AC/DC intermediate-circuit converter having a very wide AC input voltage range
An AC/DC intermediate-circuit converter has a very wide AC input voltage range with a ZVS three-level DC/DC resonant converter with an LLC series-resonant circuit. Two intermediate-circuit capacitors are connected in series between DC intermediate-circuit connections with their common connection point forming a DC intermediate-circuit center connection ( 5 ). The DC intermediate-circuit connections are connected to the DC connections of a rectifier whose AC input connections have an AC input voltage applied thereto. A range changeover switch is arranged between an AC input connection and the DC intermediate-circuit center connection. The range changeover switch is closed in a lower AC input voltage range, when the ZVS three-level DC/DC resonant converter is operated on the basis of a “two-level operating mode” modulation strategy, such that the LLC series-resonant circuit has the full DC input voltage present between the DC intermediate-circuit connections applied to it. The range changeover switch is open in a central AC input voltage range when the ZVS three-level DC/DC resonant converter is operated on the basis of the “two-level operating mode” modulation strategy. The range changeover switch is open in an upper AC input voltage range when the ZVS three-level DC/DC resonant converter is operated on the basis of a “three-level operating mode” modulation strategy, such that the LLC series-resonant circuit has only half the DC input voltage that is present between the DC intermediate-circuit connections applied to it.
1. An AC/DC intermediate-circuit converter having a very wide AC input voltage range with a ZVS three-level DC/DC resonant converter, which has four primary switches that are arranged in series between first and second DC intermediate-circuit connections and that include a first and a second outer primary switch, and a first and a second inner primary switch, the AC/DC intermediate-circuit converter comprising:
a transformer having a primary winding;
an LLC series-resonant circuit having a resonant inductance connected to a common connection point between the two inner primary switches;
a magnetization inductance connected in parallel with the primary winding of the transformer and a resonant capacitor to a common connection point between the second outer primary switch and the second DC intermediate-circuit connection;
an input capacitor connected between a common connection point between the first outer primary switch and the first inner primary switch and a common connection point between the second inner primary switch and the second outer primary switch;
two intermediate-circuit capacitors being connected in series between the first and second DC intermediate-circuit connections with a common connection point between the two intermediate-circuit capacitors forming a DC intermediate-circuit centre connection;
a rectifier having, on a DC side thereof, DC connections connectable to the first and second DC intermediate-circuit connections, and, on an AC side thereof, AC connections being configured to have an AC input voltage applied thereto; and
a range changeover switch arranged between an AC input connection and the DC intermediate-circuit centre connection, wherein:
the range changeover switch is configured to be closed in a lower AC input voltage range, when the ZVS three-level DC/DC is operated in accordance with a two-level operating mode in which, according to a first level of the two-level operating mode, the first outer primary switch and the first inner primary switch are driven jointly, and, according to a second level of the two-level operating mode, the second inner primary switch and the second outer primary switch are driven jointly, such that the LLC series-resonant circuit has the full DC input voltage, which is present between the first and second DC intermediate-circuit connections, applied thereto;
the range changeover switch is configured to be open in a central AC input voltage range when the ZVS three-level DC/DC resonant converter is operated according to the two-level operating mode;
the range changeover switch is configured to be open in an upper AC input voltage range when the ZVS three-level DC/DC resonant converter is operated according to a three-level operating mode, in which, according to one level of the three-level operating mode, the first outer primary switch and the second inner primary switch are operated in a complementary manner, and, according to another level of the three-level operating mode, the first inner primary switch and the second outer primary switch are operated in a complementary manner, such that the LLC series-resonant circuit has only half the DC input voltage, which is present between the first and second DC intermediate-circuit connections, applied thereto.
2. The AC/DC intermediate-circuit converter according to claim 1 , wherein the resonant inductance is at least partially constituted by the stray inductance of the transformer.
3. The AC/DC intermediate-circuit converter according to claim 1 , wherein the rectifier is constituted by a non-controllable full-bridge rectifier having a smoothing inductance on the AC side.
4. The AC/DC intermediate-circuit converter according to claim 1 , wherein the rectifier is constituted by a non-controllable full-bridge rectifier with a smoothing inductance, which comprises two components coupled to one another on the DC side.
5. The AC/DC intermediate-circuit converter according to claim 1 , wherein the rectifier is constituted by a controllable three-level booster rectifier with two smoothing inductances, which are located at an output of a bridge rectifier, and which are split and are coupled to one another, two output diodes which are connected to the first and second DC intermediate-circuit connections, and two series-connected switches which are connected to the smoothing inductances.
6. The AC/DC intermediate-circuit converter according to claim 1 , wherein the rectifier is constituted by a controllable single-phase Vienna booster rectifier with an AC-side smoothing inductance, two output diodes and a switch connected between DC connections of a bridge rectifier.
7. The AC/DC intermediate-circuit converter according to claim 1 , wherein the rectifier is constituted by a controllable two-switch, three-level booster rectifier with an AC-side smoothing inductance, two output diodes, and a bridge rectifier having two diodes and two switches.
8. The AC/DC intermediate-circuit converter according to claim 2 , wherein the rectifier is constituted by a non-controllable full-bridge rectifier having a smoothing inductance on the AC side.
9. The AC/DC intermediate-circuit converter according to claim 2 , wherein the rectifier is constituted by a non-controllable full-bridge rectifier with a smoothing inductance, which comprises two components coupled to one another on the DC side.
10. The AC/DC intermediate-circuit converter according to claim 2 , wherein the rectifier is constituted by a controllable three-level booster rectifier with two smoothing inductances, which are located at an output of a bridge rectifier, and which are split and are coupled to one another, two output diodes which are connected to the first and second DC intermediate-circuit connections, and two series-connected switches which are connected to the smoothing inductances.
11. The AC/DC intermediate-circuit converter according to claim 2 , wherein the rectifier is constituted by a controllable single-phase Vienna booster rectifier with an AC-side smoothing inductance, two output diodes and a switch connected between DC connections of a bridge rectifier.
12. The AC/DC intermediate-circuit converter according to claim 2 , wherein the rectifier is constituted by a controllable two-switch, three-level booster rectifier with an AC-side smoothing inductance, two output diodes, and a bridge rectifier having two diodes and two switches.
13. An AC/DC intermediate-circuit converter having a very wide AC input voltage range with a ZVS three-level DC/DC resonant converter, which has four primary switches that are arranged in series between first and second DC intermediate-circuit connections and that include a first and a second outer primary switch, and a first and a second inner primary switch, the AC/DC intermediate-circuit converter comprising:
an LLC series-resonant circuit having a resonant inductance connected to a common connection point between the two inner primary switches;
two intermediate-circuit capacitors being connected in series between the first and second DC intermediate-circuit connections with a common connection point between the two intermediate-circuit capacitors forming a DC intermediate-circuit centre connection; and
a range changeover switch arranged between an AC input connection and the DC intermediate-circuit centre connection, wherein:
the range changeover switch is configured to be closed in a lower AC input voltage range, when the ZVS three-level DC/DC is operated in accordance with a two-level operating mode in which, according to a first level of the two-level operating mode, the first outer primary switch and the first inner primary switch are driven jointly, and, according to a second level of the two-level operating mode, the second inner primary switch and the second outer primary switch are driven jointly, such that the LLC series-resonant circuit has the full DC input voltage, which is present between the first and second DC intermediate-circuit connections, applied thereto;
the range changeover switch is configured to be open in a central AC input voltage range when the ZVS three-level DC/DC resonant converter is operated according to the two-level operating mode;
the range changeover switch is configured to be open in an upper AC input voltage range when the ZVS three-level DC/DC resonant converter is operated according to a three-level operating mode, in which, according to one level of the three-level operating mode, the first outer primary switch and the second inner primary switch are operated in a complementary manner, and, according to another level of the three-level operating mode, the first inner primary switch and the second outer primary switch are operated in a complementary manner, such that the LLC series-resonant circuit has only half the DC input voltage, which is present between the first and second DC intermediate-circuit connections, applied thereto.
14. The AC/DC intermediate-circuit converter according to claim 13 , comprising a rectifier having, on a DC side thereof, DC connections connectable to the first and second DC intermediate-circuit connections, and, on an AC side thereof, AC connections being configured to have an AC input voltage applied thereto.