Name
of the experiment:
Observation
of pulse width modulation.
Theory:
Pulse width modulation is the technique by which a low-frequency signal is being generated from high-frequency pulses. The main use of pulse width modulation is to let the higher load electrical devices to take over the control of the power supplied to the system. In a simpler sense, pulse width modulation uses digital
signals to control high power applications. Besides, it is easy to convert the
PWM signals back to the analog form with the minimum use of hardware. The power
is controlled by turning a switch on and off between the supply and load at an
increased rate. The power supplied to the load is directly proportional to the
duration of the on-time. Pulse width modulation is also called pulse duration
modulation.
The proportion of ‘on’ time to a period of time is called the duty cycle. The duty cycle is
expressed in percentage. The duty cycle is the inverse of the frequency of the
waveform. The switching frequency of pulse width modulation must be higher than
the rate which would affect the power device. This frequency can be different
for different applications and devices.
By
imparting pulse width modulation in an application, the power loss in the
switching device can be considerably reduced. When the switch is made on, the
voltage drop across the switch is practically zero. And when the switch is off,
there is no current. In this case, also power loss is negligible, as the power
is the product of voltage and current.
The
on/off nature of pulse width modulation is another advantage because of which
the PWM is widely used in various digital control applications. It is easier
with a PWM to set the required duty cycle. Because of this property, pulse
width modulation has found its applications in communication systems as well.
The heat produced during the operation of a digital system is lesser compared to
that during the working of an analog system. The majority of the heat in a
switching device is generated during the transition phase. The device is at a
state between on and off at this time. This is because power is the product of
voltage and current. During the working of the pulse width modulation system,
either current or voltage is nearly zero. And therefore the heat produced is
almost zero in such systems.
A
pulse width modulation signal can be generated by a sawtooth waveform as well
as using a comparator.
Required apparatus:
- PWM trainer board
- Oscilloscope
- Signal generator (500KH, 6V peak-peak)
- Wires & connecting probes
Circuit
Diagram:
 |
| Circuit diagram of PWM by using uA741 |
Output:
No comments:
Post a Comment