Turning on and off AC MR16 LEDs with logic level DC

[sam_sam_sam]

Re: Turning on and off AC MR16 LEDs with logic level DC

Tore apart a Philips MR16 LED bulb. I busted it up a bit because of the glass housing and silicone glue.

The main board has a bridge rectifier and 270uF 30V filter cap with AL8821 boost-converter for MR16 LED's.

The bulb has a 20V COB LED with current control SOIC-8 PLD1B/H1A01A and 0.75R current-set, on the heatsink. I'm not sure what that is for. It's a two-pin connector between the boost and LED board.

This is different from the ones that I have taken apart

[stj]

Re: Turning on and off AC MR16 LEDs with logic level DC

Can you please provide the link to that info?
Resistive load (non inductive resistor, lamp (PTC)): An RMS voltage produces the same heating effect as a the same DC voltage.

it was on eevblog a while back, it was part of a discusion of hallogen lamps burning out much faster on dc supplies vs the ac electronic transformers / toroids.

[stj]

Re: Turning on and off AC MR16 LEDs with logic level DC

Tore apart a Philips MR16 LED bulb. I busted it up a bit because of the glass housing and silicone glue.

The main board has a bridge rectifier and 270uF 30V filter cap with AL8821 boost-converter for MR16 LED's.

The bulb has a 20V COB LED with current control SOIC-8 PLD1B/H1A01A and 0.75R current-set, on the heatsink. I'm not sure what that is for. It's a two-pin connector between the boost and LED board.

nice led,
makes me want to go look at these lights at £-land with the intension of stripping them!

[sam_sam_sam]

Re: Turning on and off AC MR16 LEDs with logic level DC

nice led,
makes me want to go look at these lights at £-land with the intension of stripping them!

I was thinking the same exact thing when I saw the insides of that LED module

[sam_sam_sam]

Re: Turning on and off AC MR16 LEDs with logic level DC

Tore apart a Philips MR16 LED bulb. I busted it up a bit because of the glass housing and silicone glue.

The main board has a bridge rectifier and 270uF 30V filter cap with AL8821 boost-converter for MR16 LED's.

The bulb has a 20V COB LED with current control SOIC-8 PLD1B/H1A01A and 0.75R current-set, on the heatsink. I'm not sure what that is for. It's a two-pin connector between the boost and LED board.

When and where did you buy them from

[eccerr0r]

Re: Turning on and off AC MR16 LEDs with logic level DC

Ah interesting, I was thinking these LEDs were buck converters but a boost converter would be equally a legitimate solution...
Now whether the rectifier can stand 100% duty cycle DC is the next question...

[stj]

Re: Turning on and off AC MR16 LEDs with logic level DC

it will be 1A atleast.
as for dc/ac the frequency of mains really isnt fast enough to make a difference to the diodes current handling.

[eccerr0r]

Re: Turning on and off AC MR16 LEDs with logic level DC

Well, if they are all 1N4001s that support 1A continuous, a bridge, two of the diodes would be conducting half of the time. So the average current for each of the pairs would be only half amp as they would not be conducting half of the time, and the RMS power dissipation would be 0.7V * 0.5A average = only 0.35W compared to now, 0.7V * 1A = 0.7W - double the power. Plus heat generated could derate the diodes.

So it depends on how the rectifiers are made, if they used something other than 1N4001s then it would be better. I saw a couple designs using 1N5820s which would give much more headroom, but the premise is still there.

[budm]

Re: Turning on and off AC MR16 LEDs with logic level DC

The way the unit is sealed like that, I will doubt that it will properly dissipate the heat.

[redwire]

Re: Turning on and off AC MR16 LEDs with logic level DC

When and where did you buy them from

The Philips glass LED MR16 I got at Home Depot. Can't remember if 35W. Their old style has a bunch of small LEDs while the new ones went single COB, across the board in their floodlights and spotlights. The COB sucks because it is very narrow angle and not as bright. But the CRI is the best I've seen. Cree products are no longer in HD stores.

I also got GU10 for mains power instead of 12VAC. The Ikea 7.5W 600lm GU10 is also very good but 2700K a bit warmish. 17 leds and also uses bridge rectifer.

[eccerr0r]

Re: Turning on and off AC MR16 LEDs with logic level DC

Well, the GU10 is completely different, it's more akin to A19 bulb systems, which we're forced to use isolation anyway and thus making this thread go off a tangent by eliminating the H-tree and open collector/drain solutions...

The 1G Soraa MR16 has a single very bright unit AFAICT. It's a 50W replacement and is significantly brighter than a 20W halogen MR16 that I have. I also have another newer MR16 LED which also claims to be a 50W replacement - it is very bright too, but just a tad dimmer than the Soraa but uses less power. I can't really tell the light output difference without a light meter. Both have similar beam output.

[redwire]

Re: Turning on and off AC MR16 LEDs with logic level DC

I think all AC-powered LED bulbs use a bridge rectifier up front, so DC operation would be possible. "dimmable" verses "non-dimmable" is an issue.

Soraa: "Works with trailing edge and leading edge phase cut dimmers, 12V AC magnetic and electronic transformers and 12V DC transformers"

Are you wanting to use AC or DC to power the LED bulbs?
I think the options so far:

1. Use a relay or triac on primary or secondary of the step-down transformer
2. MOSFET SSR on secondary
3. Use a BJT/MOSFET after a rectifier giving DC to the lamps.

[eccerr0r]

Re: Turning on and off AC MR16 LEDs with logic level DC

"12V DC transformers"... hah.

Well that's the question post in the original post, suppose I had both 12VDC and 12VAC available, which is the cheapest (primary goal; also considering damage to the LED lamp module if DC can damage the rectifiers due to 100% duty cycle) and correspondingly most efficient way (in terms of power waste) as a secondary goal to power and control them.

I'm just a bit concerned because the lamps do not explicitly say AC/DC, they just say AC.

[sam_sam_sam]

Re: Turning on and off AC MR16 LEDs with logic level DC

I'm just a bit concerned because the lamps do not explicitly say AC/DC, they just say AC.

The problem is you do not know if it has just one diode or it is a bridge rectifier unless you take it apart and look

[eccerr0r]

Re: Turning on and off AC MR16 LEDs with logic level DC

They're bridges for sure, since I can turn the DC around and it will still light!