Abstract: This invention relates to SMPS controllers employing primary side sensing. We describe a system for identifying a knee point in a sensing waveform, at which the output voltage of the SMPS may be sampled accurately on the primary side. The system identifies the knee point by fitting a tangent to a portion of a power transformer voltage waveform, and samples the voltage waveform at the knee point to determine the SMPS output voltage. In preferred embodiments this technique is implemented using a decaying peak detector, providing a timing signal indicating detection of the knee point. Sample/hold and error amplifier circuits may be employed to achieve output voltage regulation.

Abstract: A peristaltic pump unit (18) has a flexible infusate line (28) which is repeatedly compressed by a flat plate like pusher (30). Transverse valve plates (32, 34), on either side of the pusher (30), operate sequentially to close the line in front of and behind the pusher. A resistive pressure sensor (50), between the two valves, provides signals to a microprocessor (46) which provides the system monitoring capabilities. Consistency in dose rate is provided by arranging for the flexible line (28) to be received in an elongate groove or channel (58) which acts to restrain sideways bulging of the line as it is being compressed by the pusher.