Digital pulse width modulation techniques for power converters

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University of Alabama Libraries

Recently, digital controls are becoming dominant in almost every power electronic application because of the advantage when compared to analog control. This includes the ability of digital controllers to perform more advanced and sophisticated functions that potentially result in improving power conversion efficiency and/or the dynamic performance of the power converter, the ease of digital control function and loop upgradeability (or revision), and reduced sensitivity to component variations. However, there are also some challenges in digital control such as control loop delays that impact the dynamic performance of the power converters and the additional controller power consumption in some digital control implementations. Digital Pulse Width Modulation (DPWM) is one of the most important parts in digital control systems which control the power switch of the power converters. Modulation technique plays a vital role in causing control delays. There are several implementation schemes of digital pulse width modulation such as counter based DPWM, delay line based DPWM, and hybrid based DPWM. The output voltage is required to have little deviation from the reference voltage and fast settling times under transient events. Therefore, in order to maintain a well regulated output voltage, the control signal must instruct the power converter to either turn on (when there is undershoot in output voltage) or turn off (when there is overshoot in output voltage), as fast as possible. The work presented in this thesis suggests a modulation technique that reduces the turn on delay caused by trailing-edge digital modulation and turn off delay caused by leading-edge digital modulation. Reducing the digital pulse width modulation delay reduces the overshoot and undershoot in the output voltage in power converters with digital closed loop control. The proposed modified digital pulse width modulation scheme is verified using computer simulations and experimental results.

Electronic Thesis or Dissertation
Engineering, Electronics and Electrical