TB6588FG

2008-4-25

9

9.

Lead Angle Control

The TB6588FG runs in forced commutation mode with a lead angle of 0° at startup. After switching to

normal commutation mode, the lead angle is automatically changed to the value set by the LA1 and LA2

pins.

10. Overlapping Commutation Control

When SEL_LAP

= High, the TB6588FG runs in 120° commutation mode; When SEL_LAP = Low, it runs in

overlapping commutation mode. In overlapping commutation mode, there occurs an overlapping period due

to the lengthened commutation time between the zero cross point and the 120

° commutation timing upon

PWM signal switching as shown in the shaded areas. These periods vary depending on the lead angle

setting.

(3) Lead angle of 15°

W

Induced voltage

PWM signal

(1) Lead angle of 0°

U

V

W

(2) Lead angle of 7.5°

U

V

U

V

W

UV

W

30°

22.5°

15°

(4) Lead angle of 30°

U

V

W

0°

(3) Lead angle of 15°

W

Induced voltage

PWM signal

(1) Lead angle of 0°

U

V

W

(2) Lead angle of 7.5°

U

V

U

V

W

UV

W

30°

22.5°

15°

(4) Lead angle of 30°

U

V

W

0°