- 0, if the input value is smaller than the counter

output

- 1, if the input value is equal or greater than the

counter output

The comparator output is "adjusted" with a com-

binational logic with the 2 low significant bit of the

word to be converted in order to reach a 10 bit

precision.

The comparator output duty cycle is extended

with a half fsys period for every low bit step how

is showed in the figure 11.

Phase Shift Block

This block regulates the phase of the driving sig-

nal to control the dephasing between the Zero-

Cross signal and the voltage sinusoidal output

signal.

It is possible to demonstrate that the maximum

efficiency for the motor driving may be reached

ensuring a particular value PH of dephase be-

tween the Zero-Cross signal and the voltage out-

put signal.

The Phase Shift BLock, starting from the PHS in-

put signal synchronize the wave output with the

Zero-Cross

signal

to

ensure

the

optimum

dephase.

The PHS signal expresses the phase shift

through the duration of its value according to the

following rule:

Table 1.

PHS on

NPhase

Phase Shift (degree)

time

µs (Tsys = 50ns)

decimal

bit

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0

1

2

3

4

5

6

7

00000 000

00000 001

00000 010

00000 011

00000 100

00000 101

00000 110

00000 111

LATCH

1.25

2.50

3.75

5.00

6.25

7.50

8.75

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

8

9

10

11

12

13

14

15

00001 000

00001 001

00001 010

00001 011

00001 100

00001 101

00001 110

00001 111

10

11.25

12.50

13.75

15.00

16.25

17.50

18.75

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

16

17

18

19

20

21

22

23

000010 000

000010 001

000010 010

000010 011

000010 100

000010 101

000010 110

000010 111

20

21.25

22.50

23.75

25.00

26.25

27.50

28.75

.

.

.

.

.

.

.

.

.

.

.

.

16.0

16.2

16.4

16.6

16.8

17.0

17.2

17.4

80

81

82

83

84

85

86

87

001010 000

001010 001

001010 010

001010 011

001010 100

001010 101

001010 110

001010 111

100

101.25

102.50

103.75

105.00

106.25

107.50

108.75

.

.

.

.

.

.

.

.

.

.

.

.

L7203

9/13