SPRUJB6B November 2024 – May 2025 AM2612
The example given in Figure 7-287 assumes a static or constant phase relationship between legs (modules). In such a case, control is achieved by modulating the duty cycle. It is also possible to dynamically change the phase value on a cycle-by-cycle basis. This feature lends to controlling a class of power topologies known as phase-shifted full bridge, or zero voltage switched full bridge. Here the controlled parameter is not duty cycle (this is kept constant at approximately 50 percent); instead it is the phase relationship between legs. Such a system can be implemented by allocating the resources of two PWM modules to control a single power stage, which in turn requires control of four switching elements. Figure 7-288 shows a sync source and sync receiver module combination synchronized together to control a full H-bridge. In this case, both sync source and sync receiver modules are required to switch at the same PWM frequency. The phase is controlled by using the sync receiver phase register (TBPHS). The sync source phase register is not used and therefore can be initialized to zero.
Figure 7-287 Control
of Full-H Bridge Stage (FPWM2 = FPWM1)
Figure 7-288 ZVS Full-H Bridge Waveforms