Seamlessly Integrate Dual-Motor Control and Power Factor Correction in Air Conditioner Designs Using a Single Digital Signal Controller
Do your A/C system design challenges have you feeling the heat? This article will help you solve them.
New Air Conditioner Reference Design Helps Meet Stringent Energy Efficiency Ratings and Power Factor Specifications
Air conditioners and cooling equipment are major consumers of power from the electricity grid. Governments worldwide are now pushing to make these appliances significantly more efficient. Designs must implement complex motor control algorithms and Power Factor Correction (PFC), if new air conditioner designs are to meet today’s stringent power factor specifications and achieve the highest efficiency rating. An efficient and cost-effective way to meet this challenge is to replace the typical dedicated PFC controller and each individual motor controller with our dual-core dsPIC33CH high-performance Digital Signal Controller (DSC). Figure 1 is a block diagram illustrating this approach, which replaces three microcontrollers with one dual-core dsPIC33CH DSC.
Figure 1: Air conditioner application example using a dsPIC33CH DSC.
Our Air Conditioner Reference Design based on the dual-core dsPIC33CH128MP208 DSC family makes it easy to get started on your next air conditioner design (see Figure 2). Everything is included for demonstrating efficient control of air conditioner systems. It implements the condenser fan, compressor motor and PFC control, as well as hardware capabilities for realizing optional features like field communications, temperature sensors and electronic expansion valves. The reference design provides ample flexibility to support many different types of air conditioner systems.
Figure 2: Microchip’s Air Conditioner Reference Design based on our dual-core dsPIC33CH128MP20x family of DSCs.
The design offers a total system solution, implementing other key functions using MCP14E4 MOSFET gate drivers, MCP1826 Low Dropout Regulator (LDO) for voltage regulations, MCP6V92 zero-drift operational amplifiers for current and voltage sensing, and the MCP6541 comparator for over-voltage detection. The design has proven power stages for the high-power PFC (220V, 1.8 KW) as well as the condenser fan (120W) and compressor (1.34 KW) motor control. Figure 3 is a block diagram of the reference design.
Figure 3: Block diagram of Air Conditioner Reference Design.
The reference design implements several math-intensive motor control algorithms that are required in modern, energy-efficient air conditioners. These are enabled by the high-performance 100 MHz dsPIC33CH slave core. The design provides a demonstration platform for algorithms including: variable-speed control; sensor-less Field-Oriented Control (FOC) using a Phase-Locked Loop (PLL) estimator; Field Weakening (FW); and Maximum Torque Per Ampere (MTPA) control of Interior Permanent Magnet Synchronous Motors (IPSMs) for energy efficiency requirements. Also included are algorithms for improving reliability like windmilling, stall detection with recovery, voltage, and torque compensation.
The 90 MHz dsPIC33CH master core also implements an interleaved PFC with sophisticated control algorithms. This allows digital PFC to be implemented with fewer components than would be required using an analog PFC controller. A single DSC performing both PFC and motor control enables such system optimizations for cost reduction and improved energy efficiency across dynamic load conditions.
Following are some of the many benefits of using the dsPIC33CH Air Conditioner Reference Design:
Cost reduction: Replaces three separate microcontrollers (MCUs) or DSCs in an outdoor air conditioner unit. A single dsPIC33CH DSC can be used for PFC, condenser fan and compressor motor control
Improved performance: The use of a dual-core design architecture isolates the complex and time-critical motor control functions from the system and housekeeping functions and enables easy customization while simplifying development
Flexible platform: Enables the development of high-voltage PFC designs across a wide range of white goods and home appliances