How to design a charger that saves the galaxy?

Engineer Wu has been an engineer for nearly 20 years. He is often called "Engineer Wu" by his colleagues, suppliers and customers.

Although the boss was reluctant, he had to accept the title reluctantly due to public opinion.

Mr. Wu's main business is power supply. Every time he makes a product with great difficulty, he happily introduces it to customers...

The customers always look well-informed and don't take it seriously...

Engineer Wu wanted to reverse this situation, so he decided to modify a charger designed by a colleague.

This product was launched in 2017 and was the world's smallest 60W charger at the time.

In order to popularize power supply knowledge and let everyone understand the difficulties of product design, while also taking into account the appreciation ability and knowledge level of the audience of liberal arts and science,

Mr. Wu drew an easy-to-understand tutorial. Since he is not a professional painter, please forgive me for the rough style.

Friends who have studied high school physics know that the electricity in the wall socket is 220V 50Hz.

50Hz means that it goes from high to low, and then from low to high, repeating 50 times per second.

So the question is, when we charge our mobile phones and laptops, we only need a DC voltage of 5V to 20V. 220V is too high. What should we do?

Yes, we need a transformer. If the transformer converts 220V 50Hz frequency voltage into a lower voltage, then the transformer must transfer energy 50 times in 1 second.

If the transformer is made to work at a faster frequency, assuming that the total energy to be transferred remains unchanged, then the transformer only needs to transfer a small amount of energy each time it works. The transformer can become smaller, and the charger can also become smaller.

This seems perfect, but there is always some loss every time energy is transferred. The more times it works, the more it is lost.

These excess losses will be dissipated as heat, and the efficiency will decrease. The size of the power supply cannot be reduced because there is not enough area to dissipate the heat.

So engineers designed various circuits to reduce losses.

Or upgrade to devices with better performance to reduce waste and improve efficiency.

Although these increase the complexity and cost of the circuit, they improve efficiency and the power supply will not get hot when working at full load.

But a new problem arises! When in standby mode, although the heat is not generated, the power supply is still working hard at a very high frequency, and the efficiency is very low.

Maybe you may not care about the electricity bills, but the country has requirements for standby power consumption. If it exceeds the requirements, it cannot be sold.

This in turn forced engineers to design new circuits to allow the charger to work intermittently when the device is dormant, reducing losses.

But the problem arises again. Intermittent work will generate noise, which can be easily detected by the human ear and affect the user experience.

Engineers also have to find ways to reduce noise decibels: make the frequency of intermittent work not fall within the audio range that the human ear can detect; reduce the energy consumed during each work; add glue to the transformer, etc.

Do you think that's all? There are more problems than that...

For example, because of the high working frequency and working too hard, energy often flows to nearby household appliances, and in serious cases it will interfere with other people's normal work.

This is also not allowed by the National Quality Compulsory CCC Regulations.

In order to block the energy of adultery, engineers have to add something called a filter into the power supply to block them.

Unfortunately, the filter makes the energy transfer path full of bumps, which increases the size of the power supply and heat loss.

So engineers have to think of other ways to reduce losses, such as finding an energy in the power supply with the opposite polarity to the escaping energy, so that the escaping energy is killed by negative energy on the way out. Reduce the use of filters.

Of course, this is not an easy thing to do. If the negative energy you find is too strong, it will take over the main role...

It is relatively easy to make one or two units in a laboratory and cancel out the positive and negative energies. But once tens of thousands of units are produced, how can we ensure consistency?

There are still many problems that engineers need to solve. Making a product is not about which one is the best, but about who has the fewest shortcomings. In the final analysis, making a product is a process of constant compromise. So making a short, light and thin power supply is really not an easy task.

When the engineers finally put together a few prototypes with good performance in the laboratory, the nightmare had just begun...

To make a genuine Delta power supply product, we must go to the factory for trial production.

The trial-produced products must undergo three levels of testing and scoring, and they are the inseparable EVT, DVT, and PVT brothers!

👇👇👇
Engineering verification, design verification, production verification.

At each stage, experts from more than a dozen departments will gather to score the products.

Only when the EVT score is passed can you move on to DVT. If the score is not passed, the design will be modified and then it will be re-engineered.

No gifted engineer can achieve the PVT score in one go. Only by going through excruciating pain and almost peeling off one's bones can one open up the Ren and Du meridians and achieve mass production, which takes at least half a year and at most several years.

Among the thousands of tests in dozens of schools, people don’t understand the too professional tests, so Mr. Wu picked a simple one and introduced the content of product drop test:

Test 1: 10cm high, with the 6 sides of the power supply facing downwards in turn, 50 times for each side, a total of 300 times, the product cannot be damaged.

Test 2: At a height of 120cm, the six sides of the power supply are facing downwards in turn, once for each side, for a total of six times, and the product cannot be damaged.

When you are lucky enough (unlikely) to pass these tests and think everything is over, the next test comes!

Test 3: Roller test, which is to let the power supply roll up to a height of 50cm, without determining which side is facing down, and throw it randomly 72 times. The product cannot be broken.

Now the emerging device Gallium Nitride has become an Internet celebrity. It seems that a charger without the three words "Gallium Nitride" is as embarrassing as a British villa without a butler with a London accent at the door.

When this power supply from Delta was first released, it only used ordinary components, which seemed to be out of fashion at first glance. But in fact, think about it the other way around, any component is for performance, and using only ordinary components to achieve the efficiency of gallium nitride is like the battle at Juxianzhuang, where Xiao Feng used an ordinary set of Taizu Changquan to defeat more than 300 masters from various sects. Doesn't it make him look more powerful?

It's all talk and no action. I almost forgot that the theme is to design a charger to save the galaxy.

Most of Wu's clients are Americans. To them, Star Wars is like the 1986 version of Journey to the West. Wu wants to transform the world's smallest 60W into a Star Wars robot D2-R2. This robot has saved the galaxy from crisis many times in the movie and is a well-known positive character.

Because the company did not give him a budget and he was under financial pressure, he bought a D2-R2 model toy worth 10 yuan on Taobao.

Although this robot is not big, it is large enough to accommodate the world's smallest 60W power supply.

Cut the shell 👇

The bottom is dug out, and the size is just right to accommodate a 60W folding plug👇

I have to say a few words here. The nominal volume of the power supply in the industry only counts the rectangular part, not the protruding plug. Therefore, in order to compete for the smallest, the plug is fixed and exposed, because folding it will waste some volume. Although the user is holding it, they can claim that their volume is the smallest. Delta's products do not take shortcuts. From the beginning, they have chosen a self-torture path. Even if the plug is folded, it is still the smallest in the world.

Although you won't be cheated by buying this 10-yuan R2D2, the paint is a bit poor and it doesn't match the world's smallest charger.

Repainted it 👇

Comparing it with the photos I took at Disney before, I feel it's not dirty enough...

Slightly old! 👇

The next step is to put the charger into the robot's body. I asked a colleague for a 60W semi-finished product without a shell.

The following description is quite professional. Although Mr. Wu tried to simplify it, he may still be unintentionally Versailles. Non-professional audiences are welcome to skip it if they cannot bear to read it.

In the picture above, the upper one is the traditional 60W power supply, and the lower one is our miniaturized 60W.

Compared with the traditional 60W charger, this miniaturized charger only has the same large capacitor, and the rest is more than half smaller.

The transformer part uses a circuit board to replace the traditional wire-wound structure. The transformer coils are drawn on ten layers of circuit boards. Although this can save space, it also brings challenges: first, the impedance of the circuit board routing is larger than that of traditional winding, which will generate more heat loss; second, the circuit board is a multi-layer structure, and the distance between each layer of coils is close and the contact area is large. Friends who have studied high school physics may remember that the larger the contact area of ​​two charged parallel boards, the smaller the distance, and the greater the capacitance between them. In this way, the impedance of the electromagnetic noise propagation path becomes smaller, which is more likely to cause electromagnetic interference problems. If the distance between each layer of coils is increased, the leakage inductance will increase, resulting in excess energy waste. All of the above problems require engineers to continuously simulate and debug to find the optimal wiring method and the best stacking structure of the ten-layer circuit board.

Back to the topic, I bought three USB type-C adapters online. After turning them a few times, I changed the output port from the top to the side.

In the movie, the indicator light on D2-R2's head flashes. It is not difficult to install LED lights on the helmet, but such a modification will increase the standby power consumption of the product. Well, I have to sacrifice Wu's electricity bill to restore the real scene in the movie.

Engineer Wu couldn't wait to see the surprised expression on the customer's face, but unfortunately, when Engineer Wu finished the coolest power supply in the galaxy, the epidemic came. All interactions with customers were stopped indefinitely. Engineer Wu may have done something in vain again.

｜ Postscript ｜

When Wu first entered the industry, he went on a business trip to Taiwan with a great colleague. There happened to be a product of a Taiwanese colleague on the table. The great colleague picked it up and looked at it for a long time, then sneered with disdain and said, "This power supply is a modification of my design, but it can't even be copied. I used one component, but he used three!" The colleague next to him happened to hear this and asked, "Do you know that the price of three low-voltage components added together is cheaper than one high-voltage component?"

The story of these three components, together with the story of the three little pigs and three monks, enlightened Mr. Wu, who had just become an engineer. They taught Mr. Wu that there are always better people out there, and that he should never criticize other people's designs. Without experiencing it, you can't guess the ingenuity, nor can you understand the pain... Looking back on the more than ten years of working in this team, everyone may not have the highest technical level, but they all worked hard on each product and never thought of taking shortcuts. Gradually, everyone became pessimistic, not believing in luck or shortcuts, but only believing that sooner or later you will have to pay for what you have done. I remember an engineer who had just joined the company told Mr. Wu that his wife complained that he had become less and less sunny since he came to work in the company... When Mr. Wu heard this, he twisted his beard and said in joy, "You have become a master!"