Half‐wave rectifier with capacitive filter

Elettronica IIProf. Paolo Colantonio 2 | 9

Breadboard

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Source

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Oscilloscope

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VM

t

vo

t1 t2 t3

o i ONv v V

t1 < t < t2When vi > VON, the diode is ON and the current flows toward R and C. C is charging with a low

t2 < t < t3The diode turns OFF and the capacitance discharge with law

t

RCo m ONv V V e

• Let us consider a half‐wave rectifier with a capacitive load, used to produce asteadier output

RLv(t)i v (t)o

D

C

Elettronica IIProf. Paolo Colantonio 6 | 9

t

Assuming an high time constant RC>>T (period), then the exponential behaviour can be approximated with the tangent

* *

* 1tRC

B P Ptv t V e VRC

In the time interval t2‐t3, we can write

t2 t3

vp

Assuming t2‐t3 T, we can write

V

1 Pp P

V TTV V VRC RC

VP

From which

P

V TRIPPLEV RC

Elettronica IIProf. Paolo Colantonio 7 | 9

B

DR

AiD

B BD C R

dv t v ti t i t i t C

dt R

t1 < t < t2 Diode ON

t2 < t < t3  Diode OFF

iCiR

vA

t

t3

The maximum current occurs at the circuit start up, when the capacitor C is discharged.

vB

t1 t2

iD

,00

sin 2BD MAX p p

tt

dv t dI C C V t f C Vdt dt

C

Elettronica IIProf. Paolo Colantonio 8 | 9

vA

t

vBiD

V

VP

PV TV

RC

TRIPPLE

RC

, 2D MAX pI f C V

Dimensioning of RC to control the Ripple

Dimensioning of C to reduce the maximum current in the diode

Elettronica IIProf. Paolo Colantonio 9 | 9

SetupMount the circuit and apply a voltage signal Vpp=10V and f = 1kHz

Work• Determine the values for R and C in order to assure in B a Ripple < 10% of 

maxximum output voltage

D1N4001

R C

BA Datasheet

Diode 1N4001

Conducting voltage V=0.65V

Max current Imax=30A