# Don’t be afraid of inductive DC-DC boost if you are not familiar with inductance

Inductance is a component we have used for a long time in the design of transformers. Its main function is to convert electrical energy into magnetic energy and then store it. It should be noted that although the structure of the Inductor is similar to that of a transformer, it has only one winding. This article mainly introduces the principle of the inductive DC-DC booster, and this article belongs to the basic nature, suitable for those who do not know the characteristics of the inductance, but are interested in the booster at the same time. Some of the principle knowledge in the article can be found on the Internet, so I won’t go into details here.

Inductance is a component we have used for a long time in the design of transformers. Its main function is to convert electrical energy into magnetic energy and then store it. It should be noted that although the structure of the inductor is similar to that of a transformer, it has only one winding. This article mainly introduces the principle of the inductive DC-DC booster, and this article belongs to the basic nature, suitable for those who do not know the characteristics of the inductance, but are interested in the booster at the same time. Some of the principle knowledge in the article can be found on the Internet, so I won’t go into details here.

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

As you all know, the picture above is an electromagnet, a battery energizes a coil. Some people may be wondering, what is there to analyze with such a simple diagram? We just use this simple diagram to analyze what happens when it is powered on and powered off.

Coils (later called “inductors”) have a property – electromagnetic conversion, electricity can be turned into magnetism, and magnetism can be turned back into electricity. When the electricity is turned on, the electricity becomes magnetic and is stored in the inductor in the form of magnetism. The power-off transient magnetism will turn into electricity and be released from the inductance.

Now let’s take a look at the picture below, what happens at the moment of power outage:

As I said before, the magnetic energy in the inductor will change back to electricity when the inductor is powered off. However, here comes the problem: At this time, the circuit has been disconnected, and the current has nowhere to go. How can the magnetism be converted into current? Very simple, the two inductors There will be a high voltage at the terminal! How high is the voltage? Infinitely high, until it breaks through 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 to electricity in the form of infinitely high voltage, and how high the voltage can rise depends only on the breakdown voltage of the medium.

Now let’s summarize the above content:

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

Then there’s the negative pressure generator, where you keep flipping the switch and you get an infinitely high negative voltage from the input.

The above are all theories, 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 it’s just a switch to a triode. Don’t underestimate these two figures, in fact, the switching power supply is transformed from the combination of these two figures, so it is very important to master these two figures.

Finally, the question of magnetic saturation should be mentioned. What is magnetic saturation?

From the above background, we can know that the inductor can store energy and store the energy in the form of a magnetic field, but how much can it store? What happens when it is full?

1. How much to store: The parameter “maximum magnetic flux” is used for this purpose. Obviously, an inductor cannot store energy indefinitely. The amount of energy it stores is determined by the product of voltage and time. For each inductor, this is a constant, according to This constant lets you figure out what frequency an inductor must operate at in order to provide N volts M amps of power.

2. What happens when it is full: This is the problem of magnetic saturation. After saturation, the inductance loses all the characteristics of inductance, becomes a pure resistance, and consumes energy in the form of heat.

After analysis and summary, we have mastered several more important core circuit diagrams. And also have a certain understanding of the principle, I hope you can fully understand this article, so as to flexibly apply it to your own design.