Research And Design Of Single-Phase Low-Noise DC Fan Driver IC

To meet the demands of notebook cooling fan, this paper is about the design and study on a single-phase low-noise DC fan driver IC based on the UMC’s0.6μm BiCMOS process.Firstly, the working principle of the single-phase brushless DC motor was analyzed. The input of HALL signal that reflects the motor speed and rotor phase was linearly amplified by300times through the internal asymmetric structure of the power operational amplifier, thus converting into a control signal of the power tube to realize continuous driver for motor. Soft switched drive mode makes the output signal gentle when the amplitude of HALL signal is small, oppositely, it makes the output signal steep when the amplitude of HALL signal is big. In addition to the basic control functions of motor, it is designed with two protection circuit. If the motor is stalled by external force or obstacles, overdrive current may incur coil overheat/burning. To prevent this, lock detection circuit can shut down the driver for5seconds after motor lockup. Then automatic restart circuit will try to power up the driver for500mS every5seconds. The thermal protection circuit shut down the chip at176℃, and restart it at152℃.According to the functional requirements, the chip is divided into different function module, such as bandgap reference, hysteresis comparator, over-temperature protection, lock detection and automatic restart, and output driver. Following the overall design of indicators, it is designed at transistor level of several modules and the parameters of the whole circuit is simulated and analyzed. In the meantime, it does provide a brief introduction to the BiCMOS process and the design rules of layout.Finally, according to the test of this chip, majority of the electrical characteristics are according with the design indicators. Moreover, the power MOSFET’s on-resistance is just12Ω, so it has a huge load capacity. The test results shows that there is a linear relationship between the power supply voltage and the fan speed in the range from2.2V to6V of input voltage, so the speed of cooling fan could be adjusted in a wide range and low noise is obtained.