Medical power supplies produce conditioned outputs for medical devices, instruments, and equipment. There are two main types of products: DC power supplies and DC-DC converters. DC power supplies accept alternating current (AC) inputs and provide one or more direct current (DC) outputs. DC-DC converters accept DC input and provide regulated and/or isolated DC output in various applications including computer flash memory, telecommunications equipment, and process control systems. In terms of features, both DC power supplies and DC-DC converters are often fan-cooled or water-cooled, temperature compensated, and hot swappable. Medical power supplies with a battery backup, computer interface, and integral heat sink are commonly available. Overcurrent protection, overvoltage protection, and power factor correction are important safety considerations.
Medical power supplies that produce DC power differ in terms of technology type and performance specifications. There are three basic technology types: linear, switching, and silicon-controlled rectifier (SCR). Linear power supplies are low-cost, low-noise devices. Medical switching power supplies are highly efficient and provide a higher power density. SCR power supplies provide well-regulated voltage and current outputs. Inputs for medical power supplies use either single-phase or three-phase power; frequencies such as 50, 60, or 400 Hz; and input voltages such as 115, 208, 230, or 480 VAC. Most medical power supplies that produce DC power have multiple voltage outputs. Important specifications to consider include output voltage range, output current range, and DC power.
Medical power supplies that are DC-DC converters accept DC input and provide regulated and/or isolated DC output in various applications including computer flash memory, telecommunications equipment, and process control systems. They are also used frequently on vehicle-mounted systems. Common converter styles include PCB mount, PC board, internal or open frame mount, rack mount, and DIN rail. Choices for nominal DC input for DC-DC converters include 12 VDC, 24 VDC, 48 VDC, 110 VDC, 280 VDC, and 360 VDC. DC output is the most important parameter to consider when searching for DC-DC converters. Common outputs converted include 3.3V, 5V, 12V, 15V, 24V, and 48V. Other performance specifications to consider include output power, line regulation, load regulation, and minimum load. The wattage rating is the total nominal power output of a converter. The line regulation is the percent change in output voltage when VDC input is varied from lowest value to highest value. The load regulation is the maximum steady state amount that the output voltage changes as a result of a specified change in load. Minimum load is specified for the primary output for converter to meet performance specifications.
Most medical power supplies conform to regulations from agencies such as the Federal Communications Commission (FCC), or meet safety and quality guidelines from organizations such as Underwriters Laboratories (UL) and the Canadian Standards Association (CSA). The International Electrotechnical Commission (IEC) also publishes industry standards.
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