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TIDA-010210: Microcontroller Selection for 3 phase ANPC with 300Khz PWM

Namita Pawar
Intellectual 680 points
Part Number: TIDA-010210

Tool/software:

Hi,

I am working on the 3 phase ANPC inverter application. Which microcontroller is suitable for this application considering 300kHz PWM and required EPWM channels are 18.

Also if EPWM channels increase to 36 then which is the suitable microcontroller. Please suggest the microcontroller in both the case.

Thanks,

Namita

  • 0
    TI__Expert 3270 points

    Hi Namita, 

    if you follow the configuration implemented in TIDA-010210 by means of logic ports you will need for each phase one low and one high frequency PWM unit. 

    Basically, two PWM units per phase, thus leading to 6 PWM units. 

    As a suggestion, by using the integrated CLB you can avoid to use external logic ports. 

    Related to the PWM unit, since you are switching at 300 kHz, probably it will be better to adopt High resolution PWM unit.

    For example, you can use a TMS320F28P55x which can support up to 12 PWM units. Furthermore, this MCU is having also the CLB which is very useful for this topology. 

    Thanks

    Best REgards

    Riccardo 

  • 0 in reply to Riccardo Ruffo
    Intellectual 680 points

    Hi Riccardo,

    I have few questions.

    1. TIDA-010210 app note for ANPC uses modified outer HF switching method. This scheme seems to be switching in some places unconventionally.  This unconventional restricted switching method can be implemented using 12 PWM channels and logic gates, creating overall 18 PWM signals for ANPC. However as per my analysis it is creating more loss.  There are different switching methods such as full path switching which we want to use. This requires 18 high resolution PWM's without use of any logic gates. If cost is not a concern, can you please suggest any microcontroller which can generate 18 high resolution PWMs?

    2. Another reason we want to avoid CLB because of SW certification need. CLB if I understood correctly, is like a small FPGA, and we need to go for separate software certification for that if we use.

    3.PWM resolution reduces with switching frequency, so we need at least 512/1024 steps. Can you please suggest microcontroller which can provide this resolution at 300kHz switching frequency?

    4. Another point regarding the close loop current monitoring, the microcontroller has to compute the close loop function after reading the current through ADC at around 150Khz sampling frequency and updating the PWM duty cycle within the minimum PWM duty cycle such as 3nS. Please find below example of current vector processing.

    Is my assumption correct? Can you suggest a processor which can handle all above requirements?

    Thanks,

    Namita