LED Tape - Varying Brightness From Different Modules.

[Temp]

They do have drivers that do a combination of PWM and "Constant Current Reduction" but thats called Hybrid HydraDrive. 

 

https://eldoled.com/insights/how-designers-can-use-flicker-safe-dimming/

 

Probably not this unless your driver can be accidentally programmed into a mode like this.

 

I think it might be worth contacting them. Perhaps send that "odd" waveform to them and mention the Meanwell works fine.

 

[Dan F]

On 25/05/2023 at 20:44, Temp said:

They do have drivers that do a combination of PWM and "Constant Current Reduction" but thats called Hybrid HydraDrive. 

 

https://eldoled.com/insights/how-designers-can-use-flicker-safe-dimming/

 

Probably not this unless your driver can be accidentally programmed into a mode like this.

 

I think it might be worth contacting them. Perhaps send that "odd" waveform to them and mention the Meanwell works fine.

 

 

I have been in touch with them and they have insisted that they don't lower the voltage on the LinearDriver and that the issue must be down to the IC not working with the EldeLED PWM frequency.  The reality though is more complex than this, because the Meanwerll (2.5kWhz) has a very similar frequency to the EldoLED (2.4kHz).  I could try and engage the support team in the Netherlands and provide scope outputs and see where that leads.  First I'm going to wait and see what the tape supplier (Holectron) who provided both tape and drivers says.

 

[Dan F]

@Temp @Radian 

 

I never resolved this and both tape and driver manufacturers point at each other 😞 

I still haven't installed all of this tape as I was hoping to find a solution, but I think I might have to just use it and configure the driver to start at 2-3% (44-50% perceived), rather than 0.1%.

 

I did find out a few things regarding the ICs though:

The BCR420 IC (used in the LED tape that works) explicitly says that it supports up to 25kHz PWM frequency and 0.5% duty cycle (0.2uS pulse width).

The BCR430 IC (used in the tape with the issue) has a switching time of around 10us (rise) and 2uS (fall).  With a 2.4kHz PWM frequency, 12uS represents the pulse width at 3% (50% perceived) which is where I start to see dimming become ineffective/inconsistent (so maybe this is the cause?)

 

Also interestingly the Infineon versions of these ICs state >20kHZ for BCR42x but only 400Hz for BCR43x with dimming via Vs.

See: https://www.infineon.com/cms/media/eLearning/PSS/PSS_eLearning_BCR43xU-family-with-low-power-WBT_english/

 

So looks like the IC chosen by the tape manufacturer, while it may have a lower voltage drop and power consumption, simply doesn't support a decent level of dimming in combination with a good driver which uses a fairly high PWM frequency.

Edited October 10, 2023 by Dan F