Switched-mode power supply applications
Switched-mode power supplies have applications in various areas. A switched-mode supply is chosen for an application when its weight, efficiency, size, or wide input range tolerance make it preferable to linear power supplies. Initially the cost of semiconductors made switch-mode supplies a premium cost alternative, but current production switch-mode supplies are nearly always lower in cost than the equivalent linear power supply.
Switched-mode PSUs in domestic products such as personal computers often have universal inputs, meaning that they can accept power from most mains electricity throughout the world, with rated frequencies in the 50 - 60 Hz range and a voltage range between 100 - 240 V AC (although a manual voltage range switch may be required). In practice they will operate from a much wider frequency range and often from a DC supply as well.
Most modern desktop and laptop computers also have a voltage regulator module which is a DC-DC converter on the motherboard that step down the voltage from the power supply or the battery to the CPU core voltage, which may need to be as low as 0.8 V for a low voltage CPU to 1.2 - 1.5 V for a desktop CPU as of 2007. Some motherboards have a setting in the BIOS that allows overclockers to set a new CPU core voltage; other motherboards support dynamic voltage scaling which constantly adjust the CPU core voltage. Most laptop computers also have a DC-AC converter to step up the voltage from the battery to drive the cold cathode backlight in the flat-screen monitor, which typically requires around 1000 VRMS.
Due to their high volumes, mobile phone chargers have always been particularly cost sensitive. The first chargers were linear power supplies but they quickly moved to the cost-effective ringing choke converter (RCC) SMPS topology, when new levels of efficiency were required. Recently the demand for even lower no-load power requirements in the application has meant that flyback topology is being used more widely; primary-side sensing flyback controllers are also helping to cut the bill of materials (BOM) by removing secondary-side sensing components such as optocouplers.
Central power distribution
Where integration of capacitors for stabilization and batteries as an energy storage or AC hum and other interference needs to be avoided in the power distribution, SMPS may be essential for efficient conversion of electric DC energy. For AC applications where frequency and voltage can't be produced by the primary source an SMPS may be essential as well.
In 2006, at an Intel Developers Forum, Google engineers proposed the use of a single 12 V supply inside PCs, due to the high efficiency of switch mode supplies directly on the PCB. The efficiency went from ordinary 60 - 70% to 90 % with Voltage regulator modules on the motherboard instead of providing the different voltages from the PSU directly.
Applications may be found in the automobile industry where ordinary trucks uses nominal 24 V DC but may need 12 V DC. Ordinary cars use nominal 12 V DC and may need to convert this to drive equipment. Space vehicles use a variety of power systems and rely on lightweight switched-mode power supplies to convert from voltages produced by solar panels and fuel cells to the voltages required by equipment.
Some television receivers use a switch-mode power supply. For example, in some TV-models made by Philips, the power supply starts when the voltage reaches around 90 V. From there, one can change the voltage with the variac, and go as low as 40 V and as high as 260 V (a peak voltage of 260× ≈ 360 Vp-p), and the image will show absolutely no alterations.
The electrical power system on the International Space Station (ISS) uses multiple switch-mode power supplies to convert between the voltage produced by the solar array and battery system, and the voltages required by the different modules. The eight solar panels generate 262 kW at 160 V DC, used to charge nickel-hydrogen batteries that provide power when the solar array is in shadow during earth eclipse. A system voltage of 160 V DC is used for the main power distribution throughout the station. The European and American part (USOS) uses 124 V DC as the end-user voltage while the Russian part (ROS) and the space shuttle use 28 V DC.
- Switched-mode power supply
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- Archive copy at the Wayback Machine; How to Backlight an LCD
- "High-efficiency power supplies for home computers and servers"., sep 2006
- "Converters & Droppers : Pride of the Fleet - Car & Truck Accessories". 090528 prideofthefleet.org.uk
- "Hybrid DC/DC Converters Excel In AC Applications". 090528 mdipower.com
- "Modifications to CTVS TV cameras for space shuttle compatibility and evaluation". 090528 adsabs.harvard.edu
- Spacecraft power systems - Google booksearch. 090528 books.google.com