Pulse Width Modulation

PWM (Pulse Width Modulation) is a circuit that is used to create pulse wave that can be set how wide the pulse. The output of PWM is pulse wave, so we can set the frequency of the wave. PWM is used in many circuit or device. For example, we use PWM to control dc motor speed, to drive mosfet, for integration of buck-boost converter, and etc.

PWM is used to control dc motor speed in order to get the high efficiency. It is mean that we use the nominal voltage to supply the motor but we also use the low signal. So, we get the voltage average less then the nominal voltage but motor still rotate because the highest voltage that we use is same with the nominal voltage. We reduce the power consumption of motor by using hi-low pulse.

PWM is made from 2 integrated circuit (IC), Timer 555 (NE 555) and LM 393 (comparator). Timer in this circuit is to produce pulse signal (hi-low), but we can control the pulse width. Then we put the capacitor in pin 6-gnd. It can produce the charging effect of capacitor. So the wave become triangle wave. In this IC we can also set the duty cycle of the wave.

LM 393 is used to compare the triangle wave with the dc wave. Each triangle wave that placed above dc wave will transform to high condition. And the triangle wave that placed below the dc signal will transform to low condition in output wave. By setting the reference voltage, we can set the frequency also.

By doing 2 steps like that, we can get the pulse signal that can be control the pulse width.

By,

Hardhani Eko K.

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