power supply

power supply

1. Change

   • supply level(mostly reduce), suit driving e load circuit
   • AC Input wave to
     • Output DC
       • Constant
         • Not affected by changes in
           • Temp.
           • Supply
             • AC Input volt
             • Output Current Drawn
       • Only

2. ·

   • TRANSFORMER
     • windings
       • Pri join mains
       • Sec
         • electromagnetically/inductive coupled
           • isolate from pri to get suited AC volt amplitude
             • power supply processed, supply circuit
           • =transfer electromagnetic properties from one place to another w/o contact
           • to take place,need magnetic field change that's producing it
             • so DC circuits can't,only AC
           • Faraday's Law
           • due to close to each other
             • Purposely
               • Current step up/down in sec wire winding based on pri winding current level
               • No=crosstalk
     • cross
     • Sumida
       • INDUCTOR
         • Non-Shielded
           • Shielded
             • Opposite
             • Magnetic Flux kept in,safe.
               • > Non shielded:M. Flux radiate freely,operating problems. Need more windings @inductance value so DCR high.
           • High Radiation
           • per volume size
             • High
               • current ratings
               • DCR
             • Low
               • Inductance
                 • Drop (More stable) over temp/current rise
           • Low Cost
         • Choose
           • 1)Inductance-H Shows Inductor's ability to handle desired Power & Current Control. Inductor property: change in current induces a counter electromotive force which oppose that current change. Inductor's purpose:Get enough energy storage amount & enough reduction in ripple current for proper filtering. Inductance known as "open circuit nominal value".Typically measured @0.25V/100kHz,though data sheets posts related volt./freq for test condition.
           • 2)Temp Rise Current- As current pass through magnet wire,coil that makes inductor,component temp rises.DC Resistance cause 40deg C rise over initial 25deg C ambient.Takes higher current drive lower inductance,lower current drive higher inductance.
           • 3)DC Resistance,DCR- Inductor's resistance created by length & diameter of magnet wire used for winding inductor.Smaller winding area,finer wire diameter chosen to achieve specified inductance.Finer wire=higher resistance.Higer wire=longer wire to get this value. DCR-parameter which determines inductor's power efficiency.Typically,lower DCR better as power comsuption increases with higher DCR.
           • 4)Rated/Saturation DC Current- Beyond max. flux density, core's permeability reduced & inductance drop a lot. 2 ways to look I Self Temp Rise :Current using heat rise generation by component & Decreased %drop from initial Inductance

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