Inductor selection for LED driver designs | SMT

Inductor is a component we use for a long time in transformer design. Its main function is to convert electrical energy into magnetic energy and then store it. It should be noted that although the structure of Murata inductors is similar to that of a transformer, it has only one winding. The principle of the booster of Murata inductive DC-DC, and this article is of a basic nature, suitable for those friends who do not know the characteristics of Murata inductance, but are interested in boosters at the same time. Some of the principle knowledge in this article can be found online, so I won’t go into details here.Today qihe smt pick and place machine sharing Inductor selection for LED driver designs.

To fully understand the principle of inductive voltage boosting, we must first know the characteristics of the inductor, including electromagnetic conversion and magnetic energy storage. These two points are very important, because all the parameters we need are derived from these two characteristics.

As everyone knows, with electromagnets, a battery energizes a coil. Some people may wonder, what is so easy to analyze with such a simple picture? We are going to use this simple picture to analyze what happens when it is powered on and off.

The coil (called “inductor” from now on) has a characteristic—electromagnetic conversion. Electricity can be turned into magnetism, and magnetism can be turned back into electricity. When electricity is applied, the electricity becomes magnetic and is stored in the inductor in the form of magnetism. When the power is off, the instantaneous magnetism will turn into electricity and be released from the inductor.

As I said before, the magnetic energy in the inductor will turn back into electricity when the inductor is powered off. However, the problem arises: at this time, the circuit has been disconnected and the current has nowhere to go. How can magnetism be converted into current? It is very simple. The two inductors High voltage will appear at the end! How high is the voltage? Infinitely high until it breaks down any medium that blocks the flow of current.

Here we understand the second characteristic of the inductor – the boost characteristic. When the loop is disconnected, the energy in the inductor will be converted back into electricity in the form of infinitely high voltage. How high the voltage can rise depends only on the breakdown voltage of the medium.

Now let us summarize the above content:

Below is a positive voltage generator. If you keep flipping the switch, you can get infinitely high positive voltage from the input. How high the voltage rises depends on what you put on the other end of the diode to give the current somewhere to go. If nothing is connected, the current has nowhere to go, so the voltage rises high enough to break down the switch, dissipating the energy as heat.

Then there is the negative voltage generator. If you keep flipping the switch, you can get infinitely high negative voltage from the input.Smt pick and place

The above is all theory, now let’s take a look at the actual electronic circuit diagram to see what the “minimum system” of the positive/negative pressure generator looks like:

You can clearly see the evolution. In the circuit, only the switch has been replaced with a triode. In fact, all switching power supplies are transformed from the combination of these two diagrams.Smt pick and place

Finally, we should mention the issue of magnetic saturation. What is magnetic saturation?

From the above background, we can know that the inductor can store energy and save the energy in the form of a magnetic field, but how much can it store? What will happen after the storage is full?

How much to store: The “maximum magnetic flux” parameter is used for this purpose. Obviously, an inductor cannot store energy infinitely. The amount of energy it stores is determined by the product of voltage and time. For each inductor, this is a constant. , based on this constant you can calculate the frequency at which an inductor must operate to provide N volts and M amps of power.

What happens when the storage is full: This is the problem of magnetic saturation. After saturation, the Murata inductor loses all the characteristics of inductance, becomes a pure resistance, and consumes energy in the form of heat.Smt pick and place

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