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Wednesday, 7 February 2018

A Power Quality Improved Bridgeless Converter-Based Computer Power Supply

Poor power quality, slow dynamic response, high device stress, harmonic rich, periodically dense, peaky, distorted input current are the major problems that are frequently encountered in conventional switched mode power supplies (SMPSs) used in computers. To mitigate these problems, it is proposed here to use a nonisolated bridgeless buck-boost single-ended primary inductance converter (SEPIC) in discontinuous conduction mode at the front end of an SMPS. The bridgeless SEPIC at the front end provides stiffly regulated output dc voltage even under frequent input voltage and load variations. The output of the front end converter is connected to a half-bridge dc–dc converter for isolation and also for obtaining different dc voltage levels at the load end that are needed in a personal computer. Controlling a single output voltage is able to regulate all the other dc output voltages as well. The design and simulation of the proposed power supply are carried out for obtaining an improved power quality that is verified through the experimental results.
1.      Bridgeless converter
2.      Computer power supply
3.      Input current
4.      Power factor correction (PFC)
5.      Power quality



Fig. 1. Schematic diagram of the PFC converter based SMPS.


Fig. 2. (a) Performance of the computer power supply at rated condition. (b) Input current and its harmonic spectrum at full load condition. (c)Waveform across various components of the bridgeless converter.

Fig. 3. (a) Performance of the computer power supply at light load condition.
(b) Input current and its harmonic spectrum at light load condition.
A bridgeless nonisolated SEPIC based power supply has been proposed here to mitigate the power quality problems prevalent in any conventional computer power supply. The proposed power supply is able to operate satisfactorily under wide variations in input voltages and loads. The design and simulation of the proposed power supply are initially carried to demonstrate its improved performance. Further, a laboratory prototype is built and experiments are conducted on this prototype. Test results obtained are found to be in line with the simulated performance. They corroborate the fact that the power quality problems at the front end are mitigated and hence, the proposed circuit can be a recommended solution for computers and other similar appliances.
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