Hitachi RAS-25CNH2 - Rotor Magnetic Pole Position Detection Circuit

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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.