A fan control circuit for controlling a fan to dissipate heat from an electrical device includes a comparator and an electrical switch. The comparator has a comparator input terminal, a comparator reference terminal, and a comparator output terminal. The comparator input terminal is connected to a power source via a first resistor and is also connected to the electrical device to receive a working current draw of the electrical device. The comparator reference terminal is receiving a reference voltage. The comparator output terminal is capable of outputting a comparison result between a voltage received by the input terminal and the reference voltage. The electrical switch has a control terminal, a first terminal, and a second terminal. The control terminal is connected to the comparator output terminal of the comparator to receive the comparison result. The first terminal is connected to the power source via a resistor. The second terminal is grounded and connected to the terminal via a fan.