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Technical Centre
AC-DC Power Supplies FAQ
Select question from the list below or return to faq categories.
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What are the latest AC-DC power 'Brick' solutions?
There is recent development in the combination of an AC/PFHC with a DC-DC converter to form an integrated brick solution.
Click below to find out more
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What is a 2-in-1 AC-DC Power Brick?
a "2-in-1" AC-DC Power Brick combines an AC/PFHC brick with a DC-DC converter into an integrated, single-brick, AC-DC power brick.
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What are the typical applications of 2-in-1 AC-DC Power Bricks?
These integrated power bricks are well suited to many outdoor and indoor applications in many different industries.
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Can I Operate my AC-DC Power Supply with a DC Input?
You can, sometimes. Be aware that the unit's safety certification may only apply to AC input.
Please contact your supplier for guidance.
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Where and why is high voltage DC input used?
There are several applications where high voltage DC input may be required.
For example, many power generation facilities provide a high voltage DC (typically 120 or 130-330Vdc) to power the plant's equipment rather than the regular 115Vac or 208Vac supply.
One reason why this is used is because this high voltage DC can be used easily with batteries to provide a secure source of power rather than using expensive centralised or local UPS systems.
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What is the evolution of power supplies?
Linear power supplies were the mainstay of power conversion until the late 1970’s when the first commercial switched-mode power supply became available. Now switched-mode power supplies are dominant driven by market demand for miniaturisation and high efficiency levels.
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What are the differences between linear and switched-mode power supplies and how do they work?
Linear power supplies are very simple, comprising a transformer, a rectifier, large electrolytic capacitor and usually a voltage regulator. They would operate at around 60% efficiency (100W input power providing only 60W output power = 40W lost as heat).
Switched mode power supplies (SMPS) are more complicated. They typically rectify the input voltage (usually with Power Factor Correction - PFC) and smoothed by a capacitor (the boost capacitor). This is then chopped at a high frequency [200kHz+] and then rectified. The exact output voltage is set by the control loop. SMPS can operate at 90% (or even higher) efficiency levels (100W input power providing 90W [or more] output power = only 10W lost as heat [75% improvement])
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How do linear and switched-mode power technologies compare with each other?
Switched Mode power Supplies (SMPS) are higher efficiency, small, lighter and have a wider input voltage range than linear power supplies.
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Is there a future for linear power supplies?
Only in a few specialist applications – energy saving legislation, such as ErP, EISA and CEC, coupled with remorseless miniaturisation trends of electronic equipment means that linears will only be niche in the future.
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Why is my power supply input only rated from 100-240VAC?
While the power supply's label may state 100-240Vac, many safety approval agencies (UL, CSA, TUV, etc) factor in +/-10% tolerance. So the unit's label may state 100-240Vac but the unit must be able to operate from 90V - 264Vac.
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What is PFC and why do I need it?
PFC (power factor correction) reduces input current harmonics and aligns current with mains voltage, improving efficiency, lowering utility penalties and grid stress, reducing wiring heating—and meeting regulatory requirements for SMPS.
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How to choose an Input EMI Filter for a Power Supply
Select based on measured/required conducted‑emission levels and desired attenuation. Choose a topology that targets common‑mode and differential‑mode noise
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