Electric power conversion systems – Current conversion – Including d.c.-a.c.-d.c. converter
Reexamination Certificate
2000-08-29
2001-11-06
Berhane, Adolf Deneke (Department: 2838)
Electric power conversion systems
Current conversion
Including d.c.-a.c.-d.c. converter
C363S133000
Reexamination Certificate
active
06314006
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
When two DC voltage networks are connected, an energy flow may alternatively be needed in both directions. Thus, for example, in motor vehicles, in addition to the existing 14 V network, a 42 V network is introduced in order to be able to supply further loads with higher power demands. Depending on the operating state, it may be necessary to transfer energy from the 14 V network into the 42 V network or vice versa. For this purpose, in each case a DC/DC converter is intrinsically necessary, for which various circuit principles are known, for example the so-called parallel-fed push-pull converter.
These converters operate in push-pull operation on the primary and secondary side, and are distinguished by a good efficiency and simple driving of the semiconductor switches. On the secondary side, rectification is carried out in push-pull by means of two diodes which are connected to the ends of the windings and operate on an L/C filter element.
However, these known converters have the disadvantage of being usable in each case only in one direction of action (energy transfer direction), so that two of the known DC/DC converters are needed in order to connect the DC voltage networks.
SUMMARY OF THE INVENTION
The object of the present invention is to permit savings in both cost and weight in the connection of the two DC voltage networks, as compared with this known prior art.
According to the invention, this object is achieved by the respective center taps being connected to a first terminal for the respective DC voltage and further winding terminals each being connected via a semiconductor switch to a second terminal for the respective DC voltage, the semiconductor switches being controlled synchronously in pairs.
The invention has the advantage that, using a DC/DC converter, reversal of the direction of action can be carried out while using the same inductive components. In addition, in the invention, the same semiconductor switches can be operated as primary-side switches and as secondary-side rectifiers, depending on the direction of action.
In the DC/DC converter according to the invention, provision is preferably made for the center taps each to be connected via an inductor to the respective first DC voltage terminal, and for the second DC voltage terminals to be at ground potential and to be connected to the first terminals via a capacitor in each case. It is advantageous if DC voltages of the same polarity are present on the respective first terminal.
In the DC/DC converter according to the invention, the semiconductor switches are preferably field effect transistors, in particular so-called MOSFETs.
In principle, in the DC/DC converter according to the invention, the direction of action can be changed over automatically as a function of the magnitude of the DC voltages present. Without further measures, because of the transformer losses and the associated deviation of the effective transformation ratio as compared with the ratio of the number of turns, this presupposes a considerable deviation of the ratio of the DC voltages from the ratio of the number of turns. However, if the reversal of action is to take place even at small deviations, provision can be made, according to a development of the invention, for it to be possible to change the transformation ratio in order to change the direction of action.
A first advantageous refinement of this development consists in one of the windings in each case being lengthened symmetrically over the further winding terminals, the end terminals of the lengthened windings being connected via further semiconductor switches to the second terminal for the respective DC voltage, and the driving of the further semiconductor switches to be carried out alternatively with the driving of the semiconductor switches for the same DC voltage as a function of the direction of action. By selecting the turns between the further winding terminals and the end terminals with reference to the other number of turns, this DC/DC converter can be adapted very well to the respective conditions.
In this DC/DC converter, provision can advantageously be made for the further semiconductor switches to be controllable via a transformer and/or for the further semiconductor switches each to comprise a series circuit of two field effect transistors.
In a second advantageous refinement of the development, provision is made for the further winding terminals, preferably the ends, of one of the windings also to be connected via further semiconductor switches to the first terminal, the driving of the further semiconductor switches being carried out as a function of the direction of action and in antiphase with the driving of the semiconductor switch in each case connected to the same winding terminal, and for it to be possible for the center tap of the same winding to be connected via a third semiconductor switch to the first terminal as a function of the direction of action, the driving of the further semiconductor switches being suppressed when the third semiconductor switch is conductive. In this case, the further semiconductor switches and the third semiconductor switch can each comprise a series circuit of two field effect transistors.
A third advantageous refinement of the development is distinguished by a low outlay and consists in the further winding terminals, preferably the ends, of one of the windings also being connected via rectifier diodes to the first terminal, and for it to be possible for the center tap of the same winding to be connected via a third semiconductor switch to the first terminal as a function of the direction of action.
REFERENCES:
patent: 5218522 (1993-06-01), Phelps et al.
patent: 5436825 (1995-07-01), Wawra et al.
patent: 5488554 (1996-01-01), Green
patent: 5654881 (1997-08-01), Albrecht et al.
patent: 5659463 (1997-08-01), Lee
patent: 5729444 (1998-03-01), Perol
patent: 5822201 (1998-10-01), Kijima
patent: 5907481 (1999-05-01), Svardsjo
patent: 0771063 (1997-05-01), None
Berberich Reinhold
Fürbeth Andreas
Berhane Adolf Deneke
Farber Martin A.
Mannesmann VDO AG
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