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  1. Replies
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    Closed: Re: 230VAC PWM LED bulb dimmer

    How do you mean the pot wiring?
    It's just a variable resistor in this layout from 0R to 500k.

    LEDs: I'll use it just for 5-10W GU10 LED bulbs nothing extra.
    But I even tested it with two 50W...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I attach the final version (and the parts list and the LT Spice files) with these mods applied:

    series 18k resistor added to the pot to set the minimum level so the pot starts really from zero
    ...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Just a little update: there was only 2 issues I'd like to solve but they are ok now.
    I attached the new schematic with the 2 changes highlighted.

    1) The 2W 100k resistor at the PS was just a...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I just finished the completly new v2.0 of my dimmer and (rarely I have this experience... but :-))
    everything is perfect for the very first time...! :razz:

    The dimming is now perfect without...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    It's simple: the 1nF conducts right after the zero crossing to open the transistor.
    Then the transistor pulls down the voltage on its collector.
    There is also another 1nF capacitor after that to...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Wow, I tried a IRF730 MOSFET as switching device and it is much better now...!
    It can drive any of my previous loads perfectly without getting even warm.
    But being such an ideal and fast switch,...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Yes, I'll do exactly this: using a simple 555 with zero-cross triggering + delay to create a trailing edge dimmer for my LED bulbs.
    I'll report about the results... ;-)
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Out of curiousoty I measured the LED bulb current
    on the same series resistor but driving them directly
    from the mains at the current looks like this.
    So I guess it's definitely designed for phase...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I tried some snubbers on the load but it didn't help to make the BUX cooler.

    I'll try some other mods with this layout and meanwhile I'll build another
    dimmer with a zero cross synced trailing...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Now I tried to dim the LED bulbs in series with the resistive dummy load and such way it works perfectly: no flickering and the BUX is cold as well.
    The LED bulbs still have this step in current and...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Couldn't find such details from the Datasheet (Article Nr: 93068475):
    https://tungsram.com/en/documents/GE-LED-Energy-Smart-GU10-G7-Datasheet.pdf
  12. Replies
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I made a ~20W resistive dummy load to check both the flickering and BUX temperature issues:
    157487

    But with this load the switching is perfect:
    157488

    The BUX is cool not even warm......
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I checked this resonance with a same resistance dummy resistive load + normal
    5mm white led in series and the current waveform on the load was a perfect
    square so I guess it's generated by the bulb...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Ok, thanks!
    I checked the 555 consumed currents on spice (with a normal, non-CMOS 555 model)
    and I realised that there is one more "big" consumer, the 1k at the discharge ping with
    this standard...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    No opto + direct drive + common GND:
    Yeah, I also thought on this but I am not sure:
    how to calculate the current needed for switching a MOSFET?

    Let's take this example with this IRF840 Power...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Hi Guys!

    Good news...!!!
    It is working now perfectly!
    Yesterday I havent had time to investigate but tonight I jumped into it.

    First I took out the BUX BJT to check to base system and I found...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Testing a LED dimmer with incandescent lamp is misleading as the loading currents are much larger and more resistor like.

    Waweform: yes, it was taken before adding C8 of course.

    Tonight I'll...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    Donno but it's definitely and finely dimmable. The error is on my side... :-)

    Wow, that sounds great:
    https://www.radiolocman.com/news/new.html?di=157243
    (IX3180 Opto-Isolated Fast Gate Driver...
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    Closed: Re: 230VAC PWM LED bulb dimmer

    I started with the classic triac dimmer and while it's good for a conventional bulb
    it's not good for a few W LED bulb as triacs are working properly only if they have
    a specific current which...
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    Closed: 230VAC PWM LED bulb dimmer

    Hi!

    I designed a dimmer for 230VAC 50Hz for a few GU10 LED bulb with the classic 555 PWM circuit.
    It basically works but I have some major issues could you help me to improve it?

    157452

    The...
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    Closed: Re: Repair SMPS for cooktop

    I tested it with spice (such a cool tool..! :)) and here are the results.
    The simulation is a DC sweep type incrementing the output voltage from 0 to 26V.
    I measured the voltage and the current on...
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    Closed: Re: Repair SMPS for cooktop

    Thanks a lot Brian for the detailed explanation!
    I guess I'll analyze this feedback mechanism in spice to understand it fully.

    It's still not clear for example how the CTR is not so relevant if...
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    Closed: Re: Repair SMPS for cooktop

    BTW: I couldn't manage to precisely understand to design of the feedback part.
    How it is done usually? What are the "corners", the criterias during a similar SMPS feedback design?
    Is it voltage or...
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    Closed: Re: Repair SMPS for cooktop

    Ehh, strange yesterday evening I get back to this project but now everything was stable...
    There was't any turning down or instability. I even tried it with dummy load up to 500mA and it was solid...
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    Closed: Re: Repair SMPS for cooktop

    I checked the PS in the morning and it was OK for more then 5 minutes (still withoud load)
    so I could check all the voltages when it's working, I attached the voltage map.
    And after a 5-10 minutes...
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