Sharp AE-X26FR-N Service Manual page 21

5. Compressor digital position detection
5.1. 120° energizing control (digital position detection control)
This control system detects the digital position detection signal and adjusts the rate of acceleration/deceleration accordingly.
The motor's induced voltage waveform is input to the comparator in the form of PWM-switched pulse waveform, and a position detection signal is
generated as a reference voltage equaling 1/2 of 320 VDC. However, since there is no induced voltage waveform when the PWM waveform is OFF,
the microcomputer performs internal processing so that detection is enabled only when it is ON. Based on the detected position signal, actual PWM
waveform output timing is determined. Since it does not use a filter circuit, the detection accuracy is high.
The microcomputer performs internal processing to cancel spike voltage during the regenerative process.
Furthermore, even if the induced voltage is low, position detection is still possible, thus allowing sensor-less operation at low rotation speed in the ini-
tial stage of operation. This reduces the starting current and improves the IPM reliability.
Spike voltage
(cancelled)
Terminal voltage waveform
2 – 17
Reference voltage
(1/2 of DC voltage)
Comparator output waveform
(Position signal waveform)
AYXP26FRN