Selecting a transformer for LED panel

[superhp]

I have 36W 36V 900mA LED panel. I want to buy a dimable (I have **broken link removed** potentiometer) transformer for it.

I am thinking about MeanWell transformer. The manufacturer of the panel suggested to buy 42V (constant current region: 25.2-42V) or even 48V (CC region: 28.8-48V) version. I am not electrician so I am afraid if transformer labeled as 42V or 48V can burn my 36V panel. Or should I care more about the CC region?

I have an opportunity to buy **broken link removed** transformer. The manufacturer of my panel has confirmed me that this should be ok. But I really want to hear it from someone else as well.

To summarize:
1. Is LPF-60D-42 ok for my panel (36V 36W 900mA CC)?
2. Should this transformer work with **broken link removed** potentiometer?
2. Can you suggest anything better from MeanWell, maybe from HLG or ELN series?

 

[MCU88]

The **broken link removed** looks correct for your application.

But...

You need more than just a pot. You cannot use an potentiometer to directly dim your display. You will burn it out. And the other thing to remember is that LEDs are current controlled devices, not voltage... You could come up with an circuit, say an PWM (Pulse Width Modulation) -- to control the brightness of your display. It would need some beefy transistors or mosfets, however, though...

 

[Wade Hassler]

1. Yes: read the data sheet for the power supply. It looks like the current from the LPF-etc is 1.43A max and you need no more than 900mA: pay attention.
2 Again yes: the data-sheet says that a 1-10V signal will control it
3. no comment, except 'read the data sheet.'

 

[Tony Stewart]

I have 36W 36V 900mA LED panel.

To summarize:
1. Is LPF-60D-42 ok for my panel (36V 36W 900mA CC)?
2. Should this transformer work with **broken link removed** potentiometer?
2. Can you suggest anything better from MeanWell, maybe from HLG or ELN series?

When using a dimmable CC supply, if panel can only handle 63% of rated max current @0.9A then if 100k pot is 100%, then 63k Ohm max must be selected. e.g. A fixed R in parallel to adjust Rmax could be used.

Beware that Meanwell supply can only dim to 10% of max load, so not ideal.

Anything "rated" 36V or more is required for a 36V panel to operate in CC mode.

You can call them "regulators" not transformers.

 

[superhp]

You need more than just a pot. You cannot use an potentiometer to directly dim your display. You will burn it out.

I don't understand, why should it burn out? It should be a "resistance dimming", right? I would just connect + to Dim+, - to Dim- as shown in **broken link removed**. Isn't that correct?

When using a dimmable CC supply, if panel can only handle 63% of rated max current @0.9A then if 100k pot is 100%, then 63k Ohm max must be selected.

"63k Ohm max must be selected" - how can I do it?
"Anything 36V or more will do for a 36V panel." - to summarize, the voltage of panel should fit in constant current region of driver? so even 48V (CC region: 28.8-48V) driver version is ok? Is there any importance of the position in the region, I mean, is 36-42V or 25-36V region better for 36V panel?

Should I buy 40W version of the driver with less max current instead of 60W? Is it really important?

 

[Tony Stewart]

I don't understand, why should it burn out? It should be a "resistance dimming", right? I would just connect + to Dim+, - to Dim- as shown in **broken link removed**. Isn't that correct?






"63k Ohm max must be selected" - how can I do it?
"Anything 36V or more will do for a 36V panel." - to summarize, the voltage of panel should fit in constant current region of driver? so even 48V (CC region: 28.8-48V) driver version is ok? Is there any importance of the position in the region, I mean, is 36-42V or 25-36V region better for 36V panel?

Should I buy 40W version of the driver with less max current instead of 60W? Is it really important?

The LED panel is like a Zener with ESR. The CC regulator minimum voltage needs to be greater than or equal to max Zener voltage to reach rated-power. There is no need for excess power except , margin for future loads.

The Meanwell supply supports 3 modes of dim. So whatever method used , e.g. If 60W for a 36W panel then Vmax needs to be 36/40 x 10V to not exceed rating. Of course surface temperature of LED is over-riding factor and forced air cooling may help.

 

[MCU88]

I don't understand, why should it burn out? It should be a "resistance dimming", right? I would just connect + to Dim+, - to Dim- as shown in **broken link removed**. Isn't that correct?

Perhaps I should have read the datasheets. I thought you were simply talking about an 250mW pot to control an 36W power source. It would never be "resistance dimming" as you put it since you could cook your dinner on an 36 watt resistor and still have enough heat left over to warm the family home.

 

[Tony Stewart]

A 250mW POT will work on dimmer which uses low current.
Pwm or V or R value determines the current in regulator as a percentage of rated max CC current in the Meanwell supply, which is compatible 3 in 1.


Burnt out state discussed means dimmer could be too high R or V which results in W greater than LED rating.

 

[superhp]

Thank you guys! First, I will try my LED panel and dimming (<60 ohms) with **broken link removed**, because the shop has it. If the panel and dimming is working, I wil order LPF-40D-42 or LPF-40D-48.

 

[MCU88]

A 250mW POT will work on dimmer which uses low current.

A 250mW POT as part of the user interface would be fine! We take a small amount of current to control a much larger amount Hence the real work would be done with a beefy mosfet (or similar)

 

[MCU88]

I much prefer digital rotary encoders now rather than POTs in my user-interfaces... The price has come down to 50-cents a pc for an Chinese made one on eBay... They work and the quality of the part is reasonable...

 

[superhp]

MeanWell didn't recommend LPF-60D-42 because of the same reason as Tony has written. I ordered and tested LPF-40D-48 and it worked well. Thank you all!

 

[Tony Stewart]

MeanWell didn't recommend LPF-60D-42 because of the same reason as Tony has written. I ordered and tested LPF-40D-48 and it worked well. Thank you all!

The 60w supply with 100K pot could also have worked with 150k fixed on the Wiper to Gnd. to get 2/3 max power.