Electric converter with several induction coils
FIELD OF THE INVENTION 
     The present invention relates to electric current converter topologies comprising several induction coils. 
     BACKGROUND OF THE INVENTION 
     An electric current converter is a device which is used to control the electric current flowing between a current source and a load. A conventional electric converter topology basically comprises an electric switching device and a magnetic coupling means. In a known topology the switching device consists for instance of a MOSFET transistor and a diode, and the magnetic coupling means consists of an induction coil which is sometimes associated with an input or output electric filter. 
     In such a topology the transistor is controlled at a high switching frequency (e.g. 50 kHz) so as to be conducting in saturation for a determined fraction of a time period. The diode is conducting only during the time that the transistor is not conducting. The magnetic coupling means are sized so as to assure limited voltage and current ripple capability. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a family of converter topologies which offers a wide variety of topologies from which to select the optimum topology to suit any particular application. 
     The electric converters according to the invention comprise at least three reactive elements connected in series, and a switching device comprising a switching transistor operating at a high frequency so that it becomes conducting for a fraction of each period of said frequency. The transistor and the diode are connected to the connection points between the reactive elements so that the diode is conducting only when the transistor is non-conducting and so that it is non-conducting each time the transistor becomes conducting. 
     Other features of the invention will be apparent from the detailed description hereinafter, in which the invention is disclosed in detail with reference to the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of a buck converter with non-inverted voltage and continuous input and output currents, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 2 is a schematic diagram of a buck converter with non-inverted voltage, wherein the three reactive elements are connected in series between an input terminal and a common terminal; 
     FIG. 3 is a schematic diagram of a non-inverted boost converter with continuous input and output currents, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 4 is a schematic diagram of a non-inverted boost converter with continuous input and output currents, wherein the three reactive elements are connected in series between a common terminal and an output terminal; 
     FIG. 5 is a schematic diagram of a non-inverted buck/boost converter with continuous input and output currents, wherein the three reactive elements are connected in series between an input terminal and a common terminal; 
     FIG. 6 is a schematic diagram of a non-inverted buck/boost converter with continuous input and output currents, wherein the three reactive elements are connected in series between an output terminal and a common terminal; 
     FIG. 7 is a modification of FIG. 5 wherein the two induction coils are replaced by two transformers; 
     FIG. 8 is a modification of FIG. 6 wherein the two induction coils are replaced by two transformers; 
     FIG. 9 is a schematic diagram of an inverted buck/boost converter with continuous input and output currents, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 10 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 11 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 12 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an input terminal and an output terminal; 
     FIG. 13 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an input terminal and a common terminal; 
     FIG. 14 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an output terminal and a common terminal; 
     FIG. 15 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an output terminal and a common terminal; and 
     FIG. 16 is a schematic diagram of an inverted buck/boost converter, wherein the three reactive elements are connected in series between an input terminal and a common terminal. 
    
    
     DETAILED DESCRIPTION 
     As can be seen from the appended drawings, all the arrangements shown comprise three reactive elements connected in series: a first induction coil 1, a capacitor 2 and a second induction coil 3. A switching power transistor 4 and a diode 5 are connected to the connection points 12 and 13 between the reactive elements 1, 2 and 3 so that the transistor 4 and the diode 5 are never simultaneously conducting, i.e. so that the diode 5 is conducting when the transistor 4 is non-conducting and that the diode 5 is non-conducting each time the transistor 4 becomes conducting. 
     The arrangement of FIG. 1 represents a buck converter with non-inverted voltage and continuous input and output currents. In this arrangement, the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the output terminal 20. The diode 5 is connected between the common terminal 15 and the connection point 12. A second capacitor 7 and the transistor 4 are connected in series between the common terminal 15 and the connection point 13. A third induction coil 6 is connected on the one hand to the connection point 12 and on the other hand to the connection point 16 between the capacitor 7 and the drain electrode of transistor 4. 
     In the arrangement of FIG. 2, the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the common terminal 15. The transistor 4 is connected between the connection point 12 and the output terminal 20. The diode 5 is connected in series with a second capacitor 7 between the connection point 13 and the output terminal 20. A third induction coil 6 is connected on the one hand to the connection point 12 and on the other hand to the connection point 17 between the diode 5 and the capacitor 7. This arrangement is also used as a buck converter with non-inverted voltage. 
     In the arrangement of FIG. 3 the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the output terminal 20. The transistor 4 is connected between the connection point 13 and the common terminal 15. The diode 5 is connected in series with a capacitor 7 between the connection point 12 and the common terminal 15. A third induction coil 6 is connected on the one hand to the connection point 19 between the diode 5 and the capacitor 7 and on the other hand to the connection point 13. This arrangement is used as a non-inverted boost converter with continuous input and output currents. 
     The arrangement of FIG. 4 is also used as a non-inverted boost converter. The reactive elements 1, 2 and 3 are connected in series between the common terminal 15 and the output terminal 20. The diode 5 is connected between the input terminal 10 and the connection point 13. A second capacitor 7 is connected in series with the transistor 4 between the input terminal 10 and the connection point 12. A third induction coil 6 is connected between the connection point 13 and the connection point 16 between the second capacitor 7 and the transistor 4. 
     The arrangement of FIG. 5 is used as a non-inverted buck/boost converter with continuous input and output currents. In this arrangement, the reactive elements 1, 2 and 3 are connected between the input terminal 10 and the common terminal 15. The transistor 4 is connected in series with a second capacitor 7 between the connection point 12 and a terminal 18 connected to the output terminal 20. The diode 5 is connected between the connection point 13 and said terminal 18. A third induction coil 6 is connected on the one hand to the connection point 16 between the drain electrode of transistor 4 and the capacitor 7 and on the other hand to the connection point 13. 
     In the arrangement of FIG. 6, the reactive elements 1, 2 and 3 are connected in series between the common terminal 15 and the output 20. The transistor 4 is connected between the connection point 12 and a terminal 19 connected to the input terminal 10. The second capacitor 7 is connected in series with the diode 5 between the terminal 19 and the connection point 13. A third induction coil 6 is connected on the one hand to the connection point 17 between the capacitor 7 and the diode 5 and on the other hand to the connection point 12. This arrangement is used as a non-inverted buck/boost converter with continuous input and output currents. 
     The FIGS. 7 and 8 show two variations to the arrangement of FIGS. 5 and 6 respectively, in which galvanic isolation is provided between the input and the output of the quadripole. More specifically, the arrangement of FIG. 7 is similar to the one of FIG. 5, except that the induction coils 3 and 6 are comprised of two transformers. The arrangement of FIG. 8 is similar to the one of FIG. 6, except that the induction coils 1 and 6 are comprised of two transformers. 
     In the arrangement of FIG. 9, the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the output terminal 20. The transistor 4 is connected in series with a second capacitor 7 between the connection point 12 and the common terminal 15. The diode 5 is connected between the connection point 13 and the common terminal 15. A third induction coil 6 is connected on the one hand to the common point 16 between the drain electrode of transistor 4 and the capacitor 7 and on the other hand to the connection point 13. This arrangement is used as an inverted buck/boost converter with continuous input and output currents. 
     The FIGS. 10 to 16 also show arrangements for inverted buck/boost converters. In the arrangement of FIG. 10, the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the output terminal 20. A second capacitor 7 is connected in series with the transistor 4 between the common terminal 15 and the connection point 12. The diode 5 is connected between the common terminal 15 and the connection point 13. A third induction coil 6 is connected on the one hand to the connection point 16 between the transistor 4 and the capacitor 7 and on the other hand to the connection point 13. 
     In the arrangement of FIG. 11, the reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the output terminal 20. The transistor 4 is connected between the common terminal 15 and the connection point 12. A second capacitor 7 and the diode 5 are connected in series between the common terminal 15 and the connection point 13. A third induction coil 6 is connected on the one hand to the connection point 12 and on the other hand to the connection point 17 between the capacitor 7 and the diode 5. 
     The arrangement of FIG. 12 includes three reactive elements 1, 2 and 3 connected in series between the input terminal 10 and the output terminal 20. The transistor 4 is connected between the connection point 12 and the common terminal 15. The diode 5 is connected in series with a second capacitor 7 between the connection point 13 and the common terminal 15. A third induction coil 6 is connected between the connection point 12 and the connection point 17 between the diode 5 and the capacitor 7. 
     In the arrangement of FIG. 13, the three reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the common terminal 15. The diode 5 is connected between the output terminal 20 and the connection point 12. A second capacitor 7 is connected in series with the transistor 4 between the output terminal 20 and the connection point 13. A third induction coil 6 is connected between the connection point 12 on one side and the connection point 16 between the capacitor 7 and the transistor 4 on the other side. 
     The arrangement of FIG. 14 includes three reactive elements 1, 2 and 3 connected in series between the output terminal 20 and the common terminal 15. The transistor 4 is connected between the input terminal 10 and the connection point 12. A second capacitor 7 is connected in series with the diode 5 between the input terminal 10 and the connection point 13. A third induction coil 6 is connected between the connection point 12 on one side and the connection point 17 between the diode 5 and the capacitor 7 on the other side. 
     In the arrangement of FIG. 15, the three reactive elements 1, 2 and 3 are connected in series between the output terminal 20 and the common terminal 15. The transistor 4 is connected between the input terminal 10 and the connection point 12. The diode 5 and a second capacitor 7 are connected in series between the connection point 13 and the input terminal 10. A third induction coil 6 is connected between the connection point 12 and the connection point 17 between the diode 5 and the capacitor 7. 
     FIG. 16 shows an arrangement in which the three reactive elements 1, 2 and 3 are connected in series between the input terminal 10 and the common terminal 15. The diode 5 is connected between the connection point 12 and the output terminal 20. The transistor 4 is connected in series with a second capacitor 7 between the connection point 13 and the output terminal 20. A third induction coil 6 is connected between the connection point 12 and the connection point 16 between the transistor 4 and the capacitor 7. 
     Each of the arrangements described in the foregoing can be adjusted in an optimum way for a particular application by properly sizing the reactive elements so as to reduce the output current ripple and the output voltage ripple to a minimum. Further, all the topologies as disclosed have bi-directional properties, i.e. each of terminal pairs of the quadripole which a converter is comprised of, can be used either as an input port or as an output port as well.