INTRODUCTION L6234 DMOSs triple half-bridge driver with input supply v
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AN1088 APPLICATION NOTE L6234 THREE PHASE MOTOR DRIVER
INTRODUCTION L6234 DMOSs triple half-bridge driver with input supply voltage output current used very wide range applications. been realized Multipower BCD60II technology which allows combination isolated DMOS transistors with CMOS Bipolar circuits same chip. available Power (16+2+2) Power packages. inputs TTL/CMOS compatible each half bridge driven dedicated input enable. DMOS structure intrinsic free wheeling body diode external diodes, which necessary bipolar configuration, avoided. DMOS structure allows very quiescent current typ. Vs=42V irrespective load. DEVICE DESCRIPTION device composed three channels. Each channel composed half bridge with power DMOS switches typ. Rdson 300mW 25°C) intrinsic free wheeling diodes. Each channel includes TTL/CMOS compatible comparators, logic block interface inputs with drivers. device includes internal bandgap reference 1.22V, voltage reference supply internal circuitry device, central charge pump drive upper DMOS switch, thermal shutdown protection internal hysteretic function which turns device when junction temperature exceeds approximately Hysteresys about Figure L6234 Block Diagram
220nF 10nF CHARGE PUMP VREF VBOOT VREF
1N4148 1N4148 100nF 100µF
OUT1
BRUSHLESS MOTOR WINDINGS
OUT2
THERMAL PROTECTION
SENSE1
OUT3
SENSE2
D98IN940A
RSENSE
April 2001
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AN1088 APPLICATION NOTE
DESCRIPTION. INPUT SUPPLY VOLTAGE PINS). Figure
These input supply voltage pins. unregulated input voltage range from 52V. ON/OFF With inductive loads recommended operating maximum supply voltage prevent overvoltage applied (VS+VF) DMosfets. fact considering full bridge configuration (see fig. when bridge switched (ENABLE CHOPPING) current recirculation produces negative voltage ON/OFF source lower DMOS switches (point this condiA tion drain-source voltage Vsense -VSENSE Dinamically same Volts depending current Rsense slope, dI/dt, also Vsense, depending parasitic inD98IN938A ductance current slope some Volts. drainsource voltage DMOS switches reach more than over voltage. input capacitors chosen order reduce overvoltage current decay parasitic inductance. this reason placed closed possible pins. device sustain input current each pins, accordance with power dissipation. Figure Reference Voltage Junction Temperature. OUT1, OUT2, OUT3 (OUTPUTS). These output pins that correspond point each half bridge. They Vref designed sustain current
SENSE1, SENSE2. SENSE1 common source lower DMOS half bridge SENSE2 source lower DMOS half bridge Each these pins handle current resistance, Rsense, connected these pins provides feed- back motor current control. Care must taken with negative voltage applied these pins negative voltage lower than could damage device. duration lower than 300ns device sustain 0-50 pulsed negative voltage -4V. [°C] example, enable chopping current control method used, negative voltage pulses appear these pins, Figure Reference Voltage Supply Voltage. current recirculation through sensing resistor.
Vref
Vref Voltage Reference). This internal voltage reference bias logic voltage circuitry device. electrolytic capacitor connected from this ensures stability DMOS drive circuit. This externally loaded Figure show typical behavior Vref pin.
25°C
CHARGE PUMP This internal oscillator output charge pump. oscillator supplied Voltage Reference switches from with typical frequency
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AN1088 APPLICATION NOTE
1.2MHz (see When oscillator output ground charged through When rises 10V, reverse biased charge flows from through Vboot after cycles reaches maximum voltage VD1- VD2. Vboot BOOTSTRAP). This input bootstrap which gives overvoltage necessary drive upper DMOS three half bridges (see Figure Charge Pump Circuit.
Vs+Vref-VD1 Vs-VD1 f=1.2
1N4148 1N4148
Vs+Vref-VD1-VD2
0.1µF
100µF
10nF
0.22µF VBOOT
Vref HIGH SIDE DRIVER
f=1.2
CHARGE PUMP
SENSE
Vref
LOGIC INPUTS PINS. EN1, EN2, (ENABLES). These pins TTL/CMOS compatible. Each half bridge enabled dedicated with logic HIGH. logic these pins switches related half bridge (see Fig. maximum switching frequency 50kHz. Figure Control logic each half bridge. Figure Cross Conduction Protection.
INPUT level high level level time high level ENABLE high level high level
high level INPUT level level time
level level time DMOS
DMOS UPPER DMOS DMOS tdelay tdelay 300ns DMOS DMOS time
UPPER DMOS DMOS DMOS DMOS time DMOS LOWER DMOS DMOS DMOS DMOS
300ns DMOS LOWER DMOS
DMOS
time
time
IN1, IN2, (INPUTS). These pins TTL/CMOS compatible. They allow switching upper DMOS INPUT high logic level) lower Dmos (INPUT logic level) each half bridge (see Fig.
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AN1088 APPLICATION NOTE
Cross conduction protection (see Fig. avoids simultaneously turning both upper lower DMOS each half bridge. There fixed delay time 300ns between turn turn DMOS switches each half bridge. switching operating frequency 50kHz. High commutation frequency permits reduction ripple output current increases device's power dissipation, however commutation frequency causes high ripple output current. switching frequency should higher than 16kHz avoid acoustic noises. sink current INPUTS ENABLES pins approximately 30µA voltage these pins least less than Vref voltage (see Fig. Fig. avoid overload logic INPUTS ENABLES voltage should applied prior logic signal inputs. POWER DISSIPATION evaluation power dissipation driving three phase motor chopping current control application follows. With simplified approach distinguished three periods (see Fig. Figure Rise Time, period. This rise time period, which current switches from winding another. this time DMOS switched current increases peak value with i(t) (Ipk/Tr) energy lost rise time period Erise Rdson i2(t)dt Rdson I2pk
Tchop Iload Ival
Trise
Tload
Tfall
Fall Time,Tf, period. When current switches from winding another, there fall time which current that flows intrisic diode DMOS decreases from zero. voltage fall diode, energy lost Efall VD(t) i(t)dt
Tload During this time current that flows winding limited chopping current control. energy dissipated resistance DMOS Eload Rdson (Irms)2 Tload formula, Irms load current, given Irms (Iload)2 3Ival
Iload average load current. When switch energy dissipated commutation chopping current control DMOS assumed tcom Ival where tcom commutation time DMOS switch.
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AN1088 APPLICATION NOTE
When switch Eoff tcom
energy lost commutation chopping period, given Eoff, Ecom Iload tcom energy lost commutation during Tload time given Ecom Iload tcom Tload fchop
Quiescent Power Dissipation, power dissipation quiescent current which quiescent current chopping frequency, fchop 1/Tchop. Total Power Dissipation. Let's evaluate power dissipation device driving three phase brushless motor chopping current control. driving sequence only upper DMOS lower same time (see fig. 10). total power dissipation given Ptot (Erise Efall Eload Ecom)
Figure shows total power dissipation, L6234 driving three phase brushless motor input chopping current control different chopping frequency. EVALUATION BOARD. L6234 Power SO20 board been realized evaluate device driving, closed loop control, three phase brushless motor with open collector Hall effect sensors. Figure Input chopping current circulation.
PHASE CHOPPING INPUT half bridge ILOAD ON/OFF OUT1 OFF/ON IOFF ILOAD OUT2 half bridge
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AN1088 APPLICATION NOTE
Figure Three Phase Brushless motor control sequence.
IOUT1
BRUSHLESS MOTOR OUT1
OUT2
L6234
OUT3
IOUT2
IOUT3
device soldered copper heat dissipating Figure L6234 Power Dissipation Three area board ,without additional heat sink, Phase Brushless Motor Control. sustain load current Tamb approximately INPUT CHOPPING Vs=36V fchop=30kHz board provides closed loop speed torque L=2mH fchop=50kHz control, with constant TOFF chopping current conT=2ms Tj=100C trol method. allows user change direction brake motor.
Constant tOFF Chopping Current Control. When current through motor exceeds threshold, fixed ratio between control voltage Vcontrol sensing resistor, Rsense, error signal generated, output LM393 comparator switches ground. This state maintained monostable (M74HC123) constant delay time tOFF generating sig2 that achieves chopping current control. ILOAD signal used chopping INPUT pattern. During toff chopping current control, current flows side loop fig. does flow through sensing resistor. tOFF value values shown table suitable value toff majority applications 30µs. larger tOFF, higher current ripple. tOFF large ripple current becomes excessive other hand tOFF small winding current cannot decrease under threshold current regulation guaranteed.
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AN1088 APPLICATION NOTE
Figure Application board Schematic Circuit.
Vs=8V
100uF 100nF
1N4148
1N4148 10nF Vboot OUT1 OUT2 OUT3 220nF HALL EFFECT SENSORS
L7805
10uF
220nF
HALL EFFECT SIGNALS BRAKE
CONTROL LOGIC
L6234
POWER SO20
SENSE
BRUSHLESS MOTOR
Vref
CONSTANT toff CHOPPING CURRENT CONTROL
Vsense
each
Vcontrol
TORQUE SPEED CONTROL
Hall effect signal Reference Speed
REFERENCE SPEED
Figure Constant toff current control.
100nF 100k Vcontrol 330pF 100nF
Table toff selection
toff 20µs 30µs
470pF Vsense
100k 100k 100k 100k
270pF 330pF 560pF
45µs 70µs
M74HC123 monostable
LM393
Torque Speed Closed Loop Control. motor's rotational speed determined frequency Hall effect signals. speed control loop been achieved comparing this frequency with frequency reference oscillator (see fig. that corresponds desired speed limit. Figure Motor Control.
REFERENCE
FEEDBACK
PHASE/ FREQUENCY DETECTOR
Amp.
Vcontrol
MOTOR
COMPENSATION NETWORK HALL SENSORS
D01IN1209
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AN1088 APPLICATION NOTE
Figure Oscillator Reference Speed.
Reference Speed 100nF
NE555
100nF
100nF
Figure Phase Locked Loop filtering.
100nF BAT47 270K Output Aux. OP-AMP 2.5V
LM358
100nF
220nF
When hall effect signal frequency lower than reference frequency, control voltage maintained value that sets motor current limit therefore torque control limit. peak current limit given Ipeak Vcontrol/Rsense. When frequency from Hall Effect sensors exceeds reference frequency error signal generated (see Fig. 14). LM358 comparator, loop amplifier auxiliary OP-AMP ensure right gain filtering guarantee stability (see fig.16). error signal causes Vcontrol decrease value that sets chopping current control order reduce torque desired speed. motor speed regulated within 0.02 desired speed.
Vcontrol
47nF
HALL1 (Speed feedback)
100nF
+VIN
Loop Amplifier
3635
Phase/ Frequency Detector
Reference Speed
Figure Control Logic Circuit.
MOTOR HALL EFFECT SIGNALS HALL1 HALL2 HALL3 BRAKE
Control Logic Circuit. logic sequence motor generated GAL16V8, which decodes Hall Effect signals generates INPUT ENABLE pattern shown Fig. brake function obtained setting input pattern logic thus turning lower DMOS switches enabled halfbridges. signal used chopping INPUT pattern. control logic circuit decodes Hall effect sensors having different phasing. With jumper opened application achieves forward rotation motors having 120° Hall Effect sensor electrical phasing reverse rotation motors having 300° 240° Hall Effect sensor phasing. Connecting jumper ground sets reverse rotation motors having 120° Hall sensors phasing forward rotation motors having 300° 240° Hall sensor phasing. switch performs startstop function.
16V8
100nF DIRECTION CHANGE
BACK ROTATION FORWARD ROTATION BRAKE BRAKE FUNCTION BRAKE BRAKE BRAKE
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AN1088 APPLICATION NOTE
Figure
ELECTRICAL DEGREES 360°
HALL1
SENSOR SIGNALS
HALL2
HALL3
ENABLE
FORWARD ROTATION
REVERSE ROTATION
IOUT1
MOTOR DRIVE CURRENT FORWARD ROTATION
IOUT2
IOUT3
CONSTANT tOFF
D98IN912
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AN1088 APPLICATION NOTE
Layout Considerations. Special attention must taken avoid overvoltages additional negative voltages SENSE pins noise distributed inductance. Thus input capacitor must connected close pins with symmetrical paths. paths between SENSE pins input capacitor ground have minimized symmetrical sensing resistors must non-inductive. device connected with separate path input capacitor ground.
Figure Application Board Layout.
Figure Component side.
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AN1088 APPLICATION NOTE
Figure Copper side.
APPLICATION IDEAS. L6234 used many different applications. Typical examples half bridge driver using channel full bridge driver using channels. addition, bridges paralleled reduce RDSon device dissipation. paralleled configuration also used increase output current capability. Channel paralleled with Channel Channel paralleled with Channel Channel should paralleled with Channel because sources their side DMOSs connected same SENSE1 Application ideas L6234 follow. Figure Constant frequency current control
1N4148 1N4148
100uF 100nF 10nF
220nF
Vboot
OUT1 OUT2
CONTROL LOGIC
Reset
L6234
POWER SO20
OUT3
Vref
SENSE1 SENSE2
Vsense RSENSE Vcontrol 100nF
L6506
Constant frequency Current Control Fchop= 0.69 Rx>10kOhm
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AN1088 APPLICATION NOTE
Cost Application with Speed Torque Control Loops. Figure Complete three phase brushless motor application with speed torque control.
HALL EFFECT SENSORS OUT1
HALL EFFECT SIGNALS CONTROL LOGIC
L6234
POWER SO20
OUT2
OUT3 BRUSHLESS MOTOR SENSE RSENSE 0.3W V5=+5V
1,10,11,20 V5=+5V
VSENSE
M74HC123 MONOSTABLE
TSM221
1/fe 200nF HALL EFFECT SIGNAL
VCONTROL TSM221
100K
M74HC123 MONOSTABLE
Vref (Reference Speed Voltage)
100K SPEED LOOP
D01IN1210
cost solution obtain complete three phase brushless motor control application with speed torque closed control loop shown Fig. This simple cost solution useful when high dynamic performances accuracy speed loop required. current regulation limit, which determines torque given Vcontrol/Rsense. constant toff fixed Cx2. speed loop realised using Hall effect signal, whose frequency proportional motor speed. each positive transition Hall effect sensors monostable maintains pulse constant time Ton, with fixed amplitude, average value this signal proportional frequency Hall effect signal motor speed OP-AMP configured integrator filters this signal compares with reference voltage, Vref, which sets speed generated error signal control voltage, Vcontrol, currrent loop. Therefore current loop modifies produced torque order regulate speed desired value. values should chosen obtain nearly ripple free op-amp output, even motor speed. This constrain limits system bandwidth limits response time loop. regulated speed, rotor with pairs permanent magnetic poles given Vref with Rsense
[RPM]
which expressed [Nm/A] Motor Torque constant expressed [Nms], Total Viscous Friction. most cases 1/KG neglected.
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AN1088 APPLICATION NOTE
values, given KCx1Rx1, must less than period Hall effect electrical signal desired motor speed must meet requirement
motor load used this application, which have following parameters 10-4 (Motor plus Load Inertia Moment); 10-2 [Nm/A] R1=100k R2=1M ±1[kW] 10-5 [Nms] Cf=220n
regulated speed 6000RPM obtained with accuracy around +/-3%, considering accuracy +/-1% Vref mismatch +/-1% speed 6000RPM, there rotor revolution second, with n=4, Hall effect frequency 400Hz. Therefore lower than 2.5ms (according equation 1.1). phase margin about response time speed loop speed step variation around 200ms BRUSHLESS APPLICATION Figure Three Phase Brushlees Application Circuit
1N4148 1N4148 10nF Vboot OUT1 OUT2 OUT3 Vref SENSE1 SENSE2 220nF THREE PHASE BRUSHLESS MOTOR OUT1A OUT1B OUT2A OUT2B
100uF
100nF
IN1A
SPEED POSITION FEEDBACK
IN1B IN2A
L6234
CONTROL LOGIC
100nF 1N4148 1N4148 10nF Vboot OUT1 OUT2 OUT3 Vref SENSE1 SENSE2 OUT3B 220nF
100uF
IN3A IN3B IN2B
OUT3A
L6234
Constant Toff Current Control. M74HC124 plus LM339 Comparator monostable
100nF 100nF M74HC123 monostable
LM339
470pF Vcontrol Vsense3
PWM3
Comparator monostable
PWM2
Vsense2
Comparator monostable
PWM1
Vsense1
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AN1088 APPLICATION NOTE
Information furnished believed accurate reliable. However, STMicroelectronics assumes responsibility consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights STMicroelectronics. Specification mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. STMicroelectronics products authorized critical components life support devices systems without express written approval STMicroelectronics. logo registered trademark STMicroelectronics 2001 STMicroelectronics Printed Italy Rights Reserved STMicroelectronics GROUP COMPANIES Australia Brazil China Finland France Germany Hong Kong India Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom U.S.A. http://www.st.com
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