AN308

Application examples

9/16

2.2

Synchronization by the mains voltage

The schematic in Figure 10 shows a step-down circuit used to approximately divide by two

the rms voltage between the line input and the inductive load (L1). C2 and R3 provide a

turn-on delay of approximately 7 ms.

The diode bridge, with diodes D1 and D2 and R2 resistor are used to discharge C2 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 the power dissipation through R3.

Figure 10.

220/110 V step-down circuit

L1

1

2

DB1

AC Mains

BTA06 -600B

DB3

C1

100n

R1

100

200K

R3

15K/4W

R5

12K 2W

R2

1N4004

D1

1N4004

D2

1.5KE68A1

L1

1

2

DB1

AC Mains

BTA06 -600B

DB3

C1

C2

47 n

100n

R1

100

200K

R3

15K/4W

R5

12K 2W

R2

1N4004

D1

1N4004

D2

1.5KE68A1