Electronic Circuit Analysis

Switching and Ie Voltage Regulators 269
The input sine wave is positively clamped. C 1
- Dl is a positive clamped circuit. D2 - C 2 is
a peak detector circuit. When Dl is forward biased, C 1
gets charged to V p. When D is forward
biased, C 2 gets charged to 2V p. So output will measure peak to peak value. RL should be large. If the
input is not symmetrical, positive peak and negative peak are not same, the average value or rms value
measured will not be correct. In such cases, first peak to peak detector is connected and then the DC
meter or AC meter are connected. In certain measurements, peak to peak value is to be determined.
In such cases this type of circuits are used.
Ripple Factors
y Ripple Factor for 'c' filter = 4fj f CR
L
RL
y Ripple Factor for 'L' filter = 4fjroL
.fi 1 1
Y Ripple factor Lc filter = 3 x 2roC x 2roL
R
Critical Inductance Lc ~ 3~
3X L
Bleeder Resistor RB = -2-
.fixc [XCI]
y fro 1t - filter R X-
L Ll
Example : 8.3
Design a power supply using a 1t - filter to give DC output of25V at 100 rnA with a ripple factor not
to exceed 0.01 %. Design of the circuit means, we have to determine L, C, diodes and transformers.
Solution:
Design of the circuit means, we have to determine L, C, diodes and transformer
I V DC 25V
R = --= =2500
L I DC
100mA
Ripple factor
X Xc
y = .fi ._c .__
RL
I
XLI
V
i_~
V Dl'
~rot
Fig. 8.23 Ripple voltage waveform