Application examples

AN308

10/16

2.3

Pulse-train triggering circuit

The schematic in Figure 11 shows a typical circuit for welding equipment. Potentiometer P2

is used for accurate control of the maximum turn-on delay. DB1 diode bridge and R6-R7

resistors are used to discharge C1 at each line zero voltage. This resets the voltage charge

at each new half line cycle, and keeps the same turn-on delay.

The Transil reduces power dissipation through both potentiometers.

Figure 11.

Power variation circuit for arc welding transformer

AC Mains

C1

100n

ignition

Arc

220 - 45V

Transformer

2300 VA

1k

R2

27K

R3

150K

R4

P1

220K

P2

1M

10K 7W

R8

10K

R5

R7

27k 1W

27K 1W

R6

DB3

BTA40 -600B

220 1/2W

R1

C2

100nF 400V

Z0103MA

1.5KE68A

-

+

DB2

DB1