light dimmer

Discussion in 'General Electronics Chat' started by akhil k k, Jan 23, 2012.

  1. akhil k k

    Thread Starter New Member

    Jan 23, 2012
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    hi
    am developing light dimmer using igbt.am controlling number of lamps using single bridge rectifier by connecting the lamps in dc side.because of the free wheeling diode inside the igbt i cant connect the loads in ac side,is there any other possibility to connect the lamps in ac side?
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    AC dimming is done via "triacs"
     
  3. n1ist

    Active Member

    Mar 8, 2009
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    While triacs are the most common, light dimming can be done by TRIACs, SCRs, IGBTs, autotransformers, variable resistors, and variable reluctance...
     
  4. colinb

    Active Member

    Jun 15, 2011
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    Certainly the easiest and most widespread way to do dimming control of ac-powered lamps is top use a TRIAC. You will need to use a random phase TRIAC (not zero-crossing) and synchronize to the ac line frequency. Then you turn on the TRIAC at the proper phase in the ac waveform for the desired brightness.

    This page describes a number of light dimming methods. The section “Trailing Edge Dimmers” describes how MOSFETs and IGBTs are used to do a different type of phase control than TRIACs allow.
     
  5. colinb

    Active Member

    Jun 15, 2011
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  6. akhil k k

    Thread Starter New Member

    Jan 23, 2012
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    i just done a dimmer circuit using igbt.actually i just converted the ac to dc using a bridge rectifier(not filtered) and connected number of lamp loads in dc side.now i can control the lamps individually(using different pwm).loaded the circuit up to 6amps at 230V DC.the device used was FGA25N120ANTD.switching frequency was 500hz.now i faced a problem that when i replaced the igbt with a higher rating cant withstand the voltage/current.actually the device having 1200v 40a capacity.is there any specialty with FGA25N120ANTD.
     
  7. akhil k k

    Thread Starter New Member

    Jan 23, 2012
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    what is the difficulty with igbt dimming over triac?
     
  8. colinb

    Active Member

    Jun 15, 2011
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    Well IGBT dimming shouldn't be so hard since you are rectifying the ac to dc. But there is wasted power there in the rectifier diodes, and a TRIAC is a simpler and cheaper device requiring fewer components overall, so it is more commonly used.

    If your IGBT is failing, it could be because it overheated. Measure your IGBT forward voltage drop (Vce) when your circuit is loaded. (Use a true rms meter -- the true rms value of the Vce will be what you want to use for power calculation.) Then the power dissipated in the IGBT (as heat!) is current times Vce and that will be 12 watts with Vce=2 V and Ice=6 A! You'll need a massive heat sink.
     
    akhil k k likes this.
  9. akhil k k

    Thread Starter New Member

    Jan 23, 2012
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    now am using a massive heat sink.during the test time it is not hot.but the igbt fails when increasing the voltage to 200volts.when i replaced the device with other one (from fairchild) i found it work well.
     
  10. pvjabi

    New Member

    Aug 1, 2013
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    Hi..
    I am controlling a no. of incandescent lamps(around 20) using single IGBT(G60N100). IGBT switching at 1KHz frequency.. When I am operating the IGBT, it severely effect the other circuits. There is spikes in the load voltage voltage of other circuits at a frequency of 1 KHz. How can i eliminate the effect on other circits ?
     
  11. pvjabi

    New Member

    Aug 1, 2013
    2
    0
    I am controlling a no. of incandescent lamps(20 lamps) using single IGBT(G60N100) which switch at a frequency of 1 KHz. When I operate IGBT, it severely effect other circuits. I saw spikes on the load voltage of the other circuits at 1KHz frequency.. How can i eliminate the effect on other circuits..
     
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