What happens if the dcdc converter is supplied with a slightly higher voltage than in the specifications?

Question

Electronics

I have a battery that puts out 42 volts. I want to power an LED from it that consumes 9 volts.
I read that I can buy a dcdc converter to lower the voltage. But, in the maximum converter in a nearby store, the specifications indicate an input voltage of 3-40V. What happens if I connect the battery to 42v?

Answer 1

Your approach is completely wrong.

LED that consumes 9 volts.

The LED is not powered by voltage, but by current. Trying to power it with voltage will most likely cause it to burn out. An ordinary modern high-brightness LED (SMD or output) consumes from tenths of a milliamp to several milliamps, and what will be the supply voltage - at least 1000 volts.

I read that I can buy a dcdc converter to lower the voltage.

Yes, there are such converters, but to power the LED you need a current source (they are also called current stabilizers or LCD drivers). They also reduce the voltage to a level that is safe for the LED.

Specifications indicate input voltage 3-40V. What happens if I connect the battery to 42v?

Since at the same time you will exceed the maximum allowable value of the input voltage of this converter, then, as Armenian Radio correctly noted , "how lucky." If this device has a constructive input voltage margin (and usually it does, but we don’t know how much), then maybe it will work for some time - until the first input voltage surge. If there is no stock, it will burn out immediately. You need to choose an LCD driver that gives your LED the current you need (right from the datasheet), and its operating voltage range should include your 42 volts - well, something like 15 ... 60 volts. If the current required for the LED is small, then an ordinary resistor will fit as such a driver, its resistance is easily calculated according to Ohm's law.