BASIC APPLICATION

Rs

Ds

c

D

Th

Z

R

Ic

AC

MAINS

Ic

t

The

applications

of

the

lighter

using

the

capacitance discharge topology operate in 2

phases :

PHASE 1

The energy coming from the mains is stored into

the capacitor C. 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 reachesthe 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

current to flow through the capacitor C.

The positive parts of this current flow through C, Th

and the primary of the HV transformer.

The negative parts of the current flow through C, D

and the primaty of the HV transformer.

RS RESISTOR CALCULATION

The Rs resistor allows, in addition with the

capacitor 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

breakdown voltage and current of the FLC are at

the maximum.

The maximum Rs value is equal to :

Rsmax

=

∗

* : see fig 1

FLC01-200D

4/7