Functional description
UM0922
10/23
Doc ID 17259 Rev 1
6 Functional
description
The driving of the motor is based on phase-angle control.
Figure 4.
Phase-angle control
The MCU operation is synchronized with the voltage mains thanks to the zero-voltage
switching (ZVS) signal. This signal is sent directly to an MCU input pin, which is set as
external interrupt.
The Triac is turned on by sending a pulse to the Triac gate. The Triac turns off when the
voltage mains crosses 0 V.
The firing angle determines the power delivered to the motor; the lower the angle, the higher
the power.
Firing angle and gate pulse length are defined by software. At a mains frequency of 50 Hz,
the demonstration board has a firing angle ranging between 2.5 ms and 8.5 ms, and a
constant gate pulse length of 1 ms.
