Hello everyone;
I designed a circuit that generates the pulses,and my aim is to convert it to sinwave by using the low pass filter.my pwm frequency is like 50-60 Hz,and i have to convert it in to sine-wave but the RLC or RC low pass filters cannot be effective due to the low frequency.Can u guys have some idea about low frequency low pass filters.

 

If it's PWM why do you want to convert it to a sine-wave?
Or is it a higher frequency PWM modulated at 50-60Hz?

If you want power directly from the filtered pulses, then your only solution is a large LC filter.

 

Ok forget about pwm.think about a square wave in 50 Hz.i want TL conver it to sinewave,but the rlc or LC pass filtre that i Design causes triangular or sinwave-like forms.i nere sine wave form

 

Do you need to power a load directly from the pulses after it is filtered or is it just a low power signal?

 

Power Transformers are good at rounding off the edges of square shaped pulses. Feed them a two tiered step squarewave and they can make a sinewave out of it that looks almost perfect.

 

Do you need to power a load directly from the pulses after it is filtered or is it just a low power signal?

I need to power a load directly from the pulses after it is filtered

 

I need to power a load directly from the pulses after it is filtered

How much power are we talking about here?

If you cant use an amplifier then you are doomed to use an LCR filter of some kind. The components have to be good enough to handle the power also.

You may get away with an RC filter, but that will reduce amplitude by a large amount so you need an LC filter. There's no way around this unless you can use an amplifier after the filter, or some kind of converter circuit that actually produces a sine PWM first.

Do you know how to design an LC (or as it turns out an LCR) filter for a given frequency?
Do you know how chopping works (when you chop up a waveform into another waveform)? That can help reduce the size of the components in some cases.

If you show some work we can try to help with this.

 

How much power are we talking about here?

If you cant use an amplifier then you are doomed to use an LCR filter of some kind. The components have to be good enough to handle the power also.

You may get away with an RC filter, but that will reduce amplitude by a large amount so you need an LC filter. There's no way around this unless you can use an amplifier after the filter, or some kind of converter circuit that actually produces a sine PWM first.

Do you know how to design an LC (or as it turns out an LCR) filter for a given frequency?
Do you know how chopping works (when you chop up a waveform into another waveform)? That can help reduce the size of the components in some cases.

If you show some work we can try to help with this.

thankyou so much for your help,it helped me so much.i did handle.

 

Power Transformers are good at rounding off the edges of square shaped pulses. Feed them a two tiered step squarewave and they can make a sinewave out of it that looks almost perfect.

Can you speak more specific about this transformers a little bit ,please? thanks you

 

If you drive a heavy power transformer with a 60 hz sq wave, it could power small motorized devices or other things like curling irons or coffee maker
BUT it should be used at half power due to increased heating from high frequency component of square waves.

Modified square wave drive is probably the best brute force method of getting useable power from a transformer but still requires some derating of the transformer.

Whatcha makin?