S_a

S_b

V_A

V_B

V_AB

工作状态

P

P

+E/2

+E/2

0

1

P

N

+E/2

-E/2

+E

2

O

P

0

+E/2

-E/2

3

O

N

0

-E/2

+E/2

4

N

P

-E/2

+E/2

-E

5

N

N

-E/2

-E/2

0

6