An auxiliary power supply circuit operating within a wide input voltage range has a voltage follower unit and a voltage comparison unit. The voltage follower unit has an electronic switch, a resistor, and a Zener diode. The electronic switch has a first terminal electrically connected to a voltage input terminal of the working voltage conversion circuit, a second terminal electrically connected to a voltage output terminal of the working voltage conversion circuit, and a control terminal. The resistor is electrically connected between the first terminal and the control terminal of the electronic switch. The Zener diode has a cathode electrically connected to the control terminal of the electronic switch. The voltage comparison unit has a detecting terminal electrically connected to the voltage input terminal of the working voltage conversion circuit, and an output terminal electrically connected to the control terminal of the electronic switch.