Patent Publication Number: US-2011057589-A1

Title: Computer fan control system

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to computer cooling, and particularly to a computer fan control system. 
     2. Description of Related Art 
     Frequently, a computer system includes a motherboard with various chips such as central processing units (CPUs) mounted thereon, and a storage device such as a hard disk drive, each of which is known to generate heat when operating. Typically, fans are mounted on the motherboard to dissipate the heat. Generally, in-phase pulse width modulation (PWM) signals from a motherboard are used to drive the fans, around which magnetism generating members easily form during operation. As a result, mechanical and electrical components of the fans can generate high vibration and prominence ratios, and efficiency of the computer system is thus reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an exemplary embodiment of a computer fan control system. 
         FIG. 2  is an exploded, isometric view of a computer fan of  FIG. 1 , in accordance with an embodiment. 
         FIG. 3  is a waveform diagram of in-phase PWM signals. 
         FIG. 4  is a waveform diagram of out-of-phase PWM signals. 
         FIG. 5  is a contrast histogram diagram showing a prominence ratio generated by the plurality of computer fans when receiving the in-phase PWM signals in comparison with a prominence ratio generated by the plurality of computer fans when receiving the out-of-phase PWM signals. 
         FIG. 6  is a contrast histogram diagram showing a vibration value generated by the plurality of computer fans when receiving the in-phase PWM signals in comparison with a vibration value generated by the plurality of computer fans when receiving the out-of-phase PWM signals. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , an exemplary embodiment of a system  6  for controlling a plurality of computer fans  10  is shown. The system  6  includes a control chip  20  and a pulse width modulation (PWM) chip  30 . The PWM chip  30  is connected to the plurality of computer fans  10  and to the control chip  20 . The control chip  20  may be a microcontroller or other kind of chip. 
     Each computer fan  10  includes four magnetism generating members  100 , each including a supporting member  102  of silicon and copper and an induction coil  104  wound around a part of the supporting member  102 . The four magnetism generating members  100  are spaced apart from one another in the shape of a cross. When electronic current passes through the magnetism generating members  100 , a magnetic field is generated which repels a magnetic field produced by a magnet (not shown) in the fan  10 , thereby rotating the computer fan  10 . In other embodiments, more than four or fewer magnetism generating members  100  can be deployed. 
     The control chip  20  stores a setup program to output a phase setting control instruction to the PWM chip  30 . 
     The PWM chip  30  outputs a plurality of out-of-phase PWM signals to induce the magnetism generating members  100  according to the phase setting control instruction, the plurality of computer fans  10  rotate and the magnetism generating members  100  of the plurality of computer fans  10  are in different locations. In this embodiment, the computer fans  10  rotate at the same speed. Because the control chip  20  directs the PWM chip  30  to output the out-of-phase PWM signals to the plurality of computer fans  10 , vibration and prominence ratio generated by the plurality of computer fans  10  do not overlap, the magnetism generating members  100  of the plurality of computer fans  10  are not aligned with each other during rotation, and the system  6 &#39;s vibration value and prominence ratio generated by the plurality of computer fans  10  are considerably lower than in conventional systems. 
     The following describes experimental measurement of vibration value and prominence ratio generated by the plurality of computer fans  10 . Three groups of computer fans were measured, each group including four computer fans  10 . Each of the computer fans  10  receiving the in-phase PWM signals (shown in  FIG. 3 ) and the out-of-phase PWM signals (shown in  FIG. 4 ) was measured three times. Each group of four computer fans  10  received PWM signals whose difference among the phase PWM signals one another were 360/4=90°, that is, 360° are divided equally among the number of computer fans. Averages of vibration values and prominence ratios generated by the plurality of computer fans when receiving the in-phase PWM signals and the out-of-phase PWM signals were calculated, and comparisons with vibration values and prominence ratios are shown in  FIGS. 5 and 6 .  FIGS. 5 and 6  are contrast histogram diagrams showing a prominence ratio generated by the plurality of computer fans when receiving the in-phase PWM signals (blank histogram) in comparison with a prominence ratio generated by the plurality of computer fans when receiving the out-of-phase PWM signals(slash histogram).  FIGS. 5 and 6  show that prominence ratio generated by the plurality of computer fans when receiving the out-of-phase PWM signals can be reduced by 1.4% in comparison with a prominence ratio generated by the plurality of computer fans when receiving the in-phase PWM signals, and the vibration value can be reduce by 32.5%. From the results, it can be seen that when the plurality of computer fans receive the out-of-phase PWM signals, the vibration value of the plurality of computer fans is significantly reduced, as is the prominent ratio. 
     It is to be understood, however, that even though numerous characteristics and advantages of the embodiments have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in details, especially in matters of shape, size, and arrangement of parts within the principles of the embodiments to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.