Abstract: A fan linear speed controller is disclosed, which controls the rotation speed of a fan by an external fan control voltage. The fan linear speed controller includes a temperature sensor unit, a linear speed control unit and a fault detection unit. The temperature sensor unit has a thermistor for detecting the ambient temperature of the fan to generate a thermally sensitive voltage. The linear speed control unit receives the external fan control voltage and the thermally sensitive voltage to generate an output voltage for driving the fan. The output voltage is proportional to the fan control voltage when the thermally sensitive voltage is lower than a preset threshold voltage and the fan control voltage is higher than a preset reference voltage. The fault detection unit receives the thermally sensitive voltage and a rotation speed signal generated by the fan to selectively produce a fault signal indicating that the rotation of the fan is abnormal or the ambient temperature of the fan is too high.

Abstract: A fan driver is provided to drive a DC brushless fan. The fan driver has a pulse generator for receiving a signal indicating the phase of a rotor in the fan from a Hall element and generating two pulse signals whose phases are inverted by about 180.degree.. Two driving units activated by the two pulse signals, respectively, are provided to alternatively apply current to the two coils thereby generating magnetic fields to rotate the rotor of the fan. Two switch elements are connected to the two driving units so that anti-electromotive voltage generated by one of the two coils can be transferred to the other coil.

Abstract: A brushless DC fan driver is disclosed, which includes an amplifier, a pulse generator and a driving unit for rotating a fan, and further includes a tachometer unit, a lock protection unit and an overshoot voltage prevention unit for providing a reliable driving capability. The tachometer unit is provided to present a signal representing the rotation speed of the fan based on an amplified alternative polarity signal from a Hall sensor in the fan. The lock protection unit is provided to detect that the fan is locked up based on the amplified alternative polarity signal thereby generating a lock signal to shut down the fan driver and a restart signal to attempt to restart the locked fan. The overshoot voltage prevention unit is connected to the driving unit for detecting and bypassing overshoot voltages generated by the fan in operation.

Abstract: A true type single-phase shift circuit including a pair of PMOS transistors, a pair of NMOS transistors, a pair of first-type MOS transistors and one second-type transistor. The source terminals of the two PMOS transistors are both coupled to a first electric potential, the gate terminal of one PMOS transistor is coupled to a data signal, and the gate terminal of the second PMOS transistor is connected between the two first-type MOS transistors. The source terminals of the two NMOS transistors are both coupled to a second electric potential; the gate terminal of one NMOS transitors is coupled to the data signal and the gate of the second NMOS transistor is connected between the two first-type MOS transistors. The two first type MOS transistors are serially connected between the drain terminals of one of the two PMOS transistors and the drain terminal of one of the two NMOS transistors. Each gate terminal of the two first type MOS transistors is coupled to a clock pulse signal.

Abstract: Precise CMOS bandgap voltage and current references which uses the difference of MOS source-gate voltages to perform efficient curvature compensation are proposed and analyzed. Applying the developed design strategies, bandgap voltage references (BVR) with a temperature drift below 10 ppm/.degree.C. and a power supply drift below 10 ppm/V can be realized. For bandgap current references, both drifts can be under 15 ppm. An experimental BVR chip shows an average drift of 5.5 ppm/.degree.C. from -60.degree. C. to 150.degree. C. and 25 .mu.V/V for supply voltages between 5 V and 15 V at 25.degree. C. Due to novel curvature compensation, the circuit structure of the proposed references is simple and both chip area and power consumption are small.