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

1. ### mr.harm Thread Starter Member

Nov 24, 2008
29
1
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)
I0=2.5
R=V0/I0 = 2
Lm_min=(1-D)^2*R*alpha^2/(2*f)=93m
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.

Thanks,,

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,990
1,115
You need to add smoothing capacitor after the bridge rectifier.
And repeat your calculation for the new input voltage.