1 5v from the regulator 110 into two sets of power supply voltages vdd 1 vss 1 and vdd 2 vss 2 both with voltage drop 1 5v for respectively driving two different parts of ic 100 i e the first circuit 120 and the second circuit 130 in an embodiment of the present invention the configuration and functions of the first circuit 120 and the second circuit 130 are substantially the same except for insignificant differences in this circumstance with the same voltage drop across and the same circuit configuration in the first circuit 120 and the second circuit 130 it is predictable that a total current amount flowing through the first circuit 120 will be close to a total current amount flowing through the second circuit 130 in the following description of the embodiment by utilizing the mentioned voltage converting circuit structure power efficiency approaching 100 can be achieved the current driving capability of the output stage in the driving unit 114 of the regulator 110 is minimized and circuit area is thus minimized and waste of power is also reduced to a minimum please refer to fig2 fig2 is another diagram of the voltage converting circuit structure according to fig1 which further helps illustrate the power efficiency of this circuit structure in fig2 a symbol of a current source i_ckt 1 represents the total current amount flowing through the first circuit 120 a symbol of a current source i_ckt 2 represents the total current amount flowing through the second circuit 130 a symbol of a current source i_reg 1 represents a total current amount flowing from vdd to the output stage in the driving unit 114 and.