The object of the present invention is reducing power consumption of a driving power supply circuit.In the case where the driving voltage Vi is higher than the reference voltage ViH, The signal S3P, S3N of the differential amplifier 30P, 30N become level “L” concurrently, and the signal S4P, S4N of the output circuit 40P, 40N become level “H”. Subsequently, the NMOS 62 becomes on-state and decreases the driving voltage Vi of the node N6. At the above stage, the control signal CP becomes level “L”, then the operation of the constant current circuit 20P is halted.In the case where the driving voltage Vi is lower than the reference voltage ViL, the PMOS 61 becomes on-state and increases the driving voltage Vi, and concurrently the operation of the constant current circuit 20P halts. At the same time, in the case where the reference voltage ViL is lower than the driving voltage Vi and the driving voltage Vi is lower than the reference voltage ViH, the signal S4P, S4N become level “H”, respectively, the PMOS 61 and the NMOS 62 become off-state, however, the control signal CP, CH become level “H”, then monitoring the driving voltage Vi is conducted by the comparing circuits thereof.