Saturday, June 13, 2009


Closed Loop Brushless DC Motor Control Circuit

Brushless DC Motor Controller
The MC33035 is a high performance second generation monolithic
brushless DC motor controller containing all of the active functions
required to implement a full featured open loop, three or four phase
motor control system. This device consists of a rotor position decoder
for proper commutation sequencing, temperature compensated
reference capable of supplying sensor power, frequency
programmable sawtooth oscillator, three open collector top drivers,
and three high current totem pole bottom drivers ideally suited for
driving power MOSFETs.

The MC33035, by itself, is only capable of open loop
motor speed control. For closed loop motor speed control,
the MC33035 requires an input voltage proportional to the
motor speed. Traditionally, this has been accomplished by
means of a tachometer to generate the motor speed feedback
voltage. Figure 39 shows an application whereby an
MC33039, powered from the 6.25 V reference (Pin 8) of the
MC33035, is used to generate the required feedback voltage
without the need of a costly tachometer. The same Hall
sensor signals used by the MC33035 for rotor position
decoding are utilized by the MC33039. Every positive or
negative going transition of the Hall sensor signals on any
of the sensor lines causes the MC33039 to produce an output
pulse of defined amplitude and time duration, as determined
by the external resistor R1 and capacitor C1. The output train

of pulses at Pin 5 of the MC33039 are integrated by the error
amplifier of the MC33035 configured as an integrator to
produce a DC voltage level which is proportional to the
motor speed. This speed proportional voltage establishes the
PWM reference level at Pin 13 of the MC33035 motor
controller and closes the feedback loop. The MC33035
outputs drive a TMOS power MOSFET 3−phase bridge.
High currents can be expected during conditions of start−up,
breaking, and change of direction of the motor.

The system shown in Figure 39 is designed for a motor
having 120/240 degrees Hall sensor electrical phasing. The
system can easily be modified to accommodate 60/300
degree Hall sensor electrical phasing by removing the
jumper (J2) at Pin 22 of the MC33035.


The L6235 is a DMOS Fully Integrated Three-Phase
Motor Driver with Overcurrent Protection.
Realized in MultiPower-BCD technology, the device
combines isolated DMOS Power Transistors with
CMOS and bipolar circuits on the same chip.
The device includes all the circuitry needed to drive a
three-phase BLDC motor including: a three-phase
DMOS Bridge, a constant off time PWM Current Controller
and the decoding logic for single ended hall
sensors that generates the required sequence for the
power stage.

A typical application using L6235 is shown in Figure 21.
Typical component values for the application are shown
in Table 3. A high quality ceramic capacitor (C2) in the
range of 100nF to 200nF should be placed between the
power pins VSA and VSB and ground near the L6235 to
improve the high frequency filtering on the power supply
and reduce high frequency transients generated by the
switching. The capacitor (CEN) connected from the EN
input to ground sets the shut down time when an over
current is detected (see Overcurrent Protection). The two
current sensing inputs (SENSEA and SENSEB) should be
connected to the sensing resistor RSENSE with a trace
length as short as possible in the layout. The sense
resistor should be non-inductive resistor to minimize
the di/dt transients across the resistor. To increase noise
immunity, unused logic pins are best connected to 5V
(High Logic Level) or GND (Low Logic Level) (see pin
description). It is recommended to keep Power Ground
and Signal Ground separated on PCB.

175-V, 2-A, two-quadrant velocity controller Driver Circuit

The UCC3626 motor controller device combines
many of the functions required to design a
high-performance, two- or four-quadrant, threephase,
brushless dc motor controller into one
package. Rotor position inputs are decoded to
provide six outputs that control an external power
stage. A precision triangle oscillator and latched
comparator provide PWM motor control in either
voltage- or current-mode configurations. The
oscillator is easily synchronized to an external
master clock source via the SYNCH input.
Additionally, a QUAD select input configures the
chip to modulate either the low-side switches only,
or both upper and lower switches, allowing the
user to minimize switching losses in less
demanding two-quadrant applications.

Figure illustrates a simple 175-V, 2-A, two-quadrant
velocity controller using the UCC3626. The power stage
is designed to operate with a rectified off-line supply using
IR2210s to provide the interface between the low
voltage control signals and the power MOSFETs.