APEX MICROTECHNOLOGY CORPORATION TELEPHONE (520) 690-8600 FAX (520) 888-3329 ORDERS (520) 690-8601 EMAIL prodlit@apexmicrotech.com
1
FEATURES
40V TO 450V MOTOR SUPPLY
20A CONTINUOUS AND 40A PEAK OUTPUT CURRENT
OPERATION WITH 10.8V TO 16V VCC, ALLOWING
NOMINAL 12V OR 15V VCC SUPPLIES
THREE PHASE FULL BRIDGE OPERATION WITH 2 OR
4 QUADRANT PWM
AUTOMATIC BRAKING WHEN USING 2 QUADRANT PWM
THERMAL PROTECTION
ANTI SHOOT THROUGH DESIGN
25KHZ INTERNALLY SET PWM FREQUENCY, WHICH MAY
BE LOWERED WITH EXTERNAL CAPACITORS
SELECTABLE 60 OR 120 COMMUTATION SEQUENCES
COMMUTATION TRANSITIONS OUTPUT FOR DERIVING
SPEED CONTROL
MAY BE USED OPEN LOOP, OR WITHIN A
FEEDBACK LOOP
ANALOG MOTOR CURRENT MONITOR OUTPUT, MAY BE
USED FOR TORQUE CONTROL OR FOR TRANSCONDUC-
TANCE AMPLIFIER DRIVE.
APPLICATIONS
3 PHASE BRUSHLESS MOTOR CONTROL
DESCRIPTION
The BC20 Brushless DC Motor Controller provides
the necessary functions to control conventional 3-phase
brushless DC motors in an open loop or closed loop
system. The BC20 can control larger motors requiring up
to 4.5kW input power.
The controller drives the motor, generates the PWM,
decodes the commutation patterns, multiplexes the current
sense, and provides error amplification. Operation with
either 60 or 120 commutation patterns may be selected
with a logic input.
Current sense multiplexing is used to make the current
monitor output always proportional to the active motor
coils current. Therefore the current monitor output may
be used in generating transconductance drive for easy
servo compensation.
The controller may generate 4-quadrant PWM for
applications requiring
continuous transition
through zero veloc-
ity, or 2 quadrant
PWM for electrically
quieter operation in
unidirectional appli-
cations. Direction
of rotation may be
reversed in 2-quad-
rant mode by using
the reverse com-
mand input. When in
2-quadrant mode if
the motor is stopped
or decelerating
dynamic braking is
a u t o m a t i c a l l y
applied. In this way
deceleration profiles
may be followed even
when using 2-quad-
rant PWM.
H T T P : / / W W W . A P E X M I C R O T E C H . C O M ( 8 0 0 ) 5 4 6 - A P E X ( 8 0 0 ) 5 4 6 - 2 7 3 9
M I C R O T E C H N O L O G Y
HIGH PERFORMANCE BRUSHLESS DC MOTOR DRIVER
BC20 BC20A
Figure 1: Block diagram
+
+
V+
V+
V+
TOP DRIVE 1
BOTTOM DRIVE 1
BRIDGE
CONTROL
LOGIC
TOP DRIVE 2
BOTTOM DRIVE 2
BOTTOM DRIVE 3
TOP DRIVE 3
1/2
BRIDGE
1/2
BRIDGE
1/2
BRIDGE
CURRENT
SENSING
SIGNAL
CONDITIONING
POWER
FAULT
LOGIC
REF IN
FB
PWM
COMPARATOR
PWM
PWM
OSCILLATOR
TEMP
SENSING
OVERTEMP
SHUTDOWN
OVERCURRENT
COMMUTATION
DECODE
LOGIC
1
2
3
OUT 1
OUT 2
OUT 3
GROUND
MOTOR I
HV RTN
S3
S2
S1
SSC
2Q
VCC
HV
HV
HV RTN
FAULT
CT
TORQUE
HS1
HS2
HS3
120
REV
OE 19
6
7
8
22
21
23
X10
X10
18
2
20
9
10
13
15
12
14
16
1
5
17
3
4
24
11
APEX MICROTECHNOLOGY CORPORATION 5980 NORTH SHANNON ROAD TUCSON, ARIZONA 85741 USA APPLICATIONS HOTLINE: 1 (800) 546-2739
2
ABSOLUTE MAXIMUM RATINGS
SPECIFICATIONS
BC20 BC20A
The BC20 is constructed from static sensitive components. ESD handling procedures must be observed.
CAUTION
NOTES: 1. Long term operation at the maximum junction temperature will result in reduced product life. Derate internal power
dissipation to achieve high MTTF.
2. Set internally
ABSOLUTE MAXIMUM RATINGS
MOTOR VOLTAGE, V+ 450V
CIRCUIT SUPPLY, Vcc 16V
OUTPUT CURRENT, peak 40A
OUTPUT CURRENT, continuous 20 A
POWER DISSIPATION, internal 480W
ANALOG INPUT VOLTAGE 0.3V to Vcc+0.3V
DIGITAL INPUT VOLTAGE 0.3V to 5.35V
TEMPERATURE, pin solder, 10s 300C
TEMPERATURE, junction
1
150C
TEMPERATURE RANGE, storage 65 to 150C
OPERATING TEMPERATURE, case, BC20 25 to 85C
OPERATING TEMPERATURE, case, BC20A 40 to 85C
SPECIFICATIONS
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
ERROR AMP
OFFSET VOLTAGE 3.3 0 3.3 mV
BIAS CURRENT 4 pA
DC GAIN
2
19.8 20 20.2 db
BANDWIDTH 15 16 17 kHz
INPUT AMP
STAGE GAIN
2
Set by internal and/or external resistors 20 20.2 db
INPUT IMPEDANCE
2
2 Kohm
COMMON MODE VOLTAGE Applied at input terminals, Vcc = 10.8V 0.5 5.0 8.5 V
COMMON MODE VOLTAGE Applied at input terminals, Vcc = 16V 0.5 5.0 14 V
COMMON MODE REJECTI0N 50 db
DIFFERENTIAL OFFSET 3.3 0 3.3 mV
GAIN BANDWIDTH PRODUCT 700 kHz
OUTPUT
TOTAL Vce sat Junction Temperature = 125C 6.6 V
EFFICIENCY, 10A, 450V Dependent on individual application 95 %
SWITCHING FREQUENCY 22 25 28 kHz
CURRENT, continuous 20 A
CURRENT, peak 40 A
POWER SUPPLY
VOLTAGE, V+ 50 450 V
VOLTAGE, Vcc 10.8 16 V
CURRENT FROM Vcc 250 500 mA
APEX MICROTECHNOLOGY CORPORATION TELEPHONE (520) 690-8600 FAX (520) 888-3329 ORDERS (520) 690-8601 EMAIL prodlit@apexmicrotech.com
3
TYPICAL
PERFORMANCE
BC20 BC20A
I/O
SIGNAL
DESCRIPTION
PIN
I
HV
Unregulated high current motor supply voltage
9
I
HVRTN
Return line for the high motor current
16
O
OUT1
Half bridge output for driving motor coil
10
O
OUT2
Half bridge output for driving motor coil
11
O
OUT3
Half bridge output for driving motor coil
12
I/O
S1
Source of the N-rail FET in half bridge 1
13
I/O
S2
Source of the N-rail FET in half bridge 2
15
I/O
S3
Source of the N-rail FET in half bridge 3
14
I
HS1
Commutation sensor input 1
6
I
HS2
Commutation sensor input 2
7
I
HS3
Commutation sensor input 3
8
I
120
Sets commutation logic for 120 phasing
22
I
REV
Reverses direction when 2 quadrant PWM is used
21
I GROUND
Signal
ground
1
I
Vcc
Control circuit power
2
I
REF IN
Velocity/speed input
23
I
FB
Input for analog voltage proportional to velocity or speed
24
I
TORQUE
Input for an analog voltage proportional to motor current
4
O
MOTOR I
Analog voltage proportional to motor current
5
O
SSC
HCMOS level pulse for each sensor state change.
18
O
FAULT
HCMOS logic level output, a 1 indicates an over temperature
17
or over current condition.
I
OE
HCMOS 1 enables power FET operation
19
I/O
CT
The PWM frequency may be lowered by installing a
3
capacitor between this output and ground.
I
2Q
A logic 1 on this input enables 2 quadrant PWM
20
PIN FUNCTION
All Logic Positive TKUC
Position
0
60
120
180
240
300
R
0 0 0 0 0 0
2Q
0 0 0 0 0 0
120
1 1 1 1 1 1
OE
1 1 1 1 1 1
HS1
1 1 1 0 0 0
HS2
0 0 1 1 1 0
HS3
1 0 0 0 1 1
OUT1 T
+
+
T
OUT2
T
+
+
T
OUT3
+ T T +
Position
0
60
120
180
240
300
R
0 0 0 0 0 0
2Q
1 1 1 1 1 1
120
1 1 1 1 1 1
OE
1 1 1 1 1 1
HS1
1 1 1 0 0 0
HS2
0 0 1 1 1 0
HS3
1 0 0 0 1 1
OUT1 T
+
+
T
0
0
OUT2 0
0
T
+
+
T
OUT3
+ T 0 0 T +
Position
0
60
120
180
240
300
R
0 0 0 0 0 0
2Q
0 0 0 0 0 0
120
0 0 0 0 0 0
OE
1 1 1 1 1 1
HS1
1 1 1 0 0 0
HS2
1 1 0 0 0 1
HS3
1 0 0 0 1 1
OUT1 T
+
+
T
OUT2
T
+
+
T
OUT3
+ T T +
Position
0
60
120
180
240
300
R
0 0 0 0 0 0
2Q
1 1 1 1 1 1
120
0 0 0 0 0 0
OE
1 1 1 1 1 1
HS1
1 1 1 0 0 0
HS2
1 1 0 0 0 1
HS3
1 0 0 0 1 1
OUT1 T
+
+
T
0
0
OUT2 0
0
T
+
+
T
OUT3
+ T 0 0 T +
COMMUTATION AND OUTPUT TABLES
TABLE 2
TABLE 1
TABLE 3
TABLE 4
APEX MICROTECHNOLOGY CORPORATION 5980 NORTH SHANNON ROAD TUCSON, ARIZONA 85741 USA APPLICATIONS HOTLINE: 1 (800) 546-2739
4
BC20 BC20A
OPERATING
CONSIDERATONS
PROTECTION CIRCUITS
There are four protection circuits in the BC20.
1. The coil current sensing circuit, which is programmed by
the value of the current sense resistors placed by the user
between the IGBT emitters and HV return. This circuit is
reset each PWM cycle. If three current sense resistors are
used, as recommended, an analog multiplexer selects
the current sense resistor, which has the same current
as the motor coil. This technique blanks out noise and
provides an excellent sensing of actual coil current.
The programming of this circuit is accomplished by the
folowing formula:
I
TRIP
= 0.5/R
SENSE
Note that for large currents R
SENSE
becomes very small,
therefore stray resistance in the high current path can have
a large effect. Heavy etch should be used in the current
sensing path, and leads should be very short between the
resistors and the pins of the controller.
2. Thermal Protection
The junction temperature of all power devices is sensed,
and the controller is shut down when too hot. This
circuit is a a latch and can be reset when OE is turned
on, providing the power devices have cooled to a safe
temperature.
3. There is an over-current circuit which shut down the BC20
when the current provided by the HV supply exceeds
about 1.5 times the peak current rating. This circuit latches
and may be reset by cycling the OE input. Although this
is "top rail" protection, a short from output to ground will
probably destroy the BC10.
4. The output circuit will shut down if a power supply is
missing. This is not an alarmed fault.
FAULT
The FAULT output is an alarm, a logic 1 indicates the
outputs are disabled. Fault is at 1 when OE is at 0, and it is at
logic 0 when OE is at 1 during normal operation. Outputs will
latch to the disabled state and fault will be at logic 1 when any
IGBT is too hot or when peak IGBT current has exceeded a
safe level for the IGBT. This may be reset by setting OE to
logic 0 and back to logic 1.
When the coil sensing circuit senses that the average
current has exceeded the level set by the selection of current
sense resistors, the output will be disabled and the FAULT
output will go to logic 1. (Even though the output has been
disabled coil current will continue, fl owing through the diodes
in anti-parallel with each IGBT.) When coil current has
decayed to below this set level the outputs will be enabled
and FAULT will be at logic 0. Thus when limiting the average
value of coil current the output will cycle between being
disabled and enabled, and FAULT will cycle between logic
1 and 0. This action may cause an audible hiss when driving
low inertia systems.
OPEN LOOP OPERATION
The normal way of operating the controller open loop is
GENERAL
Much useful application information for these products can
be obtained from Application Notes 1 (General Operating
Considerations) and 30 (PWM Basics).
PWM CONSIDERATIONS
The BC20 can be confi gured with a logic-input (2Q) to
operate either as a 2-quadrant or 4-quadrant controller.
2-quadrant PWM holds one coil terminal at a constant level
and applies PWM at the other. PWM is applied at the positive
terminal when in 2-quadrant mode. 4-quadrant PWM switches
both terminals. 2-quadrant PWM is electrically quieter
and more effi cient, but cannot transition through zero. 4-
quadrant PWM has twice the voltage gain of 2-quadrant
PWM. Therefore 4-quadrant PWM is required for applications
such as position servos, phase locked motor control, or
accurately following complex velocity profi les. 2-quadrant
PWM is preferable for unidirectional speed control applications.
The R input may be used to reverse the motor when
using 2-quadrant PWM, but must be at logic "0" when in
4-quadrant mode.
COMMUTATION
The BC20 may be confi gured to operate with either 60
or 120 Hall sensor patterns by the state of the 120 input.
(Obviously also encoder outputs with the same logic.) When
120 is low the BC20 operates with 60 commutation; when
120 is high it operates with 120 commutation.
The relationship between commutation states and motor
drive output is tabulated in the following tables [See Tables
1-4 on previous page]. For the purposes of these tables
PWM that is mostly positive will be designated +; PWM that
is mostly low will be designated -; a constant low state will
be designated by 0; a tri-state condition will be designated
T; REF IN is more positive than FB; and "Forward" rotation
is the only direction tabulated. Position is given in electrical
degrees.
Some motor manufacturers may not use the same
conventions in identifying motor and Hall sense leads as
Apex. In that event you may have to experimentally identify
the corresponding motor and Hall Sense leads. For 3 binary
square waves with equal phase shifts between the square
waves, such as Hall sense outputs, there are only 8 possible
states. 60 commutation fi lls 6 of the states and 120
commutation fi lls the other set of 6 states. Therefore all such
patterns are truly only 60 or 120. Changing pattern is done in
the Apex controller by inverting HS2 internally.
Once the proper commutation patterns are obtained it is
necessary to determine the motor lead orientation to the
Hall sense. This may be done by turning the motor with a
test fi xture and observing the relationship between the
HS patterns and the EMF, or by running the motor at low
voltage and systematically switching motor leads until smooth
running in the desired direction is obtained. The motor can
be expected to run smoothly in the desired direction, run
reverse, run very roughly, not run at all, or vibrate violently
between 2 positions as this is done.
APEX MICROTECHNOLOGY CORPORATION TELEPHONE (520) 690-8600 FAX (520) 888-3329 ORDERS (520) 690-8601 EMAIL prodlit@apexmicrotech.com
5
OPERATING
CONSIDERATONS
BC20 BC20A
connect the input, REF IN pin 24 to a reference, and the
FB input, pin 24 to an analog voltage. When this is done
in conjunction with 2-quadrant PWM the voltage applied
to the motor coils will be:
V
M
= 25(HV)(V
IN
- V
REF
) + HV/2
Where:
HV is the motor supoply.
V
IN
is the input voltage.
V
REF
is the analog reference.
If 4-quadrant PWM is used the equation becomes:
V
M
= 50(HV)(V
IN
- V
REF
)
The input dynamic range can be as smnall as 36mV for
both 2-quadrant or 4-quadrant PWM (No larger than 40mV).
The dynamic range can be extended, with the penalty of gain
loss, by putting matched resistors in series with the FB and
REF IN inputs. The value of these resistors for a given dynamic
range is given by the following equation:
R
IN
= (V
IN MAX
/0.036) - 1
Where:
V
IN MAX
is the desired p-p input.
R
IN
is the required minimum value for the resistors to be put in
series with the FB and REF IN inputs, in kilo-ohms.
When these resistors are used gain is reduced. The new
motor voltage equation for 2-quadrant operation is:
V
M
= HV/2 + (25(HV)(V
IN
- V
REF
))/(R
IN
+ 1)
The new equation for 4-quadrant operation is:
V
M
= (50(HV)(V
IN
- V
REF
))/(R
IN
+ 1)
An alternative mode of open loop operation is to leave the
FB and REF IN inputs open, and connect the input to the
TORQUE input, either directly or through a series resistor.
When this is done the input signal is effectively referenced to
an internal 5.00V supply, V
DD
(This supply is not brought to a
pin). Just as when using the REF IN and FB inputs, dynamic
range can be increased (and gain decreased) by use of
a series resistor, but only one is required. For 2-quadrant
operation the equation for motor voltage is:
V
M
= HV/2 + (25(HV)(V
DD
- V
IN
))/(R
IN
+ 10)
For 4-quadrant operation the equation for motor voltage is:
V
M
= (50(HV)(V
DD
- V
IN
))/(R
IN
+ 10)
R
IN
can be determined for a linear dynamic range for
both 2-quadrant and 4-quadrant PWM from the following
equation:
R
IN
= (V
IN MAX
/0.036) - 10
OPERATION WITH NEGATIVE ANALOG INPUTS
The REF IN and FB inputs are inputs to a true differential
amplifi er. These inputs operate over a range between signal
ground and +10V. However, with the addition 2 resistors,
a diode, and loss of gain the circuit will operate with input
voltages below ground. To operate with these inputs going
to -10V the gain loss is 26.5 dB. When used with an external
controller, which can compensate for this lost gain, this
is insignifi cant.
To choose a resistor to hold the input to the internal amplifi er
within its range, use the following formula:
R
IN
= 2.06(4.9 + V
IN
) - 11.09
Where:
R
IN
is the minimum value of the external resistor in K-ohms.
V
IN
is the absolute value of the most negative input level.
A resistor of this value should be inserted in series with both
the REF IN and FB inputs. Since unbalance in these resistors
affects dc offset and common mode rejection, precision
resistors should be used. If the host system can produce steps
to the REF IN input with less than 11
-seconds transients
below ground on the internal amplifi er will occur. Connecting
a diode with its cathode tied to pin 23, REF IN, and its anode
to ground will clamp these to a safe level.
EXAMPLE: Assume an input voltage of -10V. The formula
gives a minimum input resistance of 19.6K. The lowest
1% value above 19.6K is 20.0K. A nominal 20.0K resistor
2% low is 19.6K, so a 20.0K resistor whose variation to
all effects is 2% is safe..
CLOSED LOOP OPERATION
The controller may be operated in a closed loop by applying
the command signal to the REF IN input, pin 23, and analog
feedback to FB, pin 24. Or, if operating with resistors in
series with pins 23 and 24, through those resistor to pins
23 and 24. In this case the gain as a servo amplifi er is
given by the equation of sections 2 or 3 of the "Open Loop
Operation" section.
TRANSCONDUCTANCE AMPLIFIER OPERATION
The BC20 can be operated in a transconductance amplifi er
mode by connecting the MOTOR I output to the TORQUE
input either directly or through a resistor.
It is convenient to chose the current sense resistors for
the desired average current limit fi rst, as described in section
1 of the protection circuits section, and then choose the
current feedback resistor for the desired transconductance.
If 2 quadrant PWM is being used the equation for calculating
transconductance is:
G
M
= 2.5(A)(V)(R
FBI
+10K)/(R
L
(R
FBI
+10K)+125000(V)(R
S
))
Where:
A is the gain of the Input Amp.
A=10K/(1K+R
IN
)
G
M
is the overall transconductance.
V is the motor supply voltage.
R
L
is the load resistance (terminal to terminal armature
resistance for the motor plus any added resistance.)
R
S
is the sense resistance.
R
FBI
is the resistor from MOTOR I to TORQUE.
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