This study proposes a direct current power supply circuit (DPS) that can match the impedance of the freestanding-sliding mode triboelectric nanogenerator (FS-TENG) with multi-harmonic characteristics and continuously supply power to the load with reduced energy loss. The proposed DPS consists of a double charge circuit (DCC) and a DC conversion circuit based on a comb filtering circuit (CFC). The proposed DPS successfully matched the high internal impedance of the FS-TENG, collected multi-harmonic electrical energy, and provided stable DC voltage for practical applications in real-time. The proposed FS-TENG and DPS supplied a continuous DC voltage of 2.2 V to loads with 0.039 % ripple, while reducing the impedance of the TENG from 221 MΩ to 11 MΩ. The present results demonstrate that the proposed DPS has higher output power than conventional buck and buck-boost converters for the FS-TENG with high impedance and multi-harmonic characteristics. This work presents a significant advancement towards continuous DC power supply utilizing the FS-TENG. In addition, the practical application of the FS-TENG and DPS was successfully demonstrated to drive a self-powered temperature sensor in real-time by generating a constant DC output voltage across a thermistor.