[This chapter is very technical. If it is a book friend in this direction, it should be understood. It is not a fabrication. There is a fundamental difference between high-precision high-frequency high-voltage DC generators and switching power supplies. Brothers, please do not confuse them. For example, the exciter in medical t is not something that can be done in China. There are only four branches, and a few Finleys have it. The aviation and military requirements are higher and the difficulty is greater. For example, the insulation of 200kv DC is difficult. It is impossible to find such a high voltage-resistant rectifier diode, because the quality requirements are small and the frequency must be high. This is not easy to achieve. There are other technical difficulties that will be mentioned later.]

...

Most of the professors have given up this project and started to have family affairs from all over the world. Zhang Zheng is quite arrogant and doesn't want to talk, and his thoughts have floated back to Nanchen, his wife and daughter. He missed him so much for the first time so long, and he wanted to go back immediately.

The reason why I was willing to participate this time was that I thought it was a sure win. At that time, I said that there were experts from Maoxiong Kingdom to help, so everyone gathered in the small border town of A Ershan. After so long, I couldn't even see a ghost.

There are all famous figures here. Not only can they not promote each other when they get together, but they are more fierce in arguments and disputes. He also proposed a new topological structure, but he always received attacks and accusations. However, he did not understand them deeply and could not answer many questions.

He sighed, and was bored, he glanced at the whiteboard casually and moved his eyes out the window. Suddenly, his mind flashed. Before the professors went to the laboratory below to check the equipment, he was studying the topological structure on the whiteboard. He was criticized by everyone at that time. He clearly remembered what he had drawn.

Suddenly, his eyes returned to the whiteboard. He was surprised when there was another waveform diagram on the whiteboard. Others might not have noticed it, but it was like a bolt from the blue to him. He was stunned. He pulled out the paper and pen and checked it over and over again. He felt that this inconspicuous picture made him touch a threshold, and the unthinkable parts began to smooth out.

The topology based on the main circuit series resonant soft switch should work.

Assuming that both the capacitor and the inductor are zero states, the inverter charges the circuit. Because the inductor blocks the current, the voltage of the capacitor must be in the first quarter of the sine waveform, and the current of the inductor must be the first quarter of the cosine!

I looked at the waveform diagram next to me again, it was indeed the case!

The last ray of sunlight slanted west outside the window shone in with glass and was sprinkling on the whiteboard. Zhang Zheng rubbed his eyes. Is this God's revelation to me?

Continue to analyze it further.

If the inverter is connected to the two switches on the top of the bridge arm or the bottom is turned on at the same time, the electrical energy in series resonance flows between the capacitor and the inductor. If everything is ideal, it will continue.

When the current of the inductor returns to the forward direction, the inverter injects energy into the circuit, and the voltage of the capacitor will continue to rise. After several cycles, the voltage can rise to a very high. After the transformation of the transformer, high-voltage alternating current is obtained, and after rectification, high-voltage DC is obtained.

The zero points of the current waveform chart were circled out. Zhang Zheng's thinking was inspired all of a sudden. He slapped a table with excited slap in his face, and his happy smile was overwhelmed. The other professors who were chatting looked at him dancing and looked at him and ignored him directly and continued to chat.

Zhang Zheng was stormy in his heart. Yes, why didn’t I expect that if series resonance wants to realize a soft switch, just switch the inverter switch at the zero point of the resonant current. If the current is zero, the switching loss must be zero. This completely eliminates the loss. How much can the switching frequency be increased? 10khz? 20khz?

In a sudden and stunning happiness, he felt that he had found the key to success, so he stood up, walked quietly to the front, suppressed his restless heart, and said calmly: "My colleagues, I may have found a solution to weight and stability."

At first, everyone hadn't reacted. In just a few seconds, everyone stopped chatting, looked at him with great fighting spirit, and was extremely enthusiastic and focused to pick the mistakes, and ruthlessly attacked.

Zhang Zheng didn't care. He felt that this time he was completely sure to win. Seeing these people's surprised expressions, he wanted to laugh happily. Unexpectedly, he finally solved this problem and this trip to the grassland did not come in vain.

Everyone is waiting.

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

"Professor Zhang, have you discussed this structure? It's a cliché."

"That's right, it's not practical."

Zhang Zheng was not in a hurry at all, nor was he angry. He suppressed his hands and smiled and said, "Everyone, I just figured out one of the key points. Please give me some time and I'll explain it."

All the professors here are knowledgeable, cultured, and respected. There must be such patience. Everyone is looking at him, but you say that.

"This topology is absolutely feasible because the capacitance and inductance in the main circuit must be strictly changed according to the waveform of sine or cosine. If the traditional pm cannot be used, the waveform will become messy."

The university professors were listening carefully to find the loopholes.

"Then we might as well change our thinking completely. What if the switch of the inverter only switches when the resonant current is zero? In other words, as long as the values ​​of the capacitor and inductor are determined, the switching frequency of the inverter is limited and cannot be changed."

Zhang Zheng said that he deliberately paused here, and he gave you time to think, pick mistakes, and be shocked.

Zhang Zheng was very happy to be able to teach so many people at similar levels.

The professors looked at each other, and most of them were still in shock. This sounded not difficult to understand. The key is that they completely broke through the boundaries of the traditional power electronics field.

It was like inventing a small saddle, and the Mongolian Empire swept the world all at once.

It was like discovering electromagnetic induction, which ushered in a scientific and technological revolution all over the world.

There is no problem yet.

"Then the control of the inverter will become very simple, with the switch fixed, and the output state of the inverter is summarized as forward resonance, free resonance and reverse resonance. Forward resonance means that the pulse voltage output by the inverter is the same as the resonant current direction, which strengthens the resonant current; free resonance means that the pulse voltage output by the inverter is zero, which has no effect on the resonant current, and the electrical energy flows in the capacitor and inductor; reverse resonance means that the pulse voltage output by the inverter is opposite to the resonant current direction, which weakens the resonant current."

Zhang Zheng was passionate and voluntarily. Just a waveform diagram inspired him too much. After all, he had a strong foundation and understood the key technology at once.

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