Freescale Semiconductor Application Note 3-phase BLDC Motor Control with Sensorless Back-EMF ADC Zero Crossing Detection using 56F80x AN1913 Rev. 3, 11/2005 Contents 1. Introduction .............................................1 2. DSC Advantages and Features ...............1 3. Target Motor Theory ..............................3 3.1 BLDC MotorTargeted by This Application ........................................... 3 3.2 3-Phase BLDC Power Stage ................ 6 3.3 Why Sensorless Control? ............
DSC Advantages and Features many dedicated peripherals like Pulse Width Modulation (PWM) module, Analog-to-Digital Converter (ADC), Multi-function Quadrature Decoder, Timers, communication peripherals (SCI, SPI, CAN), and on-chip Flash and RAM. Generally, all family members are well suited for motor control applications.
BLDC MotorTargeted by This Application The PWM block has the following features: • Three complementary PWM signal pairs, six independent PWM signals, or a mixture thereof • Complementary channel operation features • Deadtime insertion • Deadtime distortion correction using current status inputs or software • Separate top and bottom polarity control • Edge-aligned or center-aligned PWM reference signals • 15-bit resolution • Half-cycle reload capability • Integral reload rates from one to 1
Target Motor Theory the permanent magnets and their displacement on the rotor is chosen so that the Back-EMF (the voltage induced into the stator winding due to rotor movement) shape is trapezoidal. This allows the DC voltage (see Figure 3-2), with a rectangular shape, to be used to create a rotational field with low torque ripples. Stator Stator winding (in slots) Shaft Rotor Air gap Permanent magnets Figure 3-1. BLDC Motor - Cross Section The motor can have more then just one pole-pair per phase.
BLDC MotorTargeted by This Application electrical angle Figure 3-2. Three Phase Voltage System Figure 3-3 shows the number of waveforms, the magnetic flux linkage, the phase Back-EMF voltage and the phase-to-phase Back-EMF voltage. The magnetic flux linkage was measured by calculating the integration phase Back-EMF voltage, which was measured on the non-fed motor terminals of the BLDC motor.
Target Motor Theory Phase Magnetic Flux Linkage Ps i_ A Ps i_ B Ps i_ C Ph. A Ph. B Ph. A A to p B to p C to p C bot Abot Ph. C Phase Back-EMF Ph. B Ui_ A Ui_ B Ui_ C Ph. C Speed reversal Bbot Acting power switch in the power stage A-A Phase-Phase Back-EMF Ui_ A B Ui_ B C Ui_ CA B-B C-C Figure 3-3. BLDC Motor - Back-EMF and Magnetic Flux 3.2 3-Phase BLDC Power Stage The voltage for a 3-phase BLDC motor is provided by a 3-phase power stage.
Power Stage - Motor System Model AC Line Voltage ~ = Power Stage M Position Sensors LOAD Control Signals Speed Setting Position Feedback Control Unit Figure 3-4. Classical System Therefore, additional connections to the motor are necessary. This may not be acceptable for some kind of applications.
Target Motor Theory Figure 3-5. Power Stage - Motor Topology The goal of the model is to find how the motor characteristics depend on the switching angle. The switching angle is the angular difference between a real switching event and an ideal one (at the point where the phase-to-phase Back-EMF crosses zero). The motor-drive model consists of a 3-phase power stage plus a Brushless DC motor. The power for the system is provided by a voltage source (Ud).
Power Stage - Motor System Model 3.4.1 Mathematical Model The following set of equations is valid for the presented topology: C ⎛ ⎞ 1 ⎟ u A = --- ⎜⎜ 2u VA – u VB – u VC + u ix ∑ ⎟ 3 ⎝ ⎠ x=A C ⎛ ⎞ 1 u B = --- ⎜ 2u VB – u VC – u VA + ∑ u ix⎟ ⎜ ⎟ 3 ⎝ ⎠ x=A uC C ⎛ ⎞ 1--- ⎜ = ⎜ 2u VC – u VA – u VB + ∑ u ix⎟⎟ 3 ⎝ ⎠ x=A uO C ⎛ C ⎞ 1--- ⎜ = ⎜ ∑ u Vx – ∑ u ix⎟⎟ 3 ⎝x = A ⎠ x=A (EQ 3-1.) 0 = iA + iB + iC where: u VA …u VC are “branch” voltages between one power stage output and its natural zero.
Target Motor Theory The internal torque of the motor itself is defined as: C 1 T i = ---ω C ∑ x=A dΨ x ∑ dθ u ix ⋅ i x = (EQ 3-3.) ⋅ ix x=A where: Ti - internal motor torque (no mechanical losses) ω,θ - rotor speed, rotor position x - phase index, it stands for A,B,C Ψx - magnetic flux of phase winding x It is important to understand how the Back-EMF can be sensed and how the motor behavior depends on the alignment of the Back-EMF to commutation events.
System Specification Figure 3-6 shows branch and motor phase winding voltages during a 0-360°electrical interval. Shaded rectangles designate the validity of the equation (EQ 3-6.). In other words, the Back-EMF voltage can be sensed during designated intervals. 0 30 60 90 120 150 180 210 240 270 300 330 360 390 uVA uA Figure 3-6. Phase Voltage Waveforms 4. System Design Concept 4.
System Design Concept The introduced BLDC motor control drive with Back-EMF Zero Crossing using AD converter is designed as a system that meets the following general performance requirements: Table 4-1. Low Voltage Evaluation Hardware Set Specifications Motor Characteristics: Drive Characteristics: Load Characteristic: Motor Type 4 poles, three phase, star connected, BLDC motor Speed Range: < 5000 rpm (at 60V) Maximal line voltage: 60V Phase Current 2A Output Torque 0.
Sensorless Drive Concept Table 4-3. High Voltage Evaluation Hardware Set Specifications Motor Characteristics: Drive Characteristics: Load Characteristic: Motor Type 6 poles, three phase, star connected, BLDC motor Speed Range: 2500 rpm (at 310V) Max. Electrical Power: 150 W Phase Voltage: 3*220V Phase Current 0.55A Speed Range < 2500 rpm Input Voltage: 310V DC Max DC-Bus Voltage 380 V Control Algorithm Speed Closed Loop Control Optoisolation Required Type Varying 4.
System Design Concept T h re e -P h a s e In v e rte r 3 p h a s e V o lta g e s , D C B u s C u rre n t & D C B u s V o lta g e S e n s in g P o w e r lin e 3 -p h BLD C M o to r 3 phase B L D C P o w e r S ta g e 3 P h a s e V o lta g e s D C -B u s V o lta g e /C u rre n t T e m p e ra tu re PW M PW M G e n e ra to r w ith D e a d T im e ADC Z e ro C ro s s in g P C M a s te r SCI Z e ro C ro s s in g T im e m o m e n t Z e ro C ro s s in g P e rio d , P o s itio n R e c o g n itio n C o m m u
PWM Voltage Generation for BLDC A current shunt is used to measure the DC-Bus current. The obtained signal is rectified and amplified (0-3.3V with 1.65V offset). The controller’s A/D converter as well as Zero Crossing detection is synchronized with the PWM signal. This synchronization avoids spikes when the IGBTs (or MOSFETs) are switching and simplifies the electric circuit. The A/D converter is also used to sense the DC-Bus Voltage and drive Temperature. The DC-Bus voltage is divided down to a 3.
Control Technique 3-PHASE POWER STAGE PWM1 SAT PWM3 SBT B PWM5 SCT POWER SOURCE DC VOLTAGE C A PWM2 SAB PWM4 SBT PWM6 SCT 3-PHASE BLDC MOT MOSFET/IGBT DRIVERS PWM1 PWM2 PWM3 PWM4 PWM5 PWM6 PULSE WIDTH MODULATOR (PWM) MODULE DSP56F80X Figure 5-1.
Back-EMF Zero Crossing sensing Commutation Commutation 60 120 PWM1 SAt PWM2 SAb PWM3 SBt PWM4 SBb PWM5 SCt PWM6 SCb IA IB IC electrical angle Figure 5-3. BLDC Commutation with Bipolar (Hard) Switching Figure 5-3 shows that the diagonal power switches are driven by the same PWM signal as shown with arrow lines. This technique is called bipolar (hard) switching. The voltage across the two energized coils is always ±DC-Bus voltage whenever there is a current flowing through these coils. 5.
Control Technique As stated, the AD converter has individual ADC Offset Registers for each ADC channels. The value in the Offset Register can be subtracted from the AD conversion output. The final result of the AD conversion is then two’s compliment data. The other feature associated to the Offset Registers is the Zero Crossing interrupt. The Zero Crossing interrupt is asserted whenever the ADC conversion result changes the sign compared to the previous conversion result.
Sensorless Commutation Control The non-fed phase “branch” voltage Uva is disturbed at the PWM switching edges. Therefore the presented BLDC Motor Control application synchronizes the Back-EMF Zero Crossing detection with PWM. The AD conversion of phase branch voltages is triggered in the middle of PWM pulse. Then the voltage for Back-EMF is sensed at the time moments because the non-fed phase branch voltage is already stabilized. 5.
Control Technique Start motor Alignment Alignment time expired? No Yes Starting (Back-EMF Acquisition) Minimal correct commutations done? No Yes Running Figure 5-5. Commutation Control States 5.4.1 Alignment Before the motor starts, there is a short time (which depends on the motor’s electrical time constant) when the rotor position is aligned to a known position by applying PWM signals to only two motor phases (no commutation). The Current Controller keeps the current within predefined limits.
Sensorless Commutation Control Figure 5-6. Alignment 5.4.2 Running The commutation process is the series of states which is assured when the Back-EMF Zero Crossing is successfully captured. The new commutation time is calculated after Back-EMF Zero Crossing is captured and the commutation is performed.
Control Technique The flow chart explaining the principle of BLDC Commutation control with Back-EMF Zero Crossing Sensing is shown in Figure 5-7. Commutation Done No BEMF Zero Crossing detected between previous commutations? Corrective Calculation 1. Yes Service of Commutation: Preset commutation Wait for Per_Toff until phase current decays to zero Yes BEMF Zero Crossing missed? BEMF Zero Crossing missed Corrective Calculation 2.
Sensorless Commutation Control 5.4.2.2 Running - Commutation Times Calculation Commutation times calculation is provided by algorithm bldcZCComput described in Section 11.1. T_Cmt0[n-2] T_Cmt0[n-1] T_Cmt0[n] n-1 n-2 T_Next[n] n COEF_CMT_PRESET * * Per_ZCrosFlt[n-1] Commutation is preset Commuted at preset time. No Back-EMF feedback was received - Corrective Calculation 1.
Control Technique • Service of received Back-EMF Zero Crossing - The commutation time (T_Next*[n]) is evaluated from the captured Back-EMF Zero Crossing time (T_ZCros[n]): Per_ZCros[n] = T_ZCros[n] - T_ZCros[n-1] = T_ZCros[n] - T_ZCros0 Per_ZCrosFlt[n] = (1/2*Per_ZCros[n]+1/2*Per_ZCros0) HlfCmt[n] = 1/2*Per_ZCrosFlt[n]- Advance_angle = = 1/2*Per_ZCrosFlt[n]- C_CMT_ADVANCE*Per_ZCrosFlt[n]= Coef_HlfCmt*Per_ZCrosFlt[n] The best commutation was get with Advance_angle: 60Deg*1/8 = 7.
Sensorless Commutation Control • Where: T_Cnt0 = time of the last commutation T_Next = Time of the Next Time event (for Timer Setting) T_zCros = Time of the last Zero Crossing T_zCros0 = Time of the previous Zero Crossing Per_Toff = Period of the Zero Crossing off Per_CmtPreset = Preset Commutation Periof from commutation to next commutation if no Zero Crossing was captured Per_ZCros = Period between Zero Crossings (estimates required commutation period) Per_ZCros0 = Pervious period between Zero Crossing
Control Technique Motor is Running at steady-state condition with regular Back-EMF feedback Rotor magnetic Stator magnetic field field (created by PM) Motor is Starting Alignment State The rotor position is stabilized by applying PWM signals to only two motor phases Border of stator pole Rotor movement during one commutation Zero Crossing edge indicator Direction of Phase current Phase winding Starting (Back-EMF Acquisition) The two fast (faster then the rotor can move) commutation are applied to cre
Sensorless Commutation Control Phase Back-EMF’s Phase A Phase C Phase B Back-EMF Zero Crossings Ideal Commutation Pattern when position is known BTOP CBOT CTOP ABOT ATOP BBOT BTOP CTOP ABOT BTOP CTOP CBOT Real Commutation Pattern when position is estimated BTOP CBOT ATOP CTOP ABOT st 1’ 2’ nd rd 3’ BBOT 4’rd CBOT ................. Starting (Back-EMF Acquisition) Align ABOT Running Figure 5-10. Back-EMF at Start-Up Figure 5-10 demonstrates the Back-EMF during the start-up.
Control Technique T_Cmt0[1] T_Cmt0[2] T2[1] n=1 T_Cmt0[3] T2[2] n=2 T2[n] n=3 COEF_CMT_PRESET * * Per_ZCrosFlt[n-1] Per_CmtStart Commutation is preset 2*Per_CmtStart Zero Crossing Detection Signal Commuted at preset time. No Back-EMF feedback was received - Corrective Calculation 1. T_ZCros[0] T2*[n] Zero Crossing Detection Signal Per_HlfCmt[n] Commuted when correct Back-EMF feedback received and evaluated.
Low Voltage Evaluation Motor Hardware Set 5.5 Speed Control The speed-closed loop control is provided by a PI regulator as described in Section 7.2.5. The actual speed (Omega_Actual) is computed from the average of two Back-EMF Zero Crossing periods (time intervals) gained from sensorless commutation control block. The speed controller works with a constant execution (sampling) period PER_SPEED_SAMPLE_S (request from timer interrupt). 6. Hardware 6.
Hardware 40w flat ribbon cable U2 +12 Evaluation Motor Board J3 GND U1 Controller Board J1 J30 (P1) DSP5680xEVM 12VDC J2 M1 Motor ECMTREVAL IB23810 Figure 6-1.
Low Voltage hardware set 6.3 Low Voltage hardware set The system configuration is shown in Figure 6-2. 40w flat ribbon cable U2 +12 J19 GND J20 3ph AC/BLDC Low Voltage Power Stage Controller Board J13 J30 (P1) ECLOVACBLDC J16 MB1 J17 DSP5680xEVM J18 Black White Red 12VDC U1 Motor-Brake SM40N SG40N Not Connected Black White Red J5 ECMTRLOVBLDC Not Connected Figure 6-2.
Hardware 6.4 High Voltage Hardware Set The system configuration is shown in Figure 6-3 +12V DC GND 40w flat ribbon cable U2 L J11.1 J11.2 N PE 3ph AC/BLDC High Voltage Power Stage J14 40w flat ribbon cable U3 J1 Optoisolation Board Controller Board J2 ECOPT 100 - 240VAC 49 - 61 Hz U1 JP1.1 JP1.2 J30 (P1) DSP5680xEVM MB1 Black White Red J13.1 J13.2 J13.3 Motor-Brake SM40V ECOPTHIVACBLDC SG40N Not Connected Black White Red J5 ECMTRHIVBLDC Not Connected Figure 6-3.
Main Software Flow Chart 7. Software Design This section describes the design of the software blocks of the drive. The software is described in the following terms: • Main Software Flow chart • Data Flow • State Diagram For more information of the used control technique refer to Section 5. 7.1 Main Software Flow Chart The main software flow chart incorporates the Main routine entered from Reset and interrupt states. The Main routine includes the initialization of the device and the main loop.
Software Design Reset Initialize Application State Machine: proceeds/sets requirements of: Drive Fault Status Application Mode Omega Required Mechanical Control Speed Control Alignment Current Zero Crossing Offset Commutation Control proceed Status_Commutation: Running Starting Alignment Stopped Interrupt OC Cmt Timer Commutation Timer OC ISR: Motor Commutation Timing Commutation.
Main Software Flow Chart Interrupt Up Button Interrupt Down Button Up Button ISR: increment Omega Required Mechanical Down Button ISR: decrement Omega Required Mechanical Reture Reture Interrupt ADC High Limit Interrupt ADC Low Limit ADC Low Limit ISR: set Undervoltage Fault set Overheating Fault Emergency Stop ADC High Limit ISR: set Overvoltage Fault set Overcurrent Fault Emergency Stop Reture Reture Interrupt PWM A Fault PWM Fault ISR: set Overcurrent Fault set Overvoltage Fault Emergency Sto
Software Design 7.2 Data Flow The control algorithm process values obtained from the user interface and sensors, generates 3-phase PWM signals for motor control (as can be seen on the data flow analysis).
Data Flow The control algorithm of the BLDC motor drive with Back-EMF Zero Crossing using AD converter, is described in Figure 7-3 and Figure 7-4.
Software Design Protection processes are shown in Figure 7-5. It consists of processes described in the following sub-sections. DC-Bus Current (A/D) I_Dc_Bus Temperature (A/D) Temperature DC-Bus Voltage (A/D) PWM Faults (OverVoltage/OverCurrent) U_Dc_Bus Process Fault Control DriveFaultStatus Process Application State Machine Process PWM Generation PVAL0,PVAL1 PVAL2,PVAL3 PVAL4,PVAL5 Figure 7-5. Data Flow - Part 3 7.2.
Data Flow 7.2.3 Process ADC Zero Crossing Checking This process is based on the ADC Zero Crossing feature. When the free (not energized) phase branch voltage changes the sign comparing previous conversion results, the Zero Crossing interrupt is initiated. Then the BLDC motor commutation control is performed in the Zero Crossing ISR. 7.2.
Software Design 7.2.6 Process Current PI Controller The process is similar to the Speed controller. The I_Dc_Bus current is controlled based on the U_Dc_Bus_Desired Reference current. The current controller is processed only during the Alignment state. The current controller works with a constant execution (sampling) period which is determined by the following PWM frequency: Current Controller period = 1/pwm frequency. The PI controller proportional and integral constants were set experimentally. 7.2.
State Diagram 7.3.2 Initialize The Main software initialization provides the following actions: • CmdApplication = 0 • DriveFaultStatus = NO_FAULT • PCB Motor Set Identification — boardId function is used to detect one of three possible hardware sets.
Software Design Reset PC Master Software Required Speed setting Up Button Down Button Increment Required Speed Decrement Required Speed Set Required Speed (Switch = Stop) || (abs (Required Speed) <= Minimal Speed) BLDC Run with Required Speed BLDC Stop (Switch = Run) & (abs (Required Speed) > Minimal Speed) Drive Fault Drive Fault Emergency Stop Drive Fault Figure 7-7. State Diagram - Process Application State Machine 7.3.
State Diagram The drive starts by setting the Alignment state where the Alignment commutation step is set and Alignment state is timed. After the time-out the Starting state is entered with initialization of Back-EMF Zero Crossing algorithms for the Starting state. After the required number of successive commutations with correct Zero Crossing, the Running state is entered.
Software Design Running - Begin No Zero Crossing get during last commutation period motor Commutation Calculate Next Commutation after No Zero Crossing Corrective Calculation 1. commutation time (T_Next) expired Zero Crossing Detected/Missed during last commutation period Preset Next Commutation settings and timing Zero Crossing Get Calculate Next Commutation after Zero Crossing Get Zero Crossing Missed during Per_Toff Calculate Next Commutation after Zero Crossing Missed Corrective Calculation 2.
State Diagram 7.3.4.4 Commutation Control - Set Starting This state is used to set the start of the motor commutation.
Software Design 7.3.5 State Diagram - Process ADC Zero Crossing Checking Commutation Control states: Running/Starting Reset motor Commutated Zero Crossing Disabled Commutation Control states: Stop/Alignment Back-EMF Zero Crossing Detected/Missed Zero Crossing Get/Missed preset new phase Zero Crossing Per_Toff after motor Commutation Back-EMF Zero Crossing Checking Figure 7-10.
State Diagram 7.3.6 State Diagram - Process ADC Zero Crossing Offset Setting measure U_Dc_Bus and free phase average U_Phx Commutation status: Alignment Commutation status: Stopped Zero Crossing Offset Setting Disabled Commutation status: Alignment End calibration coefficient Coef_Calibr_U_Phx = = (U_Dc_Bus_Half + U_Phx)/U_Dc_Bus Commutation status: Running/Starting setting of ADC Offset registers to U_Dc_Bus_Half = Coef_Calibr_U_Phx * U_Dc_Bus Reset Figure 7-11.
Software Design 7.3.7 State Diagram - Process Speed PI Controller Reset Commutation Running U_Desired = PI (Reference Speed - Actual Motor Speed) Speed Control Request Speed Control Disabled Commutation Stopped/Alignment/Starting Speed Control Timer Interrupt (PER_SPEED_SAMPLE) Set Speed Control Request Figure 7-12. State Diagram - Process Speed PI Controller The Speed PI controller algorithm controllerPItype1 is described in the SDK documentation.
State Diagram 7.3.8 State Diagram - Process Current PI Controller Reset Commutation Status Alignment U_Desired = PI (Reference Current - Actual Current) Current Control Disabled Commutation Stopped/Starting/Running Current Control Request PWM Reload Interrupt (PWM period) Start ADC Conversions ADC Conversion Complete Interrupt (PWM period) Set Current Control Request Figure 7-13.
PC Master Software 7.3.9.2 ADC Low Limit Interrupt Subroutine This subroutine is called when at least one ADC low limit is detected. In this interrupt subroutine, the following low limit exceeds are processed: • The undervoltage of the DC-Bus voltage — DriveFaultStatus |= UNDERVOLTAGE_ADC_DCB, • The over temperature (detected here because of the sensor reverse temperature characteristic) — DriveFaultStatus |= OVERHEATING. 7.3.9.
State Diagram 9. DSC Usage Figure 9-1 shows how much memory is needed to run the BLDC motor drive with Back-EMF Zero Crossing using ADC in a speed-closed loop. A part of the device’s memory is still available for other tasks. Table 9-1. RAM and FLASH Memory Usage for SDK2.2 Memory (in 16 bit Words) Available 56F803 56F805 Used Application + Stack Used Application without PC master software, SCI Program FLASH 31.5K 14288 10568 Data RAM 2K 1481+352 1145+352 10.
Setting of Software Parameters for Other Motors 10.1 Current and Voltage Settings 10.1.1 DC-Bus Voltage, Maximal and Minimal Voltage and Current Limit Settings For the right regulator settings, it is required to set the expected DC-Bus voltage in bldcadczcdefines.h: #define x_VOLT_DC_BUS 12.0 /* DC-Bus expected voltage */ The current voltage limits for software protection are: #define x_DCB_UNDERVOLTAGE #define x_DCB_OVERVOLTAGE #define x_DCB_OVERCURRENT Notes: 3.0 15.8 48.
Commutation Control Settings 10.2 Commutation Control Settings In order to get the motor reliably started, the commutation control constants must be properly set. 10.2.1 Alignment Period The time duration of the Alignment state must be long enough to stabilize the motor, before it starts. This duration is set in seconds in bldcadczcdefines.h. #define x_PER_ALIGNMENT_S Notes: 0.
Setting of Software Parameters for Other Motors Table 10-2. Start-up Periods Motor size Notes: x_PER_CMTSTART_US x_PER_TOFFSTART_US First commutation period [µs] [µs] [s] Slow motor / high load motor mechanical inertia >5000 >10000 >10ms Fast motor / high load motor mechanical inertia <5000 <10000 <10ms Slowing down the speed regulator (see Section 10.3.1) helps if a problem with start up (using the above stated setting) is encountered. 10.2.
Speed setting 10.2.6 Commutation Timing Setting Notes: Normally these structures do not require change. If the constants described in this section need to be changed, a detailed study of the control principle needs to be studied (see Section 5. and MotorControl.pdf). If it is required to change the motor commutation advancing (retardation) the coefficients in starting and running structures needs to be changed: x_StartComputInit x_RunComputInit Both structures are in bldcadczcdefines.h.
References If you also request to change the minimal motor speed, then you need to set minimal angular speed #define x_OMEGA_MIN_SYSU 4096 /* angular frequency minimal [system unit] */ Notes: Remember that minimal angular speed is not in radians, but in system units! Where 32768 is the maximal speed done by x_SPEED_ROTOR_MAX_RPM The speed PI regulator constants can be tuned as described below. All settings can be found in bldcadczcdefines.h.
User’s Manuals and Application Notes 11.2 User’s Manuals and Application Notes • AN1627, Low Cost High Efficiency Sensorless Drive for brushless DC Motor using MC68HC(7)05MC4 • 56F800 16-bit Digital Signal Processor, Family Manual, DSP56F800FM, Freescale Semiconductor, Inc. • 56F80x 16-bit Digital Signal Processor, User’s Manual, 56F801-7UM, Freescale Semiconductor, Inc. • web page: www.freescale.com 3-Phase BLDC Motor Control with Sensorless Back-EMF, ADC, Zero Crossing, Rev.
References 3-Phase BLDC Motor Control with Sensorless Back-EMF, ADC, Zero Crossing, Rev.
User’s Manuals and Application Notes 3-Phase BLDC Motor Control with Sensorless Back-EMF, ADC, Zero Crossing, Rev.
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