Chapter 1 Device Overview MC9S12ZVMB-FamilyMC9S12ZVMB Family Reference Manual Rev. 1.3NXP Semiconductors 61Figure 1-8. DC brushed motor external configurationUsually the control consists of an outer, speed control loop with inner current (torque) control loop. Theinner loop controls DC voltage applied onto the motor winding. The control loop is calculated regularlywithin a given period. In most cases, this period matches the PWM reload period.Driving the DC motor from a DC voltage source, the motor can work in all four quadrants. Thecomplementary mode of operation with deadtime insertion is needed for smooth reversal of the motorcurrent (motor torque), hence smooth full four quadrant control. Usually the center-aligned PWM ischosen to lower electromagnetic emissions.The PWM frequency selection is always a compromise between audible noise, electromagnetic emissions,current ripples and power switching losses.The BDCM control loop goal is to provide a controlled DC voltage to the motor winding, whereby it iscontrolled cycle-by-cycle using a speed, current or torque feedback loop.The center aligned PWM waveforms generated by the PMF module are applied to the bridge as shown inFigure 1-9 whereby the base waveform for PWM0 and PWM1 is depicted at the top and thecomplementary PWM0 and PWM1 waveforms are shown with deadtime insertion depicted by the grayphases before the rising edges.Figure 1-9. BDCM complementary mode waveformPWM0PWM2PWM3PWM1+ 1/2 U- 1/2 UA BPWM0PWM1PWM2PWM3TPWMPWM0, PWM1 base PWM2, PWM3 base
