SBAU485 July   2025

 

  1.   1
  2.   Description
  3.   Applications
  4.   Features
  5.   5
  6. 1Evaluation Module Overview
    1. 1.1 Introduction
    2. 1.2 Kit Contents
    3. 1.3 Specification
    4. 1.4 Device Information
  7. 2Hardware
    1. 2.1 BP-AMC0106-LMG-MD PCB Overview
    2. 2.2 Board Configuration Information
    3. 2.3 Header Information
    4. 2.4 EVM Setup
  8. 3Software
    1. 3.1 Software Description
    2. 3.2 Importing the Project to Code Composer Studio
    3. 3.3 Universal Servo Drive Example Modifications
    4. 3.4 Change PWM Frequency and Dead Time
    5. 3.5 Running the Motor
  9. 4Hardware Design Files
  10. 5Additional Information
    1. 5.1 Trademarks
  11. 6Related Documentation

3.4 Change PWM Frequency and Dead Time

The default PWM switching frequency is 20kHz. This section explains how to modify the PWM frequency and dead time, allowing for further evaluation of the EVM.

BP-AMC0106-LMG-MD File PWM Frequency and dead time Figure 3-3 File PWM Frequency and dead time

To change the PWM frequency, open src_board\user_mtr1.h file and change the macro definition USER_M1_PWM_FREQ_kHz to desired PWM frequency (line 579).

CAUTION:

Note that as the PWM frequency increases, the control loop frequency also needs to be adjusted accordingly. This can be set using the macro definition USER_M1_NUM_PWM_TICKS_PER_ISR_TICK (line 559), which has a default value of 1. This default value means that the control computation cycle is synchronized with the PWM cycle.

Combinations in Table 3-1 have been verified at TI lab.

Table 3-1
PWM Switching Frequency (kHz) USER_M1_NUM_PWM_TICKS_PER_ISR_TICK Value USER_M1_NUM_PWM_TICKS_PER_ISR_TICK Value

15

(15.0f)

(1)

20

(20.0f)

(1)
40

(40.0f)

(1)
60

(60.0f)

(2)
80

(80.0f)

(2)

Dead time configuration is hard-coded in SysConfig tool. The default value is 10 which corresponds to 50ns. The default PWM timebase clock TBCLK = EPWMCLK = 200MHz, and the dead time is calculated as:

Equation 1. F a l l i n g   e d g e   d e l a y = [ value ] × ( 1 / EPWMCLK ) = 10 × ( 1 / 200 MHz ) = 50 n s
Equation 2. R i s i n g   e d g e   d e l a y = [ value ] × ( 1 / EPWMCLK ) = 10 × ( 1 / 200 MHz ) = 50 ns

Figure 3-4 shows SysConfig variables that allow dead time adjustment.

BP-AMC0106-LMG-MD PWM Dead Time Adjustment in SysConfig Tool Figure 3-4 PWM Dead Time Adjustment in SysConfig Tool