Bidirectional DC-DC converter and a method of controlling said bidirectional DC-DC converter

1 . A method of controlling a bidirectional DC-to-DC converter, wherein said bidirectional DC-to-DC converter comprises:

two first terminals connected to a direct current source;

two second terminals connected to a load that can be supplied with direct current;

a transformer stage provided with a primary circuit and a secondary circuit equipped with a primary winding and a secondary winding, respectively, which can be magnetically coupled to each other; said primary circuit being connected to said first terminals, and said secondary circuit being connected to the second terminals;

a switching stage operatively interposed between the two first terminals and the primary circuit of the transformer stage;

a rectifier stage operatively interposed between the two second terminals and the secondary circuit of the transformer stage;

a control unit configured to drive the switching stage and the rectifier stage;

characterised in that:

said primary circuit comprises at least a first capacitor, at least a first leakage inductance (LD 1 ) and at least a first magnetizing inductance (LM 1 ) arranged in series with each other, and at least a first switch (SW 1 ) arranged in parallel with said first capacitor (C 1 );

said secondary circuit comprises at least a second capacitor (C 2 ), at least a second leakage inductance (LD 2 ) and at least a second magnetizing inductance (LM 2 ) arranged in series with each other, and at least a second switch (SW 2 ) arranged in parallel with said second capacitor (C 2 );

and in that said control unit is also configured to switch the first switch (SW 1 ) and the second switch (SW 2 ) between an open and a closed condition as a function of a level of power transferred by the transformer stage and/or a direction of an energy flow, in order to change a topology of the primary circuit and/or the secondary circuit,

wherein the control unit is configured to switch said first switch (SW 1 ) and said second switch (SW 2 ) between said open condition and said closed condition so as to arrange the primary circuit and the secondary circuit in:

a first high power configuration, when a power transferred between the first terminals and the second terminals has a first value comprised between a first conversion value and a value of a rated power of the converter, with a first energy flowing from the primary circuit to the secondary circuit,

a second high power configuration, when the power transferred between the first terminals and the second terminals has a second value comprised between the first conversion value and the value of the rated power of the converter, with a second energy flowing from the secondary circuit to the primary circuit,

at least one low power configuration, when the power transferred between the first terminals and the second terminals has a third value lower than said first conversion value,

in a transition configuration, different from the first and second high power configurations and from the low power configuration, when the power transferred between the first terminals and the second terminals has a fourth value comprised between the first conversion value and a second conversion value, said second conversion value being lower than the first conversion value and higher than zero,

wherein:

said first high power configuration provides that the first switch (SW 1 ) is in the open condition and said second switch (SW 2 ) is in the closed condition, defining a first LLC topology for the converter;

said second high power configuration provides that the first switch (SW 1 ) is in the closed condition and said second switch (SW 2 ) is in the open condition, defining a second LLC topology for the converter;

said low power configuration provides that the first switch (SW 1 ) and the second switch (SW 2 ) are in the closed condition, defining a DAB topology for the converter;

said transition configuration provides that the first switch (SW 1 ) and the second switch (SW 2 ) are in the open condition, defining a CLLC topology for the converter,

said method comprising steps of:

monitoring a level of power transferred by the transformer stage; and

arranging the primary circuit and the secondary circuit in the first high power configuration or the second high power configuration or the low power configuration with a change in the level of power transferred.

2 . The bidirectional DC-to-DC converter according to claim 1 , wherein:

said first conversion value is comprised between 20% and 50% of the rated power of the converter, preferably between 25% and 35% of the rated power of the converter;

said second conversion value is comprised between 10% and 30% of a rated power of the converter, preferably between 15% and 25% of the rated power of the converter.

3 . The bidirectional DC-to-DC converter according to claim 1 , wherein said transformer stage has a transformation ratio varying between at least a first and a second value; said control unit being configured to modify the transformation ratio between the first and the second value as a function of a voltage level across the first and/or second terminals.

4 . The bidirectional DC-to-DC converter according to claim 3 , wherein the primary winding of the primary circuit comprises at least a first coil and a second coil arranged in series, between which a first splitting node is interposed and wherein the primary circuit comprises:

at least a first and a second charge branch parallel to each other, wherein the first charge branch is connected in series upstream of the first coil, and the second charge branch is connected in series upstream of the first splitting node;

a first selector element (SW 3 ) that can be at least selectively switched between a first position, in which it guides a current flow to or from the first coil, and a second position, in which it guides the current flow to or from the first splitting node.

5 . The bidirectional DC-to-DC converter according to claim 4 , wherein the secondary winding of the secondary circuit comprises at least a first coil and a second coil arranged in series, between which a second splitting node is interposed and wherein the secondary circuit comprises:

at least a first and a second charge branch parallel to each other, wherein the first charge branch is connected in series upstream of the first coil, and the second charge branch is connected in series upstream of the second splitting node;

a second selector element (SW 4 ) that can be at least selectively switched between a first position, in which it guides the current flow to or from the first coil, and a second position, in which it guides the current flow to or from the second splitting node.