Patient Connected Circuits All patient connections, such as pads, contacts, probes, sensors or cuffs applied to the patient, plus any associated leads, cables, components or wiring, either within or external to the appliance enclosure. As seen from the patient into the equipment, these circuits extend to the points where the required degree of isolation or protective impedance is reached.
Patient Connections (a) Isolated: Direct or indirect patient contact that is deliberately separated from the supply circuit and ground by spacing, insulation, protective impedance or a combination of these methods. (b) Ordinary: Direct patient contact that does not have the spacing, insulation or protective impedance associated with an isolated patient connection.
Patient Vicinity Area in which patients are normally cared for. The patient vicinity is the space with surfaces likely to be contacted by a patient or an attendant who can touch the patient; encloses a space within the room 6 feet (1.83m) beyond the perimeter of the bed (examination table, dental chair treatment booth, etc.) in its intended location, and extending vertically 7.5 feet (2.29m) above the floor.
Peak Current The maximum amount of current which an output is capable of sourcing for brief periods of time.
Peak Loading For transient conditions only (such as disk drive start up). The power supply may not remain within specified regulation during the peak condition. The amount of time this load can be applied (duty cycle) varies greatly from design to design. It's best to consult the factory with your load profile.
Peak Power The absolute maximum output power that a power supply can produce without immediate damage. Peak power capability is typically well beyond the continuous reliable output power capability and should only be used infrequently.
PFC - Power Factor Correction Technique of increasing the power factor of a power supply. Switching power supplies without power factor correction draw current in short, high-magnitude pulses. These pulses can be smoothed out by using active or passive techniques. This reduces the input RMS current and apparent input power, thereby increasing the power factor.
Post Regulation A linear regulator used on the output of a switching power supply to improve line and load regulation and reduce output ripple voltage.
Power Factor The ratio of true power to apparent power in an AC circuit. In power conversion technology, power factor is used in conjunction with describing the AC input current to the power supply.
Power Fail A TTL signal which indicates that the input power has failed. This signal gives the user a chance to store information or switch over to backup power before the system goes down.
Power Good Signal A delay circuit used to initialize the computer and provide a logic signal upon low line voltage.
Power Limiting The limiting of the total output power of a power supply.
Power Supply A source for the power needed for active electronic circuitry. Can consist of one or more batteries, or an electronic circuit which converts AC line voltage to the type of power required by a particular device.
Primary The input section of an isolated power supply which is connected to the AC mains and hence has dangerous voltage levels present.
Pulse Width Modulation A method of voltage regulation used in switching supplies whereby the output is controlled by varying the width, but not the height, of a train of pulses which drive a power switch.