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Fly backConverter

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Fly back converterThe flyback converter is used in both AC/DC and DC/DC conversionwith galvanic isolation between the input and any outputs.

Schematic of yback converter:

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ON state and OFF state

When the switch is closed (top of Fig! the pri"ary of

the transfor"er is directly connected to the inputvoltage source. The pri"ary current and "agnetic

flu# in the transfor"er increases! storing energy in

the transfor"er. The voltage induced in the secondary

winding is negative! so the diode is reverse$biased

(i.e.! blocked. The output capacitor supplies energyto the output load.

When the switch is opened (botto" of Fig! the

pri"ary current and "agnetic flu# drops. Thesecondary voltage is positive! forward$biasing the

diode! allowing current to flow fro" the transfor"er.

The energy fro" the transfor"er core recharges the

capacitor and supplies the load.

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APPLICATIONS:%ow$power switch$"ode power supplies (cell phonecharger! standby power supply in &Cs

%ow$cost "ultiple$output power supplies (e.g.! "ain &C

supplies ')* W

+igh voltage supply for the C,T in T-s and "onitors (theflyback converter is often co"bined with the horiontaldeflection drive

+igh voltage generation (e.g.! for #enon flash la"ps! lasers!copiers! etc.

solated gate drive

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Simulation:

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!olta"e#

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Outut o$er:

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Outut current:

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%&ciency: