power adapter

Discussion in 'Homework Help' started by mr.harm, Nov 4, 2013.

  1. mr.harm

    Thread Starter Member

    Nov 24, 2008
    Design a 10 W power adapter for with the following specifications:
    a) Input Supply: Single-phase 110 Vrms at 60 Hz
    b) Output voltage: 5 VDC, 5% (+ 2%) voltage ripple factor
    c) Output current: 2.5 A.
    d) Repeat the design for <3% ( + 2%) voltage ripple factor
    e) The design should Comply to IEC 61000-3-2 Standard: Electromagnetic Compatibility (EMC) limits for harmonic current emissions (equipment input current ≤ 16 A per phase).
    My solution:

    The circuit is an uncontrolled bridge rectifier with a flyback transformer (for isolation purposes and to step down the voltage). A voltage pulse is used to perform switching for the desired duty ratio.

    Vm=sqrt(2)*Vrms = 115.56
    alpha=51 (assumed trans turns ratio)
    V0=5 (output dc voltage)
    D=1/((Vm/(alpha*V0))+1) = .62 (duty ratio)
    f=40000 (assumed)
    R=V0/I0 = 2
    Lm=200m (has to be larger thean minimum Lm & it is used for transformer primary)
    L2=Lm/(alpha^2)=77u (used for trans secondary)
    gama=0.05 (ripple)
    C=D/(R*gama*f) = 155.27u
    PW=D/f = 15.5u (pulse width for the voltage pulse source)

    However, the pspice generates this output voltage:

    Would really appreciate your help guys.

  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
    You need to add smoothing capacitor after the bridge rectifier.
    And repeat your calculation for the new input voltage.