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TIDA-00961: Asked about difference between HS_gate and Active PWM1

Part Number: TIDA-00961

Hi, i want to ask about the difference between HS_Gate (EPWM2, 3 for GaN switching) and ACTIVE_PWM_duplicate (EPWM4).

According to both schematic and CCS code,

some circuits or code for ZCS are only related to ACTIVE_PWM (EPWM4) such as initCmpssZvs() and PWMISR().

However, the GaN switches are actived by EPWM2&3 which are not synchronized with the ZCD_Comp, ZCD_OUTPUT as i think.

(In my opinion, in the code, zero crossing of inductor currents do not affect in EPWM for GaN switches)

So I wonder what actually Active PWM stands for. Was the 'Active PWM' intended to operate the GaN switch?

Thanks. 

  • During positive half cycle of the AC input voltage one of the GaN FET is active (act as PFC boost GaN switch) and the other one in the same leg act as SyncFET (act as PFC boost diode).

    During negative half cycle of the AC input voltage the same GaN FET pair change their role. The one that was active before will now act as SyncFET and vice versa.

    The same thing happens with the other leg of the GaN FET pair.

    The 3rd leg has regular silicon FET and one of them turn on during the positive half cycle while the other turn on during the negative half cycle of the AC input voltage

    Shamim