K8055N PWM frequency

Kits PC Related Projects
1

It seems there is an error in the K8055N documentation velleman.eu/downloads/0/illu … 55n-uk.pdf

On page 11 it states the PWM frequency is fixed at 23.43 KHz, when in fact my P8055N-2 has 46.86 KHz according to my O-scope.

This is probably coming from the original K8055 documentation. The old K8055 had indeed a PWM frequency of 23.43 KHz.

Regards,
Jan

2

Thank you for the feedback.

[quote]On page 11 it states the PWM frequency is fixed at 23.43 KHz, when in fact my P8055N-2 has 46.86 KHz according to my O-scope.[/quote]Indeed, the PWM frequency of the K8055N and VM110N is 46.875kHz.

[quote]This is probably coming from the original K8055 documentation. The old K8055 had indeed a PWM frequency of 23.43 KHz.[/quote]Yes, this seems to be the case.

3

Thanks for confirming.

Note everyone, for most everyday and intended use cases of the K8055(N), this difference in PWM frequency matters little to nothing.

I stumbled across this while experimenting with things about that 5A 12V brushed DC motor control, John Broadley and I were discussing in the other thread. Using a 1N4007 as a flyback diode I noticed a significantly higher power dissipation using a K8055N compared to the K8055.

While it isn’t important for most use cases, for this sort of high power application it does matter as it affects the heat dissipated by the flyback diode.

Regards,
Jan

4

Manuals will be updated asap.
Thanks for reporting.

5

There in the K8055D.DLL v5 is an undocumented function SetPWM to set the PWM frequency.

setpwm11.png715×379

6

Interesting, that looks like the function is setting the timer2 prescaler to 1, 4 or 16.

Regards,
Jan

7

[quote]Interesting, that looks like the function is setting the timer2 prescaler to 1, 4 or 16.[/quote]Yes, exactly.