As a side note, one of the reasons why cold white LED light bulbs are a thing is because they’re a bit more efficient than warmer light colors.
The reason is because they all just have 2 kinds of light emiting diode (LED) junctions inside - red and blue - plus a phosphorus layer on top that smooths those two perfect lightwave color peaks in the wavelength domain into a broader light spectrum, and the blue is more efficient than the red, so lamps with a higher proportion of blue emitters to red emitters - and which hence emit more light towards the blue end of the spectrum (i.e. a colder white) - will emit more light for the same power consuption than those with more red emitters and hence whose light is more towards the red side of the spectrum (i.e. a warmer white).
plus a phosphorus layer on top that smooths those two perfect lightwave color peaks in the wavelength domain into a broader light spectrum
The phosphor absorbs some of the blue and downconverts it to green and red. Some of the blue is let through for us to see. The mixture of R, G and B looks like white to us (but not necessarily to other animals with different cones in their eyes).
2 kinds of light emiting diode (LED) junctions inside - red and blue
I’ve never seen a red LED die inside a white LED. I’ve only ever seen blue dies on their own.
Technically UV-pumped white LEDs exist, but they’re rare and I’ve never seen one. They’re less efficient and require a third phosphor (to make the blue).
You can remove the yellowish looking phosphors on the LED with a small pick to reveal the blue die underneath. Fun fact: some high-power “red” LEDs are actually blue leds + phosphors, not that it’s a particularly good choice but it’s a thing: https://halestrom.net/darksleep/blog/018_led_cob_cutting/
It seemed odd the lower frequency diodes would be less efficient so I did a quick bit of reading and it seems like red light is efficient, but red and blue light aren’t as effectively picked up by the human eye as green and because each light has a different operating voltage there are some consequences.
From what I read the things that makes white lights more effiecient is they only use blue diodes which probably means less circuitry is needed to operate than two sets of alternating diodes and there’s less difficulties going from higher frequency (aka higher energy) to low via filters. Hence efficient green light, blue light and red light at a single voltage.
From what I read last time I properly looked into this (so, almost a decade ago when I was considering setting up a business importing LED lamps), the blue light emitting diode junction simply uses less power to emit the same amount of light.
Electrically speaking it’s no bigger or lesser a problem in terms of circuitry to have just blue diodes or blue + red diodes in there since they’re bundled in blocks of diodes in series (and then multiple blocks are in parallel) and the only thing that differs between those two kinds of junctions from a circuit point of view is the drop voltage of one kind of diode being different from that of the other (diode junctions done with different dopants have different drop voltages), something you take into account in the design stage when deciding how many LED diodes you use per block or what DC voltage will your 110v/220V AC input be converted to to feed those LED strings.
More specifically for LED light bulbs, the messy stuff in terms of electronics is the circuitry that converts the 220v/110v AC input into a lower voltage DC suitable for the LEDs whilst limiting the current (as diodes’ only ability to “limit” current is them burning out from overheating due to too much current), not the actual LEDs.
But I’ll put it even simpler: if the problem was indeed simplicity as you believe, then LED bulbs with only red LEDs would also be very common as they’re simpler than blue+red ones.
You can’t easily use a filter to turn red light into blue. Imo if you needed to light a room for a camera or something not the human eye, red seems like it would be effective for that, but given the filter situation and the eye being best at detecting green light it doesn’t make sense to use red as the base color for indoor bulbs.
From what I read, red LEDs were most efficient at 1.8v and blue more near 4v. Maybe its trivial to do second voltage line but the filter situation is probably the limiting factor here.
As a side note, one of the reasons why cold white LED light bulbs are a thing is because they’re a bit more efficient than warmer light colors.
The reason is because they all just have 2 kinds of light emiting diode (LED) junctions inside - red and blue - plus a phosphorus layer on top that smooths those two perfect lightwave color peaks in the wavelength domain into a broader light spectrum, and the blue is more efficient than the red, so lamps with a higher proportion of blue emitters to red emitters - and which hence emit more light towards the blue end of the spectrum (i.e. a colder white) - will emit more light for the same power consuption than those with more red emitters and hence whose light is more towards the red side of the spectrum (i.e. a warmer white).
The phosphor absorbs some of the blue and downconverts it to green and red. Some of the blue is let through for us to see. The mixture of R, G and B looks like white to us (but not necessarily to other animals with different cones in their eyes).
I’ve never seen a red LED die inside a white LED. I’ve only ever seen blue dies on their own.
Technically UV-pumped white LEDs exist, but they’re rare and I’ve never seen one. They’re less efficient and require a third phosphor (to make the blue).
You can remove the yellowish looking phosphors on the LED with a small pick to reveal the blue die underneath. Fun fact: some high-power “red” LEDs are actually blue leds + phosphors, not that it’s a particularly good choice but it’s a thing: https://halestrom.net/darksleep/blog/018_led_cob_cutting/
There’s practically no chance this knowledge will ever benefit me, but I’m happy to learn something new regardless. Thanks for sharing!
It seemed odd the lower frequency diodes would be less efficient so I did a quick bit of reading and it seems like red light is efficient, but red and blue light aren’t as effectively picked up by the human eye as green and because each light has a different operating voltage there are some consequences.
From what I read the things that makes white lights more effiecient is they only use blue diodes which probably means less circuitry is needed to operate than two sets of alternating diodes and there’s less difficulties going from higher frequency (aka higher energy) to low via filters. Hence efficient green light, blue light and red light at a single voltage.
From what I read last time I properly looked into this (so, almost a decade ago when I was considering setting up a business importing LED lamps), the blue light emitting diode junction simply uses less power to emit the same amount of light.
Electrically speaking it’s no bigger or lesser a problem in terms of circuitry to have just blue diodes or blue + red diodes in there since they’re bundled in blocks of diodes in series (and then multiple blocks are in parallel) and the only thing that differs between those two kinds of junctions from a circuit point of view is the drop voltage of one kind of diode being different from that of the other (diode junctions done with different dopants have different drop voltages), something you take into account in the design stage when deciding how many LED diodes you use per block or what DC voltage will your 110v/220V AC input be converted to to feed those LED strings.
More specifically for LED light bulbs, the messy stuff in terms of electronics is the circuitry that converts the 220v/110v AC input into a lower voltage DC suitable for the LEDs whilst limiting the current (as diodes’ only ability to “limit” current is them burning out from overheating due to too much current), not the actual LEDs.
But I’ll put it even simpler: if the problem was indeed simplicity as you believe, then LED bulbs with only red LEDs would also be very common as they’re simpler than blue+red ones.
You can’t easily use a filter to turn red light into blue. Imo if you needed to light a room for a camera or something not the human eye, red seems like it would be effective for that, but given the filter situation and the eye being best at detecting green light it doesn’t make sense to use red as the base color for indoor bulbs.
From what I read, red LEDs were most efficient at 1.8v and blue more near 4v. Maybe its trivial to do second voltage line but the filter situation is probably the limiting factor here.