12Vnas

A very efficient, simple to make, cost only 5 yuan, 12V input nas power supply.

The chip used is hx1304f, which is very cheap. It has high synchronization buck efficiency and only costs a few cents a new one. The motherboard uses one channel for 5V and 5Vsb, one channel for 3.3V, and a separate channel for 5V power supply for the hard disk.

Let’s explain why it’s designed this way:

First of all, let’s start with my test of NAS power consumption. I used a Honey Badger super storage chassis, a modified 8th generation notebook U, and an ordinary large motherboard with 6-way SATA. This case can actually accommodate most large motherboards. The reason why people use small itx boards is because the power supply underneath is blocked. If you use the original small 1U power supply, you can only use itx motherboards, and itx motherboards are expensive and rare. There are even fewer that have multi-channel SATA at the same time. When the choice is small, the price will be very expensive. When using large motherboards, 6-way SATA is very common and can be bought for just over 100. The hard drives I use are six 8TB Western Digital ones, bought from one of the four major hard drive stores in Xinbao. Anyone who plays NAS knows this.

If you use a large motherboard, you cannot install a small 1U power supply. This is not a problem. Originally, such power supplies are generally not very good and expensive. They are either removed from the all-in-one computer or sold for two to three hundred per unit, which is very expensive. It was not cost-effective, so I decided to make a DC-ATX one myself.

The power consumption of NAS is very different from that of ordinary computers. The biggest difference is that the power consumption of NAS is only more than 20 watts during normal operation, and only more than 30 watts when downloading PT and the like. A high-power power supply of several hundred watts is required to reduce the load. It was not efficient and caused a lot of waste. Secondly, the NAS needs to have an uninterruptible power supply. If you use an ordinary UPS, second-hand ones are also very cheap, but after so many conversions from 220V-12V-220V-12V, the efficiency cannot be high. The electricity bill for hanging up the machine all year round is still quite considerable. One day Once or so, save when you can. Therefore, 220V-12V plus dc-dc and three 18650 power lithium batteries as backup power supply are the most cost-effective solutions. Because there are very few power outages in China now, the role of backup power is to protect the hard drive and data, and it does not need to run on batteries for a long time, which is different from the needs of laptops or enterprise servers.

Let’s analyze the voltage and power consumption of the NAS. The NAS is turned on all year round, so it doesn’t really matter whether it has 5Vsb or not. Generally, what home computers can use is the wake-on-LAN function, so it only needs to be powered, and there is no need to consider the current. -12V is generally not available on motherboards nowadays. It used to be used for serial communication, but now almost no motherboards have serial ports. The 12V input Vcc directly supplies the 12V of the hard drive and the 12V of the motherboard. It is controlled by a Pmos. I chose a 20mΩ to-252 packaged Pmos. The model is P2003ED, withstand voltage 25V, 3 hairs per piece, internal resistance and The prices are very suitable.

The hard drive power supply is the only thing that needs to be considered here. Since 12V is straight-through, you only need to use a larger capacitor for filtering, so I used a solid capacitor of several hundred uf and two mlcc. The capacitance can be marked as you like. You can have it yourself. Just solder whatever you want. I bought a plate of 47uf 25V 1206 myself, so I usually use as much as possible. 5V should be as generous as possible, with a separate power supply. The power supply of the mechanical hard disk is 12V supplied to the motor. The current is very large at startup. The read and write drive circuit consumes 5V power, 500mA during operation, and less than 10mA during standby. So I measured my six hard drives with a clamp ammeter. When uploading is relatively busy, two or three hard drives are working at the same time. The maximum current consumption at 5V can be 1.2-1.5A, and this single channel is rated at 2.5A, with a peak value of 3.5A. enough. The inductor should be slightly larger so that it does not become magnetically saturated. The inductance should also be slightly higher so that the ripple current is small and the data is safer. Because 5V power is used for data reading and writing, data may be lost if the voltage is unstable. Insufficient 12V power supply or unstable voltage may cause the magnetic head to reset and make a rattling sound, which will seriously shorten the life of the hard disk. Therefore, do not save this capacitor. Make it as large as possible. Ripple and high-frequency interference do not matter. It is driving the DC motor anyway. , will not have any impact.

Today's computers rarely use 3.3V. It depends on the design of the specific motherboard manufacturer, sound card, network card and memory. Some manufacturers use 3.3V for power supply, and some manufacturers directly use 12V or 5V. Because computers 20 years ago, the memory does not work well. The voltage is 3.3V. At that time, many computer power supplies were forward-active, and then multiple voltages were directly separated from the transformer. There was no DC-DC on the motherboard, and each voltage was taken directly from the power supply. After these years of development, the power consumption of each chip has been reduced, and the working voltage has also dropped. Most of them have become more than 1V power supply, so it does not make much difference which way to use. CPUs and graphics cards that consume particularly large amounts of power After using 12V power supply alone, then use multiple bucks to reduce it to more than 1V. As for NAS, according to my own testing, the 3.3V channel usually consumes less than 1A. I guess the wired network card does not draw power from it, but the memory only consumes one or two watts. The memory of my NAS is two 16G It's used to run virtual machines, so you don't have to think too much about this step. The ripple size doesn't matter. Anyway, you have to go through another buck to the motherboard.

The choice of 12V AC power supply and lithium battery backup depends on your actual situation. Because I run a virtual machine, the peak power reaches about 60 watts. The lithium batteries are directly connected in parallel, which just cuts the peak and fills the valley. Three 18650 power lithium batteries are connected in series and add active balancing. Without a protective board, the battery can be charged up to 4V per cell, which will benefit battery life if it is not fully charged. Lithium batteries are not suitable for long-term storage of full or empty batteries. At 4V, they have about 80% power, which is enough. Considering that the battery cannot maintain 12V output all the time after a power outage, I added a boost circuit. These are placed on another board and attached to the bottom of the NAS chassis. The battery holder is also on this board. I will release it in another project later. .

When the power supply is usually 12V, the boost does not work directly and the duty cycle is 0, so there is no additional loss. Nmos chooses 1mΩ, so it is equivalent to a wire, and the inductor and capacitor form an LC filter, which can also Makes the output cleaner. When the mains power is disconnected, no additional control circuit is needed. The lithium battery is always online, so there will be no voltage drop of tens of milliseconds that occurs in ordinary UPS. Ordinary computers will not crash or restart due to the capacitance surrounding the CPU, but NAS is different. The 12V power supply of the hard disk will still be affected, which will also affect the lifespan. Even when the CPU load suddenly changes, those poor-quality power supplies have poor dynamic response, making the hard drive's 12V power supply unstable and greatly affecting its lifespan. This is also why even though the power supply of those dedicated NAS is not good, the hard disk inside has a long life, because many of the CPUs of dedicated NAS are ARM, and the power is only a few watts. The same is true for those of Black Synology using J1900, the CPU can reach more than ten watts. , so it can protect the hard drive. Here, power lithium batteries are connected in parallel to ensure the stability of the 12V power supply, and also function as a DC UPS. The only thing that needs to be considered is battery balancing. Since it is connected to 12V for a long time, balancing the current does not matter.

Finally, to summarize: The main reason for this power supply is that it is cheap. I bought three chips for less than 1 yuan, and bought new ones for less than 2 yuan. Several solid capacitors are from my own inventory. The 3.3V uses 6.3V tantalum capacitors. , it happens to be in stock. It doesn’t matter whether you use the connector part or not. You can also directly solder the wires because the current is relatively small. ATX connector costs 3 yuan each, so it only costs 5 yuan in total.

The board uses a four-layer board, because now four layers are free, otherwise it would have to be slightly larger and some feet should be left empty. The 5V and 3.3V power supplies of most motherboards are connected together after they come out of the atx connector. Some motherboards will even leave a few pins vacant. To find out what your motherboard is like, just use a multimeter to measure the resistance. Because the current is small, the pins that are difficult to connect can be left floating. I have bought some DC-ATX power supplies sold by a certain merchant that do this, and my four-layer board is fully connected. If you want to modify the two-layer board yourself, just make the few wires connected from the mezzanine into flying wires or simply hang them in the air, and the computer will still run normally.

This power supply is designed for NAS, and can also be used on ordinary low-power office computers. The motherboard's 5V power supply is a separate channel, so the USB port power supply current is also sufficient, and it can be connected to a 2.5-inch mobile hard disk with no problem. The 12V power supply to the CPU and graphics card is not led out separately, so it is not suitable for high-power gaming computers, and 12V uses Pmos. The internal resistance is small enough for NAS with dozens of watts, and independent graphics computers with hundreds of watts. It is best to use Nmos or a relay (ATX power supply can use a relay, and the delay of tens of milliseconds has no effect). For most computers today, my two-channel 5V power supply with each rated 2.5A is enough. In the computer, only the mechanical hard drive circuit part, solid state drive, and USB interface are powered by 5V. Among these, the biggest power consumption is Solid-state drives and some USB external devices, such as handles with vibration or 2.5-inch mobile hard drives, are not suitable if you use them a lot. There are solutions for reducing voltage using ZTE zxdn10 and Huawei pw22 communication power modules. Many people have used them and it is OK. The price is also very cheap. The former is 1.5 yuan for 10A and the latter is 2.5 yuan for 20A. The reason I did not use it here is because of NAS. There is no need for such a large current, and in order to achieve high current and small size, these modules design the inductor to be very small, with an inductance value of only 1uh, and then rely on a bunch of 1206 100uf capacitors in parallel to filter. When these capacitors are removed, they are of good quality. Both esr and esl are very low, which is better than the large-capacity x5r I bought. When I measured the capacitance at the 100k level of the bridge, the capacitance was negative. Obviously the esl is too large, but the capacitance on these modules is The 100K file capacity remains basically unchanged. If you use these two modules to make it, it is best to replace the inductor with one with a larger inductance, as the saturation current will become smaller. For pw22, it is no problem to change it to 4.7uh and run 10A. For zxdn10, it is 2.2uh and run 5A. The documentation of these modules does not say whether they can be connected in parallel. It is best not to connect them in parallel directly. I use two 5V channels to supply the hard disk and the motherboard respectively, and the power consumption is about the same. If there is an nvme solid state on the motherboard and a USB removable disk is connected to each other at the same time, the 5V power supply is used to copy data to each other. It will not be enough. If there is such a need, it is not recommended to use this solution. My NAS does not have a solid state disk, and the USB can only connect to U disks, so this problem does not exist.