DM300022 Microchip Technology, DM300022 Datasheet - Page 30

• Manufacturer Part Number: DM300022
• Description: MODULE PWR DSPICDEM MC1L LV 3PHS
• Manufacturer: Microchip Technology

Specifications of DM300022

• Main Purpose: Power Management, Motor Control
• Embedded: Yes, MCU, 16-Bit
• Utilized Ic / Part: dsPIC33FJxxxMC
• Primary Attributes: 3-Phase Low Voltage Power Module
• Secondary Attributes: Motion Sensor Inputs: Hall Sensors or Optical Encoder
• Silicon Manufacturer: Microchip
• Silicon Core Number: DsPICDEM MC1L
• Kit Application Type: Power Management - Motor Control
• Application Sub Type: 3 Phase Motor
• Silicon Family Name: Piccolo
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

dsPICDEM™ MC1L 3-Phase Low Voltage Power Module
DS70097A-page 24
The hardware for providing this is now discussed with reference to the RED phase.
The other two phases have identical circuits.
• R20, R21 and R144 – A resistor divider chain with scaling, the same as the DC
• C61 – This provides filtering of the inverter output voltage in combination with
• D41 – This provides a clamp to ensure R_VPH_SENSE is protected.
• U31-B – A comparator used to provide a simple sensorless position detection
• R143, R147 – these provide a small amount of hysteresis to prevent oscillation of
• R142 – the pull-up resistor for the open-collector output of the comparator.
1.5.8
1.5.8.1
The choice of isolation strategy and how the low voltage power supplies are to be
derived are two of the major decisions that determine the architecture of a motor drive
controller. For this design, the requirement was for flexibility while maintaining user
safety. It was essential that the system could work off a wide range of input voltages.
Although the system only operates off comparatively low voltages, fault currents can
be very high. Furthermore, given the common PCB with the high voltage version of
the system, a similar isolation strategy was used.
1.5.8.2
Either optical or transformer-based isolation strategies can be used for transmitting
gate firing commands. For this design, it was decided to use optocouplers as it was
possible that a particular firing command may be used for commutation as opposed to
high frequency modulation. This could lead to transformer saturation at low speeds.
The hardware implemented is described below:
• U6-U13 – 6N136 optocouplers. These parts were chosen to provide good noise
• R153-R160 – pull-up resistors for the open collector outputs of the optocouplers.
• R162-169 – series resistors to ensure at least 18 mA flows through the emitter
• U32 and U33 – Schmitt-triggered inverters which clean up the edges from the
voltage feedback. The same scaling is required in order that the "back EMF
crossing" detection works correctly. The scaling is such that the maximum
expected output voltage will give 4.5V.
R20, R21 and R144.
scheme for BPM motors. Whenever R_PH crosses half the DC bus voltage, an
output transition will occur. The R_CROSSING signal is only valid during regions
of the electrical cycle, where the RED phase output current is zero, so that the
back EMF of the motor determines the voltage of R_VPH. Thus the scheme is
only suitable for use on BPM motors where 120 degree conduction scheme is
used. Careful decoding of all three crossing signals and appropriate angle interpo-
lation is required for correct commutation. An alternative method for commutation
feedback must be used near zero speed where the back EMF is insufficient for the
scheme to work.
R_CROSSING.
immunity, while requiring low current consumption on the output side. Speed was
also a consideration, so that too much delay or pulse distortion was not
introduced.
stage of the optocouplers. Note that the ground return is via a transistor (Q15) that
allows shutdown during detection of an over-current from one of the isolated Hall
effect current transducers.
outputs of the optocouplers.
Firing Signal Isolation and Low Voltage Power Supplies
INTRODUCTION
FIRING SIGNAL ISOLATION (APPENDIX A SHEET 5)
© 2003 Microchip Technology Inc.