In a pulse-width-modulation (PWM) direct current (DC) steady-state output circuit, there are included an electrode switch and a resistor-capacitor (RC) integrating filter. The electronic switch has a signal input end, via which a PWM signal is input, and a high-level end. The RC integrating filter includes at least one RC filtering unit and a first protection unit. There can be (1+n) order(s) of the RC filtering unit(s) with a first-order RC filtering unit connected to the electronic switch and the first protection unit and the RC filtering unit(s) at the rest order(s), if any, being sequentially connected to the first-order RC filtering unit one by one. When the electronic switch has signals input thereto, the RC integrating filter makes feedback compensation to enable output of a steady-state DC level.