IEEE Power Electronics Magazine - March 2022 - 41

whole range operation. Typically, a motor
controller uses an analog signal chain,
analog power management, and digital
components with both signal and power
traces on the same board. A welldesigned
printed circuit board (PCB) is
required for the system to operate efficiently.
This article lays the guidelines
for designing a BLDC motor drive PCB.
Controller
Gate Driver
Three-Phase
Inverter
BLDC
Sensors
Components of BLDC Motor Controller
BLDC motors are closer to us in our day-today
lives than we think. They are integral to home appliances
like washing machines, refrigerators, and fans. BLDC
motors often replace brushed DC and induction motor
drives because of their high power density, efficiency, and
efficient control. In low voltage, high current applications
BLDC motors provide significant system benefits. Technological
advancements in semiconductor technology enable
complex control algorithms for BLDC motors to perform
speed control, position control, and torque control. However,
there are several hardware design challenges, including
gate driver selection, MOSFET selection, PCB layout,
sensors placement, and control scheme. PCB design in this
mixed-signal and the mixed-power domain is not trivial and
has specific requirements.
The various components of a typical BLDC motor
driver are shown in Figure 1 and are explained briefly in the
following sub-sections.
Controller
The controller can be a microcontroller, digital signal
processor (DSP), field-programmable gate array (FPGA), or
any hardware-in-loop (HIL) simulation hardware. Its task is
to provide the commutation signals to the inverter through
gate drivers. Depending on the commutation type and control
method, the controller assesses the
motor parameters and input from the
inverter through various sensors. The controller
uses the motor parameters and enduser
requirements to generate the control
signals to drive the motor as desired.
Gate Driver
Various off-the-shelf gate drivers are available
in different configurations. Based on
the level of integration, these gate-drivers
can be classified in various forms as outlined
in the flow-chart in Figure 2.
Considering the many use cases for the
BLDC motor in high power density, batterypowered
low voltage high current applications
like robotics, hand-held tools, and
UAVs, this article presents a design guideline
for the hardware development of motor
controllers with medium-level integration
FIG 1 A typical BLDC motor driver block diagram.
gate drivers. The article focuses on three-phase integrated
gate drivers with an external power stage.
3-Phase Inverter
The inverter is a combination of three half H-Bridges connected
to a common DC rail with the midpoints of H-Bridge
legs serving as motor connection points. These are also
available in discrete switch, half H-Bridge, and three-phase
module forms. The selection of the MOSFETs or modules to
design the inverter depends on the design constraints and
motor ratings.
Sensors
BLDC motors require different sensors to drive the motor
properly. Speed control can be achieved with or without
a speed sensor and implemented as sensored or sensorless
control. The most common sensors associated with
BLDC are hall-effect sensors, which provide the sectorial
rotor position depending on the placement of hall-sensors.
More accurate resolvers or encoders can be used when
position control is required. The phase current and voltages
are also required for more complex controls like field-oriented
control (FOC), so external current sensors or integrated
current sense amplifiers are used.
Gate
Drivers
Low-Level
Integration
Mid-Level
Integration
* Discrete Gate
Driver
* Half-Bridge Gate
Driver
* Three-Phase Gate
Driver
* Three-Phase Gate
Driver With
Commutation
Logic
* Three-Phase Gate
Driver With
Integrated Current
Sensor
FIG 2 Different gate-drivers with varying levels of integration.
March 2022 z IEEE POWER ELECTRONICS MAGAZINE 41
High-Level
Integration
* Three-Phase Gate
Driver With
Integrated
Power-Stage
IEEE Power Electronics Magazine - March 2022

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