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Basic AC-DC Power Supplies
31 questions By Tony R. Kuphaldt
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Question 31 of 31
A common sub-circuit in power supplies of all kinds is an EMI/RFI filter. This LC network is all but “transparent” to the 50 or 60 Hz power line frequency, so that the transformer sees full line voltage at all times:
If this EMI/RFI filter does nothing to or with the line power, what purpose does it serve?
Reveal answerAn EMI/RFI filter has no purpose in the process of converting AC power into DC power. It does, however, help prevent the power supply circuitry from interfering with other equipment energized by the same AC line power, by filtering out unwanted high-frequency noise generated within the power supply by diode switching.
Follow-up question: calculate the total inductive reactance posed by the two inductors to 60 Hz power if the inductance of each is 100 μH.
Notes:These filters are very common in switch-mode power supplies, but they are not out of place in linear (“brute-force”) power supply circuits such as this one. Mention to your students how the abatement of electromagnetic and radio frequency interference is a high priority in all kinds of electronic device design.
i m using power supply for CCTV PTZ Camera with his adaptor rating of 230v AC input & 24V AC Output ,2A load current. what would be the power consumption is their from the main supply line? means is it taking 2 amp from main line of it would be from the adaptor itself?