[This chapter is very technical, if it is a book friend in this direction, it should be able to understand, it is not apocryphal, there is an essential difference between high-precision high-frequency high-voltage DC generator and switching power supply, brothers, don't be confused, such as the exciter in medical CT, I haven't heard of which one in China can do it, only four doors, Finlip has a few companies, and the aviation military requirements are higher, more difficult, such as 200kV DC, this insulation is difficult, it is impossible to find such a high voltage level of rectifier diodes, because the quality requirements are small, the frequency must be high, this is not easy to do, and other technical difficulties will be mentioned later. Pen @ fun @ pavilion wWw. ｂｉｑUｇE。 ｉｎｆｏ】

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Most of the professors have given up this project and started to do homework, Zhang Zheng is quite arrogant, unwilling to be idle, and his mind has drifted back to Nanchen, his wife and daughter, the first time he left home for so long, he misses it very much, and he can't wait to go back immediately.

The reason why I was willing to participate this time was that I thought it was nine out of ten, but at that time, it was said that there were experts from the Mao Xiong Country who came to assist, and everyone gathered in the small border city of Ah Ershan, and I didn't even see a ghost for so long.

There are all people with heads and faces, and when they get together, not only can they not promote each other, but the arguments are more intense than one another, and he also proposes a new type of topology, but he is always attacked and blamed, but he does not understand it deeply, and many questions cannot be answered.

Sighing, bored, casually glanced at the whiteboard and moved his eyes to the window, suddenly his mind flashed, before the professors went to the lab below to check the equipment, he was studying the topology on the whiteboard, and at that time he was criticized by everyone, he clearly remembered what he had drawn.

Suddenly his eyes returned to the whiteboard, this look was not small, when there was another waveform on the whiteboard, others may not have paid attention, but it was like a thunderbolt in the sky for him, and the whole person was suddenly stupid. He took out a pen and paper and checked it over and over again, and he felt that this inconspicuous picture had made him touch some threshold, and the places he couldn't figure out began to smooth out.

A topology based on series resonant soft switching of the main circuit should work.

Assuming that both the capacitance and inductance are in a zero state, the inverter charges this circuit. Because of the inductor's obstructive effect on the current, the voltage of the capacitor must be in the shape of the first quarter of the sine waveform, and the current of the inductor must be the first quarter of the cosine!

Look at the waveform next to it, and that's exactly what happened!

The last rays of sunlight outside the window shone through the glass, and it was sprinkled on the whiteboard, and Zhang Zheng rubbed his eyes. Is this a revelation from God?

Keep up the analysis.

If the inverter is connected to two switches above the bridge arm or at the same time at the same time, the energy from the series resonance will flow between the capacitance and the inductance, and if everything is ideal, it will continue.

When the current of the inductor returns to the positive direction, the inverter injects energy into this circuit, then the voltage of the capacitor will continue to rise, and the voltage can rise to a very high level after a few cycles.

The zero points of the current waveform are circled. Zhang Zheng's thinking was inspired at once, and he slapped a table with excitement, his face was filled with this happy smile, and the other professors who were chatting watched him dance, so they glanced at him and ignored it directly, and continued to chat.

Zhang Zheng's heart was turbulent, yes, why didn't I think of it, if series resonance wants to achieve soft switching, just switch the switch of the inverter at the zero point of the resonant current. If the current is zero, then the switching loss must be zero, which is to completely eliminate the loss, how much can the switching frequency be increased?10kHz?20kHz?

Completely in a kind of blissful that opened suddenly. Feeling that he had found the key to success, he stood up, walked quietly to the front, suppressed his restless heart, and said calmly: "Colleagues, I may have found a solution to the problem of weight and stability. ”

At first, everyone didn't react. In just a few seconds, everyone stopped chatting and looked at him with high morale, with great enthusiasm and concentration ready to pick fault and attack mercilessly.

Zhang Zheng didn't care, he felt that this time he was completely victorious, seeing the surprised expressions of these people, he wanted to laugh happily, but he didn't expect that in the end he solved this problem, and this trip to the grassland was not in vain.

The big guys are waiting.

He deliberately paused for dozens of seconds, then picked up the watercolor pen and said: "It's still this topology, based on the main circuit series resonant soft switch......"

"Professor Zhang, haven't you already discussed this structure? ”

"Well, it's not practical. ”

Zhang Zheng was not in a hurry at all, nor was he angry, he pressed his hand and said with a smile: "Everyone, just now I figured out one of the key points, please give me a little time, I will explain." ”

All of you here are knowledgeable, educated, cultivated and respected professors, and this patience must be there, everyone is looking at him, you say.

"This topology is absolutely feasible, because of the capacitance and inductance limitations in the main circuit, the current and voltage must be strictly changed according to the sine or cosine waveform, and the traditional PWM, PAM or PFM cannot be used, then the waveform will become disorganized. ”

The big professors are listening carefully, looking for loopholes.

In other words, as long as the capacitance and inductance values are determined, the switching frequency of the inverter is limited and cannot be changed. ”

Zhang Zheng said that there was a deliberate pause here, and I will give you time to think, find faults, and be shocked.

Being able to give lectures to so many people who are almost at the same level makes Zhang Zheng very happy.

The professors look at each other the same, mostly still in horror, which doesn't sound difficult to understand, but the key is to completely push the boundaries of the traditional field of power electronics.

It was as if a tiny saddle had been invented, and the Mongol Empire swept the world at once.

It was as if the discovery of electromagnetic induction had ushered in a scientific and technological revolution all over the world.

I can't fault anything with it.

"Then the control of the inverter will become simple, the switch is fixed, and the output state of the inverter is summarized as forward resonance, free resonance and reverse resonance. Forward resonance means that the direction of the pulse voltage output by the inverter is the same as the direction of the resonant current, which plays a strengthening role in the resonant current; free resonance means that the output pulse voltage of the inverter is zero, which has no effect on the resonant current, and the electric energy flows in the capacitance and inductance; reverse resonance is that the direction of the pulse voltage output by the inverter is opposite to the direction of the resonant current, which weakens the resonant current. ”

Zhang Zheng was impassioned and scolded Fang Xuan, just such a waveform diagram inspired him too much, after all, he had a strong foundation, and he understood the key technology at once.

"In the same state, different directions of the resonant current correspond to different switching conduction methods. The state of the switch is switched at the zero crossing of the resonant current so that the switching loss is zero, and the switching frequency is always the same as the series resonant frequency, and the action period of each state is set to an integer multiple of half of the series resonance period. ”

The professors were completely shocked. (To be continued.) )