Renesas RA6T2 Application Note page 40

Sensorless vector control for permanent magnetic
synchronous motor - 1shunt current detection
3.1.7.3 Duty adjustment
If the timing as shown in 3.1.7.1 can be secured, the current can be detected by one shunt resistor, but
sufficient time for A / D conversion cannot be secured depending on the PWM duty setting conditions during
operation. Therefore, the current value cannot be obtained correctly. The following two measures are
implemented for the conditions where timing cannot be secured.
(1) When the switching timings of the two phases are close to each other
When the switching timings of the two phases are close to each other and the time for A / D conversion
cannot be secured, the PWM duty is not changed and the phase switching timing to be switched later is
required for A / D conversion. The conversion time is secured by shifting only.
(2) When timing shift is not possible
If the PWM switching timing is delayed as described above, the duty is wide, and if the end of the PWM
carrier cycle is reached, the timing cannot be delayed. In such a case, the modulation factor is close to 1, so
the modulation factor is limited so that the PWM switching timing is at the end of the carrier cycle.
R01AN6840EJ0100 Rev.1.00
May 23, 2023
Carrier cycle
A
U
V
W
U
V'
W
Figure 3-5 Duty adjustment
For Renesas Flexible Motor Control Series
B
expand
shift shift
Page 40 of 73