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dsPIC33 DSC Refrigerator Compressor Reference Design

Part Number: dsPIC33_refrigerator_board

Summary:

Refrigerator compressors are now driven by brushless DC motors or permanent magnet synchronous motor to meet high energy efficiency ratings. You must use an inverter-based variable speed drive for the brushless motor to achieve this high energy efficiency. The variable speed drive allows you to operate the compressor at an optimal speed in order to maintain a constant temperature setting as

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  • Benefits
Benefits
  • Reduces development time by providing a turnkey solution:
    • Development board design similar to a final production board
    • Full motor control and application source code
    • A user’s guide for the board and software configuration including circuit schematics
  • Reduces the system level BOM cost using the dsPIC DSC’s rich analog peripheral set including comparators, DACs and op amps
  • Implements sensorless FOC using single-shunt current sensing for highest-efficiency and lowest cost
  • Provides a smoother torque response and better start/stop characteristics, resulting in quieter compressor operation and a longer lifespan
  • Implements specific control techniques to ensure a reliable start up, even in high compressor pressure conditions
  • Includes features to protect the compressor from accidental damage
  • Saves power with a low standby current consumption

Documents and Software

Product Features

    • Rated Power: 250W
    • Peak Power: 350W
    • Voltage: 187-264V
    • Supports compressors with either IPMSM or SPMSM
    • Single-shunt current sensing technique using on-chip Op Amps on the dsPIC® DSC
    • Motor Control Algorithms:
      • Sensorless Field Oriented Control (FOC)
      • Angle-Track Phase Locked Loop (ATPLL)
      • Maximum Torque Per Ampere (MTPA)
      • On-the-Fly startup (Multiple startup)
      • Stall detection with auto-recovery from failed start up
    • Protection:
      • Over-current
      • Over-voltage
      • Under-voltage
      • Speed error
      • In-rush current limit
      • Stall detection
    • Two UART ports, one isolated and one non-isolated 
      • Connect to X2C Scope for real time data visualization and debugging
    • Frequency input interface to control motor speed using a square wave signal

Summary

Refrigerator compressors are now driven by brushless DC motors or permanent magnet synchronous motor to meet high energy efficiency ratings. You must use an inverter-based variable speed drive for the brushless motor to achieve this high energy efficiency. The variable speed drive allows you to operate the compressor at an optimal speed in order to maintain a constant temperature setting as compared to a fixed-speed single-phase AC induction motor (ACIM) drive. Field-Oriented Control (FOC) of brushless motors enables you to implement the variable speed drive and add advanced motor control features like on-the-fly startup and stall detection with auto-recovery.

This refrigerator compressor reference design will help you to rapidly prototype and develop a cost-effective and innovative design using a dsPIC33EP64MC202 Digital Signal Controller. Other Microchip components utilized in the design include  a MCP16331 DC/DC converter and a MIC5239 LDO voltage regulator. The design works with a wide variety of refrigerator compressor motors, supporting both Interior Permanent Magnet Synchronous Motors (IPMSM) and Surface Mount Permanent Magnet Synchronous Motors (SPMSM).This reference design implements sensorless control and single-shunt current sensing technique to save BOM cost. This design also addresses the challenges of reliable startup of the compressor with high pressure and low standby power consumption.

Microchip provides Class-B Safety Software libraries for the dsPIC33 to reduce your development time for appliances requiring functional safety.

Ready for a live demonstration? This reference design is provided with full user’s guide, source code, schematics and PCB layout. Contact Microchip for demonstration, design files and firmware.