Cost issues, precautions, and change suggestions written at the front

1. This board is a verification board/experimental board. It only provides new ideas and is not a product. Therefore, it is slightly larger in size and costs about the same on average, including postage of less than 15 yuan. If you want to improve it yourself, the cost can be controlled within 10, but you need to pay attention to the following points

• When converting to PCB after changing the schematic diagram, please check whether the packaging, etc. are correct and meet the intended purpose.
• The PCB can be made very small. I just made it large for the convenience of verifying the function. You can change it yourself and save the opportunity for proofing.
• If you are not sensitive to cost, it is definitely better to just buy a 30uH/38MM coil, which generates less heat and has better performance. In fact, each one only costs three yuan including postage: [Taobao] https://m.tb.cn/h.fBCsiBI? tk=yqyt2t6JQlL CZ3457 "38mm30uH wireless charging coil XKT-L1 inductor coil for wireless charging solution brand new" Click the link to open it directly
• Since I don’t have an inductance measurement tool, I don’t know the exact inductance of the pcb coil, but based on the no-load current, I can tell that the inductance of the pcb coil is definitely too small (see the coil drawing for suggestions on changes).
• The battery is a little expensive, but you can change it to a bagged lithium battery with a protective plate.
• NPO capacitors are a little expensive, but remember not to replace them with X7R and remember to use the 1206 package. However, tantalum capacitors can be replaced to save costs and reduce size. When replacing the diode, please replace the package and model by yourself according to the current and voltage required by the design.
• Many components can be omitted based on experience, and some diodes in the wired power supply can be short-circuited.
• The vertical type-C male connector is extremely expensive. It is recommended that you buy a plywood male connector (with a plate, the four-legged kind) directly from Alibaba.com for a few cents and solder it directly to the output pad.
• If the output voltage requirements are not high, the internal DCDC boost and lithium battery power supply can be integrated into a chip that integrates charging, discharging and boosting ( recommended ), such as ETA6093, etc. You can select according to the following chip table. Or directly output the lithium battery voltage ( not recommended unless to save costs).

Why can't you make it perfect the first time and let us improve ourselves? Because the new training camp has opened and we want to do big things!

2. Can you still charge your phone with this chip? If you want to charge your phone, just pick up a 15W junk wireless charger that costs five or six yuan. If you really want to make it yourself, just look at the table below.

In short, they are not cheap, and some are not available. If the power is high, there is no need to consider the PCB coil.

Introduction&Design Purpose&Design Ideas

• I saw that the wireless charging module of the xkt chip solution on a certain product costs 30 to 40 yuan, and most PCB coils have an output of about 5V 60mA, so I wanted to make one myself.
• The actual thing is divided into two parts: receiving and transmitting parts. The transmitting part coil can be used as the receiving part coil (just cut it off). If it can be made smaller, the three parts can be put together into one board.
• It can be used as the base of the snowflake lamp. The lowest brightness of the snowflake lamp can be turned on for two days and two nights (actual measurement)
• Try to choose commonly used components for devices to reduce the cost and difficulty of verification. If you want to clone it for your own project, please be sure to read the precautions written above carefully.
• The functions achieved include wireless power supply, wired power supply, charging and discharging at the same time, and charging of lithium batteries. The maximum wireless charging output position should support 5V500mA.
• The output supports internal & external DCDC switching through a jumper cap. The internal DCDC I chose is the PW5100-50 chip, which is commonly used and cheap. The quiescent current is 10μA, the efficiency is 95%, the input is 0.7-5V, and the output is 5V, which can meet the needs of small projects.
• The battery charging current can be adjusted by changing the resistance of R5, as detailed in the schematic diagram. I set it to 200mA and charged the 16340 at 750maH.
• Using PCB coils for low power can achieve low prices, maintain consistent inductance in large quantities of coils, and other benefits.
• If necessary, you can choose chips such as xkt001 to charge the battery directly, but I have not tried it because T3168+XKT510 only costs 2.5 yuan.
• The chip data manual of xkt is pitiful, and the successful cases shared online are not very detailed, so the first time I did it was not perfect. If it is open sourced, everyone can optimize and change it together. I hope that wireless power supply for PCB coils will appear in everyone's projects soon. superior.

Coil drawing tutorial (coil drawing can be used for wireless charging and NFC projects simultaneously)

At first, I drew the coil myself by drawing a spiral line, but the inductance could not be guaranteed (so I printed the board three times this month for this project), so I used TI's official coil drawing tool to draw it, link: Coil Designer (ti.com)

The drawing steps are as follows (if your English is not good, just right-click on the web page to translate in full screen):

The second step is to choose a variety of coil shapes. You can use them freely.

The fourth step is to change the part marked with the red arrow. If you want the coil to be smaller, change Dout.

The fifth step is to export the AD file and unzip it.

Next, operate in Lichuang EDA (importing the AD coil generated by TI will not be judged as drawing by other EDA and the free boarding opportunity will be lost. Please eliminate your worries and design with confidence)

Open the coil file you just unzipped

Modify wire ends, vias, coil networks, etc. after importing

Freely design it here, and then copy it directly into your own project.

(Note here) Regarding the coil issue

I provided two coils in the PCB. The first one was printed and verified, but the no-load current is too large because the coil inductance is not enough. (The picture below shows the no-load current of the coil)

The large one is a bit ridiculous, because if a standard 30μH/38mm coil is used, the no-load current is as follows

But the solution is also simple, that is, just increase the coil inductance. Here I choose to increase the inductance by increasing the number of coil turns. The "coil one" I drew in the TI tool is the coil with too large no-load current. The TI tool showed it as 30μH, but after I got it, it was obvious that the inductance was insufficient. Since I didn't have an inductance test tool, I didn't know the details. How different is it from the software? The second coil I drew in the PCB is unverified. The TI software shows 38.982μH (as shown below). It should be about the same in reality. I have already replaced it in the PCB. You can rest assured to make a sample and test it. , it is definitely better than my original one and it will definitely work. It would work if I replaced my original coil, but it will burn to my hands after being used for a long time. . . (See the reason: About coil inductance)

The thinner the PCB coil board, the smaller the inductance deviation (0.8, 1.0, 1.2), but the copper thickness must be 1OZ. If necessary, you can adjust the copper thickness and other data in the TI tool.

The instrument man, please quickly measure the difference in inductance and post it in the comment area so that I can avoid detours! ! !

About coil inductance

• High inductance will affect wireless power supply performance (+5μH should have no effect)
• If the inductance is too low, the XKT510 chip will light up (personal experience)
• If the inductance is lower than the nominal value, the PCB coil will overheat and become an induction cooker (personal experience)

None of the above problems at the transmitter will cause the receiver coil to heat up or be damaged, so you don’t have to worry about the battery at the receiver exploding.

If the inductance matches, there will actually be a certain amount of heat (the specific protection method is to add a temperature protection switch, add heat dissipation copper, etc.) The picture below shows the 70°C temperature protection switch TB02-BB8D, the internal resistance is less than 25mΩ, and can also be used for lithium battery packs Make a temperature protection switch , one piece at a time with free shipping. If you don't want it, just short-circuit the switch position.

Link: [Taobao] https://m.tb.cn/h.fA3nu5Z?tk=sQyj2tJFNsF CZ0001 "Miniature temperature switch small size temperature control switch TB02-BB8D 70 degrees normally closed temperature protector" Click the link to open it directly

Power output mode description

Regarding PCB, I designed a lot of pins for measurement and experiments. The specific functions are as follows

1. External total output. It can be used to connect to other interface modules or directly output, such as type-c male modules with boards that are easy to weld, etc.

2. Wireless charging receiver output. You can connect a temperature switch to control the temperature of wireless charging (the receiving end is not very useful, so I recommend shorting it), or you can use it to power supply and test other solutions.

3. Connect external DCDC. If you use the internal DCDC boost, you can directly short-circuit it. (This part is used together with 4)

4. Internal battery power output and internal DCDC boost output switching (used in conjunction with 3). The usage method is mainly shown in the figure below.

If you have no other ideas to verify, when cloning to your own project, please connect the schematic and PCB in advance according to the internal DCDC connection method.

The dotted box represents the jumper cap connection. I have added this picture to the silk screen on the back of the receiving board.

• InternalDCDC

• externalDCDC

• Battery voltage output

Actual pictures & performance

There are currently no problems at the receiving end, and all functional tests are normal . The transmitting end is what I mentioned before. The inductance of the coil is too small. The coil gets hot after charging for a long time. I have replaced it with a larger coil. If it is still hot, it is still small. If you measure when the no-load current reaches below 50mA, it should be fine. . I hope someone with equipment can measure the difference. The coil is hot because the coil is hot. It has no effect on the chip. The chip is not hot at all. In theory, a 0.5mm wire should be able to carry a current of about 1A. The current that is only about 200mA must not be caused by the wire diameter being too small.

connection method

Dupont wire×
thin flying wire×
power cord√

As for the coil, you can just weld it directly.

some pictures

Wireless charging

Wired charging

You can also use it as an upgraded version of the snowflake lamp base

at last

I look forward to your secondary development and correction of my mistakes. I hope it can be improved and appear in your interesting projects as soon as possible.

Thanks to my friends who support me and give me the motivation to make such a thing from scratch. All my MDs are typed by hand, thank you all for your support and love.

Likewise, please pay attention to safety and caution when making.

Interlude

This is quite fun