
– 55 –
6. Rotor Magnetic Pole Position Detection Circuit
A
+12V
–5V
0.6V
+5V
0V
R101
R104
Voltage at point
about 260V-380V
C101
R105
C102
C103
R106
R102
R103
C106
C104
C105
B
C
A
Voltage at point
B
Voltage at point
B- transis-
tor ON
C- transis-
tor ON
B+ transis-
tor ON
C+ transis-
tor ON
C
Voltage at point
Fig. 6 — 1 Rotor magnetic pole position detection circuit and voltage waveform at each part
D
D
Outdoor
microcomputer
20
18
19
●
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.