DG-IRMCK203 Datasheet, PDF (62/67 Pages) International Rectifier – Application Developer’s Guide

nSYNC
PwmLoad
PhaseU
PhaseV
PhaseW
PWMUH
PWMUL
PWMVH
PWMVL
PWMWH
PWMWL
IRMCK203 Application Developer’s Guide
Tr
Td
Tpwm
Figure 27. Asymmetrical PWM Mode
Three-Phase and Two-Phase Modulation
Three-phase and two-phase Space Vector PWM modulation options are provided for the IRMCx203. The Volt-sec
generated by the two PWM strategies are identical; however with 2-phase modulation the switching losses can be
reduced significantly, especially when high switching frequency (>10Khz) is employed. Figure 28 shows the
switching pattern for one PWM cycle when the voltage vector is inside sector 1.
3-phase modulation
PhaseU
PhaseV
PhaseW
PhaseU
PhaseV
PhaseW
2-phase modulation
V3
V2
sector 2
sector 3
V4
sector 4
V
sector 1 _V1U-phase
sector 6
sector 5
V5
V6
2 zero vectors V7, V8
Figure 28. Three-Phase and Two-Phase Modulation
The field TwoPhsPwm of the PwmConfig write register group (described in Section 4.2.1) provides selection of three-
phase or two-phase modulation. The default setting is three-phase modulation. Successful operation of two-phase
modulation in the entire speed operating range will depend on hardware configuration. If the gate driver employs a
bootstrap power supply strategy, misoperation will occur at low motor fundamental frequencies (< 2Hz) under two-
phase modulation control.
There are two types of two-phase modulation schemes provided. The field TwoPhsType in the PwmConfig write
register group is used to select the type, as described in Section 4.2.1. Figure 29 illustrates the different types of
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