DSP 28335 教程 8课件.ppt

DSP24 12 Control Peripherals Module 7 TMS320C28x? MCU Workshop Learning Objectives Pulse Width Modulation (PWM) review Generate a PWM waveform with the Pulse Width Modulator Module (ePWM) Use the Capture Module (eCAP) to measure the width of a waveform Explain the function of Quadrature Encoder Pulse Module (eQEP) What is Pulse Width Modulation? PWM is a scheme to represent a signal as a sequence of pulses fixed carrier frequency fixed pulse amplitude pulse width proportional to instantaneous signal amplitude PWM energy ? original signal energy Why use PWM with Power Switching Devices? Desired output currents or voltages are known Power switching devices are transistors Difficult to control in proportional region Easy to control in saturated region PWM is a digital signal ?? easy for DSP to output ePWM Block Diagram ePWM Time-Base Module ePWM Time-Base Count Modes ePWM Phase Synchronization ePWM Time-Base Module Registers(lab file: EPwm.c) ePWM Time-Base Control RegisterEPwmxRegs.TBCTL ePWM Time-Base Control RegisterEPwmxRegs.TBCTL ePWM Time-Base Status RegisterEPwmxRegs.TBSTS ePWM Compare Module ePWM Compare Event Waveforms ePWM Compare Module Registers(lab file: EPwm.c) ePWM Compare Control RegisterEPwmxRegs.CMPCTL ePWM Action Qualifier Module ePWM Action Qualifier Actionsfor EPWMA and EPWMB ePWM Count Up Asymmetric Waveformwith Independent Modulation on EPWMA / B ePWM Count Up Asymmetric Waveformwith Independent Modulation on EPWMA ePWM Count Up-Down Symmetric Waveformwith Independent Modulation on EPWMA / B ePWM Count Up-Down Symmetric Waveformwith Independent Modulation on EPWMA ePWM Action Qualifier Module Registers(lab file: EPwm.c) ePWM Action Qualifier Control RegisterEPwmxRegs.AQCTLy (y = A or B) ePWM Action Qualifier S/W Force RegisterEPwmxRegs.AQSFRC ePWM Action Qualifier Continuous S/W Force RegisterEPwmxRegs.AQCSFRC Symmetric PWM Computation Example Determine TBPRD and CMPA for 150 kHz, 25% duty symme