SLOA338 March   2025 TSD5402-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction TO RESOLVER and LVDT sensors
  5. 2Conventional Excitation Amplifier
  6. 3Excitation Amplifier Using Class-D Amplifiers
  7. 4Class-D Resolver Excitation Design Details
    1. 4.1 Components Selection for the Power Stage
    2. 4.2 Input Filter Components Selection
  8. 5Practical Experiments
    1. 5.1 Test Setup
    2. 5.2 Output Waveforms for Default Conditions
    3. 5.3 Amplifier Transfer Function
    4. 5.4 Using PWM for Generating the Reference Signal
    5. 5.5 Thermal Image and Comparison Against the Linear Design
    6. 5.6 Output Spectrum
    7. 5.7 Total Harmonic Distortion (THD)
    8. 5.8 Fail Events
  9. 6Summary
  10. 7References

5.4 Using PWM for Generating the Reference Signal

In this experiment the arbitrary waveform generator generates a PWM. The PWM signal enters the input RC filter R2, C11. Figure 5-9 shows that the 1st order filter is not able to fully filter out higher harmonic content and the waveform has a lot of ripple. However, the amplifier acts as a low-pass filter. Figure 5-10 shows clean sine-wave on the output of the excitation amplifier. Some harmonic content is aliased as the Class-D amplifier is not able to pass frequencies past the Nyquist criterion. This contributes to increased total harmonic distortion (THD) as presented later.

Voltage on the Input RC Filter (Across C11)Figure 5-9 Voltage on the Input RC Filter (Across C11)
Excitation Amplifier Output VoltageFigure 5-10 Excitation Amplifier Output Voltage