Sensorless Regulation of Brushless DC Motors
Contents
1. Figure 5 shows the voltage energizing coils C and A stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil B Figure 4 shows the active switches of the B6 bridge and Figure 5 again the appropriate rotor position 0 T1 T6 C A T1 T3 T5 N Coil A BLDC cas PS cic Pet Motor T2 14 T6 O Figure 4 Appropriate switches T1 T6 of the B6 full bridge coil C pos coil A neg Coil A fo I MA Coil B Coil C Figure 5 Energized coils C and A of a 2 pole pair BLDC motor mechanical position 0 Page 9 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 2 Position 30 Figure 7 shows the voltage energizing coils C and B stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil A Figure 6 shows the active switches of the B6 bridge and Figure 7 again the appropriate rotor position 30 Q T1 74 4C B T1 T3 T5 N a5 Coil A BLDC cis Pe coce a Motor T2 T4 T6 Figure 6 Appropriate switches T1 T4 of the B6 full bridge coil C pos coil B neg mech 30 Coil A Coil B Coil C Figure 7 Energized coils C and B of a 2 pole pair BLDC motor mechanical position 30 Page 10 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor wit2. 6 Abbreviations ADC Analog Digital Converter BACK EMF Back electromagnetic force B6 Bridge with 6 switches e g MOSFET for 3 phases BLDC Brushless DC CAN Controller Area Network CAPCOM Capture Compare Unit peripheral that measure events or provide PWM signal CPU Central Processor Unit EHPS Electro Hydraulic Power Steering LIN Local Interconnect Network Pl Proportional Integral PWM Pulse width modulation ROM Read only memory RAM Read Access Memory Page 31 31
3. CC62 COUT62 CAPCOM 6 Portl TLE 6280GP 6 x OptiMOS C164CM Figure 19 Block diagram of block commutation using Hall sensors 2 3 2 Block diagram of block commutation without sensors Figure 20 shows a typical structure of a three phase BLDC motor drive with B EMF detection It looks similar to the BLDC drive application with Hall sensors The only difference is shown in the detection of the rotor position The back EMF voltage is recorded directly at each phase A signal conditioning unit is required to trim the voltage filtering etc The zero cross voltage is detected for calculation of the next commutation pattern via the AD channels TLE 4268G V BATT Low Drop Voltage Regulator TLE6252 58G CAN LIN Transceiver EEPROM sss E Signal o CC60 co O O A lt O TLE 6280GP 6 x OptiMOS C164CM Figure 20 Block diagram of block commutation with B EMF detection Page 17 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM Figure 21 shows a brushless DC motor evaluation kit It is subdivided into a microcontroller board and a power board In conjunction with an application node and a PC driven interface customers may start immediately with the evaluation of their own application st a faill heals at Figure 21 BLDC motor drive evaluation boards Infineon Technologies has all the semiconductors required for BLDC driven applications Figure
4. as the desired mechanical speed of the brushless DC motor The three coils of the stator are split into two groups of coils A B C and A B C As you can see in Figure 1 coils A and C are energized and coil B is not energized A 0 to 180 rotation will be shown in detail in section 2 1 to explain the setting of the appropriate switches of the B6 bridge pattern the appropriate voltages relating to the coils and the energized coils of the motor with the suitable rotor position between 0 and 180 mechanical Figure 1 Functional principle of a brushless DC motor Page 5 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 1 3 Brushless DC motor with Hall sensors A synchronous motor mainly depends on synchronous processes e g ADC measurement has to be absolutely synchronous with the energizing pattern of the coils realized by the switches of the B6 bridge In this context the change of state of the three Hall sensors gives an indication of the specific time at which the next pattern of the B6 full bridge has to be applied Each of these Hall sensors costs about 0 15 0 30 so they have a big impact on the total cost of the whole application Typically external hardware is needed such as three comparators for sensor signal conditioning Supply Stages Diagnoses Trans Bridge Driver Phase Brushless Inverter Motor Hall Sensors Signal Conditioning Microcontroller e g C164CM
5. controlling 3 phase or multiphase motor drives Period Register Mode Select Register CC Channel 0 Offset Register CC60 T120F CC Channel 1 CC61 ompare Timer T1 16Bit CC Channel 2 CC62 Prescaler Port Control Logic Control Register 3 B CTCON ompare Timer T1 ee O OUT63 10Bit CMP13 z Block C6POS0 E Commutation C6POS1 eriod Register Control T13P CC6MCON C6POS2 fce Prescaler Figure 27 Block diagram of CAPCOM6 unit In the compare mode used for driving BLDC motors the CAPCOM6 provides two output signals per 16 bit channel which may have inverted polarity pulse transitions Timer T12 can be used to control the commutation speed Timer 13 can be used to modulate the capture compare outputs to influence the speed torque of the motor For active freewheeling a dead time generation is mandatory It can be realized with offset register T12OF For more detailed information about the CAPCOME6 unit please refer to the C164 manual or to application note 1673 technical details on CAPCOME6 unit Page 22 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 3 2 2 ADC The Analog Digital Converter of the C164CM has been designed to measure up to eight analog sources with 10 bit resolution It consists of a sample and hold circuit A multiplexer allows up to eight analog input channels to be selected To fulfill the different requirements of embedded applications the per
6. time generation enable ext trap function for emergency cases ADC initialization Select P5 3 P5 5 as AD channels fixed channel single conversion sample time 1 6 us conversion time 9 7 us Timer initialization Timer 1T3 T4 in timer mode prescaler 16 external up down control disabled 4 2 2 State machine The state machine is required to generate the block commutation pattern for both directions The appropriate outputs and AD channels are also selected State machine for the 6 next_state commutation pattern Corresponding ADC Gh UA ADC channel is selected Switch corresponding output pins CAPCOM6 RETURN ADC Ch UCJ Switch corresponding output pins CAPCOM6 ADC Ch UB Switch corresponding output pins CAPCOM6 ADC Ch UAT Switch corresponding output pins CAPCOM6 ADC Ch ucT Switch corresponding output pins CAPCOM6 ADC Ch ust RETURN RETURN RETURN RETURN Switch corresponding output pins RETURN CAPCOM6 RETURN Figure 30 State machine flowchart Note The CAPCOME6 unit of the C164CM overcomes the limitation for block commutation mode Pattern generation for both directions operates properly 4 2 3 Interrupt routines The timer T3 interrupt function is applied only for the rampup phase of the motor It generates and changes the commutation period and the voltage level for the three phases Upon reaching the minimum rotation speed of the motor the timer T3 interrupt rout
7. 22 shows some of the devices needed for such applications OptiMOS TLE 6280GP 3 phase driver TLE4274 C164CM 16 bit microcontroller TLE 6250G High speed CAN transceiver TLE6258G LIN transceiver TLE4274 5 volt voltage regulator OptiMOS Power MOSFET TLE 6280GP C164CM j i Figure 22 Semiconductors for BLDC motor drive Page 18 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 3 Block commutation mode with BACK EMF detection 3 1 General As described in a previous section the commutation of a brushless DC motor is performed electronically The rectangular shaped three phase voltage system see Figure 23 is used to generate a rotational field Applied voltage with this easy to create shape helps ensure control and drive simplicity The rotor position must be known at certain angles in order to align the applied voltage with the back EMF which is induced in the stator windings due to the movement of the permanent magnets on the rotor Achieving alignment between the back EMF and the commutation events is one of the main tasks Under these conditions the motor behaves like a DC motor and runs at the best operating points Simplicity of control and good performance makes this kind of motor a good choice in low cost and high efficiency applications Voltage Phase A Phase C 360 degrees C Commutation Z Zero Crossing Figure 23 Simplified three phase voltage system back EMF 3 1 1 Ba
8. Application Note V 1 0 July 2001 e Microcontrollers C Infineon technologies Never stop thinking Infineon Sensorless Regulation of a Brushless DC Motor with a C164CM Revision History Revision Modifications Page 2 31 Edition 2001 07 Published by Infineon Technologies AG 81726 Munchen Germany Infineon Technologies AG 2006 All Rights Reserved LEGAL DISCLAIMER THE INFORMATION GIVEN IN THIS APPLICATION NOTE IS GIVEN AS A HINT FOR THE IMPLEMENTATION OF THE INFINEON TECHNOLOGIES COMPONENT ONLY AND SHALL NOT BE REGARDED AS ANY DESCRIPTION OR WARRANTY OF A CERTAIN FUNCTIONALITY CONDITION OR QUALITY OF THE INFINEON TECHNOLOGIES COMPONENT THE RECIPIENT OF THIS APPLICATION NOTE MUST VERIFY ANY FUNCTION DESCRIBED HEREIN IN THE REAL APPLICATION INFINEON TECHNOLOGIES HEREBY DISCLAIMS ANY AND ALL WARRANTIES AND LIABILITIES OF ANY KIND INCLUDING WITHOUT LIMITATION WARRANTIES OF NON INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS OF ANY THIRD PARTY WITH RESPECT TO ANY AND ALL INFORMATION GIVEN IN THIS APPLICATION NOTE Information For further information on technology delivery terms and conditions and prices please contact your nearest Infineon Technologies Office www infineon com Warnings Due to technical requirements components may contain dangerous substances For information on the types in question please contact your nearest Infineon Technologies Office Infineon Technologies Components
9. Figure 2 General block diagram for brushless DC motor drive with sensors 1 4 Brushless DC motor without Hall sensors The aim of this application note is to eliminate position sensors altogether The C164CM 16 bit uC in its small P TQFP 64 package 12 12 mm incl pins fits this type of application very well because of its flexible capture compare unit CAPCOM6 with two 16 bit timers and 6 1 output channels Many other features are listed at the end of the application Three channels of the 10 bit ADC of the C164CM and only a two resistor voltage divider with a capacitor at each of the three phases are the hardware necessary to realize a viable sensorless brushless DC motor The most important point and at the same time a big advantage of this hardware configuration is the aspect of minimized costs because even the comparators that would normally be necessary are superfluous A 16 bit microcontroller delivering high CPU performance with a fast and accurate 10 bit ADC has a big advantage at higher speeds up to 5000 rom because of the very acceptable CPU load even in these conditions A very important point in relation to the cost effective back EMF sensing is the very low leakage current of the C164CM ADC 200 nA because the back EMF is low at low speeds and the use of a high impedance voltage divider is necessary Page 6 31 Sensorless Regulation of a Brushless DC Motor with a C164CM Voa Driving Stages Protection Diagnoses
10. LIZATION OF THE ROTATION INCLUDING APPROPRIATE SWITCHES OF A 3 PHASE BRUSHLESS DC MOTOR 0 MECHANICAL TO 180 MECHANICAL sssccosssccssserecsssssesessrecssnesesssteesssesevsseesesesasecsssctesesenecessecesesanesseseseses 8 Le OSI ON I n r EOT E E AE EEE E ones setae ese 9 d O S a E E E us eee eae 10 T A N a E E E eee oa eteee Il A T O I ae ec eae gies A EAA E E vacua auecect sta aad eactes ceed a date seed sean A E eae 12 LAA EOS OV Le agree sac cro cance sate secre eee acer a E arene E AEE E A eae rescues tee eet 13 ALO OSU OI TOO a cep arhee fe op aeons E E cae Gest otceensatien E E E eevee antennae 14 da L DS caste cata eect esc et cg tec pae dante vera rap sence T ce eee seo es gence ese eee 15 L EN E r E E E eae ee eee eae nee 16 2 2 1 Hall sensor output signal ecececccccscccessseecsecsessccesscessseeseseecesceessaeessseecsseeessaeessseecessesssusceeaeeseaeeesueceeseessaseseaees 16 Dade gO SMM DESCRIPTION eraginn EE EEEE 16 2 3 1 Block diagram of block commutation using Hall SCNSOTS o ceecccccssccssssceesceseseeeseeeeseeeeeeessuseseseeseseesssees 16 2 3 2 Block diagram of block commutation without Sensors cscccescccesssesessceeceeesseessseesesesseseeessssesesesssaseesaaees 17 BLOCK COMMUTATION MODE WITH BACK EMF DETECTION essescescesocscescssosscecesoesoesoesoesoese 19 Qed MEINE Les E sane tas bos raaboasepeoucs teu ov sae E E A E E suvenscee E E E 19 dig DUE SSE a oe caesar es eset cn setae da ace cee ono secs geese teens
11. Phase Brushless Inverter Motor ceiver Bridge Driver Signal Conditioning Microcontroller e g C164CM Figure 3 General block diagram for sensorless BLDC motor drive When a brushless DC motor is energized in block commutation mode only two of the three phases are active at a given time The brushless DC motor rotor position has to be evaluated by the zero crossing of the back EMF which can be evaluated by measuring the non energized phase The voltage value of the back EMF has to be half of the maximum value to detect the precise point for changing the coil energizing pattern for the following 30 mechanical rotation It is very important to find the precise point for the next change in the energizing pattern to ensure smooth operation of this type of motor A big advantage in this context is the fact that the back EMF is proportional to the mechanical rotation speed This means that we are able to use the measured C164CM 10 bit ADC values directly without any type of linearization algorithm This allows the use of very fast regulation software because the mechanical speed of some applications should reach up to 6000 rom The amount of back EMF is a function of the number of coil windings mechanical speed and flux E N x x n Taking account of a low rotation speed it is very important to have a high resolution with regard to the ADC microcontroller 10 bit 2 LSB minimum to evaluate the back EMF with the application ne
12. Position 120 Figure 13 shows the voltage energizing coils B and C stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil A Figure 12 shows the active switches of the B6 bridge and Figure 13 again the appropriate rotor position 120 Q T3 T2 B C T1 T3 T5 N L Coil A BLDC CoilB Y T F coc PE Motor T2 T4 T6 Figure 12 Appropriate switches T2 T3 of the B6 full bridge coil B pos coil C neg mech 120 Coil A Coil B Coil C Figure 13 Energized coils B and C of a 2 pole pair BLDC motor mechanical position 120 Page 13 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 6 Position 150 Figure 15 shows the voltage energizing coils B and A stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil C Figure 14 shows the active switches of the B6 bridge and Figure 15 again the appropriate rotor position 150 T3 16 B A T3 T5 BLDC Coil A Col cic Y T o y a Motor T1 T2 14 T6 O Figure 14 Appropriate switches T3 T6 of the B6 full bridge coil B pos coil A neg mech 150 Coil A Coil B Coil C Figure 15 Energized coils A and C of a 2 pole pair BLDC motor mechanical position 150 Page 14 31 Infineon lechool
13. T3 INTERRUPT Calculate rest time RETURN Figure 32 Zero cross detection flowchart Page 27 31 m Infineon iachnolegiss Sensorless Regulation of a Brushless DC Motor with a C164CM 4 3 Performance analysis 4 3 1 Hardware requirements CPU 16xCPU 16 bit 20 MHz ROM 1KB 2 KB depending on error detection requirements RAM 200 bytes plus system stack Peripherals CAPCOM6 unit 16 bit timer 50 ns resolution three 16 bit capture compare channels ADC 3 channel 10 bit resolution 9 7us conversion time Timer 16 timer 400ns resolution 4 3 2 CPU load The CPU load was measured in a simple way A flag of a dedicated port pin is set each time an interrupt routine is entered The flag is reset after the interrupt routine is exited Tek Prevu fp LPT ET LT TAPETE E ery 7s L commutation n detect zero cross Figure 33 CPU load The CPU load depends greatly on how close to the zero cross point the AD conversions starts It is therefore mandatory to optimize the application for the motor used Here is a rough overall estimation of the CPU load without optimization Page 28 31 Sensorless Regulation of a Brushless DC Motor with a C164CM CPU frequency 20 MHz Motor speed 1000 rpm one pole pair CPU load typically 3 The CPU load depends greatly on how close to the zero cross point the AD conversion starts The CPU load may be decreased by using the DMA feature PEC transfer
14. Typically the Hall signals are connected to the inputs of a microcontroller via a signal conditioning unit For higher performance the inputs of the microcontroller have to provide fast interrupt capability To reduce system costs the signal conditioning unit has to be moved either to the microcontroller or perhaps to driver IC Further reduction of CPU load is possible by using the CAPCOM6 unit of the C164CM This supports the generation of the block commutation pattern without software support 2 3 System description 2 3 1 Block diagram of block commutation using Hall sensors Figure 19 shows a typical structure of a three phase BLDC motor drive suitable for use in automotive applications e g fan cooling or water pump The C164CM microcontroller generates the rotation patterns for the stator field and can be used for speed or torque control The TLE 6280 driver IC is used to provide the output signals for the 3 phase inverter and perform certain diagnostic functions such as short circuit current protection over undervoltage protection and overtemperature protection OptiMOS devices arranged as three half bridges switch the power to the corresponding phases of the BLDC motor Page 16 31 Infineon Sensorless Regulation of a Brushless DC Motor with a C164CM TLE 4268G Veatt Low Drop Voltage gu TLE6250G 58G Hall Sensors CAN LIN TLE4945 Transceiver EEPROM CCPOSO CC60 S COUT60 ccol_ 3Phase JL 7 couTel Driver 3x
15. ay time Phase A B C AD Channel Figure 25 Passive network for zero cross detection Basically the external circuitry consists of a passive network such as that shown in Figure 25 The network includes a voltage divider circuit and a low pass filter with a cut off frequency of 1 kHz One network is required for each phase Page 20 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM Because the back EMF voltage is a function of the rotor speed an AD converter with a higher resolution at least 10 bit is required Figure 26 shows the phase voltage Channels 1 to 3 of a 3 phase BLDC motor at the inputs of the AD channels The rotation speed of the motor is around 1000 rpm Channel 4 represents the required CPU load Tek Prevu SSS T pa Phas A gooo hi soomv ch2 soomvM10 oms A hi f 280mV s00mv chal 5 00V Figure 26 Back EMF voltage after low pass filter Page 21 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 3 2 Required peripherals 3 2 1 CAPCOM6 The CAPCOME unit of the C164CM has been designed for applications with a requirement for digital signal generation and event capturing e g pulse width modulation pulse width measurement It Supports generation and control of timing sequences on up to three 16 bit capture compare channels plus one additional 10 bit compare timer This peripheral fulfills all requirements for
16. celeration phase Timer T4 Delaytime counts down ENABLE CAPCOM6 INTERRUPT const speed 20 KHz PWM if Umax 2 is not with BEMF detected Disable CAMCOME6 Single ADC INTERRUPT MIO cos oe ee T4 old is used CAPCOM6 INTERRUPT h it Umax 2 Is detected three times Disable CAPCOM6 INTERRUPT T4 counts up plus T4 Delaytime T4 Interrupt T4 counts down h T4 T4n T4 n 1 ilur if T4 counts down ee gt BEMF is not detected Failure counter Single AD Conversion if falling edge gt Umax h T4 Interrupt next pattern is applied Figure 29 Event flow process Page 24 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 4 1 2 Management of commutation demagnetization and zero cross detection The sensorless control process of the BLDC motor is based on the following events Commutation event CAPCOME unit End of demagnetization Timer T4 Zero cross detection ADC Each 60 degree window is initiated with a new commutation pattern Timer T4 is utilized to generate a delay time between the start of the demagnetization impact and the point in time where the zero cross event gets closer This value of timer T4 is strongly dependent on the motor type and the required motor speed The timer T4 interrupt enables the CAPCOM6E interrupt The CAPCOM6 interrupt forces an AD conversion of the appropriate phase voltage every 50 us 20 kHz PWM If the converted voltage value is very close to the
17. cessary demand The 16 bit broad code and data core and the 16 16 or 32 16 bit multiply accumulate as part of the C164CM instruction set e g allows fast processing of the 16 bit integer or even float PI soeed regulator because of the multiplications 6 and divisions 8 which are necessary in this case Page 7 31 Infineon Sensorless Regulation of a Brushless DC Motor with a C164CM 2 Operation of a brushless DC motor 2 1 Visualization of the rotation including appropriate switches of a 3 phase brushless DC motor 0 mechanical to 180 mechanical Only two of the three phases are energized in each state of the B6 full bridge The non energized phase can therefore be used to detect the zero crossing of the back EMF as explained later cf the black arrow in the voltage diagram shown in Figures 5 7 9 11 18 15 17 The following explanation will show you the turning of a two pole pair brushless DC motor as a function of the state of the appropriate switches shown in Figures 4 6 8 10 12 14 16 In fact driving a two pole pair motor means that the rotation speed of the electrical field has to be double the speed of the desired mechanical rotation speed Q p where Q is the mechanical rotation speed the rotation frequency of the electrical field and p is the number of pole pairs Page 8 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 1 Position 0
18. ck EMF sensing The back EMF sensing technique is based on the fact that only two phases of a DC brushless motor are connected at the same time so the third phase can be used to sense the back EMF voltage Figure 24 uses a simple model to illustrate the situation when phases A and B are energized and phase C is used to measure the back EMF Page 19 31 Sensorless Regulation of a Brushless DC Motor with a C164CM UBack EMF Figure 22 Simplified model of 3 phase BLDC coils A and B are energized coil C will be analyzed Typically methods to detect the zero crossing of the back EMF often described in the literature utilize additional hardware such as OpAmps or other circuitry Also a soeed dependent phase delay time has been implemented to ensure proper commutation and the external circuitry has been configured for a fixed motor speed Overall the costs for these additional components have a impact on total system costs To reduce system costs further provide more flexibility and even chop one or both of the phases another system approach might be considered Each phase is connected via voltage divider circuitry and a low pass filter to an AD channel of the C164CM Each revolution of the rotor of a motor is divided into 6 commutation windows each 60 degrees wide For each window an appropriate AD channel has been selected to detect the zero cross point in order to switch to the right commutation pattern after a dedicated phase del
19. csatussepecsssavectichsessacesteasedssseisasvenssdncessecssactectacausiesiastescaches 31 Page 4 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 1 Introduction 1 1 Why use brushless DC motors advantages disadvantages Brushless DC motors are synchronous motors suitable for use as a simple means of controlling permanent drives e g ABS pumps EHPS pumps fuel pumps or cooling fans This type of 3 4 or 5 phase brushless DC motor will increasingly replace brushed DC motors Brushed DC motors require maintenance e g to service coal brushes and commutator Another major problem with a brushed DC machine is the possibility of brush burnout in the event of an overload or stall condition One of the main advantages of brushless DC motors is their robustness against obsolescence due to the absence of brushes and another major benefit is the high efficiency and high torque of a brushless DC motor A disadvantage of this type of motor is that the rotor position is usually determined by three Hall sensors in the case of three phases which are expensive and require signal conditioning and this positioning in the production process has to be done very precisely to assure proper operation 1 2 Functional principle of a brushless DC motor Figure 1 shows a three phase brushless DC motor with two pole pairs The rotation of the electrical field vector has to be applied twice as fast
20. e eee 19 3 2 RPBPOUIREDPERIPHERAL S ss scccsesesnstonsaceaueeseesuasescesoescuseosa0sss e a E Ea aE AEEA e NINS 22 Iad CAF COM O oe e E E ree 22 aia AEA E E E EE E E N A E 23 IMPLEMENTA TON criai a E T E EE 24 Page 3 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM A PUNCHONALDESCRIPTION ago cesses rs ea cenceusuncsacusesaetaocssscecsa sued sansuen un E ooeeeiegsaauececaecseviacseseessessaceasaseeeee 24 4 1 1 CCT TIP OI a i eg ise cs bce ccs cp ce sig ere sence es ates decade ns 24 4 1 2 Management of commutation demagnetization ANd zero cross detection 23 4 2 IMPLEMENTATION OF THE SOFTWARE cssssccsssscceesseccessceeessseecesseccesseeeesseeccessaecessueeessseeceesaeeceeaeeceeaeecesseeeeesaees 25 T E a T E A AN I A A AA E A E E E 25 DD SPAT A O w cement cteteahinn hse A euccesanasdantavteenencndseolmeiaceecanes 26 7 ic MS ARN OSE OLS 1 ee Om RT Ene eee eae ee reer eee eee nT nee erie eee rt Ce eee ee 26 43 PERFORMANCE ANALYSIS scrasa ri a Ara texas ccotee cs Ea Taar EAS A EE aarda 28 LoL RCV AAV regu reme S ceneni T O tions 28 7 foe A a a eR eT OEE ere rea ener rer er Manne Cn heme e Teer terrae heer E ee eee eer ere ere errr ere 28 5 CONCLUS TON cs cecscaes cesecascsatecccsccazccectectcetsecseancsuadesceiecudsaesssscisevasstuecsdetansascsccauestssuveccaebiuscdastasascssesedsaucessaaseusicisessteaiesss 30 6 ABBREVIATIONS socescesccsteacessicasecespacuscestcasesseressuysucsascxescecac
21. egian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 7 Position 180 Figure 17 shows the voltage energizing coils C and A stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil B Figure 16 shows the active switches of the B6 bridge and Figure 17 again the appropriate rotor position 180 QO T1 T6 C A T1 T3 T5 N L Coil A BLDC coilB Y T V E ch SE ST E Col Motor T2 T4 T6 Figure 16 Appropriate switches T1 T6 of the B6 full bridge coil C pos coil A neg mech 180 Coil A JIN I Coil B Coil C Figure 17 Energized coils A and C of a 2 pole pair BLDC motor mechanical position 180 Page 15 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 2 2 Sensors The BLDC motor is a synchronous motor and so the rotor position has to be known in order to generate the appropriate field 2 2 1 Hall sensor output signal Sensors are essential as a means of recognizing the positioning of a synchronous motor The signals generated after appropriate signal conditioning are shown in Figure 18 Depending on the location of the Hall sensors and the number of pole pairs different pictures emerge In this case a number of pole pairs are used and the three Hall sensors are located at a 120 degree distance Patterns CC6POS0 CC6POS1 One revolution Figure 18 Hall sensor signals
22. h a C164CM 2 1 3 Position 60 Figure 9 shows the voltage energizing coils C and B stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil C Figure 8 shows the active switches of the B6 bridge and Figure 9 again the appropriate rotor position 60 T5 74 A B T1 T3 T5 Coil A BLDC cois Y T 7 2 cic FS Motor T2 14 16 Figure 8 Appropriate switches T4 T5 of the B6 full bridge coil A pos coil B neg mech 60 Coil A Coil B Coil C Figure 9 Energized coils A and B of a 2 pole pair BLDC motor mechanical position 60 Page 11 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 4 Position 90 Figure 11 shows the voltage energizing coils A and C stator and the permanent magnet realized with two pole pairs rotor as well as indicating the zero crossing detection coil B Figure 10 shows the active switches of the B6 bridge and Figure 11 again the appropriate rotor position 90 T5 72 A C Figure 10 Appropriate switches T2 T5 of the B6 full bridge coil A pos coil C neg mech 90 Coil A Coil B Figure 11 Energized coils A and C of a 2 pole pair BLDC motor mechanical position 90 Page 12 31 Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM 2 1 5
23. ine is disabled The rampup behavior of the motor is shown in Figure 31 The rampup process is divided into three steps In the first step the motor is accelerated from 0 rom up to the minimum rotation speed in order to analyze the BEMF detection voltage Depending on the static torque of the motor the dV dT ratio of the acceleration graph has to be configured The second step handles the BEMF detection and the Page 26 31 p Infineon chnolegis Sensorless Regulation of a Brushless DC Motor with a C164CM synchronization to the appropriate commutation pattern If the BEMF detection has been successful then the motor speed can be accelerated up to the required value The timer T4 interrupt routine is enabled after back EMF detection becomes active It handles the whole process of each 60 degree window demagnetization monitoring of the window length point in time for commutation etc ADC interrupt routines validate the current voltage level and take the decision for zero cross detection The CAPCOM6 interrupt routine forces an AD conversion every 50 us It can be enabled by the timer T3 interrupt routine Q o Q dp i p Time s Figure 31 Rampup behavior ADC INTERRUPT ADC INTERRUPT Rising edge If falling edge JES ADDAT lt No No ADDAT gt Umax 2 5 Umax 2 5 Yes e max Change Counting Direction Disable CAPCOM6 Compare Rising Edge INTERRUPT Disable
24. instead of continuous verification of the phase voltage Page 29 31 Sensorless Regulation of a Brushless DC Motor with a C164CM 5 Conclusion There is an increasing demand in the automotive industry for applications using BLDC motors In the past many applications were addressed with DC motors Automotive suppliers would like to use BLDC motors in order to achieve greater robustness and efficiency Currently the only limitation is the price gap between BLDC motors and DC motors On the other hand automotive suppliers are intensely price driven and need smart solutions to meet the requirements of the market This application note aims to provide an understanding of the functionality of a BLDC motor explains how such a motor is driven describes all the necessary components and the necessity of knowing the positioning of a synchronous motor Furthermore the back EMF technique is discussed and a method to implement the back EMF algorithm in the C164CM is presented To achieve a good price performance ratio all the components used for back EMF detection have been replaced by software Thanks to the high performance of the microcontroller and its powerful peripherals this software solution consumes only limited CPU resources The system approach discussed might be considered as a starting point for designing a complete system specific closed loop BLDC application Page 30 31 Sensorless Regulation of a Brushless DC Motor with a C164CM
25. ipheral supports several conversion modes such as fixed channel conversion autoscan conversions or channel injection modes The minimum conversion time is dependent on the CPU frequency and can be programmed The minimum conversion time is 9 7 us fcou 20 MHz For more detailed information please refer to the datasheet or the user manual Channel and Mode Control Conversion Control Timing Control INTER and Successive gt FR Register NTE Hag Aref Agnd Same gt 1 Result Register for channel Injection Mode Figure 28 Block diagram of ADC unit Page 23 31 p Infineon chnolegis Sensorless Regulation of a Brushless DC Motor with a C164CM 4 implementation 4 1 Functional description 4 1 1 General description The application is divided into several subfunctions First all relevant peripherals are configured Next the rampup phase is started to accelerate the motor During this phase the commutation speed and the phase voltage are increased continuously until the back EMF voltage is interpretable Now the back EMF detection and an optional PI controller for speed or torque control may be activated Figure 29 provides an overview of the event driven flow process Commutation n Commutation n 1 mA 60 stator fies ___ _____________ lt gt Um Demagnetisation UBEMF d Zero T crossing Umax 2 tolerance NNS falling edge A Umax 2 tolerance or h without BEMF Timer T3 ac
26. may only be used in life support devices or systems with the express written approval of Infineon Technologies if a failure of such components can reasonably be expected to cause the failure of that life support device or system or to affect the safety or effectiveness of that device or system Life support devices or systems are intended to be implanted in the human body or to support and or maintain and sustain and or protect human life If they fail it is reasonable to assume that the health of the user or other persons may be endangered Infineon lechoolegian Sensorless Regulation of a Brushless DC Motor with a C164CM Contents 1 INTRODUCTION re ctcstcccconscncececsecdeceectecccsasecossocscecscvaniccsseuacctecucsiveseussandessesescsedeccesacdccececdasteadecuesicessecsectacdesiusscssscedesast 5 1 1 WHY USE BRUSHLESS DC MOTORS ADVANTAGES DISADVANTAGES E EEEE EEE TA 5 1 2 FUNCTIONAL PRINCIPLE OF A BRUSHLESS DC MOTOR cccccccsssceccccssccccccccscccsscsccunsccsccusesccccuuacesccanesesceunesees 5 1 3 BRUSHLESS DC MOTOR WITH HALL SENSORG cccccccsesecccccecccccccceccccsssceccuscsccccesesesccenscescseuscecccusecesccunesesccunesses 6 1 4 BRUSHLESS DC MOTOR WITHOUT HALL SENSORS cccccccsesccccccscccccccscccccuccccccensccccunscccccuuecececaucesccanesesccunecees 6 2 OPERATION OF A BRUSHLESS DC MOTOR 222 222 2222 cccccccccccccccccccccccscccscccccccccccccccsccsscccscccsccscccscccscccccoccs 8 4 2 1 VISUA
27. requested value three times then a zero cross detection is recognized In the interim timer T4 is used to monitor the elapsed time Depending on motor type and speed the requested time is now calculated for the next commutation pattern It is possible that the zero cross event is not recognized due to external noise In this case a failure counter is incremented and switches off the AD sampling of the phase voltage The requested time for the next commutation pattern is calculated based on previous values All tasks are interrupt driven and consume little microcontroller related time 4 2 Implementation of the software The software is divided into several routines Initialization ports CAPCOM6 GPT1 timer T3 T4 State machine 6 commutation states PI controller for closed loop optional Interrupt routines CAPCOM 6 Timer T4 Timer T3 only used for the motor rampup time ADC 4 2 1 Initialization A number of small routines perform all the necessary initializations before the motor is started Port initialization P1L 0 P1L5 CCx COUTx output Interrupt initialization CAPCOM6 emergency CC6EIC CAPCOM6 CC6CIC ADC interrupt ADCIC timer T3 T3IC timer T4 T4IC CAPCOM6 initialization Disable multichannel mode passive output level is low set timer T12 PWM 20 kHz set compare register CCx to start value center Page 25 31 Sensorless Regulation of a Brushless DC Motor with a C164CM aligned mode active dead
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