Treating light emitting elements 2 in all the display pixels in a light emitting display panel as objects, a maximum value of the forward voltages is drawn by a multi-input comparator 3a and a peak hold circuit 3b. Based on the maximum value of the forward voltages, a voltage boost circuit 6 switching operates a power FET to supply a boosted output by this operation to a constant current circuit 1 as the operational voltage VH. In the case where the maximum value of the forward voltages increases due to trouble or the like and based on this increment the operational voltage VH excessively increases, the operation of the voltage boost circuit 6 is stopped by a control output from an analog comparator 7a which functions as a voltage limiter.