Originally, they all warmly called Mr. Liu Chen, very polite, but now that the equipment has been completed, and this kind of thing is found out, and when they are unhappy, they will naturally not be polite when they speak. Pen @ fun @ pavilion wWw. ｂｉｑUｇE。 ｉｎｆｏ

Several professors blamed Liu Chen.

Qin Ming and Gong Shu still didn't speak.

Liu Chen said: "Heh, I really forgot to talk about patents, and I almost forgot about it, there is indeed such a thing." ”

Huang Jie hurriedly said: "Yes, do you know the person who applied for the patent?"

"I do know. Liu Chen said.

There was an uproar, which undoubtedly admitted that he had just stolen this technique from others, and was not original, nor was he a genius, just a student who could take exams.

A lot of ugly faces.

"Not only do I know it, but every one of you here. Liu Chen said again, and smiled.

"We know each other, that can't be. ”

"You should have said it a long time ago, but now you are so reactive. ”

Qin Ming's face was a little ugly, and he said, "Who is this person?" Our big guy is from Tiannan and Haibei, and it is impossible for everyone to know him." ”

Gong Shu said: "Even if Liu Chen is learning from others, he can master so many technical essentials, it is also extremely remarkable, it is definitely a high-achieving student specially recruited by our Jianghai University, my research group still needs such talents, and when I am enrolled, I will come to study with the doctoral degree I personally bringed, and when I graduate from the bachelor's degree, the level will be very good, maybe I can do some innovative research." ”

Learning existing technology, and innovation, those are two completely different abilities, and there is a lot of difference in rank.

This grade was lowered all of a sudden, and it was originally the treatment of an associate researcher in the research group, and the future successor, okay, now it is a student, let a doctoral student take it.

However, after saying something to Liu Chen, the voice of criticism was obviously much quieter.

Liu Chen shook his head and said, "The big guy doesn't care much about who applied for the patent." Then I'll tell you, it's nothing. ”

The crowd listened.

"That's just one of the many patents I wrote boringly during my junior year of high school, and I learned these techniques with myself, I'm afraid you won't believe it. I'll be generous and tell you what I've written, don't you really want to know how I achieved control?"

Liu Chen smiled and drew a frame diagram on the whiteboard and said.

"Control is not about how clever it is, in the field of power electronics, it has to work with the structure. In fact, a PI regulator can solve most of the control feedback, and the topology and control method of the multi-level inverter in this DC/DC converter is just a multi-level inverter topology and voltage hysteresis loop control based on series resonant soft switching with a constant switching frequency. ”

As soon as he finished speaking, the professors grew their mouths, what? Hysteresis control? This is too exaggerated, this is the simplest, most common and whitest control method in college textbooks, and they stared at it one by one.

"Technological progress lies in overcoming the shortcomings of the existing technology, and I propose a voltage hysteresis loop control of a multi-level inverter based on series resonant soft switching, and switch the switching device at the resonant current zero crossing. Therefore, the switching frequency is constant, and because it is a soft switching control, the switching frequency can reach a very high level, and the switching loss is small. The combination of a multi-level inverter based on series resonant soft switching and voltage hysteresis loop control can keep the switching frequency constant, and it is easy to realize fast and stable control of the output voltage. ”

Liu Chen was a little angry, domineering, sharp, and he wasn't ready to give these guys a little face, so he said these words very bluntly. I'm not prepared to explain too much either.

"Hey, what's the matter with your hysteresiss? Isn't that our device a hysteresis control......?" , the big guy spent more than half a month without progress. The result was solved in the simplest way.

Wouldn't it be too ironic?

"Before I finish speaking, please don't interject. ”

"For the series resonant DC/DC converter using a high-frequency multi-level inverter, the converter topology comprises: the inverter converts the input stable DC voltage into a variety of pulse level outputs, which is used to adjust the amplitude of the series resonance; the series resonant circuit is composed of an external capacitor C and the leakage inductance of transformer T1, and if the leakage inductance of transformer T1 is insufficient, an external inductance can be applied. The pulse level output by the inverter is converted into a sinusoidal waveform to facilitate the voltage boost or step-down of transformer T1, and the high-frequency uncontrollable rectifier rectifies the high-frequency sinusoidal voltage to obtain the output DC voltage Uout. ”

"There are two types of multi-level inverter topologies proposed, one is called unidirectional multi-level inverter, and the other is called bidirectional multi-level inverter. The ordinary inverter is composed of 4 switching devices with 2 bridge arms, input 1 level, can output 3 levels, unidirectional multi-level inverter adds a switch tube on one side of the front end or rear end of the ordinary inverter, adds a switching device, increases the input level by one, increases the output level by two, and inputs n levels, and needs to add n-1 switching devices on one side, a total of n+ is required3 switching devices: bidirectional multi-level inverter is based on the ordinary inverter, the front-end and back-end sides of the symmetrical increase of switching devices, the addition of a pair of switching devices, the input level increases by one, the output level increases by two, the input level is n, and the switching devices on both sides are increased by 2 (n-1), a total of 2 (n+1) switching devices are required. ”

Liu Chen's speed of speech is very fast, anyway, the patent has been applied, you might as well analyze the technical key for these guys.

"Aren't the inverters four switches?" a professor jumped out again.

Zhang Zheng was in charge of this part, and said busily: "The inverter of our set of equipment is indeed not four switches, I was still strange at the time, but the final performance says it all, I estimate that the voltage regulator unit that does not need a front may also have something to do with this." ”

It was the first time Qin Ming had seen this kind of structure, his face changed slightly, and he said, "Can you add a switching device in front of this......?" Isn't that going to be a problem?"

Before, everyone divided labor with each other, and the time was so urgent, Liu Chen was unified and coordinated, and there was almost no communication with each other, because everyone did not know the details of the inverter.

Huang Jie also expressed concern, "There won't be any problems, right?"

The inverter is four switches, just like sheep, horses, cows, and pigs are all four-legged, this is basic common sense, three-legged people are not scary? Six-legged pigs are scared to death, right?

"Not only can you add a switch in the front, but you can also add a symmetry in the rear, not only one, two, three, or even four. This is just to increase the discrete state to a five-level, seven-level, nine-level...... And so on. ”

Liu Chen's face was a little cold, "In other applications, this structure may not work." But when the resonant zero-crossing works with it, it's perfect and there will be absolutely no problems. ”

Liu Chen no longer gives everyone a chance to ask questions, "1. The collection and processing of resonant current ......"

"The initial resonant current Ires_p is measured in the form of voltage by means of a current transformer or by stringing a small resistor in a series resonant circuit. The initial resonant current is the reverse of the actual resonant current, and the voltage follower reverses and amplifies it to obtain Ires_in. The phase of the amplified resonant current Ires_in is moved forward, and the time of the forward time is the delay time of the controller, the driving circuit and the switching device, so as to ensure that the switching device switches when the resonant current crosses the zero point. The forward resonant current Ires_s is converted from a sinusoidal waveform to a pulse waveform that can be recognized by the controller and is passed into the controller to detect the zero crossing point, and the amplitude of the pulse waveform Ires is the same as the processing level of the controller. ”

"2. The acquisition of output voltage, the output voltage Uout is measured by the voltage transformer or resistance voltage division, and the power circuit and the control circuit are isolated by linear optocoupler. ”

"3. Given the voltage comparison value, the voltage hysteresis loop control is divided into direct voltage hysteresis loop control and indirect voltage hysteresis loop control, and the direct voltage hysteresis loop control is to collect the output voltage Uout. Direct comparison with a given voltage comparison value inputs the result into the controller, indirect voltage hysteresis control is the output voltage Uout with a given reference voltage Uref through a regulator that compares its result with a given voltage comparison value. ”

"The given voltage comparison value for direct voltage hysteresis control is directly determined by the number and width of the given reference voltage Uref and hysteresis loops, and varies with the change of the output voltage Uout, while the given voltage comparison value for indirect voltage hysteresis control is determined according to the parameters of the regulator and the number and width of the set hysteresis loops, and does not change with the change of output voltage. ”

"The number of values for a given voltage comparison depends on the output level of the inverter, the number of inverter input levels n, from low to high are Ui1, Ui2, Ui3、...、 Uin, then the number of inverter output levels (2n+1), from high to low, are +Uin, +Uin-1, +Uin-2、...、 +Ui1, 0, -Ui1, -Ui2, -Ui3、...、- Uin, and each state outputs a level. Therefore, there are (2n+1) states, which are called +n state, +(n-1) state, +(n-2) state、...、 0 state, -1 state, -2 state, -3 state, 、...、-n state according to the output level from high to low, respectively, and the number of given voltage comparison values is 2n and the number of hysteresis rings is n. ”

This is the most critical core technology. The professors listened in fascination, their faces froze, their eyes glazed over, and their hearts were shocked, what a genius it took to think of such an innovative idea.

Oh my God, the most powerful thing about a genius researcher is that kind of wild thinking. If it is still practical, it is an unborn genius, a genius who leads the progress of a discipline.

"For direct voltage hysteresis control, the ring width from low to high is 2h1%, 2h2% 、...、 2hnhn of the given reference voltage Uref, and the given voltage comparison values from low to high are: U1, U2,... , U2n, then U1 = (1-hn%) Uref, U2 = (1-hn-1%) Uref, U3 = (1-hn-2%) Uref,... ，Un=(1-h1%)Uref，Un+1=(1+h1%)Uref，Un+2=(1+h2%)Uref，Un+3=(1+h3%)Uref，… ，U2n=(1+hn%)Uref。 ”

"For indirect voltage hysteresis loop control, the output of the regulator is set to be stable at Ur, and the ring width from low to high is 2h1%, 2h2%、...、2hn of Ur, respectively, and the given voltage comparison values from low to high are: U1, U2,... , U2n, then U1 = (1-hn%)Ur, U2 = (1-hn-1%)Ur, U3=(1-hn-2%)Ur,... ，Un=(1-h1%)Ur，Un+1=(1+h1%)Ur。 Un+2=(1+h2%)Ur，Un+3=(1+h3%)Ur，… ，U2n=(1+hn%)Ur。 ”

Liu Chen said to himself. Ignore their reactions, and don't care if they understand it or not.

"4. Determine the next control state, for direct voltage hysteresis control, the output voltage Uout is compared with the given voltage comparison value, and the Uout is greater than the given voltage comparison value. The comparator outputs "1", Uout is less than the given voltage comparison value, the comparator outputs "0", and 2n comparisons are input into the controller, where the controller records the number of "1" signals as m. ”

The sum of m and the next output state is n, i.e., m=0, the next state is +n, m=1, the next state is +(n-1), m=2, the next state is +(n-2)、...、m=n, and the next state is 0, m=n+1. The next state is -1, m=n+2, the next state is -2, m=n+3, the next state is -3、...、m=2n, and the next state is -n. ”

"For indirect voltage hysteresis control, the output voltage Uoutr of the regulator is compared to a given voltage comparison value, the Uoutr is greater than the given voltage comparison value, the comparator output is "1", the Uoutr is less than the given voltage comparison value, the comparator output is "0", and 2n comparison results are entered into the controller. The controller records where the number of "1" signals is m, the difference between m and the next output state is n, that is, m=2n, and the next state is +n, m=2n-1. The next state is +(n-1), m=2n-2, the next state is +(n-2)、...、m=n, the next state is 0, m=n-1, the next state is -1, m=n-2, the next state is -2, m=n-3, the next state is -3、...、m=0. The next state is -n. ”

In addition, the resonant current and the voltage of the capacitor C need to be limited, and the maximum limit value should be set, if one of the two exceeds the set limit, the next output state is forced to be zero or negative, and if both exceed the set limit, the next output state is forced to be negative, so as to protect the switching device from overcurrent and overvoltage. ”

The first two times someone asked questions, Liu Chen was drunk, his face was cold and arrogant, and he didn't want to explain, but when these old professors heard such a clever technique, they were all itching, some of them had strong understanding skills, and they could barely keep up with the ideas, but some of them fell behind, and they were so anxious that they didn't dare to ask questions, so they had to raise their hands.

One who held it high and the other who did not understand followed suit.

It's like a group of elementary school students.

Ignore it and move on.

"5, the output switch control signal, the signal input to the controller has the resonant current signal Ires that changes to the pulse waveform after moving forward, the 2n results of hysteresis comparison, the next state is determined according to the result of hysteresis comparison, the half-cycle integer multiple of Ires is used as the trigger signal to determine the state, the driving signal of the switching device is output according to the next state, and the half-cycle of Ires is the trigger signal of the switching device switching state. ”

"According to the different conduction modes of switching devices, the output of multilevel inverters has three basic states, which are positive state, zero state, and negative state. The positive state is that the pulse voltage output by the multi-level inverter is in the same direction as the resonant current, which plays an enhanced role in the resonant current; the zero state is that the output pulse voltage of the multi-level inverter is zero, and the resonant circuit forms a loop, and the resonant current is only affected by the load; the negative state is that the pulse voltage output by the multi-level inverter is in the opposite direction to the resonant current, so that the resonant current is weakened. In the same state, the direction of the resonant current is different, and the output level direction of the corresponding multi-level inverter should also be changed, and the switching device corresponds to different conduction modes. The state of the switching device 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. ”

"At zero state, the basic four switching devices of the multi-level inverter take turns to conduct two upper and two lower arms, and considering the service life of the switching devices, it is not easy to turn on two upper or two lower arms all the time. If the switching device is connected to the fast diode in anti-parallel, one of the basic four switching devices can also be turned on according to the direction of the resonant current, and the corresponding fast diode can be used to replace the switching device connected in parallel to form a loop. ”

"For the negative state, if the switching devices in the multi-level inverter are all anti-parallel fast diodes, all the switching devices can be turned off, and the resonant circuit can select the fast diodes that are turned on according to its own energy to form a path, this control method is simple, but n negative states can not determine the control. To control the negative state, the switching device must be turned on, and the switching device in a negative state is different for different resonant current directions. ”

"For unidirectional multilevel inverters. Only one side adds a switching device to increase the number of input levels, and for resonant currents in both directions, the switching device can only be turned on by "complementary" means. The basic four switching devices are S1H, S2H, S1L, and S2L. S1H and S2H form a bridge arm, S1L and S2L form a bridge arm, S1H and S1L are two upper side arms, and switch devices S3, S4, S5、...、 S(n+1) are added on the front side, and the input level number is n. ”

"The flow from point H to point L is the positive direction of the resonant current. For the -t(1≤t≤n-1) state, the increased input level is -Ui(n+2-t), and when the resonant current is negative, the switching device St and S2L are turned on, or the fast diode D2L of the switching device St and S2L is reversed in parallel, and the -Ui(n+2-t) level is output to the resonant circuit, and when the resonant current is positive, the -Ui(n+2-t) level cannot be output by the conduction of the switching device St. ”

"The switching device St and S1L are turned on, or the fast diode D1L of the switching device St and S1L is turned on in anti-parallel, and the Ui(n+2-t)-Uin level is output to the resonant circuit. Therefore, for the -t state where the resonant current is positive, the switching device Sn+4-t that is complementary to the switching device St must be turned on, and the switching device S1L or the fast diode D1L in anti-parallel with S1L must be turned on at the same time, and the level Ui(t-2)-Uin must be output to the resonant circuit, and the levels Ui(t-2) and Ui(n+2-t) must be complementary to each other for the same effect. ”

That is, the sum of the two is Uin, and for each negative state, a "complementary" conduction mode can be adopted, which requires the input level of each state to have an equal linear relationship, that is, Ui2=2Ui1, Ui3=3Ui1, Ui4=4Ui1、...、Uin=nUi1. For the unidirectional multilevel inverter on the rear side. Negative states are controlled, also through a "complementary" conduction mode. ”

With this quick talk, many professors are on the verge of collapse, and they are all very stealthy. I understand very well the super high value of the content that Liu Chen is talking about, as long as he learns it, he has mastered the most cutting-edge technology in this field, and if he misses this opportunity to explore it on his own, I am afraid that he will not be able to learn it for the rest of his life.

Watch the most advanced technology slip away from your eyes.

It is no exaggeration to say that these well-known professors, who are usually arrogant, have long ceased to personally supervise students, and have long ceased to attend classes. At least I haven't used my brain so quickly for more than ten years, and there are many beads of sweat the size of beans on my foreheads.

I don't know when it started, the big guys spontaneously took paper and pen and worked hard to write, but Liu Chen in front of him was full of a blank board and immediately erased it, and then wrote, if he didn't record it, and he didn't understand, then he missed it.

"Little sir, can you explain more slowly. ”

"Slow down, little sir, we're all old bones, and we can't keep up with your train of thought. ”

Breathless as he spoke.

"Slow down, little sir. ”

The titles were all changed back in one fell swoop.

Then Liu Chen ignored it completely, he held his breath in his heart, and he couldn't get out of this depression if he didn't finish saying this in one bite.

"For bidirectional multilevel inverters, the switching devices are added symmetrically on both sides, S3H, S4H, S5H、...、 S(n+1)H are added on the front side, S3L, S4L, S5L、...、 S(n+1)L are added on the rear side, and for the -t(1≤t≤n-1) state, the input level is Ui(n+2-t), and the input level of StH and StL is Ui(n+2-t) When the resonant current is negative, the switching device StH and S2L are turned on, or the fast diode D2L of the switching device StH and S2L is turned on in parallel. ”

"When the resonant current is positive, the switching device StL and S2H are turned on, or the fast diode D2H of the switching device StL and S2H is turned on, and the fast diode D2H of the switching device StL and S2H is reversed in parallel, and the -Ui(n+2-t) level is output to the resonant circuit. For bidirectional multilevel inverters, the levels of the state inputs do not require an equal linear relationship. ”

For the t(1≤t≤n-1) state, the increased input level is Ui(n+2-t), the resonant current is positive, and the switching devices St and S2L are turned on, and the output Ui (n+2-t) level is output to the resonant circuit. ”

"When the resonant current is negative, the switching device Sn+4-t that is complementary to the switching device St is turned on, and the switching device S1L is turned on at the same time, and the Ui(n+2-t) level is output to the resonant circuit, and when the resonant current is positive for the t(1≤t≤n-1) state of the bidirectional multilevel inverter, the switching device StH and S2L are turned on, and the Ui(n+2-t) level is output to the resonant circuit when the resonant current is negative, the switching device StL and S2H are turned on, and the Resonant circuit is output Ui(n+2-t) Level. ”

"For the +n state, the resonant current is positive, the switching devices S1H and S2L are on, the resonant current is negative, the switching devices S1L and S2H are on; in the -n state, the resonant current is positive, and the switching devices S1L and S2H are turned on, if the switching device is anti-parallel fast diode, it can also be turned on by the fast diodes D1L and D2H, and the resonant current is negative, the switching devices S1H and S2L are turned on, or the fast diodes D1H and D2L are self-conducting. ”

It's another quick explanation.

The professors fell into a deep despair, oh my God, the last time I had this emotion was to go back to the last time I was in college, when the teachers marked the last key class for the exam, and some of the very bad teachers deliberately spoke super fast, leaving the students incompletely recorded and grief-stricken.

"A DC/DC converter with a multi-level inverter based on resonant soft switching technology switches the switching device on and off at the zero crossing of the resonant current, eliminating switching losses, and in addition, multiple switching devices are connected in parallel as a switching valve to achieve the effect of voltage and current sharing, making up for the capacity of MOSFETs or IGBTs. ”

Wipe rub, wipe off all the whiteboards.

Liu Chen spread his hands, "The control strategy I want to talk about and the cooperation of multi-level inverter are all finished, this is the core technology used in the equipment." ”

Damn, the sweaty professors stopped impatiently, and looked at him with expectant old eyes, full of desire and enthusiasm, just like the eighteen-nineteen-year-old hairy young man who saw the goddess wearing a high-slit cheongsam walking in front of him, and the white thighs pushed his steps and swayed.

"Little sir, can you tell us more? Qin Ming took the lead.

"Say it again, little sir. ”

……

There was a wailing and begging.

Liu Chen ignored it completely, looked at everyone indifferently, showed a little smile, and said, "It doesn't matter if you don't understand, you can go and check the original text of my patent application when the time comes." ”

Oh, everyone breathed a sigh of relief, and the heart that was lifted up was also put back, and I deeply felt that I was a big ****, and I was in a hurry to remember that just now, just go to see the original text of the patent, and I relaxed all of a sudden.

I wiped the sweat from my forehead, it was really uncomfortable to get soaked.

"Yes, look at the original patent. ”

"You have to read it, God. ”

"It must be seen that the whole research group studies together. ”

Huang Jie looked at the relaxed people, really didn't want to pour cold water, said with a bitter face: "This patent has been applied for secrecy, and the big guy wants to see the original text of the patent, I'm afraid it will be twenty years later." ”

Yes?

This Nima's heart lifted again.

The old guy, who had a bad heart, quickly covered his chest and took out medicine.

Twenty years?

Will Nima survive until then?

The usually polite and well-cultivated professors want to explode foul language.

……

[The reason why some technical details have not been deleted, considering that this technology is real, the full version, interested brothers may be able to gain something.] (To be continued.) )