Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
2000-08-09
2001-08-07
Sterrett, Jeffrey (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
Reexamination Certificate
active
06272032
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a rectifier with midpoint feed, in particular to a rectifier with midpoint feed.
BACKGROUND OF THE INVENTION
FIG. 1
shows such a rectifier with midpoint feed which is known from the prior art, the input being formed by the input terminals A and B while the output is formed by the output terminals P and M. In this arrangement, the output terminal P corresponds to the positive pole and the output terminal M corresponds to the negative pole. In order to be able to operate a rectifier at the output of a free-running inverter, i.e. the switching transistors are driven by direct feedback of the load current, it is desirable for the character of the rectifier following the inverter to be slightly inductive.
The rectifier shown in
FIG. 1
comprises a series circuit comprising a first coupling capacitor C
1
and a second coupling capacitor C
2
, the midpoint of which is connected to the input terminal B. The input terminal A is connected via an inductor L
1
to the midpoint of a series circuit comprising a first diode D
1
and a second diode D
2
. Each diode has a polarity-reversal capacitor C
D1
or C
D2
connected in parallel with it. The series circuit comprising the first and the second coupling capacitor C
1
, C
2
is connected to the output terminal P via an inductor L
2
. Connected in parallel with the output is a storage capacitor C
3
. By way of example, a series circuit comprising a plurality of light-emitting diodes is shown as the load.
In the circuit arrangement shown in
FIG. 1
, the inductor L
2
assumes the function of a smoothing inductor, i.e. it smoothes the direct current provided at the output terminals P, M, while the inductor L
1
caters for the inductive character of the rectifier.
In the circuit arrangement shown in
FIG. 1
, the inductors L
1
and L
2
in particular, have a disadvantageous effect, since they are by nature relatively large in comparison with other components and therefore take up a lot of the limited space on a circuit board. Furthermore, they are expensive and complicated to install as compared with SMD components.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a circuit arrangement which is improved as compared with the prior art shown in FIG.
1
and in which the disadvantages of the prior art are reduced.
This solution affords the advantage that the two inductors simultaneously act as a polarity-reversal inductance, namely the parallel circuit comprising L
1
and L
2
, and as a smoothing inductance, namely the series circuit comprising L
1
and L
2
. This means that the load is evenly distributed over the two inductors, which is why simpler components can be used. This results in a significant reduction in cost. In particular, the inductor L
1
does not need to be as powerful and the inductor L
2
does not need to be as large as in the circuit arrangement which is known from the prior art and is shown in FIG.
1
. The space requirement for the inductors L
1
and L
2
on the circuit board has therefore been significantly reduced.
In one particularly advantageous embodiment, for each further output of the rectifier, the following combination can be connected in parallel with the corresponding combination for the first output: a further storage capacitor, a further second inductor, a further second diode and a further second coupling capacitor. In the prior art shown in
FIG. 1
, a plurality of outputs can be provided as a result of a plurality of loads being connected in parallel at the output P, M. In the case of light-emitting diodes, a load is defined by a respective series resistor in series with a series circuit comprising a plurality of light-emitting diodes. In this case, the differential output impedance is determined by the respective series resistor. In contrast to this, the differential output impedance can be increased, on the basis of the resistance of an individual path, by more than a factor of 5 as a result of the inventive measure mentioned, i.e. different voltages at the respective outputs result in a current difference between the respective outputs which—in comparison to the prior art—is reduced by more than a factor of 5.
Preferably, the first diode has a first polarity-reversal capacitor connected in parallel with it, and/or at least one and/or each second diode has a respective second polarity-reversal capacitor connected in parallel with it. The polarity-reversal capacitors are preferably in the form of ZVS resonance capacitors.
The capacitance value of the first coupling capacitor is preferably essentially the same as the sum of the capacitance values of all the second coupling capacitors and is preferably between 10 nF and 200 nF. The capacitance value of each storage capacitor is essentially approximately twice the capacitance value of the first coupling capacitor.
The coupling of the first inductor to at least one second inductor and/or the coupling of at least two of the second inductors to one another is particularly advantageous. This affords the option of producing at least two inductors using a single component, i.e. at least two inductors are wound on a single core. This results in a further reduction in the space required for the inductors.
If the first and at least one of the second inductors are coupled to one another, then the coupling is preferably such that the principal inductances of the first and of the at least one second inductor cause the output current to be smoothed, and that the leakage inductances of the first and of the at least one second inductor act as a polarity-reversal inductance. The load distribution which this achieves permits smaller dimensions for the components and results in the useful life thereof being increased.
Further advantageous refinements of the invention can be found in the dependent claims.
REFERENCES:
patent: 5793626 (1998-08-01), Jiang
patent: 5831846 (1998-11-01), Jiang
Bessone Carlo S.
Patent -Treuh nd-Gesellschaft fuer elektrische Gluehlampen mbH
Sterrett Jeffrey
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