Hello,My company has been putting 1A power LEDs from Cree and Osram in parallel for soome time now.
We only ever use a single current source, and NEVER use series current equalisation resistors or current mirrors.
We have encountered no problems......so why is everyone telling us we are doing wrong?...i just dont understand. A batch of the same type of power LEDs always have virtually exactly same Vf's, and so no LED hogs the current.Driving paralleled LEDs with no equalisation resistors is the cheapest way to drive LEDs.....you can just usually use a cheap simple hysteretic buck converter......Why are so many people (even some prospective customers) telling us we are doing wrong?....we have had no problems. On our production line, each finished product gets left ON for 20 minutes before being bagged and despatched..........if a failure was going to occur, it would occur there...but it never has, so we are thinking of doing away with this mini soak test. Our LED lights are in the power range of 2W to 50W.
Why is what we are doing wrong?
Do you agree with us that this talk of unequal Vf's is a myth?
This is not always the case. It all depends on the type of LED, and the quality of the manufacturer. Apparently most people don't trust the manufacturer enough to leave current balancing in their hands.We have encountered no problems......so why is everyone telling us we are doing wrong?...i just dont understand. A batch of the same type of power LEDs always have virtually exactly same Vf's, and so no LED hogs the current.
Probably not. When stressed, LEDs don't always burn out immediately. It can take many, many hours. Especially when you consider that current imbalances are increased by positive temperature feedback.each finished product gets left ON for 20 minutes before being bagged and despatched..........if a failure was going to occur, it would occur there
No of course it's not a "myth." There will always be some degree of mismatch. Whether the mismatch is tolerable and whether balancing resistors are necessary depends greatly on the requirements of the design and the LED itself. Balancing becomes quite critical as you push the LEDs towards their maximum current ratings.Do you agree with us that this talk of unequal Vf's is a myth?
Hello,My company has been putting 1A power LEDs from Cree and Osram in parallel for soome time now.
We only ever use a single current source, and NEVER use series current equalisation resistors or current mirrors.
We have encountered no problems......so why is everyone telling us we are doing wrong?...i just dont understand. A batch of the same type of power LEDs always have virtually exactly same Vf's, and so no LED hogs the current.Driving paralleled LEDs with no equalisation resistors is the cheapest way to drive LEDs.....you can just usually use a cheap simple hysteretic buck converter......Why are so many people (even some prospective customers) telling us we are doing wrong?....we have had no problems. On our production line, each finished product gets left ON for 20 minutes before being bagged and despatched..........if a failure was going to occur, it would occur there...but it never has, so we are thinking of doing away with this mini soak test. Our LED lights are in the power range of 2W to 50W.
Why is what we are doing wrong?
Do you agree with us that this talk of unequal Vf's is a myth?
LED in parallel will work for months or years without any noticeable failure.
It will have a shorter lifespan than a properly design LED circuit.
If led receive higher voltage or current, brignest will be lower very soon.
Vf variance can be as little as 0.1% in a batch
Parts supplied from 2 adjacent bins for Vf will not be exactly the same.
Vf variance can be as little as 0.1% in a batch
- Steady state DC is ok but some designs shut down abruptly faster than the reverse 1MΩ typ leakage and junction xxx pF values.
- When pulsing LEDs the junction capacitance changes with voltage and off state and reverse voltage leakage resistance can vary significantly
- This RC parallel equivalent circuit forms a value in series with all the others. If they are all equal. The voltage declines equal. If unequal then the device with the highest resistance gets REVERSE BIASED.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?