NEED SOME SUPPORT:In choosing a lowpass filter for the below application

Discussion in 'Homework Help' started by krnth31, Jul 5, 2013.

  1. krnth31

    Thread Starter New Member

    Jul 3, 2013
    Hello All,

    My self kranthi.

    Am designing a low pass filter for PWM.
    PWM generated output is a TTL level PWM signal at frequency that can be set at a constant value within the range 1-30 kHz. The PWM driver is equipped with a mos-fet allowing picking up the voltage width of the PWM at 24V. Voltage output will vary with the applied duty cycle within the range 0-24V. It can be filtered.
    We want to filter the PWM modulated output only to avoid that EMI can be emitted out of the enclosure along the outgoing not shielded cables.

    1. Confirm is filter module is necessary to avoid EMI for filtering a PWM signal at 24VDC with different duty cycles working at frequencies between 1 and 30 kHz to avoid EMI along the cables. What EMI does the PWM produce and why?
    2. If point 1 confirms the need to use a filter to avoid EMI, So what type of filters (more than one solution) are the best choices and why for this application. PWM frequency can be set at a value within the range 1-30 kHz by our micro controller, considering that the filter is a low pass filter and that it can have a cut off frequency within the range 20-100Hz, allowing for an output voltage varying fast with a duty cycle variation and that maximum wattage absorbed by the single heating element connected to each filtering channel is 57-60W.

    Thanks and regards,
  2. WBahn


    Mar 31, 2012
    So.... are you expecting us to just work YOUR homework problem for you? You need to provide YOUR best effort to work YOUR homework. Besides, we need it to have a starting point for discussion.