This circuit can be used for generating the PWM output signal.Īpart from these methods, it is also possible to generate this PWM output signal using the microcontrollers. So here, by changing the value of the resistance R1, it is possible to change the duty cycle of the output waveform. And we have already discussed this circuit whenever we have talked about the astable mode of operation of the 555 timer IC. So, this is a very simple way by which we can generate this PWM output signal.Īpart from that this signal can also be generated using the 555 timer IC. In this way by controlling this voltage it is possible to change the pulse width of the output waveform. So, suppose if we reduce this control voltage, in that case, the width of the output pulse will increase. So, depending on the value of this control voltage, the width of the pulse can be changed. Whenever the voltage of this triangular wave just goes above this control voltage, then the output of the comparator will become high. So, whenever this triangular wave voltage is less than the control voltage, then the output of the comparator will be low. While the control voltage is applied at the inverting node of the comparator. So, here the triangular wave is applied at the non-inverting node. The simple way of generating this PWM output signal is using the comparator circuit. So, by changing this duty cycle, we can control the different devices. And by doing so, we are actually changing the average voltage which is applied to the load. So, here by changing the duty cycle of the waveform, we are actually changing the average value of the output waveform. When I increase the duty cycle the output voltage also increases and when I decrease the duty cycle the output voltage also decreases keep in mind that the output voltage can only oscillate between the minimum and the maximum of the PWM signal. Let us consider that we have a PWM signal that oscillates between 0 and 5 volts let’s say this signal has a duty cycle of 50% something interesting will happen to the output voltage instead of being 5 volts is expected it will now be 2.5 volts simply putting it. We get 60% meaning that the signal is high 60% of the time. Now let’s use a simple rule to calculate the percentage of the period in which the signal is high 6 relates to 10 the same way as our variable in percentage relates to 100%. Let us set our high time as 6 milliseconds our down time as 4 milliseconds and our period as 10. The frequency is 1 over a time period which gives you how many cycles are in a time unit.Ī very important concept in PWM is the duty cycle the duty cycle represents how much of the period in which the signal is high in our wave the signal here is high and here is low to calculate a duty cycle you need to know how much of the period the signal is high. A cycle is the interval of the wave where you can find one full repetition the time a cycle takes to finish is called period. The space between the maximum and minimum value is called amplitude. The wave oscillation can be limit by using PWM signal maximum and minimum voltage values. It is simple but digital way to control the digital signals that we use to vary the energy that is send to a load or to encode information within the signal. PWM stands for pulse width modulation which consists of a square wave with the help of which we can control the up or high time. Applications of the Pulse width modulation:.
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