Embedded Solutions for CPAP Machines

Continuous Positive Airway Pressure (CPAP) machines deliver therapy for obstructive sleep apnea (OSA). People who suffer from OSA experience a collapse of the airway during sleep, which prevents normal breathing. As a result, they partially awaken many times per night, leading to sleep deprivation and associated health issues, including daytime tiredness. By providing air at a dynamically controlled pressure, a CPAP machine keeps the airway open, allowing a normal sleep pattern.

Essentially an air pump, every CPAP machine includes a motor to drive a fan which pressurizes the air. Each system calls for a unique optimization of system parameters such as noise, response time, air volume, power consumption, size and cost. To meet their objectives, system designers use various types of motors, all of which can be controlled with Microchip's flexible integrated motor control peripherals.

With 40 MIPS performance and DSP capability, designers can use the dsPIC33 digital signal controller family to implement their choice of control strategies, including sensorless BLDC control. To reduce design time and risk, Microchip offers a portfolio of free and low-cost code examples, software libraries and development tools specifically for motor control. The versatile dsPIC33 family has Flash program memory sizes ranging from 12K to 256K, in packages from 20 pins to 100 pins, to cover a broad range of application options. Cost-sensitive designs can easily migrate to Microchip's PIC24F 16-bit microcontroller family for system cost reduction.

Besides logic circuitry, CPAP machines also use a number of sensors to gather physical data during operation. Pressure sensors monitor the pressure of the air being delivered, along with the patient's breathing. Pressure sensor data is conditioned with analog circuitry and routed to the analog-to-digital converter on the microcontroller. Likewise, air temperature and humidity can be measured and adjusted, to make the therapy more comfortable for the patient. Microchip's full range of operational amplifiers allows designers to condition analog data before converting it to digital for processing. In addition, our temperature sensors provide an accurate, precise and easy-to-use thermal measurement solution.

Visit Microchip's Medical Design Center for all current application notes, circuit diagrams, development tool support and complete product information: www.microchip.com/medical.

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