To control by PWM requires 2 factors:

1-crossing detection signal by 0.

2-? determine the time, every time you walk by 0.

to detect the zero crossing can be performed
through an operational amplifier connected
comparator.

TCA = 785

Pin Symbol Function

1 GND Earth

2 Q2 *Output 2 Inverted

3 Output U QU

4 Q1 * Output 1 Inverted

5 5Synchronizing voltage Vsync (to detect

zero crossing)

6 Inhibitor

7 QZ Z Output

8 8 Vref voltage stabilized (continuous signal for the

integrator)

9 9 ramp resistor R9 (for the integrator)

10 C10 ramp Capacitance (for the integrator)

11 11 V11 Control Voltage (for comparator)

12 12 C12 pulse Extension

13 LLong pulse

14 Q1 Output 1

15 Q2 Output 2

16 l sSupply voltage.