Linear Power Supplies

Linear power supplies accept AC inputs and provide one or more DC outputs for a wide variety of computer and industrial applications. They use an active element (normally a power transistor) operating in its linear region to generate a desired voltage. With linear power supplies, the incoming AC voltage is stepped down to a lower AC voltage. For example, 120-VAC is stepped down to 24-VAC. The 24-VAC is then rectified through a full-wave bridge rectifier, typically with a high-current and low-voltage bridge. A filter capacitor maintains a constant DC level with minimum ripple. A power transistor acts as a variable resistor in series with the load, and receives it control from a circuit that sense the output voltage. The control circuit modifies the transistor bias to maintain a constant voltage output, regardless of changes in the load current. 

Linear power supplies differ in terms of mounting style and form factor. Board-mounted devices use either through-hole technology (THT) or surface mount technology (SMT). Linear power supplies with a printed circuit board (PCB) form factor are also available. Products with an open-frame design have exposed circuitry and components. Enclosed units protect these same circuits and components inside a case. Tool or chamber mounted linear power supplies can be mounted on a chassis or to a cabinet. Modular linear power supplies are designed to mount on desktops, racks, or walls. External linear power supplies, products that mount inside floor-standing cabinets, and units that mount on a standard DIN rail are commonly available. Rack-mounted linear power supplies may have rack mount size of 1U, 2U, 3U, 4U, or 5U. 

Voltage level and output voltage qualities are important specifications to consider when selecting linear power supplies. AC inputs differ in terms of phase, input voltage, and input frequency. AC outputs also differ in terms of phase and waveform, but carry additional parameters such as AC output voltage, output frequency, and output current. Other specifications include AC output voltage, output frequency, output current, and apparent power. There are many different DC output voltages for linear power supplies. Examples include +0.75 V, +1.0 V, +1.5 V,  +1.8V, +2.5 V, +3.3 V, +5 V, -5 V, +12 V, -12 V, +15 V, -15 V, +24 V, -24 V, +28 V, -28 V, +30 V, -30 V, +48 V, and -48 V.   

• Design Considerations: Specifying Power Inductors for Switch Mode Power Supplies
  The rapidly evolving consumer electronics market is driving the transition from less expensive, less efficient linear power supplies to the switch mode power supply (SMPS). This shift is accompanied...
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• Inverters- Powering Switched Mode Power Supplies
  Power supplies are used to convert AC voltages like 120 VAC to various DC voltages like 3.3 V, 5 V, 12 V, 24 V, 48 V etc. Majority of modern day electronic devices use embedded general purpose Switch...
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• Switch Mode Power Supplies and their Magnetics
  In today's day and age the most often used topology for electronic power supplies is that of the Switch Mode Power Supply (SMPS), which is a major user of magnetics. In some applications the "older...
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Part Numbers for Linear Power Supplies