| 摘要 |
A flow generator (10) comprises an electric motor (12) that drives a turbine (14). The turbine (14) provides a supply of air for the administration of CPAP treatment, transported to the patient's mask by an air delivery tube (not shown). The motor (32) receives electrical power from a power supply (16). Also comprising a part of the flow generator (10) is a motor controller (18), which issues a control signal (20) to the power supply (16) to control the motor speed and thus the speed of the turbine (14) and, in turn, the flow rate in the air delivery tube. Furthermore, a speed feedback signal (22) is input to the motor controller (18) to provide a signal upon which speed regulation can be based. One of the interconnecting wires between the power supply (16) and the motor (12) is provided with a current sensing resistor (24). This resistor therefore detects current demanded by the motor (12), represented as the voltage appearing across the resistor (24). That voltage is sensed and input to a differential amplifier (26) thus producing an output signal representative of motor current (and thus also motor power). This output signal is then provided to a low-pass filter circuit (28) having an upper limiting frequency of, say, 20 Hz. The low-pass filter circuit (28) removes high frequency electrical noise, and also tends to average the signal. The filtered signal is then passed through a high-pass filter (30), typically with 0.5 Hz cut-off, to remove the non-respriatory components. |
