Frontline engineer switching power supply design sentiment

Recall that I just started the power learning phase, Buck, Boost, Flyback, half bridge, phase shift full bridge, LLC a lot.

From the confusion, the hardship, step by step.

Now I have withdrawn from the frontline research and development, recalling the difficulties in my initial stage: all kinds of materials, various tutorials, overwhelming, incomprehensible, seemingly understand.

Now I am old and fragile. I am also a relatively diligent person. I have been doing it for five years. I have played various topologies and various powers. I basically played it again.

If the technology is put down for too long, it will be unfamiliar. In order not to waste the hard work of learning and accumulating, the novice can quickly find a way to learn, quickly get started, really enter the world of switching power supply, I am ready to write a tutorial, now commonly used The topologies are written one by one, using the simplest, most common language, the most reliable theory that has been tested with engineering practice.

Science is understandable, and it is not a mystery. It is not a Chinese medicine practitioner.

I hope that you can support a lot, and welcome all seniors to make a brick.

Let me talk about the theoretical basis for switching power supply: we do power supply engineers, divided into two categories, one is engaged in research, the other is engaged in engineering.

The so-called research is to study various new technologies, new materials, new processes, new topologies and so on. These people need a very high theoretical foundation. Of course, they must be highly educated, mathematics, electromagnetism, electronics, automatic control, etc., all kinds of professions, all kinds of bulls.

Another is our most common power engineer, an electronic engineer who works on the company's development department.

This article is faced with the second category, that is, the power supply design engineer facing the application hierarchy.

It must be added, such as the book written by the master of the monster level such as Teacher Tao Xiufang, teacher Zhao Xiuke, the novice does not need to be hard-working, it is very time-consuming and laborious. Look at it, you can understand how much it is. Then, in the process of growing up slowly, looking back, there will be great gains.

We are doing engineering, they are based on theory. The book written by the master is completely understandable at once, and it is unlikely. Many of those books are written in great detail, with complete theoretical derivation, and are also very comprehensive. But I still advise newcomers not to tangled in the mathematical formula.

Those books can be used as technical manuals. There is a process of growth in technology, and to a certain extent, those books are very useful.

The theoretical foundations that our application engineers need must have: the basics of analog electronics. Let me talk about the depth of learning of analog electronic technology. Just graduated, it is generally impossible to make the model electricity well. If you really feel that you have just graduated, it is very powerful. There are two possibilities, either you are arrogant and ignorant, or you have actually done the project with the tutor. A person who studies the theory diligently. For the engineers we are working on, the ones that the mold must understand must be listed:

1 resistance. The resistor is the most basic original in various electronic circuits. The application of the resistor in the switching power supply mainly has various voltage-dividing networks that control the return circuit, and then the power dissipation in the absorption circuit. Our design must pay attention to the resistor package, power consumption, withstand voltage, accuracy.

2 Transistor. Transistors have two types of uses in switching power supplies: first, to make switching tubes. The switching tube of the switching power supply now mainly has a Mos tube, a triode, and an IGBT. Second: do signal processing. The triode is used in the control circuit of the switching power supply. The most used one is to make a simple small signal Switch inside the protection circuit, and then to do the linear regulated power supply (the auxiliary power supply in the main circuit).

Need to know what, at first, know how to open the triode, how to close it is OK. Then know what is the linear working state and what is the switching state. The messy calculations in the book are first put down, usually not used, usually used, and then checked, and soon I understand. Don't rush into the theory, waste time, waste energy, when you use it, the first reference Component specification, the second ask others, and then read back.

3 diodes. Positive guidance, reverse cutoff. Knowing what is the diode junction capacitance, diode turn-off time, reverse withstand voltage, forward conduction voltage, forward continuous current, pulse current are OK, basically enough. I have a problem at work and then read back.

4 operational amplifier. This thing is really important in the power supply design. The teacher in the school said that the short and false, must understand, this can not be discounted, feedback amplifier, current amplifier, design calculation of various amplifiers, it is the basis. As for the frequency characteristics, phase characteristics, and of course the ability to learn, it is also very useful, and let's put it down for the time being.

5 comparator. In the switching power supply is mainly used to do fast protection circuit, of course, the operational amplifier can also be used for protection, but especially the overcurrent protection, the operational amplifier will not work, the reflection time is too long; then the frequency generator, PWM comparator , hysteresis comparators, etc. The comparator is simpler than the op amp.

Then what electrical and electronic technology must master:

1 Single phase AC.

2 Single-phase AC rectification.

3 Three-phase AC.

4 Three-phase AC rectification.

5 capacitors. Classification of capacitors: electrolytic capacitors, the most commonly used rectifying and filtering capacitors. The electrolytic capacitor is polarity-polarized, the polarity is reversed, and the capacitor reacts chemically, and the short-circuit is blown up. The main parameters of electrolytic capacitors: withstand voltage, capacitance, equivalent resistance (esr), operating temperature, service life, appearance size. Ceramic capacitors, metal film capacitors, these capacitors are not polar, ESR is small, generally used for high-frequency bypass, because the electrolytic capacitor ESR is relatively large, usually parallel to the electrolytic capacitor parallel ESR small high-frequency capacitors. Y capacitors are required by various standards. (Own Baidu). Regarding the capacitor, when analyzing the circuit, there is one of the most important ones I must emphasize: the capacitor is charged, the current must be from the positive pole of the power supply, through the capacitor, to the negative pole of the power supply; the discharge of the capacitor: the current must be from the positive end of the capacitor, through the external loop, back to the capacitor Negative end.

5 inductance. The poles in the switching power supply are divided into two categories, one is for energy storage, and the other is for filters.

6 Transformer, the transformer inside the switching power supply refers to the transformer, which works in the same way as the power frequency transformer. (Flyback, LLC transformer, in the strict sense, not a transformer, these two are coupled inductors).

7 magnetic core. Must know: What is the core cross-sectional area Ae, what is the window area Aw, what is the BH curve, this must be understood.

8 copper wire. You must know what penetration depth is and what is current density. Why use a three-layer insulated wire, why do you want to hit the wall?

The basics above should be almost the same. If there are any omissions, please slap the bricks. Welcome to make up, don't miss the children.

If a power engineer who has just entered the line can fully understand some of the basic concepts listed above, then you can be a qualified helper, and welcome to join the power industry.

What I want to emphasize is that we are engaged in engineering, not in theory. The most effective learning is to find problems in work and solve problems in learning and experimentation. Pure death-deduction theory and pure trials are not advisable.

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