BASIC APPLICATION

Rs

D

T

s

c

D

Th

Z

R

Ic

AC

MAINS

Ic

t

Sensor

The applications of the FLC02 using the capaci-

tance discharge topology operate in 2 modes :

- Ignition mode : Transistor T is OFF

- Blanking mode : Transistor T is ON

PHASE 1:

The energy coming from the mains is stored into

the capacitorC. For that, the AC voltage is rectified

by the diode Ds.

PHASE 2 :

At the end of the phase 1, the voltage across the

capacitor C reaches the avalanche threshold of

the zener. Then a current flows through the gate of

the thyristor Th which fires.

The firing of the thyristor causes an alternating cur-

rent to flow through the capacitor C.

The positive parts of this current flow through C, Th

and the primary of the HV transformer.

The negativeparts of the current flow through C, D

and the primary of the HV transformer.

RS RESISTOR CALCULATION

The Rs resistor allows, in addition with the capaci-

tor C, to adjust the spark frequency and to limitate

the current from the mains. Its value shall allow

the thyristor Th to fire even in the worst case. In

this borderline case the system must fire with the

lower RMS mains voltage value while the break-

down voltage and current of the FLC are at the

maximum.

The maximum Rs value is equal to :

Rsmax

=

®

FLC02-200D

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