This reference design is implemented using a PCB with two-layer, 2-oz
copper with the bottom-side SMD component placement to save cost
and board area. There are several important aspects to remember
while designing the PCB. In the following bullets, system-level
placement and layout of each block is explained.
- Separate components (or singles) into high and
low voltage, high and low current, high and low independence
groups. Place and route low-voltage and high-impedance
components and signals together, such as
microcontroller-related signals and the input side of IPM.
Use a whole copper pour to provide an integrated GND plane
for these area. AC input, filter, and rectifiers and IPM
output sides are high-voltage, high-current and
low-impedance parts and signals, route them with wider
traces or copper pours to provide high-current paths, and
also separate them from above low voltage and high-impedance
signals to reduce interference.
- Components in the high power path are kept on the
outer edges of the PCB with the minimum distance possible.
The microcontroller is placed at the center considering the
optimum distance from all the power blocks that need to be
controlled. Pin assignment is set to minimize the control
signal or feedback signal trace distance and the crossing
between analog and digital signals.
- AC Line Protection and EMI Filter
- AC line protection components are closely placed
within the minimum distance to the connection
path. Earth connection guarding is provided around
protection and EMI filter circuit.
- Motor Drive
- For the high ripple requirement, the motor drive
is placed as close as possible to the film
capacitor and DC bus capacitor bank.
- The low-side shunt resistor method with four-wire
sensing is implemented for current sensing. A
differential pair with impedance matching resistor
is used to connect the sensing signal from the
shunt resistors to the op-amp circuit. Shunt
resistors are placed near the module with an
immediate ground copper plane connection.
- Auxiliary Power Supply
- The GND of the auxiliary power supply connects
the DC bus capacitor bank directly and
independently to separate low current from high
current and high frequency GND trace for the
inverter.