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"Ac/Dc Converter with Passive Power Factor Correction Circuit and Method of Correcting Power Factor" in Patent Application Approval Process

June 25, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- A patent application by the inventors PAN, Ching-Tsai (Hsinchu, TW); CHEN, Po-Yen (Taipei, TW); HUNG, Ta-Sheng (TAICHUNG, TW), filed on December 4, 2013, was made available online on June 12, 2014, according to news reporting originating from Washington, D.C., by VerticalNews correspondents.

This patent application is assigned to Hep Tech Co., Ltd.

The following quote was obtained by the news editors from the background information supplied by the inventors: "The present invention relates generally to a power factor correction circuit, and more particularly to an AC/DC converter with passive power factor correction circuit and a method of correcting power factor.

"Typically, an AC/DC converter is used to convert an alternate current (AC) into a direct current (DC). A conventional AC/DC converter is shown in FIG. 1, which includes a rectifier circuit 10 and an output capacitor C, wherein the rectifier circuit 10 converts an alternate current (AC) provided by an AC power supply S into a direct circuit (DC), and the output capacitor C bridges over the output of the rectifier circuit 10 and are in parallel with a loading R. While the AC/DC converter is working, the phases of the input voltage v.sub.in and the input current i.sub.in of the AC are different, which leads to low power factor and poor total harmonic distortion. In addition, the output capacitor C is charged only when a voltage of the DC is higher than that of the output capacitor C, hence the charging time of the output capacitor C is shortened. As a result, the conduction time of diodes in the rectifier circuit 10 is also shortened, which increases the peak value of the conduction current, distorts the waveform of the input current i.sub.in, and lowers the power factor. Low power factor not only wastes energy, but also poses unnecessary burdens for the power supply systems of the power company. Therefore, the AC/DC converter with power factor correction circuit is emerged.

"In general, there are two types of the conventional power factor correction circuits of the AC/DC converters, which are active type and passive type. The active power factor correction circuit controls the input current with active switch components, and this type of the power factor correction circuit has several advantages, such as the power factor could excess 0.99, and the total harmonic distortion could be less than 10%. And moreover, the active power factor correction circuit is compatible with a wider range of input voltage, generates a stable output voltage, and it's unaffected by the variation of output power. However, the active power factor correction circuit has several drawbacks too, such as higher cost due to additional active switches, high electromagnetic noises, and low durability. Please refer to FIG. 2, the conventional passive power factor correction circuit has an inductor L in serial with the input of the rectifier circuit 10 of the AC/DC converter. Since the structure of the passive power factor is simple, it is more durable. And there is no active switch which causes electromagnetic noises needed. Because the inductor L has to be made from a bulk of silicon steel plate, its size increases along with the decreasing of output power and rated input voltage, and the power factor could merely achieve around 75%, which is insufficient to meet the demands nowadays. If the power factor of passive power factor correction circuits of AC/DC converters could be increased, those AC/DC converters which have more expensive active power factor correction circuits could be replaced. Besides, in order to reduce the ripple of the output voltage of the loading R, the aforementioned output capacitor C has to adopt a high capacity electrolytic capacitor, but the electrolytic capacitor is easy to leak out the contained electrolyte due to being heated for a long period of time, which shortens life of circuit."

In addition to the background information obtained for this patent application, VerticalNews journalists also obtained the inventors' summary information for this patent application: "In view of the above, the primary objective of the present invention is to provide an AC/DC converter and a method of correcting a power factor, which effectively increases a power factor of the AC/DC converter, and has no need to adopt an electrolytic capacitor, thus prolongs life of the AC/DC converter.

"The present invention provides an AC/DC converter which includes a rectifier circuit and a power factor correction circuit, wherein the rectifier circuit converts an alternate current (AC) into a direct current (DC), which has an input port and an output port, wherein the input port receives the AC, and the DC comes out via the output port; the power factor correction circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, a first diode and a second diode, an end of the first inductor is electrically connected to a positive pole of the output port of the rectifier circuit, and the other end thereof is electrically connected to two series routes which are in parallel to each other, wherein the first capacitor and the second diode are on one of the series route; an end of the first capacitor is electrically connected to the first inductor, and the other end thereof is electrically connected to a cathode of the second diode, and an anode of the second diode is electrically connected to a ground terminal of the output port of the rectifier circuit; the second inductor and the second capacitor are on the other series route; an end of the second inductor is electrically connected to the first inductor, and the other end thereof is electrically connected to an end of the second capacitor, the other end of the second capacitor is electrically connected to the ground terminal of the output port of the rectifier circuit; the second capacitor is connected to a loading in parallel; an anode of the first diode is electrically connected to a point between the first capacitor and the cathode of the second diode, and a cathode of the first diode is electrically connected to a point between the second inductor and the second capacitor.

"According to the aforementioned concepts, the present invention further provides a method of correcting power factor with a power factor correction circuit, wherein the power factor correction circuit includes a first inductor, a second inductor, a first capacitor, a second capacitor, a first diode and a second diode, wherein an end of the first inductor is electrically connected to a positive pole of a DC power supply, and the other end thereof is electrically connected to two series routes which are in parallel to each other, wherein the first capacitor and the second diode are on one of the series route; an end of the first capacitor is electrically connected to the first inductor, and the other end thereof is electrically connected to a cathode of the second diode, and an anode of the second diode is electrically connected to a ground terminal of the DC power supply; the second inductor and the second capacitor are on the other series route; an end of the second inductor is electrically connected to the first inductor, and the other end thereof is electrically connected to an end of the second capacitor, the other end of the second capacitor is electrically connected to the ground terminal of the DC power supply; the second capacitor is connected to a loading in parallel; an anode of the first diode is electrically connected to a point between the first capacitor and the cathode of the second diode, and a cathode of the first diode is electrically connected to a point between the second inductor and the second capacitor; the method includes the steps of:

"A. Receive a direct current (DC) from the DC power supply.

"B. Conduct the second diode, and provide energy into the loading from the first capacitor and the DC power supply until the second diode is cut off.

"C. Provide energy into the loading from the DC power supply until the first diode is conducted.

"D. Charge the first capacitor by the DC power supply, and provide energy into the loading until the first diode is cut off.

"E. Provide energy into the loading from the DC power supply until the second diode is conducted; and

"F. Repeat the steps from the step B to the step E until the DC power supply stops providing the DC.

"With such design, it may prolong the conduction time of diodes in the rectifier circuit to control the input current of the AC power supply, which could increase the power factor effectively.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

"The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which

"FIG. 1 is a circuit diagram of the conventional AC/DC converter;

"FIG. 2 is a circuit diagram of the conventional AC/DC converter with the passive power factor correction circuit;

"FIG. 3 is a circuit diagram of the AC/DC convert with passive power factor correction of a preferred embodiment of the present invention;

"FIG. 4 is a circuit diagram of the first state of the preferred embodiment of the present invention;

"FIG. 5 is a circuit diagram of the second state of the preferred embodiment of the present invention;

"FIG. 6 is a circuit diagram of the third state of the preferred embodiment of the present invention;

"FIG. 7 is a circuit diagram of the fourth state of the preferred embodiment of the present invention; and

"FIG. 8 is an oscillogram of the AC/DC converter of the preferred embodiment of the present invention."

URL and more information on this patent application, see: PAN, Ching-Tsai; CHEN, Po-Yen; HUNG, Ta-Sheng. Ac/Dc Converter with Passive Power Factor Correction Circuit and Method of Correcting Power Factor. Filed December 4, 2013 and posted June 12, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4167&p=84&f=G&l=50&d=PG01&S1=20140605.PD.&OS=PD/20140605&RS=PD/20140605

Keywords for this news article include: Electronics, Hep Tech Co. Ltd, Electrolytic Capacitor.

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Source: Electronics Newsweekly


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