Patent ID: 7615946
Filing Date: 2009-11-10
Classification: H02P

Abstract:
1. A fan speed control device adapted for controlling a speed of a fan, comprising: a management selection module, selectively outputting an indicative signal of a serial input and output interface or an indicative signal of a baseboard management control, according to whether a motherboard supports a system of the baseboard management control or not, wherein the indicative signal is indicative of a power-on status; a first buffer, having a first power source terminal coupled to a first voltage, a second power source terminal coupled to a second voltage, an input terminal receiving a pulse width modulation signal and an output terminal generating a control signal to the fan; a resistor, having a first end coupled to the first power source terminal of the first buffer, and a second end coupled to the output terminal of the first buffer; a transistor, having a control terminal, a first terminal, and a second terminal coupled to the second voltage; a switch, coupled to the management selection module and determining to transmit the indicative signal to the control terminal of the transistor or the first terminal of the transistor according to a logic level of the indicative signal; and a second buffer, having a first power source terminal coupled to the first voltage, a second power source terminal coupled to the second voltage, an input terminal coupled to the first terminal of the transistor, and an output terminal coupled to the output terminal of the first buffer.