I am designing a 3-phase inverter board for BLDC Motor control. The H-bridges i use are IFX007 from Infineon. The mentioned IC has the possibility to adjust the slew rate.
From what i have read, i've understood that higher slew rates result in a more "perfect square wave" shape which in return gives rise to more high frequency components (Fourier Analysis).
Those extra high frequency components lead to EMI ( Electromagnetic Interference).
I plan to control the H-bridges with 20 KHz PWM (suitable range for Field Oriented Control). The problem is, if i limit the slew rate and make it as small as possible, the valid duty cycle with 20kHz drops to between 20 % and 80 % due to the rise time. (the rise time consumes nearly % 30 of a whole duty cycle).
On the other hand, i can just increase the slew rate and make the rise time way faster, having a larger range of duty cycle(which i would love to have) as a result but higher EMI.
My question/dilemma is: Would increasing the slew rate with the flowing specifications be ok:
- 14 V Power supply feeding the motor
- The motor wont draw more than 5 amps in any case
- the H-bridges switching at 20kHz
- no wireless component or delicate analog circuitry that would be 'victimized' by the EMI. (only the MCU will be stacked on the far side of my pcb.)