dutycycle

[jinbao78]

Posted on April 17, 2008 at 23:35

dutycycle

[jinbao78]

Posted on May 17, 2011 at 10:14

hello everyone,

who can tell me how to output 100% dutycyle when using complementary? I'm using ST7FMC1K2T6, there is always a deadtime when the dutycycle is equal to period value. the period value = 400(40kHz,25uS) deadtime = 250nS(40) the maximum dutycycle is 99%, how to output 100%?

[gianluigi]

Posted on May 17, 2011 at 10:14

Hello jinbao,

to drive BLDC sensorless motor applying 100% of duty cycle you have to use the so called ''sampling method during the Ton''. You can find more details in the attached application note. Best regards Gigi

[jinbao78]

Posted on May 17, 2011 at 10:14

yes,I used, but I still can't get 100% dutycycle.

[jinbao78]

Posted on May 17, 2011 at 10:14

sensorless control, complementary PWM, mixed zero-crossing dectection method, when dudycle value is equal to PWM period value, why there is still pwm, not all high-level. I set the deadtime 250ns. can anybody tell me?

[gianluigi]

Posted on May 17, 2011 at 10:14

Hello Jinbao,

so if you have setup the external resistor to perform the samplig during the Ton like described in the AN, what is also required is to set the peripheral to sample during the Ton. In the GUI there is a list box called ''Z event sampling method'' in the Advanced setting. You can set for instance one of the other setting excluding the first ''at the end of the PWM low state'', then you can set the delay required in the control delay for sampling. Or if you don't use the GUI you can modify manually the MTC_Setting_Sensorless.h file writing properly the #define mem_MCRC remember that bit 3 is SPLG that must be set to 1 for sampling during the Ton. The you can write the #define mem_MCONF bit 7-4 Dsx with the correct value to fix the delay after the Ton (if required) At least you must check that #define Max_Duty is set correctly. For instance for PWM freq of 40kHz must be set to 401. But I suggest to use the GUI. Of course, even setting the bemf sampling during Ton, the PWM is switched off if current limitation (or regulation) will occurs. Best regards Gigi

[jinbao78]

Posted on May 17, 2011 at 10:14

:D thanks, I find the reason and solve it!