DC CONSTANT VOLTAGE SOURCE

PURPOSE:To surely perform the operation of a positive and negative sharing power source three-terminal regulator and to realize a DC constant voltage source with high reliability by comprising a system without receiving the influence of an opposite side voltage by separating a positive voltage three-terminal regulator from a negative voltage three-terminal regulator by a relay. CONSTITUTION:A first relay 6 is connected to the output side of the positive voltage three-terminal regulator 3, and a second relay 7 to the output side of the negative voltage three-terminal regulator 10, and the serial connection part of first relay contacts 6b, 6c and second relay contacts 7b, 7c is connected between the output side of respective three-terminal regulator and a load 8. Thereby, the first and second relays 6, 7 are operated by outputting a voltage to the output of each of the three-terminal regulators 3, 10, and a source voltage is supplied to the load 8 via the relay contacts 6b, 6c, 7b, and 7c, therefore, latch down is perfectly prevented occurring, and the DC constant voltage source with high reliability is obtained.