Patent ID: 8098056

Claim:
A bidirectional converter comprising: a reactor connected in series between a first input-output terminal and a second input-output terminal; a first switch connected in series between a first end of the reactor and the first input-output terminal; a second switch connected between the first end of the reactor and a reference point of potential; a third switch connected in series between a second end of the reactor and the second input-output terminal; a fourth switch connected between the second end of the reactor and a reference point of potential; and a switching control circuit which performs switching control of the first to fourth switches, wherein a buck-boost output from the first input-output terminal to the second input-output terminal, and a buck-boost output from the second input-output terminal to the first input-output terminal are performable under the switching control by the switching control circuit, wherein the switching control circuit switches between control modes, thereby performing the switching control, the control modes including: a first buck mode which causes the first switch and the second switch to perform a switching operation to step down a voltage from the first input-output terminal to the second input-output terminal; a first boost mode which causes the third switch and the fourth switch to perform a switching operation to boost a voltage from the first input-output terminal to the second input-output terminal; a first buck-boost mode which causes the first switch and the fourth switch to be turned on so that an electric current flows through the reactor, and then to be turned off while causing the second switch and the third switch to be turned on so as to output an electric current; a second buck mode which causes the third switch and the fourth switch to perform a switching operation to step down a voltage from the second input-output terminal to the first input-output terminal; a second boost mode which causes the first switch and the second switch to perform a switching operation to boost a voltage from the second input-output terminal to the first input-output terminal; and a second buck-boost mode which causes the second switch and the third switch to be turned on so that an electric current flows through the reactor, and then to be turned off while causing the first switch and the fourth switch to be turned on so as to output an electric current, and wherein the bidirectional converter further comprises: a loss calculation circuit which calculates a loss between an input and an output; a trial unit which determines a control mode in which the loss is lowered, by executing the control modes on a trial basis; and a storage unit which stores the control mode in which the loss is lowered, determined by the trial unit, in association with an input and output voltage or an electric current when executing the control mode, wherein the switching between the control modes is performed based on contents stored in the storage unit.