Start-up circuit for DC fan

A start-up circuit for a DC (direct current) fan, comprising:

• a digital-analog converter for converting a digital control signal to an analog control signal, the digital-analog converter comprising an output terminal;
• a voltage sampling device connected to the output terminal of the digital-analog converter, the voltage sampling device comprising an output terminal;
• a comparator comprising two input terminals and an output terminal, one of the input terminals being connected to the output terminal of the voltage sampling device;
• a buffer connected between the voltage sampling device and the comparator, for preventing a large current flow at the instant of power turn-on of the start-up circuit;
• and
• a switching device for controlling start-up of the DC fan, the switching device being connected to the output terminal of the comparator;
• wherein the switching device comprises a transistor, and the transistor has a first end connected to the output terminal of the comparator via a first resistor, a second end for connecting to the DC fan, and a third end grounded via a second resistor.

A start-up circuit for a direct current (DC) fan, comprising:

• means to receive a pulse width modulation (PWM) signal and translate said PWM signal to a control signal capable of being output by said means;
• a buffer electrically connecting with said means for accepting said control signal so as to be electrically chargeable within a predetermined period before further transmitting said control signal;
• a switching device electrically connecting with a direct current (DC) fan so as to be capable of activating said fan;
• and
• a voltage stabilizer electrically connected between said buffer and said switching device, said voltage stabilizer capable of accepting said control signal from said buffer and a feedback signal from said switching device so as to transmit said control signal to said switching device for controlling said switching device to activate said fan.