A bridgeless power factor correction rectifier with boost converter is introduced. This converter substantially improves efficiency at low line of the universal-line range. By eliminating input bridge diodes during conduction, the proposed rectifier's efficiency is further improved. Moreover, the rectifier doubles its output voltage, which extends useful energy of the bulk capacitor after a dropout of the line voltage. Also second stage boost converter is included to maximize the output. The efficiency difference between low line and high line is less than 0.5% at full load. A second-stage half-bridge converter is also included to show that the combined power stages easily meet Climate Saver Computing Initiative Gold Standard. Keywords— power factor (Pf), bridgeless rectifier, boost converter, phase difference. I. Introduction In universal-line (90-264V) applications, maintaining a high efficiency across the entire line range poses a major challenge for ac/dc rectifiers that require power factor correction (PFC). Driven by economic reasons and environmental concerns, maintaining high efficiency across the entire load and input-voltage range of today's power supplies is in the forefront of performance requirements. Specifically, meeting and exceeding U.S. Environmental Protection Agency's (EPA) Energy Star, and Climate Saver Computing Initiative (CSCI) efficiency specifications have become a standard requirement for both multiple- and single-output offline power supplies. Generally, the EPA and CSCI specifications define minimum efficiencies at 100%, 50%, and 20% of full load with peak efficiency at 50% load. For decades, a bridge diode rectifier followed by a buck converter has been the most commonly used PFC circuit because of its simplicity and good PF performance. This drop of efficiency at low line can be attributed to an increased input current that produces higher output voltage. However, in practical application the Buck PFC converter has the following disadvantages: 1) The output voltage is below the limit of the input voltage. 2) There is the poor performance during the startup, the overloading and the non-load. 3) The high switching losses and EMI. They are resulted from the great ripple current flowing from the power switch and diode. 4) The bridge type converter increases the losses. 5) The control circuit is complex and high cost. In order to overcome these problems, in this paper, a single-phase bridgeless PFC rectifier with boost converter is presented. In conventional method, a bridgeless buck PFC rectifier that further improves the low-line (115 V) efficiency of the buck front-end by reducing the conduction loss through minimization of the number of simultaneously conducting semiconductor components is introduced. It also works as a voltage doubler, it can be designed to meet harmonic limit specifications with an output voltage that is twice that of a conventional buck PFC rectifier. As a result, the proposed rectifier also shows better hold-up time performance. Although the output voltage is doubled, the switching losses of the primary switches of the downstream dc/dc output stage are still significantly lower than that of the boost PFC counterpart. Also the buck PFC converter does not shape the line current around the zero crossings of the line voltage, i.e., during the time intervals when the line voltage is lower than the output voltage, it exhibits increased total harmonic distortion (THD) and a lower PF compared to its boost counterpart. As a result, in applications where IEC61000-3-2 and corresponding Japanese specifications (JIS-C-61000-3-2) need to be met, the buck converter PFC employment is limited to lower power levels. The conventional buck converter operation and control is described in (1)(2)and(3). In proposed method PFC rectifier with boost converter is introduced to improve the PF furthermore, which is different from the normal bridge type rectifier and boost converter where, the operation consists of two diodes in conduction at each half cycle simultaneously ,one is in from upper leg and other is from lower leg. Here, the positive half cycle has two diodes and similarly the negative half cycle has two diodes. This type of operation requires high power to switching than the bridgeless operation. Also it increases the conduction loss. The bridgeless rectifier with boost converter increases the output nearly double the value or higher than that. When the supply is positive the first half cycle has one diode and one switch in conduction another will not conduct for a while this will continue until the switch is ON. When the switch is open another diode starts freewheels the current. In the same way, for negative half cycle the diode in lower leg with second switch will conduct until the switch will open. When the switch is open another diode in the lower leg
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Oct 1, 2022
Zhengge Chen + 4
Open Access