����������� E910.40 SENSORLESS POSITION CONTROL OF DC-MOTORS, RIPPLE COUNTER IC Scope Features This application note provides information about Ripple Detection method, external part configuration and schematic examples in conjunction with the E910.40 IC. ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ General Description The Ripple Counter IC E910.40 allows a µC to track the position of a DC-motor by counting its current ripples. The ripple signal is available on an output pin to connect to microcontrollers or dedicated logic. With the bidirectional interface the actual position can be read out and IC parameters are motor and PWM to control high side drivers. The IC can be adapted to different motor characteristics by changing a few external components. Operating voltage range VDD 9V to 16V Full motor control and diagnosis Driving N-channel-power-MOSFET full bridge 8-bit PWM resolution for high-side drivers Nominal PWM frequency of 23kHz Smooth motor acceleration and deceleration Active motor braking -40°C to +125°C operating temperature SO20w package Applications ÿ Seat adjustment ÿ Steering column adjustment ÿ Fuel pump VBAT VCC VDD RB VSA VGH 2 VDD Reg AVDD VREF µC VGH 1 BIAS BSI slewrate controlled VREF RSR FET Driver Control TEMP M Short Circuit Detect DATA IMPOUT Incr. Detect BRTH VGL 1 VGL 2 SENSE 1 SENSE 2 Filter & Amplifier S/H ODIF IDIF OLP VREF ELMOS Semiconductor AG Application Note 1/25 QM-No.: 03AN0401E.01 E910.40 Package Pin Out � ��� 1 20 �������� ���� 2 19 ������� ���� 3 18 ���� ���� 4 17 ���� ���� 5 16 ���� ��� 6 15 �� ��� 7 14 ��� ������ 8 13 ���� ������ 9 12 ���� 10 11 ��� ��� Pin Description 1) Pin-No. Name Typ 1) Description 1 GND S 2 VGH1 AO Gate voltage for high side driver 1 3 VGH2 AO Gate voltage for high side driver 2 4 VGL1 AO Gate voltage for low side driver 1 5 VGL2 AO Gate voltage for low side driver 2 6 VDD S Input supply voltage 7 BSI AI Input bootstrap voltage 8 SENSE1 AI Voltage sense bridge 1 9 SENSE2 AI Voltage sense bridge 2 10 RSR AI External resistor to adjust the slew rate 11 OLP AO Output low pass filter 12 IDIF AI Inverting input differentiating amplifier 13 ODIF AO Output differentiating amplifier 14 VSA AI Internal 9V analog supply 15 RB AI External bias resistor 16 VREF AO Internal 5V supply voltage 17 BRTH AI Input brake threshold 18 TEMP AI Input temperature monitor 19 IMP OUT AO Incremental output for counting pulses, open drain 20 DATA I/O AO Serial data I/O Ground D = digital, A = Analog, S = Supply, I = Input, O = Output, HV = High Voltage (max. 40V) ELMOS Semiconductor AG Application Note 2 /25 QM-No.: 03AN0401E.01 E910.40 SO20w Package Outline 2 1 E Index Area H 3 N D h x 45˚ Seating Plane A e ELMOS Semiconductor AG B C A1 phi L Application Note 3 /25 QM-No.: 03AN0401E.01 E910.40 1 Introduction to ripple detection An applied voltage across the the DC-motor terminals causes a current flow which establishes a rotation of the rotor. To keep the rotor turning the motor windings need to be activated at the right moment to create a torque which is the cause of the mechanical rotation. The commutation (activating the windings at the right moment) is done mechanically by the commutator. Figure 1 shows a DC-motor with stator (2 permanent magnets), rotor with 3 windings, brushes and the commutator. Figure 1: Simple example of a DC motor Electrically a DC motor can be viewed as a series RL network with a voltage generator V(ω). The generator represents the back electromotive force (BEMF) generated by the motor’s rotation and which opposes the electromotive force of the supply. The value of the BEMF is a function of the motor’s angular velocity. If the motor has no external load and its velocity is not limited, it will accelerate up to the velocity which equals V(w) at the supply voltage Vs. In our example the BEMF is a vector sum of the three winding voltages P1, P2 and P3 which is shown below. Figure 2: Electrical schematics of motor windings ELMOS Semiconductor AG Application Note 4 /25 QM-No.: 03AN0401E.01 E910.40 � �������������� � ���� � �� �� �� � �������������� � ������������������ � ������������� � ��������� � ������������� � � � � � � � � � � Ripple � Figure 3: Generation of Commutation During rotor‘s movement the resistance measured at the motor terminals for a short period of time (during the commutation) changes its value; here from R tot=R || 2 R= 2 R to 3 1 R tot=R || R= R 2 (excluding effects caused by switching of winding inductances). Brush Winding Resistance R R tot = R ll 2R = 2/3 R R tot = R ll R = 1/2 R Figure 4: Generation of Commutation Spikes This causes a change of the current value seen as short commutation spikes, also called commutation ripple which follows this equation: Imot: Motor current BEMF: Back ElectroMotive Force ELMOS Semiconductor AG I mot= V BAT BEMF Rtot Vbat Rtot Application Note 5 /25 : Battery voltage : Total winding resistance QM-No.: 03AN0401E.01 E910.40 ��� �� �� �� �� �� �� �������� ���� �� �� �� �� �� �� ����� �� �� ����� � � � ������ ����� ����� ����� ����� ����� ����� ����� ����� ����� ����� � � � ����� ������� Figure 5: Motor resistance change with resulting current ripple (neglecting the armature inductance) Additional inductance in the windings reduces the peak amplitude and creates an quasi-sinusoidal signal shape of the current. ELMOS Semiconductor AG Application Note 6/25 QM-No.: 03AN0401E.01 E910.40 �� � � � � � � � ����� �� ������ ����� � � � ����� ����� ����� ����� ����� ����� ����� ����� ����� ����� � � � ����� ������� Figure 6: Quasi-sinusoidal current shape To improve the inductive coupling between the windings they can be wrapped around two armatures. In this case the DC-motor can have unsymmetrical windings, the ripple current gets additional dynamic component as a superpositioned sinusoidal wave with lower frequency which corresponds with the motor speed. This is caused by different copper wire lengths of the different windings. Consequently the different winding resistance causes fluctuating current flowing through the motor. Figure 7: Unsymmetrical windings ELMOS Semiconductor AG Application Note 7 /25 QM-No.: 03AN0401E.01 E910.40 Figure 8: Low frequency signal superposition Further parasitic effect on the ripple current is the magnetic flux weakening across the rotor and motor housing caused by its geometry. potentially saturated Figure 9: Stator field weakening Another unwanted effect is the bending of the stator magnetic field caused by superposition of the rotor‘s magnetic flux. This effect is strongly motor current and turning direction dependent and is intensified when the motor current rises. Figure 10: Stator field distortion The result are double pulses which can be out of the commutation phase and must be recognized by the ripple counter. ELMOS Semiconductor AG Application Note 8 /25 QM-No.: 03AN0401E.01 E910.40 Figure 11: Undefined Phase Relation due to Field Bending 2 Motor ripple signal processing with E910.40 The E910.40 measures the motor current fluctuation indirectly via the SENSE1/2 pins. The voltage drop across the MOSFET‘s RDSON is measured and subsequently filtered. The filtered analog ripple signal is provided to a min/max detection circuit which further generates a TTL compatible signal provided to the µC. The SENSE1/2 input is internally connected to a 2nd order low-pass filter with an edge frequency of 2.5kHz to surpress the PWM frequence Following the low-pass filter a band pass filter using external components is implemented: ÿ Pin 11 – OLP output internal 2nd order low pass filter, ÿ Pin 12 – IDIF Inverting input differential amplifier, ÿ Pin 13 – ODIF Output differential amplifier Vbat 0 - M + LOWPASS SENSEx OLP C1 R1 Internal LP Filter 2,5kHz 4V IDIF + ODIF >> Ripple Detection Unit (min/max) - R2 RDSon C2 0 Figure 12: Filter schematics ELMOS Semiconductor AG Application Note 9 /25 QM-No.: 03AN0401E.01 E910.40 Mathematical description of the low pass filter followed by a band pass circuit: 2nd order Low Pass frequency response: 2 1 A 1= 1 j 0 with ω0 = 2πf0 ; f0 = 2.5kHz Band pass frequency response: 1 j C1 X 1= R 1 X 2 =R2 || |A 2 |= 1 j C2 X2 = X1 R2 R1 1 R1 j R2C 2 1 j C2 = 1 1 j C1 1 R1 The expressions R 2 || 1 R2 j R2 = = 1 = R2 R2 R1 1 R2 C 2 R1 C 1 j 1 C1 R2C 2 R1C 1 j R1 R2 C 2 1 R2C 2 R 1 1 j C1 R2 C 2 C1 1 j 1 R1 C 1 R2 C 2 the frequency independent amplification factor of the amplified voltage across the motor and MOSFET voltage. The equation 1 1 R2 C 2 R1 C 1 can be simplified to R2 R1 which is more suitable for further empiric component adjustment. ELMOS Semiconductor AG Application Note 10/25 QM-No.: 03AN0401E.01 E910.40 With ω = 2πƒ the expression f 2= 2 1 R2 C 2 f 1= 2 1 R1 C 1 indicates the lower edge frequency of the band pass filter. on the other hand is the higher band pass frequency of the band pass. The equation for both filters in series: R2 |A|= A1 A2 = R1 2 1 1 j 1 0 R2 C 2 R1 C 1 1 j R2 C 2 1 R1C 1 3 Adjusting the parameters C1, C2, R1, R2 of the band pass filter First the amplification factor R2 must be adjusted to the expected voltage drop across the switching MOSFET. R1 The voltage range at the SENSE1/2 pin is -1.5V..2V. The internal OPA‘s supply voltage is 9V and the working voltage was set to 4V. Later on the edge frequencies f 1 and f2 are adjusted to the expected frequency range of the motor current ripple. These steps are done by empirical measuring and analyzing of the signal quality at OLP/IDIF/ODIF pins. Examining several automotive DC-motors allowed to extract following suitable start parameters for further “fine-tuning” approach: ÿ ÿ ÿ ÿ R1 = 10kΩ R2 = 330kΩ C1 = 1µF C2 = 470pF ÿ f1 = 16Hz ÿ f2 = 1026Hz ELMOS Semiconductor AG Application Note 11 /25 QM-No.: 03AN0401E.01 E910.40 Frequency response of the band pass filter with listed parameters above (including the internal E910.40 2nd-order low pass filter): �� �� �� � � �� � �� ����� ���������� ����� ���� ���� ����� ����� ������ ������ ����� � ��������� ���������� Figure 13: Proposed filter frequency response 4 Dynamic ripple amplification gain adjustment Because the analog ripple counting signal processing bases on a standard OPA circuit it can be modified to your application needs. Depending on the ripple counter application, a possible modification of the described band pass filter is the dynamic amplification gain adjustment of the OPA to prevent the OPA from overdrive. Circuit which decreases the amplification factor of the OPA during high motor current ripple. ELMOS Semiconductor AG Application Note 12/25 QM-No.: 03AN0401E.01 E910.40 0 0 + IN V1 = V2 = TD = TR = TF = PW = PER = -1 1 1ms 1ms 1ms 2ms 4ms + C5 R2 + 5 IN_OP 6 4 V+ + V2 9V OUT 7 V11 - 10k 1µF V4 - V1 4V R3 - 330k C2 0 470p R1 D3 D4 33k R6 10k C1 100nF 0 Figure 14: Dynamic gain reduction (schematics) Measured signal at IN_OP and digital ripple counter output: �� �� � ����� � �� ���� ������������������������ ���� ���� �� � ���� ����� ������ ����� ������� ����� ����� ����� ����� ����� ����� ����� ����� ����� � � � ����� ������� Figure 15: Dynamic gain reduction (simulation) ELMOS Semiconductor AG Application Note 13/25 QM-No.: 03AN0401E.01 E910.40 Figure 16: Dynamic gain reduction (measured) Circuit which increases the amplification factor of the OPA during high motor current ripple. 0 0 + IN V1 = V2 = TD = TR = TF = PW = PER = -1 1 1ms 1ms 1ms 2ms 4ms + V4 C1 1µF R2 - V1 4V + 5 IN_OP 6 10k + - 4 V+ V2 9V OUT 7 V11 R3 - 330k C2 0 470p R1 D3 D4 33k R6 10k C1 100nF 0 Figure 17: Dynamic gain amplification (schematics) ELMOS Semiconductor AG Application Note 14/25 QM-No.: 03AN0401E.01 E910.40 Measured signal at IN_OP and digital ripple counter output: �� �� �� �� ����� � ���� ������������������������ ���� �� � ���� ����� ����� ����� ������ ����� ����� ����� ����� ����� ����� ����� ����� ����� � � � ����� ������� Figure 18: Dynamic gain amplification (simulation) Figure 19: Dynamic gain amplification (measured) ELMOS Semiconductor AG Application Note 15/25 QM-No.: 03AN0401E.01 E910.40 Example of misconfigured filter parameters The following oscilloscope screenshot shows a misconfigured bandpass filter. The ripple frequency signal is suppressed. Some of the ripple counter pulses are lost. Figure 20: Example of misconfigured bandpass filter Example of well configured filter parameters The following screenshot shows well configured filter parameters. No pulses are lost. Figure 21: Example of well configured bandpass filter ELMOS Semiconductor AG Application Note 16/25 QM-No.: 03AN0401E.01 E910.40 5 Temperature supervision The E910.40 provides temperature supervision of any connected application device. Two possible temperature sensitive devices or a digital information circuit can be used: ÿ 1. ÿ 2. ÿ 3. NTC device PTC device external digital signal source 1. 2. Vref (PIN 16) 3. Vref (PIN 16) Vref (PIN 16) TEMP (PIN 18) TEMP (PIN 18) NTC TEMP (PIN 18) PTC Figure 22: Temperate supervision circuits As soon as the voltage at the pin TEMP (pin 18) reaches the threshold of 0.5±0.1 V ref the OVERLOAD bit will be set to ‚1‘. The following formula is used for estimation of V TEMP at pin 18. Using an NTC: V TEMP=V ref Using a PTC: V TEMP=V ref R =V ref R R NTC R PTC =V ref R R PTC 1 1 1 R NTC R where R NTC = f T 1 where R PTC= f T R R PTC Using a digital signal source: V TEMP high V TEMP low ÿ OVERLOAD bit ‚1‘ ÿ OVERLOAD bit ‚0‘ ELMOS Semiconductor AG Application Note 17/25 QM-No.: 03AN0401E.01 E910.40 6 Adjusting the slew rate of Power MOSFET gate signals The E910.40 provides an EMI conform switching behavior of the Power MOSFETs by reducing the gate signal‘s slew rate. The resistor RSR connected to pin 10 of the E910.40 is responsible for the slew rate adjustment which can reach values from 2 to 15 V/µs. Note: The slew rate adjustment strongly depends on the gate capacitance of the Power MOSFET. Note: RSR = 47kΩ @ CGS = 1.5nF provides a good EMI performance of the circuit. 7 Adjusting the motor braking ripple threshold After a stop or direction change command during motor run it will be smoothly stopped by increasing/decreasing of the switching PWM duty cycle. In addition the ripple signal is evaluated again and the braking PWM change actively adjusted. Figure 23: Smooth PWM duty cycle change from 100% to 0% The threshold of the succeeding ripple signal can be adjusted by an external voltage (i.e. Voltage divider) at the pin BRTH. The equation for the braking threshold: V BRTH brake threshold = 5V 50 mV brake threshold = V BRTH 50 mV 5V A use of a voltage divider of 2x10kΩ: brake threshold = ELMOS Semiconductor AG 2.5 V 50 mV =25 mV 5V Application Note 18/25 QM-No.: 03AN0401E.01 Application Note 19/25 MOTOR 2 MOTOR 1 GND 220p C27 GND NO REVERSE POLARITY PROTECTION !!!! RIPPLE COUNTER UNIT X5 X4 GND VS 100nF 50V GND 22 R4 8 7 6 5 4 3 1k NC SI SO GND 47µF 35V C5 E910.18 TXD RXD BUS TEST GND3 RESET VTR GND2 EN GND1 VDD SENSE VS IC2 100nF 50V C2 9 100nF 50V C3 10 11 12 13 14 15 16 VSUP GND R2 100k R3 100k T3 FQB30N06 T1 FQB30N06 GND 1µF C1 GND GND GND 100nF 16V C14 10 9 8 7 6 5 4 3 2 1 T4 FQB30N06 T2 FQB30N06 GND R1 100k GND 1µF C15 IDIF OLP SENSE2 RSR E910.40 ODIF SENSE1 VGL2 RB VREF VGL1 VSA BRTH VGH2 BSI TEMP VGH1 VDD DATA_I/0 IMP_OUT GND IC1 VCC 11 12 13 14 15 16 17 18 19 20 1µF C11 10k R13 33k R12 10k R11 R10 330k D2 470p C10 100nF 100nF BAV99 GND C8 C9 R14 4,7k 100nF 16V C7 100nF C12 GND GND R9 330k GND R8 10k R7 10k GND 1k R6 R15 4,7k GND T7 BC847BSMD R16 4,7k To µC Dokument-No.: 03SP0275E.xx X3 X2 100µF 35V GND 2 1 D3 R17 BAW56 C13 D1 ELMOS Semiconductor AG C4 BAW56 (LIN TRANSC.USED AS LEVEL SHIFTER + VOLT.REG.) ELMOS RELIN VCC POWER SUPPLY + LEVEL SHIFTER E910.40 8 E910.40 DATA I/O protocol For detailed information and examples please refer to the E910.40 datasheet. Specification E910.40 9 Typical E910.40 Application Figure 24: E910.40 Typical application QM-No.: 03AN0401E.01 E910.40 10 E910.40 Evaluation Kit For evaluation of the E910.40 ELMOS Semiconductor AG provides an E910.40 Evaluation Kit which can be ordered at [email protected]. Figure 25: E910.40 Evaluation Board Figure 26: E910.40 Evaluation Board Control ELMOS Semiconductor AG Application Note 20/25 QM-No.: 03AN0401E.01 E910.40 Features: ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ ÿ Designed for 12V automotive applications, Driving motor with a blocking current up to 30A, Based on an easy to use ATMEGA32L™ * µC, C-sources available, Basic functions like: ÿ speed up motor, ÿ slow down motor, ÿ motor position counter reset, are accessed by integrated on-board switches, Processing of 2 end position switches, Feedback and diagnosis available via RS232, PC connection via parallel port, PC based LabVIEW GUI, allows operations like: ÿ cyclic motor speed ramp generation, ÿ cyclic direction change, ÿ watchdog function, ÿ graphical motor position tracking, ÿ processing of end switches, Easy accessible test points to adjust the filter components, External ripple filter components designed to be in SMD and through hole technology * ATMEGA32L is a Trade Mark of Atmel Corparation ELMOS Semiconductor AG Application Note 21/25 QM-No.: 03AN0401E.01 E910.40 11 Record of Revisions Chapter 1 Rev. Change and Reason for Change Date 1 Initial Revision 18.01.2006 2 New Figure 7 18.05.2006 ELMOS Semiconductor AG Application Note 22/25 Released ZOE/EM QM-No.: 03AN0401E.01 E910.40 Contents Package Pin Out....................................................................................................................................................................................... Pin Description......................................................................................................................................................................................... SO20w Package Outline........................................................................................................................................................................ 1 Introduction to ripple detection .................................................................................................................................................... 2 Motor ripple signal processing with E910.40 ............................................................................................................................ 3 Adjusting the parameters C1, C2, R1, R2 of the band pass filter ............................................................................................. 4 Dynamic ripple amplification gain adjustment ....................................................................................................................... 5 Temperature supervision ................................................................................................................................................................. 6 Adjusting the slew rate of Power MOSFET gate signals ........................................................................................................ 7 Adjusting the motor braking ripple threshold .......................................................................................................................... 8 E910.40 DATA I/O protocol .............................................................................................................................................................. 9 Typical E910.40 Application ............................................................................................................................................................ 10 E910.40 Evaluation Kit..................................................................................................................................................................... 11 Record of Revisions............................................................................................................................................................................ 2 2 3 4 9 10 12 17 18 18 19 19 20 22 List of Figures Figure 1: Simple example of a DC motor .......................................................................................................................................... 4 Figure 2: Electrical schematics of motor windings ....................................................................................................................... 4 Figure 3: Generation of Commutation Ripple ................................................................................................................................ 5 Figure 4: Generation of Commutation Spikes ................................................................................................................................ 5 Figure 5: Motor resistance change with resulting current ripple (neglecting the armature inductance) .................. 6 Figure 6: Quasi-sinusoidal current shape......................................................................................................................................... 7 Figure 7: Unsymmetrical windings..................................................................................................................................................... 7 Figure 8: Low frequency signal superposition ................................................................................................................................ 8 Figure 9: Stator field weakening ......................................................................................................................................................... 8 Figure 10: Stator field distortion ......................................................................................................................................................... 8 Figure 11: Undefined Phase Relation due to Field Bending ......................................................................................................... 9 Figure 12: Filter schematics ................................................................................................................................................................... 9 Figure 13: Proposed filter frequency response ................................................................................................................................ 12 Figure 14: Dynamic gain reduction (schematics) ........................................................................................................................... 13 Figure 15: Dynamic gain reduction (simulation) ............................................................................................................................ 13 Figure 16: Dynamic gain reduction (measured) ............................................................................................................................. 14 Figure 17: Dynamic gain amplification (schematics) .................................................................................................................... 14 Figure 18: Dynamic gain amplification (simulation) ..................................................................................................................... 15 Figure 19: Dynamic gain amplification (measured) ...................................................................................................................... 15 Figure 20: Example of misconfigured bandpass filter ................................................................................................................. 16 Figure 21: Example of well configured bandpass filter ................................................................................................................ 16 Figure 22: Temperate supervision circuits ....................................................................................................................................... 17 Figure 23: Smooth PWM duty cycle change from 100% to 0% ................................................................................................. 18 Figure 24: E910.40 Typical application .............................................................................................................................................. 19 Figure 25: E910.40 Evaluation Board .................................................................................................................................................. 20 Figure 26: E910.40 Evaluation Board Control ................................................................................................................................. 20 ELMOS Semiconductor AG Application Note 23/25 QM-No.: 03AN0401E.01 E910.40 WARNING – Life Support Applications Policy ELMOS Semiconductor AG is continually working to improve the quality and reliability of its products. Nevertheless, semiconductor devices in general can malfunction or fail due to their inherent electrical sensitivity and vulnerability to physical stress. It is the responsibility of the buyer, when utilizing ELMOS Semiconductor AG products, to observe standards of safety, and to avoid situations in which malfunction or failure of an ELMOS Semiconductor AG Product could cause loss of human life, body injury or damage to property. In development your designs, please ensure that ELMOS Semiconductor AG products are used within specified operating ranges as set forth in the most recent product specifications. General Disclaimer Information furnished by ELMOS Semiconductor AG is believed to be accurate and reliable. However, no responsibility is assumed by ELMOS Semiconductor AG for its use, nor for any infringements of patents or other rights of third parties, which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of ELMOS Semiconductor AG. ELMOS Semiconductor AG reserves the right to make changes to this document or the products contained therein without prior notice, to improve performance, reliability, or manufacturability . Application Disclaimer Circuit diagrams may contain components not manufactured by ELMOS Semiconductor AG, which are included as means of illustrating typical applications. Consequently, complete information sufficient for construction purposes is not necessarily given. The information in the application examples has been carefully checked and is believed to be entirely reliable. However, no responsibility is assumed for inaccuracies. Furthermore, such information does not convey to the purchaser of the semiconductor devices described any license under the patent rights of ELMOS Semiconductor AG or others. Copyright © 2006 ELMOS Semiconductor AG Reproduction, in part or whole, without the prior written consent of ELMOS Semiconductor AG, is prohibited. ELMOS Semiconductor AG Application Note 24/25 QM-No.: 03AN0401E.00 ELMOS Semiconductor AG – Headquarters Heinrich-Hertz-Str. 1 | 44227 Dortmund | Germany Phone + 49 (0) 231 - 75 49 - 0 | Fax + 49 (0) 231 - 75 49 - 149 [email protected] | www.elmos.de 25/25