Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-04-27
2001-07-03
Nguyen, Matthew (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S098000
Reexamination Certificate
active
06256209
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to AC to DC conversion arrangements, by which is meant arrangements capable of converting an input electrical supply of alternating waveform to an output electrical supply in which an alternating component is at least substantially reduced (hereafter a “DC supply”). Preferably the output supply is electrically isolated from the input supply. Preferably also the input supply comprises the AC mains supply and the output supply comprises a substantially steady unidirectional voltage.
A well known and simple form of mains-powered AC to DC converter capable of converting a substantially sinusoidal input supply to a DC output, generally at a lower voltage level but with electrical isolation between the input and output, comprises a step-down transformer and a half-wave rectifier. Such converters, however, exhibit poor power factors and are thus lossy and inefficient, although some improvement in efficiency can be achieved by full wave rectification of the transformer's output. In any event, however, since the transformer must operate at the relatively low mains frequency, it is bulky and expensive.
Further increases in efficiency, coupled with a reduction in transformer dimensions, can be achieved by interposing a full-wave rectifier and a high frequency inverter between the mains supply and the transformer, and it is also known that an inductor and inverter duty-cycle modulator circuitry can be used to control the level of the output voltage or current.
Today's EMC standards place high demands on, inter alia, the input power factors of mains-powered equipment, with the result that the input current waveform needs to track closely that of the input voltage. It is known to provide, for this purpose, so-called boost or buck mode pre-converter stages between the mains input rectifier and the transformer driver inverter to draw a controlled current from the supply, or to use flyback converter or buck converter topologies that combine output isolation with input power factor correction.
The foregoing arrangements exhibit various undesirable features, such as high cost, size and/or complexity of components and it is an object of at least the preferred embodiments of this invention to provide an AC to DC converter arrangement which is economical, efficient and compact. Preferably the arrangement also exhibits a controlled output, a near-unity power factor and can accommodate a wide range of input voltages.
SUMMARY OF THE INVENTION
According to the invention there is provided an arrangement for converting an AC supply to a DC supply comprising an inverter circuit and a boost power factor correction stage wherein said inverter circuit comprises switchable components and means for utilizing a pulsed waveform indicative of power factor correction for causing some at least of said components repeatedly to adopt a condition permitting said boost power factor correction stage to draw current from said AC supply characterized in that the switchable components are semiconductor devices connected to form a full bridge inverter, a first series connected pair of said devices being caused to conduct simultaneously for periods determined by the duration of alternate pulses of said waveform, a second pair of series connected said devices being caused to conduct simultaneously for periods determined by the duration of the intervening alternate pulses of said waveform, one device of each of said pair remaining conducting whilst the other pair of devices is conducting.
Such simultaneous conduction repeatedly short-circuits the inverter's input.
It is preferred that the semiconductor devices comprise MOSFET or IGBT devices.
The boost power factor correction stage preferably comprises an inductor which is repeatedly charged by current drawn from said AC source each time the inverter's input is short-circuited.
Each device of each pair may be individually switchable between substantially conductive and non-conductive conditions.
Preferably the other device of each of said series-connected pairs is caused to assume conductive or non-conductive conditions in dependence upon the level of a respective switching waveform applied thereto, said switching waveforms being in anti-phase.
One device of each of said series-connected pairs may be caused to assume conductive or non-conductive conditions in dependence on the level of a respective switching waveform applied thereto, the switching waveform for each of said other devices comprising a composite waveform derived from said pulsed waveform indicative of power factor correction and the switching waveform applied to the first device of the other series-connected pair.
The switching waveform applied to said devices may be such as to cause both devices in one series-connected pair to assume their conductive conditions during alternate pulses of said pulsed waveform and to cause both devices in the other series-connected pair to assume their conductive conditions during the intervening pulses of said pulsed waveform.
The arrangement may comprise a transformer, said inverter circuit having input and output connections, said output connection being coupled to a primary winding of said transformer, and said boost power factor correction stage being coupled between said electrical input supply and the input connection of said inverter.
There may be a temporary energy storage means configured to limit transient voltages applied to the inverter circuit.
The temporary energy storage means may comprise a unidirectionally conductive device and a capacitor connected in series, said unidirectionally conductive device being shunted by an electronically operable switch.
The electronically operable switch may be actuated to shunt said unidirectionally conductive device substantially in antiphase with said pulsed waveform indicative of power factor correction.
The electronically operated switch may shunt the capacitor to discharge it into the boost stage.
The arrangement may be for connection to a three-phase supply, said boost power factor corrector stage comprising a plurality of inductors each for connection in series to a respective phase of the three-phase supply.
REFERENCES:
patent: 4591963 (1986-05-01), Retotar
patent: 5081570 (1992-01-01), Chibani et al.
patent: 5355294 (1994-10-01), De Doncker et al.
patent: 6115267 (2000-09-01), Herbert
patent: 2 226 197 (1973-12-01), None
patent: 42 14 918 A1 (1993-11-01), None
patent: 44 26 018 A1 (1996-02-01), None
patent: 196 32 023 A1 (1998-02-01), None
patent: 56-132766 (1982-08-01), None
patent: 07184375 (1995-07-01), None
patent: WO 96/19037 (1996-06-01), None
Single-Stage Single-Phase Parallel Power Factor Correction Scheme, Yimin Jiang, et al., Virginia Power Electronics Center, The Bradley Department of Electrical Engineering Virginia Polytechnic Institute and State University, Blacksburg, VA, Jun. 20, 1994, pp. 1145-1151.
Gurwicz David
Thompson Kevin
Kirschstein et al.
Nada Electronics Limited
Nguyen Matthew
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