Generate pulses by Pulse Modulation Width PWM technique

Generate pulses by Pulse Modulation Width PWM technique :-

Introduction of PWM TECHNIQUE:-
Pulse Modulation Witdh is a technique in which the width of pulse is critically controlled and used which refelects the duty cycle. The PWM is oftenly used to control the power of a load. for example the typical use of PWM is the DC motor speed control, or the power of heater or speed of fan. The PWM is generated at low voltage and then feeded to transistors or IGBTs to drive the high current load.Pulse width modulation (PWM) is a technique in which a series of digital pulses is used to control an analog circuit. The length and frequency of these pulses determines the total power delivered to the circuit. PWM signals are most commonly used to control DC motors, but have many other applications ranging from controlling valves or pumps to adjusting the brightness of an LED.


Generation of PWM Technique:-

First of all we will discuss the generation of PWM.Using digital pulses to create some analog value other than just ‘high’ and ‘low’ signal levels. Many digital systems are powered by a 5-Volt power supply. Here we will learn how to generate the pulse width modultion of a fixed frequency pulses. The method used to generate the train of pulses which are generated through PWM circuit here is made up of a simple PWM circuit made of Op-Amp, which consists of Schmitt Trigger circuit, integrator and comparator. Here OPAMPs will be used to generate the PWM signal and then generated pulses will be feeded to IGBT to control the power of speed.The duty cycle is defined as the percentage of digital ‘high’ to digital ‘low’ signals present during a PWM period.

PWM signals from Op-Amps circuit:-

The Op-Amps are used to have Schmitt Trigger function which will produces a square wave. This square wave will be converted by the integrator sawtooth wave (which is also called Ramp), and this Ramp is compared with a reference voltage. To adjust therequired voltage level that can be changed much voltage. So the result of the RAMP is a PWM signal output, ready to use any where.The PWM resolution is defined as the maximum number of pulses that you can pack into a PWM period.

Here are two different versions of the circuits. These two schematics are variations on another PWM circuit. The circuit diagrams are for 12V operation only. There are high side in which positive PWM signal is generated (common ground) and low side in which negative PWM signal is generated(common +12V) versions. The low side version of the circuit uses an N Channel FET, the high side version of the circuit uses a P Channel FET. N Channel devices tend to handle more current than P Channel devices, they are also less expensive. The high side version of the circuit is useful when one side of the load has to be grounded.
Uses for PWM:
1) To digitally create an analog output voltage level for control functions and power supplies.
2) To digitally create analog signals for arbitrary waveforms, sounds, music and speech.
This circuit can switch a fairly high amount of current, an IRFZ34N MOSFET can handle over 35 Amps if connected to a proper heat sink. Higher power FETs, such as the IRFZ48N or IRF1010Z can be substituted if even larger currents are required. It is also possible to connect multiple FETs in parallel for even more current capacity. Always use thermally conductive grease between the FET and the heat sink, and remember that the heat sink is electrically live.Pulse-Width Modulation (PWM) allows for electronic control over DC motor speed or LED brightness.

Pulse-Width-Modulation (Pwm) Control Circuit

Pulse width modulation (PWM) is a technique in which a series of digital pulses is used to control an analog circuit. If you wish to use the Inductive loads (like motors), then you may require special care since they can generate large voltage spikes that can damage the MOSFET. Replacing the 1N4002 with a fast recovery diode may help absorb the reverse voltage kick when driving an inductive load such as a motor. If you use these circuits for experiments with electric vehicles, be sure to install a circuit breaker in series with the battery, the circuit breaker should be easy to reach by the driver. This is especially important due to the fact that when MOSFETs fail, they often short out, leaving the motor on at full speed.