FOR
CAPACITIVE
DISCHARGE
IGNITION
OPERATION
s
HIGH PULSE CURRENT CAPABILITY
I
FRM
= 90A @ tp = 10
S
s
AC OR DC OPERATION CAPABILITY WITH
SUPPLY FROM THE AC MAINS OR A DC
BATTERY
s
FAST TURN-ON OPERATION
s
DESIGNED
FOR
HIGH
AMBIENT
TEMPERATURE (up to 120C)
FEATURES
1
2
3
s
SPACE SAVING THANKS TO MONOLITHIC
FUNCTION INTEGRATION
s
H I G H
R E L I A B I L I T Y
W I T H
P L A N A R
T E C H N O L O G Y
BENEFITS
DEVICE
TYPE
APPLICATION
MODE
FLC21-135A
BATTERY
OPERATION
Ignition
FLC21-65A
100V Mains
Ignition
FLC21 Series
2/6
Symbol
Parameter
Value
Unit
Rth(j-a)
Junction to ambient
150
C/W
THERMAL RESISTANCE
FLC
2
1
135
A
-
FIRE LIGHTER CIRCUIT
CIRCUIT NUMBER:
SCR + diode + Zener + Resistance
ITRM = 90A
PACKAGE A: TO92
135: V
= 135V
65: V
= 65V
RM
RM
ORDERING INFORMATION
Symbol
Parameter
Value
Unit
I
TRM
Repetitive surge peak on state current for thyristor
-30C
Tamb
120C
tp = 10
s
( note 1)
90
A
I
FRM
Repetitive surge peak on state current for diode
-30C
Tamb
120C
dI/dt
Critical rate of rise on state current -30C
Tamb
120C
50
A/
s
Tstg
Tj
Storage junction temperature range
Maximum junction temperature
- 40 to + 150
125
C
Tamb
Operating temperature range
- 30 to + 120
C
T
L
Maximum lead temperature for soldering during 10s
260
C
Note 1 : Test current waveform
ABSOLUTE RATINGS (limiting values)
100ms
10s
FLC21 Series
3/6
Symbol
Parameters
V
RM
Stand-off voltage
V
BO
Breakover voltage
V
T
On-state voltage
V
F
Diode forward voltage drop
I
BO
Breakover current
I
RM
Leakage current
T
Temperature coefficient for V
BO
ELECTRICAL CHARACTERISTICS
I
I
F
VF
V
T
IRM
I BO
I T
V
V
BO
V
RM
Symbol
Test Conditions
Value
Unit
V
F
I
F
= 1A
tp
500s
Tj = 25C
Max.
1.7
V
DIODE (D) PARAMETER
Symbol
Test conditions
Value
Unit
FLC21-65A
FLC21-135A
Min.
Typ. Max. Min. Typ. Max.
I
RM
V
RM
= 65V for FLC21-65A
Tj = 25C
1
1
A
V
RM
= 135V for FLC21-135A
Tj = 125C
10
10
A
V
BO
at I
BO
Tj = 25C
70
80
140
160
V
I
BO
at V
BO
Tj = 25C
500
500
A
V
T
I
T
= 2A
tp
500s
Tj = 25C
1.7
1.7
V
T
0.07
0.16
V/C
THYRISTOR (Th) and ZENER (Z) PARAMETERS
-20
0
20
40
60
80
100
0
0.5
1
1.5
2
2.5
Tj (C)
k = I
(Tj) / I
(25C)
BO
BO
Fig. 1: Relative variation of breakover current
versus junction temperature.
FLC21 Series
4/6
Rs
S
1
Ds
c
D
Th
Z
R
Ic
AC
MAINS
Ic
t
Fig. 2: BASIC AC MAINS APPLICATION.
1/ IGNITION MODE
PHASE 1
The AC voltage is rectified by the diode Ds.
The ignition energy is supplied by the mains
and stored into the capacitor C.
S
1
c
D
Th
Z
R
Ic
Ic
t
Ds
DC/AC
Oscillator
Rs
Fig. 3: BASIC DC APPLICATION.
PHASE 2
At the end of the phase 1, the voltage across the
capacitor C reaches the avalanche threshold of
the Zener diode Z. Then, a current flows through
this Zener diode into the gate of the thyristor Th
which is triggered.
The thyristor turn-on generates an alternating
current through the capacitor C. Its positive parts
flow through the capacitor C, the primary of the HV
transformer and the thyristor Th. Its negative parts
of the current flow through C, D and the primary of
the H.V transformer.
FLC21 Series
5/6
RS RESISTANCE CALCULATION
The Rs resistance allows, in addition with the
capacitance C, the spark frequency to be adjusted
and the current supplied by the mains to be limited.
This resistance allows the thyristor triggering in
any requested cases. In the worst case scenario,
the system must fire when the a.c. line voltage is
minimum while the breakdown voltage V
BO
and
the current I
BO
of the FLC are maximum.
The maximum Rs value is equal to:
Rs
V
V
T
T
k I
AC
BO
amb
BO
max
(
min.
)
[
max .(
.(
))]
.
*
=
-
+
-
2
1
25
* : see fig 1
10
12
15
18
22
27
33
39
47
10
20
30
50
F (Hz)
Rs (k )
Vac=100Vrms, Vbo=75V, Tamb=25C
C=1
F
C=1
F
C=1.5
F
C=1.5
F
C=2.2
F
C=2.7
F
C=3.3
F
FLC21-65A
10
12
15
18
22
27
33
39
47
10
20
30
50
FLC21-135A
Vdc=300V, Vbo=150V, Tamb=25C
F (Hz)
Rs (k )
C=3.3
F
C=2.7
F
C=2.2
F
C=1
F
C=1
F
C=1.5
F
C=1.5
F
Fig. 4: Spark frequency versus Rs and C.
The couple Rs/C can be chosen with the previous
curve. Keep in mind the Rs maximum limit for
which the system would not work when the AC
mains is minimum.
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