Abstract:
When a HDD is operating at a temperature below a threshold, a partial sine wave is input to the spindle motor to activate the motor to reduce undesirable speed oscillations of the motor. At normal operating temperatures a full sine wave is input for noise reduction.

Description:
I. FIELD OF THE INVENTION 
     The present invention relates generally to disk drives, and in particular to hard disk drives (HDD). 
     II. BACKGROUND OF THE INVENTION 
     Hitachi&#39;s U.S. Pat. No. 5,569,988, incorporated herein by reference, discloses a motor driving circuit for driving a three-phase brushless spindle motor of a hard disk drive (HDD). The disks of the HDD are rotated by the spindle motor. Variations on the Hitachi circuit may be found in USPP 2004/0108827, also incorporated herein by reference. 
     Feedback from the motor output has been used to establish a sinusoidal input current to the motor. In such an implementation, because the pattern of the three-phase output does not switch the current-supply pattern suddenly, but “softly” within predetermined phase criteria, it is colloquially referred to as a “soft switch”. 
     In any case, the effect of such a control circuit is salutary, because it reduces the acoustic noise that is produced. As critically recognized herein, however, when the HDD is operating at relatively cold temperatures, such as at start-up, the soft switch feature can lead to undesirable speed oscillations of the spindle motor. With this critical recognition in mind, the invention herein is provided. 
     SUMMARY OF THE INVENTION 
     A controller chip for a hard disk drive having at least one disk rotated by a spindle motor includes logic that includes receiving a signal that varies with temperature. Based on the signal, it is determined whether to input a full sine wave drive current to the spindle motor. 
     As set forth in non-limiting implementations below, the signal may be a temperature signal, but more preferably is a spindle motor speed signal or a spindle motor current. A full sine wave drive current is input when the signal satisfies a threshold, and otherwise a partial sine wave drive current is input to the spindle motor. The partial sine wave includes a sinusoidal part and a non-sinusoidal part that may be part of a trapezoid. 
     In another aspect, a data storage device includes at least one storage disk, a spindle motor turning the disk, and a spindle driver supplying input drive current to the spindle motor. Means are provided for causing the driver to configure the drive current as a full sine wave under a first condition, and causing the driver to configure the drive current as a partial sine wave under a second condition. 
     In still another aspect, a disk drive includes a micro processor that establishes a spindle motor input current profile to be other than full sinusoidal when a signal received by the micro processor indicates that a temperature of the disk drive is below normal operating temperature, such that a phase detect window results that is relatively longer than it would be were a full sinusoidal profile to be used for the input current. 
     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of a non-limiting HDD implementation of the present invention; 
         FIG. 2  is a block diagram showing the motor control circuitry; 
         FIG. 3  is a flow chart of the logic; 
         FIG. 4  is a non-limiting graph of various signals including the partial sine wave input current signal; and 
         FIG. 5  is a non-limiting graph of various signals including a full sine wave. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1  for a general overview of one non-limiting environment in which the present invention can be used, a rotary actuator is shown, although the invention described herein is also applicable to linear actuators. 
     A disk drive  310  includes a housing  312 , and a housing cover  314  which, after assembly, is mounted within a frame  316 . Rotatably attached within the housing  312  on an actuator shaft  318  is an actuator arm assembly  320 . One end of the actuator arm assembly  320  may include an E block or comb like structure  322  having a plurality of actuator arms  323 . Attached to the separate arms  323  on the comb or E block  322  are spring suspensions  324 , and at the end of each spring suspension is a slider  326  which carries a magnetic transducer. On the other end of the actuator arm assembly  326  opposite the spring suspensions  324  and the sliders  326  is a voice coil  328 . 
     Attached within the housing  312  are a pair of magnets  330 . The pair of magnets  330  and the voice coil  328  apply a force to the actuator assembly  320  to rotate it about the actuator shaft  318 . Also mounted within the housing  312  is a spindle shaft  332  that is rotated by the spindle motor shown in  FIG. 2  and described below. The spindle shaft  332  rotates a number of disks  334 . In  FIG. 1  eight disks are attached to the spindle shaft  332 . The disks  334  are attached to the spindle shaft  332  in spaced apart relation. 
     Referring to  FIG. 2  for further details, in a simplified embodiment a system  10  includes a spindle motor  12  that is coupled to the above-described spindle shaft. The motor  12  may be, e.g., a fluid-bearing three phase motor that receives “u”, “v”, and “w” input power to each of its respective three windings from a spindle driver  14 . The spindle driver  14  also supplies a center tap signal “CT” to the center tap of the three phase Y-wound motor  12  as shown. The spindle driver  14  functions in cooperation with a control component, such as a micro processor  16 , in accordance with the logic below. The micro processor  16  may be implemented by the HDD controller of the HDD or by another logic component within the HDD. In any case, as shown a summer  18  receives feedback (such as a motor pulse count rate) representing motor speed from the output of the spindle driver  14  and also receives a target speed, combining the two and sending input to the micro processor  16  for purposes to be shortly disclosed. 
     Now referring to  FIG. 3 , the present logic may be seen. Commencing at block  20 , an indication of temperature in the HDD is received. The indication may come directly from a temperature sensor in the housing of the HDD, but in one non-limiting implementation the temperature indication is a spindle motor control parameter which is affected by temperature. For instance, a control parameter such as the motor current from, e.g., a digital to analog converter (DAC) in the microprocessor can be received as an indication of temperature. 
     Proceeding to decision diamond  22 , it is determined whether the signal violates a threshold. For example, by comparing the spindle control DAC value from the summer control  18  to a target threshold value, the micro processor  16  can determine whether the motor current (and, hence, temperature) violates an empirically determined threshold, e.g., 125% of desired current. If not, at block  24  the micro processor  16  signals the spindle driver  14  to generate a full sine wave input current to the appropriate winding of the motor  12 , to reduce acoustic noise generated by the HDD. If, however, the comparison at decision diamond  22  indicates that the HDD is operating at low temperature, the logic flows to block  26  wherein the micro processor  16  signals the spindle driver  14  to generate a partial sine wave input current to the appropriate winding of the motor  12 , to reduce speed oscillations of the spindle motor. By “partial sine wave” is meant that one temporal portion of the signal is a sine wave and another temporal portion of the signal (to the same winding) is something else, e.g., a portion of a trapezoidal wave that in any case produces in a larger temporal window for detecting the flyback signal than would otherwise be produced by a full sine wave. 
       FIG. 4  illustrates this in greater detail. In  FIG. 4 , current, represented by the curve  28 , is the current flowing through the Wphase winding of the motor, scope CH “D” is the motion feedback signal associated with the Wphase windings for the example shown in  FIG. 4  and is indicated at  30 , while the scope CH “A” is Wphase voltage of the windings and is indicated at  32 . As shown, a sinusoidal part  34  of the input current  28  is a sine wave, while a non-sinusoidal part  36  of the input current is, e.g., a portion of a trapezoid, i.e., can be a ramp. The relatively long phase detect window resulting from the generation of the non-sinusoidal part  36  is indicated at  38 . Because of the larger window, errors in determining motor speed (and, hence, motor speed oscillations) are reduced.  FIG. 5  presents a full sine wave to contrast with  FIG. 4 , and as indicated provides insufficient time at low temperatures for the flyback to settle. 
     While the particular SYSTEM AND METHOD FOR ESTABLISHING SPINDLE MOTOR CURRENT DURING COLD TEMPERATURE OPERATION OF HDD as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and is thus representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more”. It is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. Absent express definitions herein, claim terms are to be given all ordinary and accustomed meanings that are not irreconcilable with the present specification and file history.