Research Of Single-Stage PFC

Conventional bridge rectifier plus the power supply filter capacitor, making the grid a serious distortion of input current, power factor can not be improved. While a large number of harmonics on the power grid caused serious pollution and disruption of other electrical equipment. Active power factor correction circuit for off-line power supply shape the input current, load supply current and supply voltage changing with the phase, power factor close to 1. This makes the active power drawning the largest power supply from the power grid, improving the power supply equipment power efficiency. Today, the European electrical equipment must comply with European norms EN61000-3-2. This requirement applies to most of the input power of 75 W or more appliances, and it provides up to 39 harmonics including frequency harmonics, including the most significant. Although the United States has not made such a request. But hope to sell products in the global power supply manufacturers are working to design products that meet this requirementCommonly used in active power factor correction circuit is the bipolar power factor correction circuit to improve the power factor, pre-BOOST level (AC-DC) of pre-class, followed by a DC-DC to provide power for the load. This circuit has high power factor, and easy to adjust the circuit, but requires two power supply circuit, increasing the cost of the circuit, reducing the power efficiency. Single-stage power factor correction circuit, with only one AC-DC conversion, reduce the number of components to improve the efficiency of the circuit. Therefore become a research hotspot.ON Semiconductor NCP1651 is the company produced dedicated control chip for the single-stage Flyback PFC. I use this chip. Design a single-stage PFC of 90W power circuit. Founding in the process of making the circuit of the transformer is too large. Through analysis, Semiconductor companies using the average current instead of RMS current to design the transformer. This is because in continuous current mode flyback single-stage PFC circuit, the current through the transformer primary and secondary are a series of trapezoidal pulses, pulse amplitude and width, and rate of current changing with the input voltage frequency instantaneous value of sinusoidal. Therefore, accurate calculation of the rms circuit is a complex issue. This paper proposes a method of calculating rms. And designed a circuit in this way, making the transformer volume greatly reduced. In this thesis, debug circuit also encountered some problems which were analyzed and the corresponding solutions.