DM300022 Microchip Technology, DM300022 Datasheet - Page 28

• 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 22
Instead of actually physically implementing the bus shunt, in this instance, the signal
has been derived as the sum of the three inverter leg shunts. In this way, power circuit
layout was not compromised. In a commercial application, it is normal to implement all
three leg shunts or the bus shunt rather than both schemes. The summing amplifier
circuit used can be seen on Sheet 3 in Appendix A.
1.5.6.4
Knowledge of the brake resistor current magnitude is not required for control of the
DC bus voltage with a brake chopper. Only feedback of the DC bus magnitude is
required. Knowledge of the brake resistor value and the applied PWM can be used to
determine peak and average current flowing for thermal protection of both the resistor
and the power devices. However, knowledge of the brake chopper current is useful for
protection of the switch should a wiring fault occur or the resistor fail. Although a fuse
could be used, it is often difficult to design and expensive, requiring very fast acting
types. In this instance, instead of a fuse, the switch current is monitored by a shunt
between the source and the -DC bus in exactly the same way as used for the inverter.
This is used for an over-current trip and is also made available as an optional
feedback signal. Thus, the brake chopper can also be used as either an open or
closed loop, low-side chopper for single quadrant applications. The differential
amplifier circuit is shown on Sheet 3 of Appendix A. See Section
1.5.6.1 “Introduction” for a more detailed explanation.
1.5.7
1.5.7.1
Provision has been made for three different types of voltage feedback:
• DC bus voltage feedback – This is required for regulation via the brake chopper. It
• Inverter output voltage feedback – As well as providing the feedback signal, a
The first of these signals is available as an isolated signal whereas the inverter output
voltages are only available when the system is used in the non-isolated manner (see
Section 1.2.6.3 “Non-isolated Feedback” and Section 1.6.3.4 “Accessing The
Additional (non-isolated) Feedback Signals”).
1.5.7.2
There are many different ways that the isolated voltage feedback signals could be
provided. Clearly, the DC level must be correctly maintained while still giving sufficient
bandwidth. There was also an additional requirement for a second higher bandwidth
isolated feedback signal. This is due to the high voltage version of the unit that uses
the same PCB. All the above requirements can be met by the use of an inexpensive
PIC
In this case, an 8-pin PIC12C671 PIC microcontroller was chosen, as it had the
necessary ADC on-board and was low cost. Full advantage could be taken of the
on-board 4 MHz RC clock. Three different methods for representing the magnitude of
the two signals (only one required for this version of the system) were considered. In
all cases, only two optocouplers were required.
is also used to compensate for variations in the inverter output voltages that occur
due to any ripple on the DC bus and as a FAULT trip.
comparator circuit is included for sensorless operation.
®
microcontroller, along with two additional low current optocouplers.
BRAKE SHUNT RESISTOR FEEDBACK
Voltage Feedback (Appendix A Sheets 1, 6 and 7)
INTRODUCTION
ISOLATED VOLTAGE FEEDBACK
© 2003 Microchip Technology Inc.