ICC03-400B2 Datasheet, PDF (5/7 Pages) STMicroelectronics – IGNITION CONTROL CIRCUIT

BASIC APPLICATION
ICC03-400B2
STOP BUTTON
1
SUPPLY
CO IL
D1
8
L1
D3
N
Ic
D2
4
ICC03
C1
6
7
Ig
TH
Ic
D4
3
t
IGNITION
COIL
PR _SE
P
FLY-WHEEL
SENS OR
COIL
R
Vs
Vs
+
C2
_
t
SPARK
PLUG
see functional diagram page 1
The applications using the capacitive ignition
system (CDI) operate in 3 phases.
PHASE 1
Storage of the energy in the capacitor C1
PHASE 2
Discharge of the capacitor C1 and spark
generationto the ignition coil.
PHASE 3
Engine stop.
1) ENERGY STORAGE IN C1
The coil L1 generates an alternative voltage. Its
positive part charges the capacitor C1 through the
diode D2.
The negative waves are clamped by the diode D3.
2) SPARK GENERATION
For each fly-wheel revolution the sensor coil
produces a bidirectional pulse Vs and triggers the
ignition coil.
The negative sinewave generated is clamped by
D4 while the positive sinewave initiates a current
IG through the thyristor gate (Th)
The firing of the SCR causes an alternating
discharge current Ic through the capacitor C1.
The positive parts of this current flow in the loop
C1, Th and the primary of the ignition coil PR.
The negative parts flow through C1, PR and both
diodes D3 and D2.
3) ENGINE STOP
The engine stop is obtained by short circuiting the
supply coil L1 (stop button). The diode D1 avoids
the accidental connection of battery voltage.
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