JP2517926B

PURPOSE:To realize a large capacity and high accuracy, by determining a switching so that a sum or difference of DC voltages may be added to a load at a change rage of a set value of current. CONSTITUTION:To a DC power source E1, switching elements S1-S4 and diodes D1-D4 for regeneration are connected to form a switching circuit I, and also to another DC power source E2 of different voltage, the same switching circuit II is formed. To a space between the connecting point of the elements S1, S3 and the connecting point of elements S6, S8, a load 1 is connected via a current- limiting reactor L0 suppressing the change of current. Besides, as the control circuit, an error detector 3, a hysteresis comparator 7 provided with a first-a second hysteresis loops, an interlocking change-over switch 8, and the like are arranged. In this case, when the change rate of a set value of current is small, a hysteresis action takes place to follow up the set of current value with the different voltage of the power sources E1, E2, and when the change rate is made higher, the second comparator 7 is worked to switch the change- over switch circuit 8.