LED diodes - question. What is the maximum voltage the diode can withstand?

what max voltage can an ordinary LED withstand, super bright, is there a diode that can withstand 4-6V? where you can buy such small light bulbs the size of small diodes that illuminate the panels in car radios

Gentlemen, who taught you the basics of electronics?

After all, the power supply of the LEDs does not depend on the voltage but on the current flowing through this element.

For R = 1kom and Uz = 12V

Id = 12mA

Here it is. And we already have a shortcut from theory to practice ...
Each LED has a specific brightness for a given current that flows through it. And this current causes a corresponding voltage drop on it - characteristic for the type (color) of the diode. Further straight on: we calculate the voltage we have to "lose" on the series resistor, we have the current value, Ohm's law - and we have the value of the resistor. In this way, you can power the LED with any voltage - of course not less than the threshold voltage. With higher voltages, think about the power dissipated on the resistor.
The lowest voltages are on the red diodes - approx. 1.7 V. For the above reasons, the diode cannot be lit with a universal meter - at low ranges the voltage does not exceed 1.5 V and on "megohms", even if there is a converter with a higher voltage, there is a built-in limitation current.
When it comes to miniature bulbs, they are definitely available at the table on the Volume - if you have a relatively close proximity, you can buy it without any problem.

andk1eltd wrote:

Further straight on: we calculate the voltage we have to "lose" on the series resistor

And what do we need it for, possibly only so that we do not exceed the permissible power of this resistor for the resistance reduction, we do not need it.

For the LED (red) we assume the current value between Ip and Imax
e.g. 20mA

The current that will flow through our diode at Uz (Id = 20mA)

Uz - supply voltage

We find the value of the series resistor R from the Ohm law:

Rsz = Uz / Id

later, a possible correction is made with the finished project due to the tolerances of the resistor used.

I don't think it can be simpler.

what is the maximum current that can flow through the diode?

Repciu wrote:

what is the maximum current that can flow through the diode?

The maximum current that can flow through the LED is given in the directory.

If you know the type of diode, you look in the application note there you have it:

conduction current Ip, maximum current Imax that can flow through this element without damaging the connector.

For the red LED it is about 25..30mA, I don't remember exactly, but in any case it does not exceed 30 [mA]

If you want its value to be, for example, 15 [mA], then depending on the value of the supply voltage, the value of the series resistor R must be:

1. I assume that the current flowing through the diode is 15mA

Id = 15 [mA] = 0.015 [A]

2. It is assumed that I will power the diode from a voltage of 20 [V]

Uz = 20 [V]

Ud = 1.2 [V] - voltage drop across the diode

3. I calculate the value of the resistor:

R = Uz-Ud / Id = 20-1.2 / 0.015 = 1253.33 ? = 1.3k?

Its value is 1.3k?

4. Builds a circuit: instead of a fixed resistor with a value of 1.3k, I put a variable resistor of the same value, connect an ammeter in series and adjust it so that I get the assumed 15mA.

5. I disconnect the circuit and measure the value of the variable resistor with an ohmmeter and in its place I put a permanent resistor of the same value as I obtained when measuring the variable resistor.

6. It connects completely and I have a ready project

PS Points 4 and 5 are not necessary, I have just mentioned for understanding the problem.

Where should I get this catalog, I know everything, I only need given diodes

You buy a pig in a poke!

How did you buy these LEDs?

When a project is done, a list of elements is made:

e.g . LED type CQPXXX, BD496 transistor.

If you accept the current of 15mA for an ordinary LED (red), I can give you a guarantee that you will not damage it. If it will be too low (low illumination), you will increase it by lowering the value of the series resistor R. The most important thing is not to exceed the value of 25..30mA carefully check the catalog.

Google search button.
and after

and whether the voltage drop across the diode should not be taken into account, e.g. for a red diode, work is about 1.2 V, and a super bright white diode of 3.5 V, if I have them connected in series, and the terminals will be 12 V, the permissible diode current will be 20mA, we will get:
(12-3.6-1.2) /0.02=7.2V/20mA=360? am I right ??????????

I wanted to connect to the topic - contrary to appearances, it is not always obvious what the diode current and voltage drop are:

Quote:

You buy a pig in a poke!

How did you buy these LEDs?

Well, sometimes you buy a cat in a poke -> I bought a lot of super-bright blue LEDs, when I asked in the store what the electricity was intended for, the guy shrugged his shoulders and spread his hands. Well, I asked about the symbol or the manufacturer - the guy spread his hands again and said "it's some Chinese" ... So - you can cover yourself with catalogs and not know.

PS By the way, I wanted to ask what current and what decrease to assume for blue LEDs, because 4 LEDs in series with 12V burn out quickly (after a few weeks).

Thanks in advance for your help! Greetings!

... and what resistor did you put in series with these diodes?
According to me, you can safely let go through the 20mA diode and it will be on.
The diode can burn out due to current pulses, i.e. de facto from its overload, it must also be taken into account in the system in which the diodes work, e.g. in a car, there may be disturbances in the installation that finish the diodes.

I use the following laboratory definition of the diode max current:

I connect the bire diode to the regulated power supply and run the current through it - at the beginning around 5 mA, then more and more and I watch the brightness, as the current increase stops causing the brightness increase, I reduce the current by 10% and I consider this current as Imax of the diode

And this is quite risky - the diode can shine much brighter with too much current, but it will not last for a long time.

Usually the diodes are for 20mA, the red ones are bigger - from 30; CEMI gives 50mA for red ones,
30 for yellow and green, the question is how much did they endure it. Too high current causes excessive heating,
which leads to accelerated degradation of the diode - as a result, the diode shines fainter and weaker.

The standard design of the diode does not provide sufficient cooling with more
current - diodes designed for higher currents must have a special design and are quite expensive.
Many of the "20mA" diodes withstand such a current, but at the cost of degradation - they will spend several hundred hours with it.
For greater durability, a lower current should be used - I suppose 15mA will be just right.

The maximum voltage that a LED (Light Emitting Diode) can withstand varies depending on its design, materials, and manufacturer specifications. Typically, the maximum forward voltage rating of a LED is provided by the manufacturer in the datasheet. For standard LEDs used in common applications, this voltage is often in the range of 1.5 to 4 volts.

Exceeding the maximum forward voltage can lead to irreversible damage to the LED, such as burning out or thermal degradation. Therefore, it's crucial to operate LEDs within their specified voltage range to ensure optimal performance and longevity.

The topic is a bit old, but maybe the information will be useful: a few months ago I bought LED "bulbs" on Allegro, they have different voltages. They have an E10 base (suitable for typical threaded flashlights), available in 3V, 4.5V, 12V (maybe some other) versions; the "12V" one at 4.5V also lights up, but much weaker - it looks like they differ in the resistor, so I wouldn`t recommend using the "12V" one for a long time when powered by 12V, because the resistor heats it up. If the backlight is DC, and the base and polarization match (unfortunately, these "bulbs" are only in one polarization, probably `+` on the foot, `-` on the thread; apart from E10, there are some, e.g. with a collar, but these were expensive) , then you can use. They are slightly more expensive than classic light bulbs, but the difference is not drastic and they consume much less electricity.

The LED maintains similar stabilization properties as the Zener diode. Therefore, the designer`s mistake is to rely only on the "rigid" voltage drop without controlling the junction polarization current.

For red LEDs, the maximum safe voltage drop is 1.5-1.8V, but this is inextricably linked to the value of the bias current, which determines this drop. Newer designs have greater efficiency and emit light more strongly, so when replacing an old damaged one, the polarization current must be appropriately lowered to obtain a similar intensity of the light beam.

The safest option for testing LEDs is to use a branded laboratory power supply with adjustable current limitation and a smooth start system.

michald wrote:

The safest option for testing LEDs is to use a branded power supply

Maria Curie-Skłodowska asked children at school a question: what can be done to make the water in an open pot cool down more slowly? The children came up with all sorts of ideas, such as wrapping a blanket around the pot... and she replied: "I would start by putting a lid on it."

A series resistor will be safer than a branded power supply - there is no knob that can be accidentally touched.

To determine the maximum voltage that a diode can withstand, you need to consider its breakdown voltage rating. The breakdown voltage is the maximum reverse bias voltage that can be applied across the diode before it breaks down and conducts heavily in the reverse direction.

There are two common breakdown mechanisms for diodes:

Zener Breakdown: Zener diodes are specifically designed to operate in the breakdown region. They have a well-defined breakdown voltage and are used for voltage regulation purposes. The breakdown voltage (V_Z) for a Zener diode is specified by the manufacturer and can range from a few volts to several hundred volts or more.

Avalanche Breakdown: Standard diodes not designed for Zener breakdown can still experience breakdown due to high reverse bias voltage. This is called avalanche breakdown. The breakdown voltage (V_BR) due to avalanche effect is typically higher than Zener breakdown and can also be specified by the manufacturer.

To find the maximum voltage a diode can withstand:

For Zener Diodes: Look for the breakdown voltage (V_Z) specified in the datasheet of the diode.

For Standard Diodes: Check for the reverse breakdown voltage (V_BR) in the datasheet. This value will indicate the maximum reverse bias voltage before the diode breaks down.

It's crucial to ensure that the reverse voltage across the diode does not exceed these specified breakdown voltage ratings to avoid permanent damage to the diode. Always consult the datasheet of the specific diode model you are using for accurate information on its breakdown voltage and other specifications

The maximum voltage a light-emitting diode (LED) can withstand varies depending on the specific type and design of the LED. Typically, the maximum voltage rating is specified by the manufacturer in the datasheet for the LED.

For standard LEDs used in everyday applications, the maximum voltage is usually in the range of 3 to 5 volts for typical low-power LEDs. However, high-power LEDs used in specialized applications can have higher voltage ratings.

Exceeding the maximum voltage rating can lead to the LED burning out or being permanently damaged. It's essential to check the datasheet provided by the manufacturer for precise information regarding the maximum voltage rating of a particular LED