Abstract

Single phase ac power supplies are used to power hybrid fiber/coax (HFC) networks. These power supplies are required to produce a trapezoidal-shaped voltage waveform. Conventional power supplies having a front-end diode bridge rectifier and a large dc bus capacitor are an unacceptable approach for this application as they draw a highly distorted current waveform resulting in a poor power factor. An intermediate boost stage is used to waveshape the input current thus providing power factor correction. Owing to the additional power conversion stage, this topology results in reduced efficiency. In this thesis a novel power supply topology is proposed which eliminates the use of the boost stage and the large dc bus capacitor while maintaining high efficiency and good power factor. Three voltage controlled PWM pattern generators namely, Hysteresis, Triangular-carrier and One-cycle technique are identified and implemented for the power supply based on the proposed topology. Performance comparison of the power supply using the three techniques is done based on criteria such as input power factor, input current total harmonic distortion and efficiency. Experimental results on a laboratory prototype confirm the feasibility of the proposed power supply.