Electric power conversion systems – Current conversion – With means to introduce or eliminate frequency components
Reexamination Certificate
1999-11-15
2001-09-11
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
With means to introduce or eliminate frequency components
C363S086000, C363S021100, C323S209000, C323S218000
Reexamination Certificate
active
06288918
ABSTRACT:
OBJECT OF THE INVENTION
The present invention relates to a switched power converter which is connected to an alternating current (AC) power mains for rectifying the received voltage sine wave and converting it to a voltage level suitable for feeding to at least one load, such as a telecommunications equipment.
For performing the conversion switching elements are employed which are switched at high frequency and, as a result, generate harmonics in the input current, possibly producing distortion that interferes with the normal operation of other devices connected to the AC power mains.
Known techniques, as power factor correction, are used to reduce the harmonics content in the input current, by approximating the input current waveform to a sinusoid, said power factor correction circuits being in general complex.
STATE OF THE ART
At the present time a switched power converter is known for maintaining a high power factor at its input terminals from the U.S. Pat. No. 4,903,181, being incorporated in the present patent application by reference.
According to the power converter proposed in this document, its input terminals are connected to the AC power mains, and it provides across its output terminals a regulated DC voltage. The power converter has a first switching circuit the output of which is connected to an impedance inverting circuit, the two working together as a current generator.
A second switching circuit is connected in parallel with the output of the impedance inverting circuit for obtaining the regulated output voltage of the power converter.
A phase delay controller controls the switching of this second switching circuit and synchronises it with the switching of the first switching circuit, in such a manner that a storage capacitor, which is included in the second switching circuit, is charged for obtaining the second regulated output voltage. The phase delay controller determines the voltage on the storage capacitor.
The first switching circuit comprises means for correcting the power factor obtaining, thereby, a high power factor.
The switched power converter proposed in the patent U.S. Pat. No. 4,903,181 comprises a high number of switching elements, separate control circuits and, consequently, the circuitry of the proposed converter is complex and costly, and in addition, results in a converter that is bulky as a whole, this proving to be a drawback for applications where compact devices are required, this last feature being a major design parameter in the down-sizing of all equipment.
As a consequence, there exists a requirement to develop a switched power converter that comprises a reduced number of switching elements and control circuits, having a reduced harmonics content and a high overall performance, avoiding thereby the aforementioned problems.
SUMMARY OF THE INVENTION
The switched power converter with hold-up time and harmonics reduction of the present invention has a power factor close to unity, a high overall performance and a regulated output voltage; comprises a reduced number of switching devices and has a high integration density and reduced size; and, consequently, the overall cost of the switched power converter is low.
The switched power converter is connected to an AC power mains, comprising a first rectifier means, the input terminals of which are connected to an alternating current (AC) power mains, that produces at its output a rectified voltage sine wave which is applied to a converter means, through conductors (
14
,
15
), that produces a regulated voltage across its output terminals.
A bi-directional energy storage means is connected in parallel with the output of the first rectifier means, for, as required, absorbing or supplying current from or to the input terminals of the converter means, so that the waveform of the input current follows the waveform of the input voltage and maintains constant the voltage level on the energy storage means.
The energy storage means comprises a series combination of a second switching device and a third switching device, connected in parallel with a storage capacitor, and a node between the second switching device and the third switching device is connected through an inductance to the conductor.
A first control means adapts each of the conducting periods of the second switching device and of the third switching device for determining the voltage level of the energy storage means and ensures a sinusoidal current at the input terminals of the power converter, based on a signal representative of the rectified voltage sinusoidal waveform and a signal representative of the storage capacitor voltage.
The first control means swatches the second switching device and the third switching device in a complementary manner.
Thus, the energy storage means supplies or absorbs current at the output of the first rectifier means, achieving a reduction in the harmonics content in the input current to the first rectifier means. As a result, the switched power converter has a power factor close to unity.
The switched power converter of the invention maintains a high power factor at its input, satisfying as a result the international standards, such as the EN-1000-3-2 standard, which relate to the harmonics content in the input current in devices connected to the AC power mains, and its implementation is straightforward.
REFERENCES:
patent: 5535112 (1996-07-01), Vazquez et al.
patent: 5721481 (1998-02-01), Narita et al.
patent: 5781427 (1998-07-01), Moreau
patent: 5796182 (1998-08-01), Martin
patent: 5804952 (1998-09-01), Chen
patent: 5912812 (1999-06-01), Moriarty, Jr.
patent: 5923152 (1999-07-01), Guerrera
De La Cruz Moreno Enrique
Fontan Tarodo Antonio
Ollero Velasco Salvador
Alcatel
Laxton Gary L.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Wong Peter S.
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