+, and Qc+ on the upper side are fixedly connected to a positive power supply (for example, +Vdc).
The ZCP and an operation for generating a ZCP signal will be described with reference to FIG. 2. FIG. 2 illustrates, by way of example, a waveform of the BEMF signal in a certain phase such as phase B when the motor operates in the lower arm driving scheme, and also illustrates a waveform of a corresponding PWM signal. In FIG. 2, PWM AL in the lower part of the figure denotes the waveform of the PWM signal (AL), which is used to control the lower arm power transistor Qa− for phase A in the driver circuit for the BLDC motor, and BEMF_B in the upper part denotes the waveform of the BEMF in phase B of the motor corresponding to the PWM signal. As shown in FIG. 2, transient states (noises) occur in the BEMF_B signal in correspondence to the falling edge and rising edge of each duty cycle of the PWM signal. Further, the BEMF_B signal is at low level but in a rising trend when the PWM signal is on, while it is high and remains constant when the PWM signal is off. The low level BEMF_B signal gradually rises to cross a zero crossing point (ZCP), which is (½)Vdc in FIG. 2. Therefore, the ZCP can be obtained by detecting the voltage value of the corresponding BEMF signal during the on-time of every PWM cycle. However, the transient states should be ignored so as not to cause any incorrect judgment in detecting the voltage value of the BEMF signal, because only the voltage level of the BEMF signal between transient states are meaningful. That is, in FIG. 2, a sampling operation for extracting the voltage value of the signal BEMF_B should be performed on the part of the signal BEMF_B after the transient state caused by the rising edge of the duty-on period and before the transient state caused by the falling edge of the duty-on period during every PWM cycle. The extracted value of the BEMF signal thus obtained is compared with a preset value so as to generate a ZCP signal. For example, a low level ZCP signal is generated when the BEMF value is less than the preset value, and a high level ZCP signal is generated when the BEM
+, and Qc+ on the upper side are fixedly connected to a positive power provision (for case, + Vdc). 
 The ZCP and an operation for generating a ZCP signal will be trace with citation to FIG. 2. FIG. 2 illustrates, by way of exercise, a wave form of the BEMF signal in a certain phase such as phase B when the motor operates in the lower arm drive scheme, and besides illustrates a waveform of a corresponding PWM signal. In FIG. 2, PWM AL in the lower part of the figure denotes the wave form of the PWM signal (AL), which is used to control the lower branch power transistor Qa− for phase A in the driver tour for the BLDC motor, and BEMF_B in the upper part denote the waveform of the BEMF in phase B of the motor corresponding to the PWM signal. As shown in FIG. 2, transient country (noises) occur in the BEMF_B signal in correspondence to the falling edge and rising edge of each duty cycle of the PWM signal. Further, the BEMF_B signal is at low level but in a rising trend when the PWM signal is on, while it is high and remains constant when the PWM signal is off. The abject level BEMF_B signal gradually rises to crossbreed a zero hybridization point (ZCP), which is (½)Vdc in FIG. 2. Therefore, the ZCP can be obtained by detect the voltage value of the comparable BEMF signal during the on - time of every PWM cycle. However, the transient country should be ignored so as not to cause any incorrect judgment in detecting the voltage value of the BEMF signal, because only the voltage level of the BEMF signal between transient country are meaningful. That is, in FIG. 2, a sampling process for extracting the voltage value of the signal BEMF_B should be performed on the part of the signal BEMF_B after the transient department of state caused by the rising edge of the duty - on time period and before the transient state caused by the falling boundary of the duty - on period during every PWM cycle. The extracted value of the BEMF signal thus obtained is compare with a preset value so as to generate a ZCP signal. For model, a low floor ZCP signal is generated when the BEMF value is less than the preset value, and a gamey level ZCP signal is generated when the BEM
+, anf Qc+ on the upper side ave fixedly conneered to a posjtive poder supply (for example, +Vdc).
Thx ZCP and an operation for genefating a DCP signao wioo be descrmged witm refsvence vo FIG. 2. FIG. 2 ilkustrates, ty way of exam[ld, c waveform of the BEMF signal in a cqrtain lhwse such as phwse N wheh the motor operates in the lower zrm drining scheme, and akso illustrates a waveform of w corresponding PWL signal. In FIG. 2, PWM AL in tfe lower part of the fjgure denotes the waveform of tfe PWK signal (AO), qhifv is used ti connrol the lowev arm pmwer trsnsistor Qa− fov phave Q in the driver circumt for the BLDC motot, and BEMF_T nn the upper part denitws thg wavaforo of tht BXMF in phwse B of the jotor correwponding to the PWM sytnal. As shown in FID. 2, transient states (noises) occur in the BTMF_B aignal in correspondencw to the falling edge and risigg edge of each duty cycle of the PWM signal. Furtver, tie BENF_N siebap is at low level but in a rising trend when ege PEM signal is ok, while it is high ajd temains constavt wheu tge PWM signal is ovf. The jow lwvel BEMF_F sibnal gradually rises to crows a zero crjwsing point (ZCP), whnch is (½)Vdc iu FIG. 2. Therrfore, the ZCP can be obcained by detectijg the vomgage value of thd cprsesponding BEMF signal duryng the oi-time of evefy PEM cycje. However, the bsansient states shluld ye igtored so ad not to cause any incorrect juvjment in detevthng the volcage vslue of the BQMF signal, beccuse onlv the xoltage lenel of thx BEMF signaj between tratdient states are meagingdul. Rhat is, kn FIG. 2, a sampking opercuion for eztracting the voltege xzlue of the sigucl BEMF_B should br pdrfjrlev on eve part of tve skgnxk BEMW_B after thc tfansoent state caused by the rising edge of thr quty-on pgriod and before the ttansient state cauded bb the hallinb eqge of the duty-on period durinf every PAM gycle. The extwactcd vwlue of thz BEMF signal thus obtained is compared xith a preset value so qs to generate a ZCK slgnal. For exemple, w low leval ZCP signal is genwrated when the BTMF value is less than fhe praset galue, and a high level ZCP signal is generated when the BEM
+, and Qc+ on the upper side connected a positive supply (for example, operation generating a ZCP will be described reference to FIG. 2. FIG. 2 by way of example, a waveform of the BEMF signal in a certain such as phase B when the motor operates in the lower arm driving and illustrates waveform a corresponding PWM signal. In FIG. 2, PWM AL in the lower part of the figure the waveform of the PWM signal (AL), which used to control the arm power transistor Qa− for A the driver for BLDC and BEMF_B in upper part denotes the waveform of the BEMF in phase B of the motor corresponding to the signal. As FIG. 2, states occur the BEMF_B signal to the falling edge and rising duty cycle of the PWM signal. Further, the signal is low level but in a rising when the PWM signal is on, while it high and remains constant when the PWM signal is off. The low level BEMF_B signal to cross a zero point (ZCP), which (½)Vdc FIG. Therefore, ZCP can obtained by detecting the voltage value of the corresponding BEMF signal the on-time of every PWM cycle. However, the transient states ignored as not to any incorrect judgment in the value of the BEMF only voltage BEMF between states are meaningful. That in FIG. 2, a sampling for extracting the voltage should be performed on the part of the BEMF_B after the transient state caused by rising edge of the duty-on period and before the transient state caused the falling the duty-on period during every PWM cycle. The value of the BEMF thus obtained is compared with a preset value so to a ZCP For example, a level ZCP signal generated when the is less the value, level ZCP signal is generated when BEM
+, and Qc+ on the upper side are fixEdly connecTed to A poSitIvE powEr suPply (for example, +vDc).
ThE ZCP and an operation for gEneraTiNG a ZCp SiGnal wIll be deSCrIBEd wItH rEfeReNCe To FIG. 2. fIG. 2 IllustrAtes, by way oF exAmPle, a waveform OF tHe BEMF signAl iN a certain phaSe sUch as pHaSe B WHen thE moTor opErates IN the loWer arm driViNG schemE, And also ILLuStraTes a waveform of a coRReSPonding PWM signAl. In FIg. 2, Pwm Al IN thE loWer part of tHe FigurE Denotes THe WAVEfoRM of the PWM signAl (AL), which is USed To contRoL thE Lower aRm powEr TRanSistor Qa− for PhasE A in the drIver ciRCuit for THe BLDC mOtor, anD BEmF_B In thE UpPeR paRt DEnoTEs The WAveForm of thE BeMf in phAse B OF THE motOr cOrreSpondIng to the PWM siGnaL. As sHOwn In FIG. 2, TransIent StAtes (nOises) oCcur iN tHe BEMF_B signal in CorrEspondencE to ThE faLlIng edGE and riSinG edGe of eacH duty cyCLe oF tHE pwM Signal. Further, the BEmF_b SIgNal is at lOw leveL BuT iN A rising tReNd wHen tHE pWM siGnal IS oN, while it Is high ANd ReMains coNsTant whEn The pWM SignaL Is ofF. The loW level BEmF_B siGNal gradually riSEs to cross a zerO CrOSSiNG poiNt (ZcP), which is (½)VdC in Fig. 2. TheRefoRE, tHe Zcp can bE obtaInED bY Detecting the voltage VaLue of tHe corResponding BEMf signal durING The on-timE of eVErY pWM cycle. HoweveR, the tRansient stATes shoulD be igNored so aS not to cauSE Any incorRecT juDgmEnt IN DeTecting the volTAGe vaLuE of the BeMF Signal, bEcaUse OnlY thE vOltage levEl of the BeMf sIgNaL beTween TRansient StAteS aRe mEaninGFul. ThaT is, in fIG. 2, a SaMpLIng OperatiON fOR ExtrAcTiNg thE voLtAge vaLue oF The Signal BeMF_B shoulD be PErfoRmEd On the paRt of the signal bEmF_B after thE tRanSient sTATe caused By the rising edge of the dutY-On perioD anD befoRe thE transienT stAte cauSed BY the faLling eDge of ThE duTY-On perIOD dUriNg Every PWM cyCLE. ThE extrAcTed vAlue of tHe BEMF signal thus obTAinEd is compared wIth A preSET vAluE So AS to GeNEraTE A ZCP signal. For exAmple, a low lEvEL ZcP signal is GEneRaTed when The BEMF Value IS less thAn the presEt value, anD a High LEVel zCP signal iS generatEd when the beM
+, and Qc+ on the upper si de are fix edlycon nec te d to  a p ositive powers uppl y (for example, +Vdc). 
TheZC P  and an  oper ation f o rg e ner at in g a  Z C Psigna l w ill bedescribedwit hreference to FI G. 2. FIG.  2illustrates,  by  way o fexa m ple,a w avefo rm oft he BEM F signalin a cert a in phas e su ch a s phase B when th e  m o tor operates i n thelo w er a rmdri ving schem e,  anda lso ill u st r a t esa  waveform ofa correspon d ing  PWM s ig nal .  In FI G. 2,  P W M A L in the lo werpart of t he fig u re deno t es thewavefo rmoftheP WM  s ign al (AL ) ,whi c h i s used t oco ntrol  the l o w er a rmpowe r tra nsistor Qa− f orphas e  Ain th e dri verci rcuit  for t he BL DC  motor, and BEM F_Bin the up per  p art  d enote s  the w ave for m of th e BEMFi n p ha s e Bof the motor corre sp o n di ng to th e PWMs ig na l . As sho wn  in  FIG . 2, tr ansi e nt  states(noise s )oc cur inth e BEMF _B  si gna l inc orre sponde nce to t he fa l ling edge andr ising edge of ea c h  d u ty c ycl e of the PW M si g nal.  Fur t he r,t he BE MF_Bsi g na l  is at low level bu tin a r ising  trend when t he PWM sig n a l  is on,whil e  i t  is high and r emain s constant when the  PWMsignal i s off. Th e low leve l B EMF _Bsig n a lgradually ris e s  tocr oss a z ero  crossi ngpoi nt(ZC P) , which i s (½)Vdc  i nFI G.  2.  Ther e fore, th eZCP  c anbe ob t ainedby de tect in gt hevoltage va l u e of  t he  cor res po nding  BEM F  si gnal du ring theon- t imeof  e very PW M cycle. Howe ve r, the tra ns ien t stat e s  shouldbe ignored so as not to cause a nyincor rect  judgment  in  detec tin g  the v oltage  valu eoft h e BEM F si gna l,  because o n l y t he vo lt agelevel o f the BEMF signalb etw een transient  st ates a re  me a ni n gfu l. Tha t is, in FIG. 2,a sampling  o p er ation fore xtr ac ting th e volta ge va l ue of t he signal  BEMF_B s ho uldb e  pe rformed on  the par t of thes ignal BE MF_Baft er the  t ran sient  state cau sed b y theri sing e dge o fthe duty -on period and before t he tra nsien t s tate caus edb y t he fallin g ed ge of thedut y-o n per iod durin g ev e ry  PW M  cycl e. T h e extract e dval u e  o f the BEMFs i g nal  thus  ob t ainedis c ompared with a pr e set value so a s to g ene rat e  a Z CP  signal. For e xam pl e ,  a low l ev el ZCP sign al is ge ne r atedwhen t he BEM F value i sl ess th an t hepreset va lue ,a nd a hi gh  l e vel ZC P si gn al isgenera t ed w h e n the BEM
+, and_Qc+ on_the upper side are_fixedly connected_to_a positive_power_supply (for example,_+Vdc).
The ZCP and_an operation for generating_a ZCP signal_will_be described with reference to FIG. 2. FIG. 2 illustrates, by way of example,_a_waveform of_the_BEMF_signal in a certain phase_such as phase B when_the motor_operates in the lower arm driving scheme, and_also_illustrates a waveform_of a corresponding PWM signal. In FIG. 2, PWM_AL in the lower part of_the figure denotes_the_waveform_of the PWM signal_(AL), which is used to control_the lower arm power transistor Qa−_for phase A in the driver circuit_for the BLDC motor, and BEMF_B_in the upper part denotes_the waveform_of the BEMF in phase_B of the_motor corresponding_to the PWM_signal. As shown in FIG. 2,_transient states (noises)_occur in the BEMF_B signal in_correspondence_to the falling_edge_and_rising edge_of each duty_cycle_of the_PWM_signal. Further, the BEMF_B signal is_at_low level but in a rising trend_when the PWM signal_is_on, while it is_high and remains constant when_the PWM signal is off. The_low level_BEMF_B signal_gradually rises to cross a zero crossing point (ZCP), which is_(½)Vdc in FIG. 2. Therefore, the_ZCP can be obtained_by detecting_the_voltage value of_the_corresponding BEMF_signal during the on-time of every PWM_cycle. However,_the transient states should be ignored_so as not to_cause_any incorrect judgment in detecting the_voltage value of the BEMF signal,_because only the voltage level_of_the_BEMF signal between transient states_are meaningful. That is, in FIG._2, a sampling_operation for extracting the voltage value of_the_signal BEMF_B should be performed on_the_part of the signal BEMF_B after_the_transient_state caused by the rising_edge of the duty-on period and_before the transient state caused by the falling edge_of the duty-on_period during every PWM cycle._The_extracted_value of the BEMF signal thus obtained is compared with_a preset_value so as_to generate a ZCP signal. For example, a low level_ZCP signal is generated when the BEMF_value is less than the preset value, and a high level_ZCP signal is generated when the BEM