An output voltage regulator of step-down switching power converters is described, with the regulator provided with digitally adjusted output voltage. It solves the problem of low regulation due to low error amplifier (EA) gain. This invention includes a power converter with the function of Digitally Error Correction, having Logic Control, EA, PWM comparator, Driver, power devices and passive components. A Digital Calibration Circuit whose input terminal is connected to the output voltage and output terminal is connected to the error signal. When the output voltage exceeds the tolerance range, this Digital Calibration Circuit will increase or decrease the error signal step by step, keeping the output voltage in the tolerance range. The Digital Calibration Circuit can be applied not only in nanometer scale process, but also in traditional process. For those power converters in traditional process, it is also quite promising in applications.