DC/DC converter

A DC/DC converter which performs power transmission between a first DC power supply and a second DC power supply, the DC/DC converter comprising:

• a transformer;
• a first converter unit formed by a full-bridge circuit including two bridge circuits each having a plurality of semiconductor switching elements to which antiparallel diodes are respectively connected, the first converter unit being connected between the first DC power supply and a first winding of the transformer;
• a second converter unit formed by a full-bridge circuit including two bridge circuits each having a plurality of semiconductor switching elements to which antiparallel diodes are respectively connected, the second converter unit being connected between the second DC power supply and a second winding of the transformer;
• a second reactor connected on an AC input/output line of the second converter unit;
• and
• a control circuit which calculates an output duty cycle on the basis of a difference current value between a current detection value and a current command value of current inputted to or outputted from the second DC power supply, and performs drive control of the semiconductor switching elements in the first converter unit and the second converter unit, wherein
• the control circuit includes a first circuit for performing feedback control so as to reduce the difference current value, and a second circuit for correcting one of control input and output of the first circuit on the basis of the current detection value and the current command value, and
• in first power transmission from the first DC power supply to the second DC power supply,
• using, as a first reference element, one of the semiconductor switching elements on a positive side and a negative side of a first bridge circuit which is one of the bridge circuits in the first converter unit, and using, as a second reference element, one of the semiconductor switching elements on a positive side and a negative side of a second bridge circuit which is one of the bridge circuits in the second converter unit, the control circuit turns off all the semiconductor switching elements of the second bridge circuit among the four bridge circuits in the first and second converter units, and controls, at the same ON time ratio, the semiconductor switching elements on a positive side and the semiconductor switching elements on a negative side in the other three bridge circuits,
• the control circuit controls a first phase shift amount which is a phase shift amount between a drive signal for the first reference element and a drive signal for the semiconductor switching element as a first diagonal element which is diagonal to the first reference element, and a second phase shift amount which is a phase shift amount between a drive signal for the first reference element and a drive signal for the semiconductor switching element as a second diagonal element which is diagonal to the second reference element, and
• the second circuit adjusts the first and second phase shift amounts by the correction, to cause the current detection value to follow the current command value
• the DC/DC converter further comprising a first reactor connected on an AC input/output line of the first converter unit, wherein
• in second power transmission from the second DC power supply to the first DC power supply,
• the control circuit turns off all the semiconductor switching elements of the first bridge circuit among the four bridge circuits in the first and second converter units, and controls, at the same ON time ratio, the semiconductor switching elements on a positive side and the semiconductor switching elements on a negative side in the other three bridge circuits,
• the control circuit controls a third phase shift amount which is a phase shift amount between a drive signal for the second reference element and a drive signal for the second diagonal element, and a fourth phase shift amount which is a phase shift amount between a drive signal for the second reference element and a drive signal for the first diagonal element, and
• the second circuit adjusts the third and fourth phase shift amounts by the correction, to cause the current detection value to follow the current command value.