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AVR430 

 

 

 

 

11

 

8124C-AVR-10/08 

4.4 Back-EMF 

For sensorless applications, the driving logic uses back EMF from the motor’s phases 
to  keep  track  of  the  motor  position.  To  observe  the  back  EMF  from  a  phase,  the 
phase is left floating, i.e. with the high or low side MOS not powered, and the voltage 
on the phase is read. For motors with center tap, Vn (V neutral) provides feedback to 
device board.  

4.4.1 Back-EMF feedback filters 

Each  phase  (U/V/W/X)  and  the  center  tap  (Vn)  are  fed  via  a  filter/damping  block  to 
the device board interface. The block for phase U is shown in Figure 4-5. The board 
is shipped with a zero ohm resistor, so  it has no damping/filter function. The signals 
are named U’, V’, W’, X’ and Vn’ after going through the filter blocks. 

Vmotor  (Vm)  is  also  fed  thru  a  filter/damping  block,  and  is  available  on  the  device 
board interface as Vm’.  

Figure 4-5. 

Filter/damping block for back-EMF feedback.

 

 

Содержание 8-bit AVR Microcontrollers AVR430: MC300

Страница 1: ...d Electric specifications Driver circuit Vin 10 20V Motor Vm 0 40V Immax 6A Dimension 100x100mm 1 Introduction The MC300 is a general purpose power stage board able to drive brushless DC brushed DC and stepper motors The board is designed to be a flexible platform for developing motor control applications Power and all signals needed for a controller AVR CPU are available on the left side of the b...

Страница 2: ... the Hall sensors Vm Vin and Vcc each have their own LED to indicate power 2 1 Specifications MC300 maximum ratings with components as delivered Input Vin 10 20VDC Vm 0 40VDC Immax 6A Output ratings Vcc 3 3 5V Imax 0 5A Vha 5V Imax 0 1A The driver stage consists of four half bridges capable of 40V 30A Warning Other components such as shunt resistors limit the maximum current to 6A 2 1 1 Necessary ...

Страница 3: ... Table 2 2 The connectors are mounted on the same 0 1 grid The grid is positioned so the connectors will fit an angled pin header on a prototype Vero board shown in Figure 2 1 2 2 2 Power and motor connectors The board has two power connectors located on the top one 4 pin 3 81mm connector J3 and one DC jack J5 with 2 0mm center tap J3 allows for separate power inputs to Vin and Vm while J5 powers ...

Страница 4: ... for location of jumpers Table 2 1 Jumpers and their functions Designator Use and settings J1 VHa Selects voltage source to Hall sensors VHa J1 open VHa not connected J1 pin 2 3 connected VHa Vcc J1 pin 1 2 connected VHa 5V from separate regulator J2 VCC Selects voltage from onboard regulated supply Vcc J2 connected Vcc 3 3V J2 open Vcc 5V ...

Страница 5: ...hase X Highside control input 16 J11p8 XL Input Phase X Lowside control input 17 J13p1 GNDm Motor ground Vmotor 18 J13p2 Vmotor Output Vmotor filtered divided 19 J13p3 ShCom Output Voltage over ShCom filtered divided 20 J13p4 ShU Output Voltage over ShU filtered divided 21 J13p5 U Output BackEMF phase U filtered divided 22 J13p6 ShV Output Voltage over ShV filtered divided 23 J13p7 V Output BackEM...

Страница 6: ...tant components and jumper information are written on the silk screen For individual component placement refer to the component floorplan Figure 3 1 MC300 PCB layout In Figure 3 1 the following areas are marked 1 Device board connector 2 Power connectors 3 Motor connector 4 Phase area 5 Indicator LEDs for power ...

Страница 7: ...d and above shunt resistor 4 Bootstrap voltage testpoint denoted Vboot 5 MOS Gate voltage testpoints denoted VGl low side and VGh high side 3 1 2 Common shunt and filters dividers The common shunt R62 with testpoints is found above phase U and denoted ShCom Filters dividers for Vm ShCom and Vn are found on the left of the phase areas 3 2 Schematics component floorplan and bill of materials The sch...

Страница 8: ... Vm But it is also possible to power the MC300 from a single DC Jack connector J5 J5 is connected to Vin and Vm via diodes as shown in Figure 4 1 When J5 is used as power input the supply voltage must not exceed 20V and maximum current is 5A Figure 4 1 MC300 Power input 4 1 2 Fuses Vin is protected by a resettable 0 75A polyfuse F1 If the current through it exceeds 0 75A the fuse will heat up and ...

Страница 9: ...bridge for phase U is shown in Figure 4 2 Figure 4 2 Phase U half bridge 4 2 1 High side driving considerations The high side of the half bridge uses a bootstrap circuit This means the duty cycle and the on time are limited by the requirement to refresh the charge in the bootstrap capacitor If the driving logic fails to do this the gate voltage to the high side MOS will decrease and the RDS will i...

Страница 10: ... to a zero ohm resistor and the zero ohm resistors on each phase ShU R27 ShV R38 ShW R49 and ShX R64 should be replaced with appropriate shunt resistors 4 3 1 Shunt feedback filters The voltages over the shunt resistors ShCom ShU V W X are fed to a filter damping block ShU as shown in Figure 4 4 The board is shipped with a filter that consists of a 10k ohm resistor in series with a 10nF capacitor ...

Страница 11: ...neutral provides feedback to device board 4 4 1 Back EMF feedback filters Each phase U V W X and the center tap Vn are fed via a filter damping block to the device board interface The block for phase U is shown in Figure 4 5 The board is shipped with a zero ohm resistor so it has no damping filter function The signals are named U V W X and Vn after going through the filter blocks Vmotor Vm is also...

Страница 12: ...dge drivers IR2101S can handle up to 600V but the layout of the PCB spacing between tracks should be considered before operation at high voltages If filters dividers for Vm U V W or X have been mounted verify that they can handle Vm 4 5 2 Current limitations For an Im 5A use power connector J3 and not DC Jack J5 If an Immax larger than 6A is required components listed in Table 4 2 are affected Tab...

Страница 13: ...TUTORY WARRANTY RELATING TO ITS PRODUCTS INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTY OF MERCHANTABILITY FITNESS FOR A PARTICULAR PURPOSE OR NON INFRINGEMENT IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT INDIRECT CONSEQUENTIAL PUNITIVE SPECIAL OR INCIDENTAL DAMAGES INCLUDING WITHOUT LIMITATION DAMAGES FOR LOSS OF PROFITS BUSINESS INTERRUPTION OR LOSS OF INFORMATION ARISING OUT OF THE USE O...

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