 secondary side which is not connected with the primary side transmits power only through electromagnetic induction for maintaining the stability and quality of the power which is received by the load. Further, the isolation transformer is used to separate the different voltage potentials of the power input terminal and the load terminal so as to ensure the safety thereof. Another example is TWP No. M334349, entitled “Light tube driving device”, in which the light tube driving device includes an inverter, a first transformer, a second transformer, at least one light tube, a control unit and a third transformer. In this patent, FIG. 2 disclosed that two transformers (32, 34) are utilized to transmit energy between the high voltage inverter (30) and the light tube (36) and also to isolate the power fluctuation at the primary and the secondary sides. However, the use of two transformers increases the cost and also the volume.
Consequently, the size and the adaptability of the transformer are restricted by the insulation strength and the power waveform at the primary and the secondary sides. 1. Field of Invention
The present invention relates to a hinge unit. More particularly, the present invention relates to an auto-lock hinge unit.
2. Description of Related Art
Convertible tablet PCs (personal computer) integrate a normal notebook and tablet PC in a shell. FIG. 1 is a schematic diagram of a conventional convertible tablet PC. The convertible tablet PC 100 comprises a display unit 110, a base 130, a hinge unit 120 and a fastener unit wherein the fastener unit secures the display unit 110 to the base 130. The fastener unit is a latch or includes both a mortice 131 and a tenon 111, An easy way to convert the convertible tablet PC 100 from one operating status (such as normal notebook) to another operating status (such as tablet PC) is to directly rotate the display unit 110 in a preset rotation direction a of 180 degrees and then push the display unit 110 down to cover the base 130. To convert the convertible tablet PC 100 back to its original operation status (normal notebook), a user inverses the steps above.
During the rotation operation, while rotating the display unit 110 180 degrees, the display unit 110 can only be rotated in one direction, clockwise or counterclockwise, depending on the hinge unit 120 (for the foregoing example, rotation direction a is allowed while rotation direction b is not allowed). In other words, when rotating the display unit 110, the user has to remember
secondary side which is not connected with the primary slope air power only through electromagnetic induction for conserve the stability and quality of the might which is receive by the load. farther, the isolation transformer is used to separate the unlike voltage potentials of the power input end and the load terminal so as to guarantee the safety thereof. Another model is TWP No. M334349, entitled “ Light tube driving device ”, in which the abstemious tube driving device includes an inverter, a first transformer, a second transformer, at least one luminosity tube, a control unit and a third transformer. In this patent, FIG. 2 disclosed that two transformers (32, 34) are use to transmit energy between the high voltage inverter (30) and the light tube (36) and also to isolate the power fluctuation at the primary and the secondary sides. However, the use of two transformers increases the cost and besides the bulk. 
 Consequently, the size and the adaptability of the transformer are restricted by the insulating material forte and the exponent waveform at the primary and the secondary sides. 1. Field of Invention 
 The present invention relates to a hinge unit. More particularly, the present invention relate to an auto - lock hinge unit. 
 2. Description of Related Art 
 Convertible tablet PCs (personal calculator) integrate a normal notebook and tablet PC in a shell. FIG. 1 is a schematic diagram of a conventional convertible tablet PC. The convertible tablet PC 100 comprises a display unit of measurement 110, a base 130, a hinge unit 120 and a fastener unit wherein the fastener unit secures the display unit of measurement 110 to the base 130. The fastener unit is a latch or includes both a mortise 131 and a tenon 111, An easy means to convert the convertible tablet PC 100 from one manoeuver status (such as normal notebook) to another engage status (such as tablet PC) is to directly revolve the display unit 110 in a preset rotation guidance a of 180 degrees and then advertise the display unit 110 down to report the base 130. To convert the convertible pill PC 100 back to its original operation condition (normal notebook), a user inverses the steps above. 
 During the rotation operation, while rotate the display unit 110 180 degrees, the display unit 110 can only be rotated in one guidance, clockwise or counterclockwise, depending on the hinge unit 120 (for the predate example, rotation direction a is allowed while rotation direction b is not allowed). In early words, when rotating the display unit 110, the user has to remember
 sefondary side which is nou connected with jhw primery sids transmkts power only through electcomatnetix induction for maintakning the stabiliry aid quality of thx power which jd reeemved by the loac. Further, dhe isolation drxndformer is used to separate the difserent foptage potentiajs og the iocer input terminal and the load terminel so as to ensire the safety thereof. Anohher example is TWP No. M334349, entitled “Ligrr tube drivivg device”, pu which the light tube driving device incljdes cn inverter, a figvt transforner, a second transformer, dt leasy one light tune, a ronteol unit and a third vransformer. In this katent, FIG. 2 bisclosed that two trqnwformgrs (32, 34) are ytiuiztd vo fransmlt xnergy betwsen the higy voltage inverter (30) age the light thbe (36) agd also to isolate the power fluctuation dt fhe primary and the secindary sides. However, jhe use of two transformers increases the cost and also the volujd.
Couwequevrlj, the size and the adaptability of the transfjdmtr sre restricted by the insilwtojn strength avd the poser waveform at thf primaty and the secogdaru sides. 1. Field of Invention
Rhe present pnvebtion relates to a hinge unit. Morg partocularly, the present inrentioh relates tl an auto-muck hinge unit.
2. Ddscgipthon of Rtuated Art
Convertifle tablev PCs (personxl cpmputew) integratf a normal notebook and hablej PC it a shell. VIG. 1 is a schematic diagram of e conventionak wonnertible cablet PC. The convewtible tablet KC 100 comprnses a display uhit 110, a uase 130, a hingq unit 120 and a vastener univ wherein the fasrener uvkt secures the display lnnt 110 to thw base 130. The fastencr unkf is a latch or inxludes both a mprtkce 131 wnv a tqton 111, An easy way to vonveft the convcrtkble tablet PC 100 from one opedating status (such af normal notebooh) to another pperating status (skch av teblet LC) ys to directly rotate the dispmay unit 110 in a preset roeatiin direction a of 180 degrees and then push the displab unit 110 down to cover jhe base 130. To convert jhe convertiblx tablqt PC 100 bawk to its original operation status (nprmal notebook), a user inverves tje steps above.
During the rotation operation, while rotating the display unut 110 180 dxgwees, the diaplau unin 110 ean only fe rlvated in one direbtion, clockwise or counterclockwmse, dependhny on the hinge unit 120 (for the gofegoing exampue, rotation direction a js allowrd while rotation direction b ix not allowed). In other wprds, wheb rotzting nge display unit 110, the user kas to remembwr
secondary side which is not connected with side power only electromagnetic induction for of power which is by the load. the isolation transformer is used to the different voltage potentials of the power input terminal and the load terminal as to ensure the safety thereof. Another example is TWP No. M334349, entitled tube device”, which light tube driving device includes an inverter, a first transformer, a second transformer, at least one tube, a control unit and a third transformer. this patent, FIG. 2 that two transformers (32, 34) utilized transmit energy the voltage (30) and the tube (36) and also to isolate the power fluctuation at the primary and the secondary sides. However, use of increases the and the Consequently, the size adaptability of the transformer are restricted strength and the power waveform at the primary the secondary 1. Field of Invention The present relates to a hinge unit. More particularly, the invention relates to an auto-lock hinge unit. 2. Description of Related Art Convertible tablet PCs integrate a normal notebook tablet PC in shell. 1 a diagram of conventional convertible tablet PC. The convertible tablet PC 100 comprises a unit 110, a base 130, a hinge unit 120 and unit the fastener unit the display unit 110 the 130. The fastener unit latch includes 131 a 111, An easy way convert the convertible tablet PC from one operating status another operating status (such as tablet PC) is directly rotate the display unit 110 in preset rotation direction a of 180 degrees and then push the display 110 down the base 130. To convert the convertible tablet 100 back to its operation status (normal notebook), a user inverses the steps During rotation operation, rotating the display 110 180 degrees, display unit 110 be rotated one clockwise on the hinge unit 120 (for foregoing rotation direction a is allowed rotation is not allowed). In other words, when rotating the display unit 110, the user has
 secondary side which is not coNnected witH the pRimAry SiDe trAnsmIts power only thROugh Electromagnetic inductiOn for MaINtaiNInG the sTabilitY AnD QUalItY oF thE pOWeR whicH is ReceiveD by the load. furThEr, the isolatiON tRansformer Is uSed to separatE thE diffeReNt vOLtage PotEntiaLs of thE Power iNput termiNaL And the LOad termINAl So as To ensure the safety THeREof. Another examPle is TwP nO. M334349, ENTitLed “light tube dRiVing dEVice”, in wHIcH THE liGHt tube driving Device incluDEs aN inverTeR, a fIRst traNsforMeR, A seCond transfoRmer, At least onE light TUbe, a conTRol unit And a thIrd TraNsfoRMeR. IN thIs PAteNT, FiG. 2 dISclOsed that TwO tRansfOrmeRS (32, 34) ARE utiLizEd to TransMit energy betwEen The hIGh vOltagE inveRter (30) AnD the lIght tuBe (36) and AlSo to isolate the pOwer FluctuatiOn aT tHe pRiMary aND the seConDarY sides. HOwever, tHE usE oF TWO tRansformers increasEs THE cOst and alSo the vOLuMe.
cOnsequenTlY, thE sizE ANd the AdapTAbIlity of tHe tranSFoRmEr are reStRicted By The InsUlatiON strEngth aNd the powEr wavEForm at the primaRY and the secondARy SIDeS. 1. fielD of invention
ThE preSEnt iNvenTIoN reLAtes tO a hinGe UNiT. more particularly, the PrEsent iNventIon relates to aN auto-lock hINGE unit.
2. DesCripTIoN Of Related Art
CoNvertIble tablet pcs (personAl comPuter) intEgrate a noRMAl noteboOk aNd tAblEt Pc IN a Shell. FIG. 1 is a scHEMatiC dIagram oF a cOnventiOnaL coNveRtiBlE tablet PC. the conveRtIbLe TaBleT PC 100 coMPrises a dIsPlaY uNit 110, A base 130, A Hinge uNit 120 anD a faStEnER unIt whereIN tHE FastEnEr Unit SecUrEs the DispLAy uNit 110 to thE base 130. The fAstENer uNiT iS a latch Or includes botH a Mortice 131 and A tEnoN 111, An easY WAy to convErt the convertible tablet pc 100 from onE opEratiNg stAtus (such aS noRmal noTebOOk) to anOther oPeratInG stATUs (sucH AS tAblEt pC) is to direCTLy rOtate ThE disPlay uniT 110 in a preset rotation DIreCtion a of 180 degreEs aNd thEN PuSh tHE dISplAy UNit 110 DOWn to cover the basE 130. To convert ThE CoNvertible tABleT Pc 100 back to Its origInal oPEration Status (norMal noteboOk), A useR INveRses the stePs above.
DUring the rOTatioN OpEratiOn, wHile roTaTinG the dIsplay UNit 110 180 DegreEs, the dIsPlay unIt 110 can OnLy be rotaTed in one direction, clockwIse or cOunteRclOckwise, dePenDIng On the hingE uniT 120 (for the forEgoIng ExampLe, rOTatioN dirECtIon A Is allOwed WHile rotatIOn DirECTiOn b is not allOWED). In Other WorDS, when rOtatIng the display unit 110, THe user has to remEmbeR
 secondary side which is n ot connect ed wi ththe  p rima ry s ide transmitsp ower  only through electrom agnet ic indu c ti on fo r maint a in i n g t he  s tab il i ty  andqua lity of  the power  wh ic h is receive d  b y the load . F urther, theiso lation  t ran s forme r i s use d to s e parate  the diff er e nt vol t age pot e n ti alsof the power inpu t  t e rminal and the  loadte r mi n a l s o a s to ensur ethe s a fety th e re o f .  An o ther exampleis TWP No.M 334 349, e nt itl e d “Lig ht tu be dri ving device ”, i n which t he lig h t tubed rivingdevice  in clu desa nin ver te r , a fi rst tra nsformer ,asecon d tr a n s f orme r,at l eastone light tub e,a co n tro l uni t and  a t hi rd tr ansfor mer.In  this patent, F IG.2 disclos edth attw o tra n sforme rs(32 , 34) a re util i zed  t o t ra nsmit energy betwe en t he  high vo ltagei nv er t er (30)an d t he l i g ht tu be ( 3 6)  and als o to i s ol at e the p ow er flu ct uat ion  at t h e pr imaryand thesecon d ary sides. How e ver, the useo ft w ot rans for mers increa sest he c osta nd  al s o the  volu me . 
C o nsequently, the siz eand th e ada ptability ofthe transf o r m er are r estr i ct e d by the insul ation  strengtha nd the p owerwaveform  at the p r i mary and  th e s eco nda r y  s ides. 1. Fiel d of I nv entionThe  presen t i nve nti onre lates toa hingeun it .Mo reparti c ularly,th e p re sen t inv e ntionrelat es t oan aut o-lockh in g e  uni t. 
2 . De scr ip tionof R e lat ed ArtConvertib let able tPC s (pers onal computer )integrateanor mal no t e book and  tablet PC in a shell.F IG. 1 i s a  sche mati c diagram  of  a con ven t ionalconver tible  t abl e t  PC.T h econ ve rtible tab l e t P C 100  c ompr ises adisplay unit 110,a  ba se 130, a hin geunit 1 20  an d  a fas te n eru n it wherein thefastener u ni t  s ecures the dis pl ay unit  110 to  theb ase 130 . The fas tener uni tis a l atc h or inclu des both  a mortic e  131a nd  a te non  111,An  ea sy wa y to c o nve rt th e conv er tibletable tPC 100 f rom one operating statu s (suc h asnor mal noteb ook )  to  anotheroper ating stat us(su ch as  ta b let P C) i s  t o d i rectl y ro t ate the d i sp lay u ni t 110 in ap r e set  rota tio n  direc tion  a of 180 degrees and then pushthed i spl ayu nit11 0 down to cove r t he b ase 130.  T o convert t he conve rt i ble t abletPC 100  back t o it s  origi nalope ration st atu s( normalno te b ook),a us er  inver ses th e  ste p s  above.
During t he ro t a tiono per ation ,while r o tati ng the dis play unit 1 10 180  deg rees,  the di sp lay un it11 0 can only be rotate d inone dir ec tion , c lockwi se o r count ercl oc kwi se, depen d i ng on  t h e h inge  unit  1 20 ( for the f o regoingexa m ple, ro ta tio n direct i on a  is allowe d w hiler o tation dir e ctio n  b is no t allo wed).In othe r  wo rd s, when  ro t a ting thedisplay u n it11 0, t he userha s to  r eme mb er
 secondary_side which_is not connected with_the primary_side_transmits power_only_through electromagnetic induction_for maintaining the_stability and quality of_the power which_is_received by the load. Further, the isolation transformer is used to separate the different_voltage_potentials of_the_power_input terminal and the load_terminal so as to ensure_the safety_thereof. Another example is TWP No. M334349, entitled_“Light_tube driving device”,_in which the light tube driving device includes an_inverter, a first transformer, a second_transformer, at least_one_light_tube, a control unit_and a third transformer. In this_patent, FIG. 2 disclosed that two_transformers (32, 34) are utilized to transmit_energy between the high voltage inverter_(30) and the light tube_(36) and_also to isolate the power_fluctuation at the_primary and_the secondary sides._However, the use of two transformers_increases the cost_and also the volume.
Consequently, the size_and_the adaptability of_the_transformer_are restricted_by the insulation_strength_and the_power_waveform at the primary and the_secondary_sides. 1. Field of Invention
The present invention_relates to a hinge_unit._More particularly, the present_invention relates to an auto-lock_hinge unit.
2. Description of Related Art
Convertible_tablet PCs_(personal computer)_integrate a normal notebook and tablet PC in a shell. FIG._1 is a schematic diagram of_a conventional convertible tablet_PC. The_convertible_tablet PC 100_comprises_a display_unit 110, a base 130, a hinge_unit 120_and a fastener unit wherein the_fastener unit secures the_display_unit 110 to the base 130._The fastener unit is a latch_or includes both a mortice_131_and_a tenon 111, An easy_way to convert the convertible tablet_PC 100 from_one operating status (such as normal notebook)_to_another operating status (such as tablet_PC)_is to directly rotate the display_unit_110_in a preset rotation direction_a of 180 degrees and then_push the display unit 110 down to cover the_base 130. To_convert the convertible tablet PC_100_back_to its original operation status (normal notebook), a user inverses_the steps_above.
During the rotation_operation, while rotating the display unit 110 180 degrees, the_display unit 110 can only be rotated_in one direction, clockwise or counterclockwise, depending on the hinge unit_120 (for the foregoing example, rotation direction a_is allowed while rotation direction b is_not allowed). In other_words,_when rotating the display unit 110, the_user_has_to_remember