Differentiate constant frequency control technique, PWM and variable frequency control technique principle

Sr No.

Parameter

PWM control
(Constant f control)

Variable
frequency control

Current limit
control

1.

Variable
parameter

T_ON is
variable, (f or T is constant) to vary average output voltage.

T_ON is
constant, f is varied to vary average output voltage.

Both T_ON
and T i.e f are variable their values depend on the upper and lower
current levels and current ripple.

2.

Design of
output filter for continuous current operation

East due to
constant frequency operation.

Difficult due
to variable frequency operation.

Difficult due
to variable frequency operation.

3.

Filter cost

Lowest

Highest

Filter is
normally not required.

4.

Application

DC motor
speed control

Not used much

DC motor
control and SMPS

5.

Output
voltage waveforms

 Refer
figure (a)

 Refer
figure (b)

 Refer
figure (c)