Abstract:
A refrigeration apparatus includes a fan and a motor for driving the fan. The motor is a single phase synchronous alternating current motor. In comparison with the traditional motor, the single phase synchronous alternating current motor has a reduced size and reduced cost, while ensuring the stable performance.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation-in-Part of co-pending Application No. PCT/CN2015/086422, filed on Aug. 7, 2015, for which priority is claimed under 35 U.S.C. §120; and this application claims priority of Application No. 201510543842.6, filed in China on Aug. 28, 2015, 201610390208.8 filed in China on Jun. 3, 2016, 201410390592.2 filed in China on Aug. 8, 2014, and 201410404474.2 filed in China on Aug. 15, 2014 under 35 U.S.C. §119, the entire contents of all of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to refrigeration apparatus, and in particular to a refrigeration apparatus having a single phase synchronous alternating current motor. 
       BACKGROUND OF THE INVENTION 
       [0003]    A cooling fan of a refrigeration apparatus, such as a freezer or refrigerator, includes a motor. The structure, size and cost of the motor affect the structure and cost of the whole refrigeration apparatus. How to balance between cost and motor performance has become a main subject of motor design. 
       SUMMARY OF THE INVENTION 
       [0004]    Accordingly, there is a desire to provide a refrigeration apparatus which includes an internal motor with low cost and stable performance. 
         [0005]    A refrigeration apparatus includes a fan and a motor for driving the fan. The motor is a single phase synchronous alternating current motor. 
         [0006]    Preferably, the single phase synchronous alternating current motor includes a stator and a rotor rotatable relative to the stator. The stator includes a stator core and windings wound around the stator core. The stator core includes a plurality of pole shoes. The rotor includes a plurality of permanent magnetic poles disposed along a circumferential direction of the rotor. The outer surface of the permanent magnetic pole and an inner circumferential surface of the pole shoe form a symmetrical uneven air gap therebetween. 
         [0007]    Preferably, the stator core includes an outer ring portion and a plurality of tooth bodies extending inwardly from the outer ring portion, the pole shoes extend from distal ends of the tooth bodies respectively, and each of the pole shoes extends toward two circumferential sides of the corresponding tooth body. 
         [0008]    Preferably, the rotor is received in a space cooperatively defined by the pole shoes, an outer surface of each permanent magnetic pole is spaced from a central axis of the rotor by a distance progressively decreasing from a circumferential center to two circumferential sides of the outer surface, and the air gap is symmetrical about a center line of one of the permanent magnetic poles. 
         [0009]    Preferably, each permanent magnetic pole is formed by one or more permanent magnet members, or all permanent magnetic poles are formed by a single ring shaped magnetic member. 
         [0010]    Preferably, the rotor comprises a rotor core, the one or more permanent magnetic members are mounted to an outer circumferential surface of the rotor core, the outer circumferential surface of the rotor core defines a plurality of axially extending grooves, and each groove is located at a junction between two permanent magnetic poles. 
         [0011]    Preferably, the one or more permanent magnetic members have a uniform thickness, and the outer circumferential surface of the rotor core matches with the one or more permanent magnet members in shape. 
         [0012]    Preferably, the outer circumferential surface of the rotor core and an inner circumferential surface of the one or more permanent magnet members are located on a same cylindrical surface, and each permanent magnet member has a thickness progressively decreasing from a circumferential center to two circumferential ends of the permanent magnet member. 
         [0013]    Preferably, a radial thickness of the pole shoe progressively decreases in a direction away from the tooth body. 
         [0014]    Preferably, the windings are wound around the tooth bodies respectively. 
         [0015]    Preferably, the symmetrical uneven air gap has a maximum thickness that is at least 1.5 times of its minimum thickness. 
         [0016]    Preferably, a slot is formed between each two adjacent pole shoes, and a width of the slot is greater than zero and less than or equal to four times of a minimum thickness of the symmetrical uneven air gap. 
         [0017]    Preferably, a width of the slot is greater than zero and less than or equal to two times of the minimum thickness of the symmetrical uneven air gap. 
         [0018]    Preferably, the single phase synchronous alternating current motor is powered by an alternating current power source, the single phase synchronous alternating current motor comprises a stator, a rotor rotatable relative to the stator, and a driving circuit, the stator comprising a stator core and windings wound around the stator core, the driving circuit comprises an integrated circuit and a controllable bidirectional alternating current switch connected with the integrated circuit, the controllable bidirectional alternating current switch and the windings are connected in series between two terminals which are configured to be connected to the alternating power source, at least two of a rectifier, a detecting circuit and a switch control circuit are integrated in the integrated circuit, the rectifier is configured to produce a direct current voltage at least for the detecting circuit, the detecting circuit is configured to detect a polarity of a magnetic field of the rotor, and the switch control circuit is configured to control the controllable bidirectional alternating current switch to be switched between turn-on and turn-off states according to a predetermined manner based on the polarity of the alternating current power source and the polarity of the magnetic field of the rotor that is detected by the detecting circuit. 
         [0019]    Preferably, the switch control circuit is configured to control the controllable bidirectional alternating current switch to turn on only when the alternating current power source operates in a positive half cycle and the detecting circuit detects a first polarity of the magnetic field of the rotor, or when the alternating current power source operates in a negative half cycle and the detecting circuit detects a second polarity of the magnetic field of the rotor, the second polarity being opposite to the first polarity. 
         [0020]    Preferably, the refrigeration apparatus is a freezer. 
         [0021]    Preferably, the single phase synchronous alternating current motor rotates at a constant 1800 RPM or 1500 RPM speed in a steady state. 
         [0022]    Preferably, the single phase synchronous alternating current motor has an input voltage of 120 v or 220 to 230 V, an input power of 6 to 20 W, and an efficiency of 50% to 80%. 
         [0023]    The refrigeration apparatus of the present invention includes the single phase synchronous alternating current motor in its interior for driving the fan. In comparison with the traditional motor, the single phase synchronous alternating current motor has a reduced size and reduced cost, while ensuring the stable performance. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  illustrates a refrigeration apparatus of the present invention, the refrigeration apparatus including a single phase synchronous AC motor. 
           [0025]      FIG. 2  is a perspective view of the single phase synchronous AC motor of  FIG. 1  according to a first embodiment of the present invention. 
           [0026]      FIG. 3  illustrates the single phase synchronous AC motor of  FIG. 2 , with the outer housing being removed. 
           [0027]      FIG. 4  is a top view of the single phase synchronous AC motor of  FIG. 3 . 
           [0028]      FIG. 5  illustrates the stator core of the single phase synchronous AC motor of  FIG. 3 . 
           [0029]      FIG. 6  illustrates permanent magnet members and the rotor core of the single phase synchronous AC motor of  FIG. 3 . 
           [0030]      FIG. 7  shows a torque curve of the single phase synchronous AC motor of the  FIG. 2  during rotation. 
           [0031]      FIG. 8  illustrates the stator core of the single phase synchronous AC motor of  FIG. 1  according to a second embodiment of the present invention. 
           [0032]      FIG. 9  illustrates the stator core of the single phase synchronous AC motor of  FIG. 1  according to a third embodiment of the present invention. 
           [0033]      FIG. 10  is a top view of the stator core and a rotor of the single phase synchronous AC motor of  FIG. 1  according to a fourth embodiment of the present invention. 
           [0034]      FIG. 11  is a schematic circuit diagram of the single phase synchronous AC motor of  FIG. 1  according to one embodiment of the present invention. 
           [0035]      FIG. 12  is a block diagram showing one implementation of the integrated circuit of  FIG. 11 . 
           [0036]      FIG. 13  is a block diagram showing another implementation of the integrated circuit of  FIG. 11 . 
           [0037]      FIG. 14  is a schematic circuit diagram of the single phase synchronous AC motor of  FIG. 1  according to another embodiment of the present invention. 
           [0038]      FIG. 15  is a block diagram showing one implementation of the integrated circuit of  FIG. 14 . 
           [0039]      FIG. 16  is a schematic circuit diagram of the single phase synchronous AC motor of  FIG. 1  according to still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0040]    It should be noted that the figures are not drawn to scale and that elements of similar structures or functions are generally represented by like reference numerals for illustrative purposes throughout the figures. It also should be noted that the figures are only intended to facilitate the description of the preferred embodiments. The figures do not illustrate every aspect of the described embodiments and do not limit the scope of the present disclosure. 
         [0041]    Referring to  FIG. 1 , the refrigeration apparatus  1  of the present invention includes a fan  90  and a single phase synchronous alternating current (AC) motor  10  for driving the fan  90 . The refrigeration apparatus  1  may be a refrigerator or a freezer. 
       First Embodiment 
       [0042]    Referring to  FIG. 2  to  FIG. 6 , the single phase synchronous AC motor  10  in accordance with a preferred embodiment of the present invention includes a stator  20  and a rotor  50  rotatable relative to the stator  20 . The stator  20  includes a cylindrical outer housing  21  with one open end, an end cap  23  mounted to the open end of the outer housing  21 , a stator core  30  mounted in the outer housing  21 , an insulating bracket  40  mounted to the stator core  30 , and windings  39  wound around the stator core  30  and supported by the insulating bracket  40 . The stator core  30  includes an outer ring portion  31 , a plurality of tooth bodies  33  extending inwardly from the outer ring portion  31 , a pole shoe  35  extending from a radial distal end to two circumferential sides of each tooth body  33 . The windings  39  are wound around the corresponding tooth bodies  33 , and are isolated from the stator core  30  by the insulating bracket  40 . 
         [0043]    The rotor  50  is received in a space cooperatively defined by the pole shoes  35  of the tooth bodies. The rotor  50  includes a plurality of permanent magnetic poles  55  disposed along a circumferential direction of the rotor. An outer surface of each permanent magnetic pole  55  is an arc surface. The outer surface of each permanent magnetic pole  55  is spaced from a central axis of the rotor  50  by a distance progressively decreasing from a circumferential center to two circumferential sides of the outer surface. The outer surface of the permanent magnetic pole  55  and an inner circumferential surface of the pole shoe  35  form an uneven air gap  41  therebetween that is symmetrical about a center line of the permanent magnetic pole  55 . Preferably, the symmetrical uneven air gap  41  has a maximum thickness that is at least 1.5 times of its minimum thickness. 
         [0044]    Referring to  FIG. 6 , in this embodiment, each permanent magnetic pole  55  is formed by a single permanent magnet member  56 . The rotor  50  further includes a rotor core  53 . The permanent magnet member  56  is mounted to an outer circumferential surface of the rotor core  53 . The outer circumferential surface of the rotor core  53  defines a plurality of axially extending grooves  54 . Each groove  54  is located at a junction between two permanent magnetic poles  55  to reduce magnetic leakage. In order to form the uneven air gap  41  between the permanent magnetic pole  55  and the inner circumferential surface of the pole shoe  35 , the outer circumferential surface of the rotor core  53  and the inner circumferential surface of the pole shoe  35  are located on two concentric circles in an axial plan view, and a thickness of the permanent magnet member  56  progressively decreases from a circumferential center to two circumferential ends of the permanent magnet member  56 . 
         [0045]    The rotor  50  further includes a rotary shaft  51  passing through and fixed to the rotor core  53 . One end of the rotary shaft  51  is mounted to the end cap  23  through a bearing  24 , and the other end of the rotary shaft  51  is mounted to a bottom of the cylindrical outer housing  21  of the stator  20  through another bearing, such that the rotor  50  is capable of rotation relative to the stator  20 . 
         [0046]    The stator core  30  is made from a magnetic-conductive magnetic material. For example, the stator core  30  is formed by stacking magnetic laminations (silicon steel laminations commonly used in the industry) along an axial direction of the motor. In the stator core  30 , a slot  37  is formed between every two adjacent pole shoes  35 . Preferably, each slot  37  is located at a middle position between two adjacent tooth bodies  33 . It should be understood that the slot  37  may be offset from the middle position between the two adjacent tooth bodies. This design can reduce the induction potential of the motor, thus increasing the output torque of the motor. The slot  37  has a width greater than zero and less or equal to four times of a minimum thickness of the symmetrical uneven air gap  41 . Preferably, the width of the slot  37  is greater than zero and less than or equal to two times of the minimum thickness of the symmetrical uneven air gap  41 . As configured above, the motor startup and rotation is smooth, which can improve the motor startup reliability and reduces the possible dead points. The term “ring portion” used in this disclosure refers to a closed structure formed by extending continuously along a circumferential direction, such as circular ring, square, polygon or the like. And the term “thickness” of the symmetrical uneven air gap  41  refers to a radial thickness of the air gap. 
         [0047]    Preferably, a radial thickness of the pole shoe  35  progressively decreases in a direction from the tooth body  33  to the slot  37 , such that the magnetic reluctance of the pole shoe  35  progressively increases in the direction from the tooth body  33  to the slot  37 , thus forming a magnetic bridge with progressively increasing magnetic reluctance. This design can make the motor operation smoother and improve the reliability of the motor startup. 
         [0048]    In this embodiment, the pole shoe  35  between each two adjacent tooth bodies  33  defines a positioning slot  38 . The number of the positioning slots  38  is the same as the number of the poles of the stator  20  and the number of the ring-shaped permanent magnetic poles  55 . In the present embodiment, the number of the positioning slots  38  is four. In the present embodiment, the stator winding is a concentrated winding and, therefore, the number of the tooth bodies  33  is the same as the number of the poles of the stator  20 . In an alternative embodiment, the number of the tooth bodies  33  can be an integer times of the number of the stator poles, such as, two times, three times or the like. 
         [0049]    In this embodiment, the positioning slots  38  are spaced along the axial direction of the motor, and are disposed in the inner circumferential surface of the pole shoes  35 . In an alternative embodiment, the positioning slots  38  extend continuously along the axial direction of the motor. Each positioning slot  38  is spaced from the two adjacent tooth bodies  33  by different distances. The positioning slot  38  is closer to one of the two adjacent tooth bodies  33 , and a center of the positioning slot  38  is offset from a symmetry center of the most adjacent tooth body  33 . 
         [0050]    When the motor  10  is not energized, i.e. at an initial position, a center line L 1  of the permanent magnetic pole  55  of the rotor  50  is offset from a center line L 2  of the adjacent tooth body  33  of the stator  20 . An angle Q formed between the center line L 1  and the center line L 2  is referred to as a startup angle. In this embodiment, the startup angle is greater than 45 degrees electric angle and less than 135 degrees electric angle. When the windings  39  of the stator  20  of the motor is supplied with an electric current in one direction, the rotor  50  can be started along one direction. When the windings  39  of the stator  20  of the motor is supplied with an electric current in an opposite direction, the rotor  50  can be started along an opposite direction. It should be understood that, when the startup angle is equal to 90 degrees electric angle (i.e. a center of the permanent magnetic pole  55  of the rotor  50  is aligned with the symmetry center of one adjacent tooth body  33 ), the rotor  50  can be easily started in both directions, i.e. it is the easiest angle to achieve bidirectional startup. When the startup angle is offset from the 90 degrees electric angle, the rotor is easier to start in one direction than in the opposite direction. It has been found from a large number of experiments that, when the startup angle is in the range of 45 degrees to 135 degrees electric angle, the startup of the rotor in both directions has good reliability. 
         [0051]      FIG. 7  shows a torque curve of the single phase synchronous AC motor  10  of the above embodiment during rotation, where the horizontal axis represents the rotation angle with the unit being degree, and the vertical axis represents the torque with the unit being Nm. As can be seen, during motor rotation, the torque curve of the motor is smooth, which reduces or avoids the startup dead point and hence improves the reliability of the motor startup. 
       Second Embodiment 
       [0052]    Referring to  FIG. 8 , different from the first embodiment, in order to increase the winding efficiency of the windings  39 , the stator core of the single phase synchronous AC motor includes a plurality of stator core parts  300  joined along a circumferential direction of the stator. Each stator core part  300  includes an arcuate yoke segment  300   b,  one tooth body  33  extending from the arcuate yoke segment  300   b,  and a pole shoe  35  extending from a radial distal end of the tooth body  33  to two circumferential sides of the tooth body  33 . In this embodiment, each stator core part  300  includes a single tooth body  33  and one corresponding pole shoe  35 . It should be understood that, each stator core part  300  may also include more than one tooth body  33  and corresponding pole shoes  35 . After the winding process of each stator core part  300  is completed, the plurality of the stator core parts  300  are joined to form the stator core  30  with stator windings. 
         [0053]    A recess-protrusion engagement structure is formed at a joining area between the arcuate yoke segments  300   b  of two adjacent stator core parts  300 . Specifically, in forming the recess-protrusion engagement structure, two ends of the arcuate yoke segment  300   b  of each stator core part  300  for being connected to form the outer ring portion may be provided with an engagement recess  34  and an engagement protrusion  32 , respectively. The engagement recess  34  and the engagement protrusion  32  together form the recess-protrusion engagement structure. In assembly, the engagement protrusion  32  of each stator core part  300  engages with the engagement recess  34  of one adjacent stator core part  300 , and the engagement protrusion  34  of each stator core part  300  engages with the engagement protrusion  32  of an adjacent stator core part  300 . 
         [0054]    Because the stator core  30  is formed by joining multiple stator core parts  300 , the slot  37  between the adjacent pole shoes can have a very small width. In this disclosure, the width of the slot refers to the distance between the two adjacent pole shoes. 
       Third Embodiment 
       [0055]    Referring to  FIG. 9 , different from the second embodiment, plane surfaces are formed at the joining areas of the arcuate yoke segments of the adjacent stator core parts  300  of the single phase synchronous AC motor of this embodiment. In this case, the joining areas of the arcuate yoke segments can be connected by soldering. 
         [0056]    Fourth Embodiment 
         [0057]    Referring to  FIG. 10 , in this embodiment, the pole shoe  35  between each two adjacent tooth bodies  33  of the single phase synchronous AC motor likewise forms a positioning slot  38 . Differently, the positioning slot  38  of this embodiment is disposed between the outer circumferential surface and the inner circumferential surface of the pole shoe  35  and, preferably, disposed close to the inner circumferential surface of the pole shoe  35 . 
         [0058]    In this embodiment, the rotor  60  includes a plurality of permanent magnetic poles  65  arranged along a circumferential direction of the rotor  60 . An outer circumferential surface of each permanent magnetic pole  65  is an arc surface, such that the permanent magnetic pole  65  and the inner circumferential surface of the pole shoe  35  form a symmetrical uneven air gap  41  therebetween. Preferably, the symmetrical uneven air gap  41  has a maximum thickness that is at least 1.5 times of its minimum thickness. Each permanent magnetic pole  65  is formed by a single permanent magnet member. The permanent magnet member is mounted to an outer circumferential surface of the rotor core  63 . The outer circumferential surface of the rotor core  63  defines a plurality of axially extending grooves  64 . Each groove  64  is located at a junction between two permanent magnetic poles  65  to reduce magnetic leakage. Different from the first embodiment, the thickness of the permanent magnet member of this embodiment is uniform, and the outer circumferential surface of the rotor core  63  matches with the permanent magnet member in shape. That is, the outer circumferential surface of the rotor core  63  and the inner circumferential surface of the pole shoes  35  are no longer located on concentric circles in the axial plan view. As such, the outer surfaces of the permanent magnetic poles  65  and the inner circumferential surfaces of the pole shoes  35  can still form the symmetrical uneven air gap  41  therebetween because the outer surface of the permanent magnetic pole  65  is still an arc surface. Alternatively, all the permanent magnetic poles  65  may be formed by a single permanent magnet member. 
         [0059]    In the above embodiment, the slot  37  between every two adjacent pole shoes  35  has a uniform circumferential width. It should be understood that, in an alternative embodiment, each slot  37  may also have an non-uniform circumferential width. For example, the slot  37  may be trumpet-shaped with a smaller inside and a larger outside. In this case, the width of the slot  37  refers to a minimum width of the slot  37  in this disclosure. In the above embodiment, the slot  37  extends along a radial direction of the motor. Alternatively, the slot  37  may also extend in a direction deviating from the radial direction of the motor, which can reduce the induction potential of the motor. 
         [0060]    In the single phase synchronous AC motor provided by the present invention, the slots  37  are formed between the adjacent pole shoes  35 , and the width of each slot  37  is greater than zero and less than or equal to four times of the minimum thickness of the air gap  41 , which can reduce sudden change of the magnetic reluctance caused by a slot opening, thereby reducing the cogging torque of the motor. In addition, the outer surface of the permanent magnetic pole is configured to be an arc surface, such that the thickness of the air gap  41  progressively increases from a center of the permanent magnetic pole to two circumferential sides of the permanent magnetic pole, thus forming the symmetrical uneven air gap. This design reduces the vibration and noise produced in the conventional motor due to the unduly large slot openings, reduces or avoids the possible startup dead point, and improve the reliability of the motor startup. In addition, the startup angle and the cogging torque needed during startup of the exemplified single phase synchronous AC motor can be easily adjusted according to design requirements, thus ensuring the reliability of the motor startup. For example, the motor startup angle can be easily adjusted by adjusting the position of the positioning slot of the pole shoe. When the startup angle Q is greater than 45 degrees electric angle and less than 135 degrees electric angle, the motor rotor can achieve bidirectional startup. The cogging torque prior to the startup of the motor can be adjusted by adjusting the shape, size and depth of the positioning slots of the pole shoes. The stator core is of a split-type structure, such that the winding process can be performed by using a double-flyer winding machine prior to the assembly of the tooth bodies and the outer ring portion, which increases the winding efficiency. 
         [0061]      FIG. 11  illustrates a schematic circuit diagram of a driving circuit of the single phase synchronous AC motor  10  of the refrigeration apparatus according to one embodiment of the present invention. The winding  39  of the stator of the motor and an integrated circuit  70  are connected in series between two terminals of an AC power source  80 . The driving circuit of the motor  10  is integrated in the integrated circuit  70 . The driving circuit can drive the motor to start along a fixed direction each time the motor is energized. 
         [0062]      FIG. 12  illustrates an implementation way of the integrated circuit  70 . The integrated circuit  70  includes a housing  71 , two pins  73  extending out of the housing  71 , and a driving circuit packaged in the housing  71 . The driving circuit is disposed on a semiconductor substrate, including a detecting circuit  75  for detecting a polarity of the rotor magnetic field of the motor, a controllable bidirectional AC switch  77  connected between the two pins  73 , and a switch control circuit  79 . The switch control circuit  79  is configured to control the controllable bidirectional AC switch  77  to be switched between turn-on and turn-off states according to a predetermined manner based on the rotor magnetic field polarity detected by the detecting circuit  75 . 
         [0063]    Preferably, the switch control circuit  79  is configured to control the controllable bidirectional AC switch  77  to turn on only when the AC power source  80  operates in a positive half cycle and the detecting circuit  75  detects a first polarity of the rotor magnetic field, or when the AC power source  80  operates in a negative half cycle and the detecting circuit  75  detects a second polarity of the rotor magnetic field, the second polarity being opposite to the first polarity. This configuration can make the winding  39  of the stator drive the rotor to rotate along a fixed direction during the motor startup. 
         [0064]      FIG. 13  illustrates another implementation way of the integrated circuit  70 , which differs from  FIG. 12  main in that: the integrated circuit of  FIG. 13  further includes a rectifier  74  which is connected between the two pins  73  in parallel with the controllable bidirectional AC switch  77 , for producing a direct current for the detecting circuit  75 . In this embodiment, the detecting circuit  75  is preferably a magnetic sensor (also referred to as position sensor), and the integrated circuit is mounted adjacent to the rotor such that the magnetic sensor can sense the change of the rotor magnetic field. It should be understood that, in some other embodiments, the detecting circuit  75  may also not include the magnetic sensor. Rather, the detecting circuit  75  detects the change of the rotor magnetic field by other means. In embodiments of the present invention, the driving circuit of the motor is packaged in the integrated circuit, which can reduce cost of the circuit and improve the reliability of the circuit. In addition, the motor may not use a printed circuit board. Rather, the integrated circuit is simply fixed to a suitable location and then connected the winding of the motor and power source through wires. 
         [0065]    In this embodiment, the stator winding  39  and the AC power source  80  are connected in series between the two pins  73 . The AC power source  80  is preferably a city AC power source with a fixed frequency such as 50 Hz or 60 Hz, a voltage of, for example, 110 V, 220 V or 230 V, and an input power of 6 to 20 W. The controllable bidirectional AC switch  77  is connected between the two pins  73 , in parallel with the series-connected stator winding  39  and AC power  80 . The controllable bidirectional AC switch  77  is preferably a triode AC switch (TRIAC) having two anodes connected to the two pins  73 , respectively. It should be understood that the controllable bidirectional AC switch  77  may also be implemented by two unidirectional thyristors reversely connected in parallel that are controlled by a corresponding control circuit according to a predetermined manner. The rectifier  74  is connected between the two pins  73 , in parallel with the controllable bidirectional AC switch  77 . The rectifier  74  converts the AC power between the two pins  73  into a low voltage DC power. The detecting circuit  75  may be powered by the low voltage DC power outputted from the rectifier  74 , for detecting the position of the magnetic poles of the permanent magnet rotor  50  of the single phase synchronous AC motor  10  and outputting corresponding signals. The switch control circuit  79  is connected with the rectifier  74 , the detecting circuit  75  and the controllable bidirectional AC switch  77 , and is configured to control the controllable bidirectional AC switch  77  to be switched between turn-on and turn-off states in a predetermined manner based on the rotor magnetic pole position information detected by the detecting circuit  75  and polarity information of the AC power source  80  obtained from the rectifier  74 , such that the stator winding  39  drives the rotor  50  to rotate only along the above described fixed startup direction during the motor startup. In this embodiment, when the controllable bidirectional AC switch  82  is turned on, the two pins  73  are short-circuited, and the rectifier  74  does not consume power because no electrical current flows therethrough, such that the power utilization efficiency can be greatly enhanced. 
         [0066]    In one embodiment, an input power the AC power source  80  provides to the motor having a voltage of 120 V, a frequency of 60 Hz and a input power of 14. W, and the rotor of the motor rotates at a constant 1800 RPM speed in a steady state. In another embodiment, the motor has an efficiency of 50% to 80%. 
         [0067]      FIG. 14  illustrates a schematic circuit diagram of a driving circuit of the single phase synchronous AC motor  10  of the refrigeration apparatus according to another embodiment of the present invention. The winding  39  of the stator of the motor and an integrated circuit  70  are connected in series between two terminals of an AC power source  80 . The driving circuit of the motor  10  is integrated in the integrated circuit  70 . The driving circuit can drive the motor to start along a fixed direction each time the motor is energized. In this embodiment of the invention, the driving circuit of the motor is packaged in the integrated circuit, which can reduce cost of the circuit and improve the reliability of the circuit. 
         [0068]    In this embodiment, all or part of the rectifier, detecting circuit, switch control circuit and controllable bidirectional AC switch are optionally integrated in the integrated circuit. For example, as shown in  FIG. 12 , only the detecting circuit, the switch control circuit and the controllable bidirectional AC switch may be integrated in the integrated circuit, while the rectifier is disposed outside the integrated circuit. 
         [0069]    For another example, as in embodiments shown in  FIG. 14  and  FIG. 15 , a voltage reduction circuit  76  and the controllable bidirectional AC switch  77  are disposed outside the integrated circuit  70 , while the rectifier  74  (which may only include a rectifier bridge but does not include a voltage reduction resistor or another voltage reduction element), the detecting circuit  75  and the switch control circuit  79  are integrated in the integrated circuit  70 . In this embodiment, low power elements are integrated in the integrated circuit, and high power elements such as the voltage reduction circuit  76  and the controllable bidirectional AC switch  77  are disposed outside the integrated circuit  70 . In another embodiment as shown in  FIG. 16 , it is also possible to integrate the voltage reduction circuit  76  into the integrated circuit  79 , with the controllable bidirectional AC switch  77  disposed outside the integrated circuit  70 . 
         [0070]    Although the invention is described with reference to one or more preferred embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Therefore, the scope of the invention is to be determined by reference to the claims that follow.