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LM3450AEV120V30: Increasing power for application

Stephen Karlsgodt
Prodigy 200 points
Part Number: LM3450AEV120V30
Other Parts Discussed in Thread: LM3424, UCC28051, LM3409HV, LM3450, TPS92641

Hello,

I need to know if a solution based on the LM3450AEV120V30 would work for our needs.

We need a solution to convert 120VAC that has forward phase dimming, and have that drive high power LEDs up to 150W (max output voltage of about 60VDC, and max current about 2.5A) The 'chopped' AC is created by a triac circuit. This triac circuit does not have a snubber circuit, which is something I have had to work around in some cases.

Currently I have a UCC28051 PFC feeding a UC28600 converter, with that output powering an LM3424 LED Driver (all EVM boards). I've implemented a custom zero cross detector circuit and have an MCU converting that timing into a PWM for the LM3424. It works, but the main issue is that the power factor is terrible at <0.5 at the dimmest settings, and I'm having some issues with my zero-cross circuit, and the lack of a snubber on the triac

My question: Would it be possible to use the LM3450 and LM3409HV combination (like found on the LM3450AEV120V30) to drive our max LED load of ~150W?

I know that at least I would need to find a different MOSFET and transformer, but is there anything else to be concerned with?

  • 0
    TI__Intellectual 2925 points

    Stephen, 

    The TI team that will reply to this thread is celebrating Chinese New Year 2/9 through 2/17 US Central Time. Thank you for your patience. You can expect a response some time during the week of 2/19 through 2/23.

    Regards,

    Dave

  • 0
    TI__Genius 15335 points

    Hi Stephen,

    Thanks for your patience. 

    Stephen Karlsgodt said:
    My question: Would it be possible to use the LM3450 and LM3409HV combination (like found on the LM3450AEV120V30) to drive our max LED load of ~150W?

    I think it is possible to drive a maximum load of 150W with LM3450A. However, I am not sure if the power factor / THD / dimming performance is good at such large power output. As is mentioned in the datasheet, this device is ideal for implementing a dimmable off-line LED driver for 10-100W loads.

    If you want to have a try, please make sure you are using LM3450A, but not LM3450. Also, I would recommend you consider using a synchronous controller like TPS92641 rather than an asynchronous controller like LM3409HV as the second stage LED driver for better efficiency and thermal performance.  

    Best Regards,

    Steven

  • 0 in reply to Steven Li
    Prodigy 200 points

    Thank you.

    I purchased this dev board, and it doesn't respond well to the forward phase dimming. The triacs are on all the time, unable to switch off. This is surprising, should the input into the dev board look like a resistive load?

    Also, regarding synchronous vs asynchronous LED driver, can you give me a quick description of the difference, or point me to some articles?

  • 0 in reply to Stephen Karlsgodt
    TI__Genius 15335 points

    Hi Stephen,

    Stephen Karlsgodt said:
    I purchased this dev board, and it doesn't respond well to the forward phase dimming. The triacs are on all the time, unable to switch off. This is surprising, should the input into the dev board look like a resistive load?

    Yes, the input into the EVM should look like a resistive load.

    Stephen Karlsgodt said:
    Also, regarding synchronous vs asynchronous LED driver, can you give me a quick description of the difference, or point me to some articles?

    There are lots of resources online explaining synchronous vs asynchronous DC/DC converters (similar to LED drivers). For example, you can refer to this video - Comparing Synchronous and Non-Synchronous DC/DC Converters | Video | TI.com

    Best Regards,

    Steven