PURPOSE: To keep the constant cut-off timing of the output electric power regardless of the set level and to facilitate the output stop control, by changing the voltage drop rate in response to the set level in case the output electric power of a fixed level is cut off after it is temporarily reduced down to the set level.
CONSTITUTION: In a steady mode, a load signal control means 77 supplies the output electric power 73 (Pos) of a fixed level to a load 75. When the output stop of the electric power 73 is controlled, the 1st output control means 83 is energized by a control means 89 to output the integration signal 81 in response to combination of the 1st control signal 71 and the 2nd control signal 79. Then the means 77 changes the electric power 73 supplied to the load 75 into the value (Po1, Po2) corresponding to the signal 79 in response to the signal 81. The 2nd output control means 87 is energized by the means 89 to cut off the supply of the electric power 73 to the load 73.