how to convert pulse to sinwave

Discussion in 'The Projects Forum' started by jblueink, May 27, 2008.

  1. jblueink

    Thread Starter Member

    May 27, 2008
    24
    0
    how do i convert a squarewave form to pure sinewave form?. im in a fix and need help fast...tanx
     
  2. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    why do you need to do this?

    if you search in google for "square wave to sine wave converter" you get plenty of answers
     
  3. jblueink

    Thread Starter Member

    May 27, 2008
    24
    0
    because i want to convert a 50Hz squarewave form to a 50Hz sinewave and step its voltage up to 220V.
     
  4. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    A dual op amp integrator will come very close, or maybe an active filter simulating a 50 hz resonant LC circuit. Voltage is easy, but if you need power (as in wattage) it gets harder, a lot harder. What are you trying to do?
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Are you trying to make an inverter? If so, how much power must it supply?
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    A sine-wave inverter that uses a linear amplifier wastes half the battery power in heating its power transistors.

    Sine-wave inverters use pulse-width-modulation at a high frequency so that the output transistors or Mosfets are switches (on and off) and do not get hot. Then a simple filter at the output smooths away the many high frequency steps.
    A class-D audio amplifier is similar because it also switches its power transistors using pulse-width-modulation.
     
  7. aac9876

    Active Member

    Dec 9, 2006
    124
    0
    please explain completely why it gets harder when the watts go up......
     
  8. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    When an output device is switched "Hard on", it dissipates very little heat/power because there is very little voltage across it..(i.e., the voltage across a switch in the ON position)
    When an output device is switched "OFF" then obviously, there is no heat dissipated as there is no current thru that same "switch"

    When feeding an output device with a square wave, the output device is alternately switched hard on and off, and the device spends very little time in the transistional period between those two states (where the dissipation problems occur). Most of the power is passed on to the output, and not wasted as heat in the output devices.

    IF however, you drive that same output device with a sine wave, the opposite occurs, in that MOST of the time the output device has both voltage across it AND current thru it, which means LOTS of heat and a loss of efficiency... it is rarely (or never) in a "Hard On" or Off state.
    This is why modern "Sine Wave" inverters use PWM methods which put the output devices back into "Hard On, Off" states for the majority of their operation.
     
  9. jblueink

    Thread Starter Member

    May 27, 2008
    24
    0
    ok i now understand that i need a PWM to build a sine wave inverter but the problem is,i don't know about PWM and the circuit to produce the sine wave.can you explain it and give me a circuirt.
     
  10. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Yes, I'll have to draw it though. I'll be back.
     
  11. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    OK, I haven't had time to calculate values, but here is how I would do it in two steps...

    Sine Wave
    [​IMG]

    PWM (Class D Amplifier)
    [​IMG]
     
Loading...