– 74 –
6. Rotor Magnetic Pole Position Detection Circuit
(_
£ £ £ £
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0
0 0
0
0
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0
0 0
0 0
0
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0 0
0
0 0
0
0
0
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0
0 0
0
0
0
0
0
0
0
0
0
0
0
0
0
+
-
+
-
+
-
A
B
C
D
)
(_
HIC
R101
R102
R103
C104
C105
C106
C103
C102
C101
R106
R105
R104
63
61
60
62
59
58
57
Outdoor
microcomputer
_
5V
0V
+ 12V
+
zzz
+
zzz
+
zzz
+
z zz
+
z zz
+
z zz
4
3
Voltage at point
C
Voltage at point
D
0.6V
Voltage at point
B
B- transis-
tor ON
C- transis-
tor ON
B
+
transis-
tor ON
C
+
transis-
tor ON
Voltage at point
A
about 230V
Fig. 6 - 1 Rotor magnetic pole position detection circuit and voltage waveform at each part
●
Motor-induced voltage signal (voltage at point
A
) is phase-shifted by 90
°
by passing lowpass filter
consisting of R101, R104 and C101 to make triangular wave (voltage at point
B
). In HIC, 3 phases of
this triangular wave are synthesized to produce composite wave (voltage at point
C
). This composite
wave becomes a triangular wave with period of 1/3 times compared with original triangular wave.
●
Voltages at points
B
and
C
are compared by comparator to make voltage at point
D
.
Voltage at point
D
is taken into microcomputer and timing of switching from V– transistor to W– transistor
is made by rising waveform, and timing of switching from V+ transistor to W+ transistor is made by failling
waveform.
●
For other 2 phases (V phase and W phase), the operation is the same and phases are shifted by 120
°
and 240
°
respectively compared with U phase waveform.
