SPRUHX5I August 2014 – May 2024 TMS320F28374S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378S , TMS320F28379S
A popular power topology that makes use of phase-offset between modules is shown in Figure 14-71. This system uses three PWM modules, with module 1 configured as the master. To work, the phase relationship between adjacent modules must be F = 120°. This is achieved by setting the slave TBPHS registers 2 and 3 with values of 1/3 and 2/3 of the period value, respectively. For example, if the period register is loaded with a value of 600 counts, then TBPHS (slave 2) = 200 and TBPHS (slave 3) = 400. Both slave modules are synchronized to the master module 1.
This concept can be extended to four or more phases, by setting the TBPHS values appropriately. The following formula gives the TBPHS values for N phases:
Where:
N = number of phases
M = PWM module number
For example, for the 3-phase case (N=3), TBPRD = 600,
TBPHS(3,2) = (600/3) x (2-1) = 200 (that is, Phase value for Slave module 2)
TBPHS(3,3) = 400 (that is, Phase value for Slave module 3)
Figure 14-72 shows the waveforms for the configuration in Figure 14-71.