Microchip Technology dsPICDEM MCHV-3, Руководство пользователя, Страница: 40 / 68

dsPICDEM™ MCHV-3 Development Board User’s Guide
DS50002505A-page 40

2016 Microchip Technology Inc.
3.2.2 Power Supplies
The system default configuration is to get the 15V, 3.3V and 3.3V analog rail voltages
from the PFC stage board. However, it is also possible to use an external 24V power
supply to generate these voltages.
U19, C70, C73, C71 and C74 regulate the voltage applied to the system via J15 (28V
max). The output of the regulator is connected to the system through R109. The circuit
is shown in
Appendix A. “Board Layout and Schematics”
.
U18, C67, R110, C68, D16, D15, L3, R111, R112 and C75 regulate the 15V to create
a 3.3V digital rail. This auxiliary 3.3V digital rail is applied to the system through R106.
The circuit is shown in
Appendix A. “Board Layout and Schematics”
.
R114, R107, C69 and C72 form a decoupling circuit for generating a 3.3V rail for the
analog circuitry, such as the ADC reference and the current feedback reference. This
auxiliary 3.3V analog rail is applied to the system through R108.
3.2.3 Power Module
The three-phase inverter is embedded in a power module (U16). This power module
contains:
• 600V/30A 3-phase IGBT inverter bridge
• Gate driver circuitry for each IGBT
• Three independent connections to the negative DC bus for current sensing
• Short-circuit protection circuitry
• Thermal shutdown
• Gate driver power supply undervoltage protection
• Gate driver power supply overvoltage protection
• Single grounded power supply
• Isolation of 2.5 kV per minute
• Maximum switching frequency: 20 kHz
The Microchip PIC MCU/dsPIC DSC devices provide the PWM signals to this power
module in order to turn on/off the IGBT and therefore, apply power to the motor phases.
R95 and R124 set the threshold limit for the overcurrent circuitry. If this voltage is
greater than 0.5V (typical), a Fault signal is asserted and the low-side IGTBs are turned
off. R94 and C53 form a low-pass RC filter that filters out the frequencies above
88.4 kHz.
C56 sets the Fault pulse duration; the value of C56 is given by the following equation:
C56 = 18.3E – 6 x 1.8E – 3 seconds. Therefore, the Fault pulse duration is 54 µs.
The power module Fault Output pin (VFO) is configured as an open-collector. R50 pulls
up the Fault output to the analog 3.3V rail. R53 and C40 form a low-pass RC filter that
filters out the frequencies above 53 kHz.
For more information about this power module, please refer to the manufacturer’s
data sheet.
Note:
It is the responsibility of the user to populate these components if an
external power supply is used.
Note:
It is the responsibility of the user to populate these components if an
external power supply is used.
Note:
It is the responsibility of the user to populate these components if an
external power supply is used.