AN303

Application examples

Doc ID 3654 Rev 3

3/13

1.2

Example 2: inductive load control

In Figure 3 the impact of the gate pulse width on the TRIAC conduction is shown.

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In continuous lines: A short gate signal (T1) is applied. The TRIAC doesn’t remain in

before the gate current removal.

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In dotted lines: A longer gate signal (T2) is applied. In this case, the TRIAC turns on

and remains in the on state. The TRIAC turns off when the load current reaches zero

after the gate current removal.

Figure 3.

Control of an alternating current (AC) motor

For correct operation a gate current has to be applied until the load current reaches the

TRIAC latching current. The control mode shown in Figure 3 is a square pulse.

Another TRIAC control mode is to apply a gate pulse train. Application note AN308 offers

some TRIAC control circuits specially designed to work with inductive loads.

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