Microchip dsPIC33CK64MC102T | Demoboard DS50003310A- Low-Voltage Fan Reference Design

Description

Changing from a high-voltage single-phase ACIM to a lower-voltage 3-phase PMSM/BLDC motor requires a 2-stage power conversion circuit. First, a fly-back converter circuit converts the 90-265 VAC input power into an intermediate 32 VDC with a high Power Factor Correction (PFC) to maintain energy efficiency. The power factor is kept above 0.9, even during low-power conditions. This creates the voltage bus needed to spin most PMSM motors. The 32 VDC is dropped to 10V by an MCP16331 Peak Current Mode PWM DC/DC Converter. This is used to efficiently power the three MIC4605 Half-Bridge MOSFET Gate Drivers, which switch the six MOSFETs on and off as directed by the dsPIC Digital Signal Controller (DSC) PWM outputs. The 10 volts is also dropped to 3.3V by a highly efficient MIC5205 Low Drop-Out (LDO) Voltage Regulator to power the dsPIC.The components for the reference design were chosen to optimize the Bill of Materials (BOM) for the minimum number of components and achieve the lowest cost. For example, the highly integrated dsPIC33CK64MC102 DSC includes two op amps for motor phase current amplification and a comparator for detecting an over-current condition, saving both the space and cost of using external circuits. Instead of dual or triple shunt motor phase current measurement circuits, a single current implementation is used to reduce cost and space. The resulting compact, round 10cm diameter board fits into the top of a typical fan motor, resembling an actual end-product solution. The BOM is also China RoHS 50 and EU Reach compliant.In order to obtain the highest energy efficiency, the maximum motor torque output, and quiet operation, the dsPIC DSC runs an advanced Field Oriented Control (FOC) algorithm with sinusoidal PWM outputs. An Initial Position Detection (IPD) software algorithm ensures the correct direction of fan movement on startup. Flying Start and Braking algorithms provide smooth restarts when the fan is windmilling or if a fan direction change is required.Supporting further customization, four General Purpose Input/Output (GPIO) pins are brought out to the edge of the board. These pins can be configured by software as a UART or SPI or for input capture functionality. This allows the user to create an interface to a wide range of sensors or communication protocols such as Infrared (IR), Bluetooth, WiFi, or a propriety home automation protocol.This low-voltage fan reference design board can be used with any existing 3-phase BLDC or PMSM fan by swapping the stock control board with the reference design board. FOC parameter changes may be required if the motor parameters differ from the stock demonstration motor. After connecting the AC power and motor wires to the board and an IR receiver, the remote control can be used to start and stop the fan and change the speed or direction setting.

Features

• Reference design shortens fan development time
• Low-voltage three-phase PMSM implementation saves energy over typical ACIM implementation
• Competitive BOM cost
• Compact board design fits on top of the fan motor
• Runs single shunt sensorless Field Oriented Control (FOC) algorithm for quiet and efficient fan operation
• Initial Position Detection (IPD) ensures fan starts turning in the correct direction
• Windmilling and active braking provide smooth fan restarts
• Infrared (IR) remote control for fan functions

Typical applications

• Three-Phase BLDC Motor Using Rotary Inductive Position Sensor

More information

• IC product information