Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2000-11-09
2003-05-13
Patel, Rajnikant B. (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S021110, C323S222000
Reexamination Certificate
active
06563721
ABSTRACT:
FIELD OF THE INVENTION
In general, the present invention relates to a DC power supply with multiple AC input voltages. More particularly, the present invention is directed to a simple circuit for a DC power supply having only two wires from an AC input that can be connected to any voltage within a wide range of AC input voltages.
BACKGROUND OF THE INVENTION
In industrial applications, DC power supplies such as DC/DC converters must adapt to various AC input voltages. A multiple source power supply may be required in certain applications wherein the requisite output of a power supply is dependent upon the application of the device being supplied. A multiple source power supply may derive its source from multiple AC lines, one or more batteries or even solar collectors to power to a load connected at an output terminal.
Two conventional solutions for implementing multiple input power supplies that are well known and widely utilized in emergency lighting and related industries are illustrated herein in
FIGS. 1 and 2
. As illustrated in
FIG. 1
, one such solution implements an output transformer
10
to establish electrical communication of a multi-input transformer AC supply to a DC regulator. A plurality of input sources
12
is provided wherein each input source has a unique input voltage value. Input sources
12
are applied to primary windings
14
of output transformer
10
. Power flows from each input source through a secondary winding
16
for derivation of a resultant voltage that is dependent upon which input source has been selected. Secondary winding
16
supplies this voltage as an input voltage V
in
to a power supply for rectification of such input voltage and production of a DC power supply therefrom. A second solution for effecting a similar result is further shown in
FIG. 2
, wherein power sources
12
are capacitively coupled to derive a resultant AC voltage that is subsequently input to a power supply circuit.
In each of the above configurations, it is often necessary for a user to manually select the input wires for the AC voltage available at installation. Even in industries where power supplies have only two AC wires, manual set-up for the input voltage is still required via incorporation of a multiple-position switch or “intelligent” power supplies having automated voltage selection (i.e., voltage level detector and electronic multi-switch). Because these solutions incorporate a multi-input circuit for various AC voltages, an undesirable selection must be made between manual set-up for a particular voltage or the use of sophisticated and costly automatic voltage selection techniques. Not only are additional costs incurred due to the expense of purchase, installation and maintenance of such voltage selection techniques. Inherent risks associated with the selection of an improper voltage can result in improper functioning of the circuit and possible damage to the system within which it is implemented, thereby incurring additional financial and personal risk.
It is therefore desirable to retain the range of AC input voltages that may be applied to a DC power supply circuit while minimizing the number of inputs thereinto. Such a power supply circuit advantageously obviates any restriction on predetermined AC input values.
SUMMARY OF THE INVENTION
It is an advantage of the present invention to provide a single input transformer AC supply to a switching power supply for generation of a constant DC output thereby.
It is another advantage of the present invention to provide such a single input to enable a switching power supply to deliver a constant DC output (voltage or current) for a large AC voltage range.
In the fulfillment of these and other advantages, the present invention provides a simple circuit for a DC power supply. The power supply circuit of the present invention includes a transformer in combination with a switching power supply circuit. The transformer includes a primary winding to which a wide range of AC input voltages is applied and a secondary winding for supplying the resultant AC voltage range as an input voltage to the switching power supply circuit. The switching power supply circuit further includes an input terminal having the input voltage applied thereto by the secondary winding and further having an output terminal from which a DC power supply output is generated. The transformer can be selected from a group of transformers consisting of step-down, step-up and repeater transformers.
The switching power supply circuit may be selected from any conventional switching power supply circuit including step-up, step-down and inverter converters, and combinations thereof, or even linear configurations. The switching power supply circuit may alternately be a self-supplied DC/DC switching power supply circuit having an igniter circuit in electrical communication with a control circuit. The igniter circuit delivers a minimum activation voltage to the control circuit for a predetermined time duration sufficient for activation of the control circuit. After the time duration lapses, the power supply output voltage supplies the control circuit with a stable DC voltage independent of the input voltage.
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Hoffmann & Baron , LLP
Patel Rajnikant B.
Thomas & Betts International Inc.
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