Change PWM frecuency

[juanmas]

Hi! I changed PWM frecuency from 20Khz to 70Khz but the CPU use was very high (about 98%). So I add a counter inside ADC1_IRQHandler before call rda_push_int(); and now the CPU use is 51%.

I ran the motor to 30KRpm and everything was ok, but when I configure the motor to 60KRpm, after two minutes, the D3 mosfet has broken. It's happened two time.

does anybody know why?

thanks!

[linestream-adam]

Juan,

There could be a couple different things going on here.

1. When you added the decimation into ADC1_IRQHandler the KMS tool didn't take that into account when it calculated the gains.

KMS provides a way to do that decimation so that it will account for it correctly in the gain calculations.  The PWM / Fast ISR is used for this purpose.  We've ran up to 80kHz PWM with a divider of 4 successfully on the TWR eval kit.

2. If you are not using the reference hardware make sure that your power device is configured correctly.  When you get into high speeds you are also at high modulations and if the deadtime isn't configured correctly this will destroy your power devices.  See AN5254 for more information.