Reviewing a legacy product with UC2625-EP.
New to motor control and currently have no hardware to verify the following which is why I am requesting verification of the interpretation of Data Sheet and U-115 app note.
BLDC Motor running 100% duty cycle( No PWM switching) using just Hall Sensors for commutation, 120degree Hall Sensor
Referencing the standard 6 step commutation model with 2 electrical cycle per 1 mechanical cycle
motor rpm =16K (61.5uS/ rotation), 1 electrical cycle = 31.25uS, 6.25uS per each of the six commutation periods
When driven the Power switches are on for two consecutive commutation periods, with appropriate sequencing, in this case, for a period of 12.5uS.
Q1) Are the above relationships correct?
One of the Power Switch is on for two commutation steps while while 2 Power Switches will change state over that time period, standard six step model.
The RC oscillator is set to 181KHZ (nominal, tolerances excluded for this example), clk period = 5.52uS => dead time period, Controller injects 1-2 clk period results in a dead time of 5.52uS up to 10.5uS
Q2) Is the following correct?
Two commutation period = dead time + Power Switch on time
Power Switch on period = 12.5uS - (n*5.25us) with n=1 or 2 results in a Power Switch on period ranging from 7.25uS to low of 2uS.
Q3) What Power Switch(s) is the dead time applied too; 1) both transiting devices or 2) just delay the Power Switch turning on?
