To prevent the notebook computer from crashing and accidentally dropping damaged data

In order to prevent violent collision, accidental fall damage data, notebook computer manufacturers to take a lot of hard disk protection methods, this paper introduces the use of accelerometer to determine whether the hard drive vibration, drop, timely adjustment of hard disk read and write head to the safe zone, to achieve protection purposes. The following is an analysis of the APS Circuit of the HDD active protection system.

1 Basic working principle of APS

A dual-axis or triaxial accelerometer chip is installed in the notebook circuit, also called the accelerometer, the notebook tilt angle, vibration, impact detection, and then use the special monitoring software to judge, if the judge exercise is harmful, in less than half a second time, before the impact, the control head quickly back to the safe area, protect hard disk data can also identify such regular motions as the vibration of carriages to prevent them from affecting normal use.

After analysis and calculation, the notebook accidentally crashed from the table, the acceleration x, Y, or z-axis voltage outputs are very small for the time derivative squared and are very large during the rollover period, after static, flip, free fall, and impact four consecutive processes, while in stationary and free fall, the square sum of the accelerometer is very great; This feature can be used to determine the timing This method of using derivative squares and judging falls is called differential acceleration algorithm. The advantages are obvious, through the detection of the flip, in advance to determine the occurrence of falls, so that the notebook has more time to take protective measures. At present, the monitoring software mainly uses this kind of algorithm, its flow chart is shown in figure one, simple description: Two-axis or triaxial accelerometer x, Y, Z axis output analog voltage, A/D conversion, into digital signals; the derivative of the circuit by the number of squares and (DGX/DT) ^2+ (DGY/DT) ^2=gsum or (DGX/DT) ^ Dgy/dt ^2+ (DGZ/DT) ^2=gsum, compared with valve value gth, if Gsum is higher than gth, determine the notebook accidentally flip, protect the circuit action, so that the head quickly back to the safe zone, to prevent hard disk damage. The APS circuit with differential acceleration protection algorithm can be used for triaxial accelerometer and two-axis accelerometer.

2 Common acceleration Sensor chip introduction

2.1 Double axle ADXL322 chip

ADXL322 is a low-power, dual-axis acceleration measurement chip, the acceleration Measurement range ±2G;LFCSP Plastic package, 16 pins, the chip consists of a sensor, AC amplifier, demodulator and two output amplifiers.

Working process: sensor internal fixing plate by the difference of 180 ° square wave Drive, under the action of Accelerating force, the movable crossbeam between the fixed plate is offset, the output amplitude of the AC amplifier is proportional to the acceleration of two square wave voltage, and is amplified by the demodulator rectifier and the output amplifier, and the analog voltage of x and Y axis is output by 32kω resistor respectively.

2.2 Tri-axis LIS302ALB chip

Lis302alb is a low-power 3 axis accelerometer chip, measuring range ±2g, 3-axis output and multi-channel selection output; Tlga plastic package, 14 pins; The working principle is basically the same as that of a biaxial accelerometer.

3 Accelerometer usage on notebook computer

At present, IBM, Lenovo, Toshiba and other mainstream notebook installed HDD active protection system, although the accelerometer chip installation location is different, some in the motherboard, some in the hard disk line, but the circuit structure, the principle of the same work.

According to statistics, about 50% of the notebook computer installed with accelerometers.