Application examples

AN308

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2

Application examples

2.1

Synchronization across the TRIAC

The schematic in Figure 9 is used to set the speed of a low-power induction motor, such as

those which can be found in fan applications.

Capacitors C1, C2 and C4 are used to filter the noise coming from TRIAC commutations. C1

and C4 capacitors have to be from Y2 technology, whereas C2 has to be from X2

technology.

Figure 9.

Speed-control circuit for a small asynchronous motor

Motor

C3

3.3uF

47nF

C5

DB3

1.5K

R1

R2

1M

P1

1M

BTB04-600SL

AC Mains

3.3nF

C1

3.3nF

C4

3.3nF

C2