Tell you how to understand the power supply test items

First: Why do novices frequently encounter setbacks in building computers?

With the continuous increase of new products and technologies in the power supply market, various brands and models are flooding every computer mall in the world. For a time, consumers have a wider range of choices, but there are also more frauds. Therefore, it is particularly important for consumers to choose a high-quality or suitable product.

According to the author's survey, many users do not understand some of the data and items in the power supply test articles. So they will naturally feel dizzy when purchasing a power supply, but when everyone understands the power supply test items, they will have a relatively clear context for purchasing a power supply.

Why is it a must-read for novices? Because when someone recommends a power supply to you, the other party may still give you a layman's comment that the brand is good and the wattage is high, but at this time, the novices have already developed a deep respect for this person. However, if you want to be a real DIYer, it is very unwise to worship such a pseudo-expert.

In 2009, our team developed a standard specification for power supply testing. After a year of operation, we basically test every power supply according to this specification. Therefore, this article will also focus on this specification to show users which item determines the quality of the power supply.

● Specification 1: Industrial-grade electronic load tester

As the saying goes, if you want to do your work well, you must first sharpen your tools. Therefore, if you want to test a power supply thoroughly, you cannot do it without a suitable tool. In order to provide authoritative test data to users, Zhongguancun Online has invested heavily in the purchase of the most advanced instruments to ensure that the error of each parameter is within the international standard.

Second: The origin and goal of power supply testing

First of all, we need to know what a power supply is. A power supply is not a simple small box, it is equivalent to the heart of our human body, providing energy to the computer continuously. The function of a power supply is to convert the 220V high voltage mains electricity into the low voltage direct current such as +3.3V, +5V, +12V required by the computer.

Since it is power conversion, there must be the speed of power conversion (rated power), the loss in power conversion (conversion efficiency), the quality of power conversion (voltage stability, output ripple), the working noise of the power supply (quiet effect), what platform the power supply is suitable for (plug specifications), and the working life of the converter (power supply materials).

The seven black parts above together constitute the performance of a power supply. In traditional power supply testing, we can only analyze the rated power, internal workmanship and plug specifications, but the most critical conversion efficiency, voltage stability, output ripple, and silent heat dissipation cannot be tested. In order to solve the biggest puzzle of selecting accessories for computer assembly, we have invested heavily in the purchase of related equipment for testing these parameters, so PBzone can thoroughly explore the quality of a power supply.

Beware of fraud by unscrupulous merchants

PBzone has no intention of defining the standard of "good" or "bad" power supplies, but hopes to tell consumers the meaning of the seven parameters of power supplies, and then test any power supply according to these seven parameters to get the results. We believe that instead of defining the good and bad of all products, it is better to put all the parameters and data in front of the user and let consumers choose according to their needs. The reason we choose to do this is that the dark side of power supplies is too heavy. If we are unable to uncover it, we can only rely on consumers who know more about power supplies.

Third: Text description of seven test items and their significance

● Rated power

The speed of electrical energy conversion is actually the rated power of the power supply, which means the maximum energy that the power supply can convert per unit time, and the unit is joules per second. Power represents the concept of "speed". The higher the power, the better, but the higher the power supply, the more expensive it is. We don't need to buy a 400-watt power supply for a computer configuration that is sufficient for 200 watts.

● Conversion efficiency

Conversion efficiency represents the ability to save electricity. The conversion process from the power supply to the wire is accompanied by a lot of losses. 100 watts may come out as 60 watts or 80 watts. If 100 watts of energy is converted into 60 watts, it means the conversion efficiency is 60%, and if it is 80 watts, it means 80%. The more advanced the design, the better the materials, the lower the power loss, and the higher the conversion efficiency. Why do you need high efficiency? Because the lost power is also included in your electricity bill.

● Voltage stability

Stability is the most noble quality of a power supply. When 220V mains electricity enters the power supply, the power supply wire ideally outputs low voltage electricity of +12V, +5V, +3.3V, but there is no such thing as an output voltage that is as accurate as an electrocardiogram. The power supply outputs a voltage that fluctuates up and down like +12.1, +4.9, +3.4. Correspondingly, the operating voltage of components such as the CPU, graphics card, and north bridge will also fluctuate up and down. Frequent and large fluctuations in output voltage will damage the hardware and affect system stability.

● Output ripple

Ripple, like voltage, represents the quality of power supply. A perfect low-voltage DC should be a very smooth waveform, but in fact, the DC waveform after capacitor filtering still has a small fluctuation, which is the ripple. Current ripple is a difficult concept for ordinary consumers to understand. You only need to know that when the conversion efficiency and output voltage of two power supplies are comparable, ripple can serve as the final arbitrator.

● Quiet and heat dissipation

The quietness and heat dissipation effect actually depend on the fan speed. The lower the fan speed, the quieter it is, but the worse the heat dissipation performance is; the higher the fan speed, the higher the noise, and the better the heat dissipation performance is. When setting the fan speed, the manufacturer will consider the life of the power supply, because high temperature will sharply reduce the life of the power supply, and the promised 3-year warranty period may not be achieved. Therefore, the fan speed of the power supply is generally relatively high, and the noise is higher, which deserves the user's attention.

● Wire specifications

If a 1000W power supply only has one graphics card power supply plug, it cannot be used with a mid-range graphics card like the GTX 260, right? Although the actual situation is not so exaggerated, many power supplies ignore the interface specifications and cable length, resulting in powerful performance but unusable, or incompatibility with the chassis.

● Internal materials

The internal materials determine the service life of the power supply. The reason why many excellent power supplies can be used for up to 5 years is because they use relatively abundant materials internally. Excellent materials can improve the overall quality of the power supply.

Below we will explain in detail the PBzone test equipment and test solutions for these seven points.

Fourth: Current and voltage are the prerequisites for system stability

When we buy power supplies, we often say 300W, 400W, and 500W. In fact, these are the easiest parameters to understand when purchasing power supplies. Power supply power is a concept that describes the output capacity of the power supply. A rated power of 300 watts means that the power supply can output 300 joules of energy per second to supply the motherboard, graphics card, hard disk and other accessories. Better graphics cards or more hard disks will have higher power requirements. If the power cannot meet the demand, the computer will stop working.

We have said before that the power supply converts 220V high-voltage AC into low-voltage DC such as +12V, +5V, +3.3V, -12V, and +5VSB. The power of these channels is determined by the power supply design and materials used. The sum of their output capabilities is the rated power. Manufacturers will set this value according to the power that a power supply can continuously output at 50°C.

The rated power is the sum of the low voltage output powers of several channels.

However, as I just said, the rated power of the power supply is set by the factory. In other words, if the user buys a power supply with random power written by a bad manufacturer, it will have no reference value. What is a randomly written power supply like? This will be introduced later.

Power ratio of general computer

The above figure shows the power ratio of a general computer. It can be said that most computers can be calculated according to the above table. For current computer configurations, it is normal for the graphics card to consume more power than the CPU, so the current supplied to the graphics card is very important. Blue screens and black screens caused by insufficient current are common.

● PBzone power supply rated power test setting

In actual testing, we will fully load the power supply with rated power and fully load +12V respectively, record the voltage and ripple of the two full-load tests, and then compare them with Intel's ATX12V 2.31 standard. If it does not exceed the standard, the rated power is considered to meet the standard.

Intel's regulations on power supply voltage stability

Voltage Test Example

The stability of the power supply is closely related to whether the power supply is stable. Just like the current mentioned above, the voltage determines whether the hardware powered by the power supply is stable. In our test specifications, we will test the voltage of 3.3V, 5V, and 12V under 10% to 100% load. The final result will appear in the form of a chart. From the above figure, we can see that the 5V exceeds the limit range of 5.25 and the lower limit of 4.75. If it does not exceed, it means that the voltage stability test of this power supply has passed.

Fifth: The quality of power ripple is like the spectrum of sound

● Introduction to power supply output ripple

Ideally, the DC voltage output by the power supply should be a fixed value, but in many cases it is obtained by rectifying and filtering the AC voltage, and there will be more or less residual AC components. This kind of noise signal containing periodic and random components is called ripple. Large ripple will affect the normal operation of the CPU and GPU, and the smaller this value is, the better.

● Criteria for determining ripple

Intel stipulates in the ATX12V 2.31 specification that the +12V output ripple shall not exceed 120 mV, and the +3.3V and +5V ripples shall not exceed 50 mV. This amount is very generous for most brands of power supplies. The vast majority of power supplies I have tested will not exceed this value, but almost all copycat power supplies will exceed the ripple standard when fully loaded, and the internal material design can be imagined.

In fact, we can completely link the ripple pattern of the power supply with the spectrum of sound. When the sound vibration frequency is very high, the sound spectrum will often be messy or even have obvious deviations from the highs and lows. This is relatively the same as the performance of the power supply ripple.

Intel ATX12V 2.31 regulations on power ripple

● PBzone output ripple test setting

The ripple value of each output load of the power supply is closely related to the current value of that output. Generally, the ripple of the power supply will never exceed the standard under light load, so we recorded the ripple under three conditions: 100% load, +12V combined output full load, +3.3V output full load, +5V output full load. When testing the three outputs at full load, we set one of them to full load according to the nameplate nominal load, and the current of the other two is set to 2A.

Digital oscilloscope used to test ripple

The ripple test results are not difficult to understand. The two pictures above are screenshots of high frequency and low frequency respectively. The sum of the two ripple values ​​is the final result. Please click on a picture to enlarge it. You will find that there are two values ​​in the bottom row of the picture, the vertical division value is 20.0mV, and the horizontal division value is 10.0us. We only need to pay attention to the value of mV. 20.0mV means that each grid of the Y-axis grid is equal to 20mV. The peak and trough of the first picture are separated by about one grid, which means that the peak-to-peak value of the high-frequency ripple of 10.0us is about 20mV*1=20mV. In addition, we should also pay attention to the 10.0ms representing the low frequency, that is, the right picture. The peak-to-peak value of the high-frequency ripple after removing the burrs in the right picture is about 1 grid, that is, 20.0mV. The sum of high frequency and low frequency is the ripple value of the output of this channel. The sum of the two is 40mV, which is much less than the 120mV specified by Intel, so the test result can be said to be very excellent.

Sixth: Change efficiency test settings power supply to save money analysis

● Two parameters affect energy saving

Both power factor and conversion efficiency can affect energy saving. Simply put, power factor determines the power supply's utilization rate of AC power, and conversion efficiency determines how much energy can actually be used by the hardware. The former can reduce the burden on the power grid, and the latter truly saves energy for users.

Why is conversion efficiency important? Assuming that the conversion efficiency of power supply A is 75%, the conversion efficiency of power supply B is 85%, and the rated power of both power supplies is 450W, and they are fully loaded for 5 hours every day, the power saving of power supply B in one year is: [(450÷75%)-(450÷85%)]×5×365÷1000=128.8 kWh. The national electricity fee is 0.52 yuan/kWh, and power supply B can save 67 yuan per year! The 3-year warranty period of the power supply is 201 yuan. In fact, it is not just money, the conversion efficiency will also affect the quietness and service life.

● 80% is the passing efficiency standard

We follow the 80Plus certification standard to determine the quality of power conversion efficiency and power factor. For users who are not familiar with the domestic power supply market, please read this article: How many watts is worth buying for one dollar? Analysis of the domestic power supply market; for users who are interested in 80Plus, please read this article: Analysis of the 80Plus power supply market structure.

80Plus Certification Standard

80Plus is an energy-saving standard advocated by the two American organizations, Ecos and EPRI. It stipulates the power conversion efficiency of desktop computers and servers when the output power is 20%, 50%, and 100% of the rated power. It is divided into white label, bronze, silver, and gold certifications.

● PBzone power conversion efficiency test settings

In the PBzone power supply test, we divide the rated power of the power supply into ten loads from 10% to 100%, and record the conversion efficiency under the ten loads. When dividing the load to each output, by default, we set the +12V combined output power to 85%, and 15% to +3.3V, +5V, and +5VSB. If the +12V combined output of the power supply cannot reach 85% of the rated power, it will be allocated according to the ratio of +12V combined output to +3.3V&5V combined output.

Quietness and heat dissipation test the most luxurious attributes of power supply

● The cost of achieving both heat dissipation and quietness is high

The quietness and heat dissipation of the power supply actually depend on the fan speed. The lower the fan speed, the quieter it is, but the worse the heat dissipation performance; the higher the fan speed, the higher the noise, and the better the heat dissipation performance. When setting the fan speed, the manufacturer first considers the heat dissipation problem, because heat dissipation is related to the life of the power supply. High temperature will sharply reduce the life of the power supply, and the promised 3-year warranty period may not be achieved. Therefore, the fan speed of the general power supply is relatively high, and the noise is generally high.

How is a silent power supply designed? First of all, the conversion efficiency must be high enough. Assuming that the conversion efficiency of a 500-watt power supply is 80%, it means that 100 watts of electrical energy will be converted into heat. If the conversion efficiency is 90%, only 50 watts of energy will be converted into heat, and the heat dissipation workload will be reduced by half! The fan speed can naturally be placed at a lower level, and silence will follow.

Furthermore, the silent power supply must use high temperature resistant components inside. Only by using components with higher temperature resistant values ​​can the power supply dare to ignore slightly higher temperatures and boldly lower the fan speed, but this approach will bring certain costs.

● PBzone heat dissipation and silent test

We are unable to test the noise level for the time being and can only record the power supply fan speed to represent the quietness of the power supply under various loads.

When testing the fan speed, we record the speed under ten loads from 10% to 100%, using a photoelectric tachometer. When testing the temperature, we place the thermistor head of the multimeter at the hottest spot where the air flows out from behind the power supply, and also record the temperature under ten loads.

Silent power supplies on the market are very rare, because high-efficiency power supplies are relatively rare, and there are even fewer who dare to sacrifice life in exchange for silent effects. Therefore, real silent power supplies often have a conversion efficiency of 80Plus Bronze or above, and are high-end products that use excellent components inside.

Power cable specifications and full text summary outlook

It is difficult to unify the power cable specifications and internal material analysis into a standardized testing standard. We list the common practices below:

● Power cable test settings

There are three properties of power cables: interface specifications, wiring length, and cable material. We will make a chart of the cable length and interface according to the purpose, and the cable material will be explained with photos.

Wiring material description

● Analysis of internal materials used in power supply

The analysis of the materials used in the power supply is still described in four parts: EMI filtering, high-voltage filtering, transformer area, and low-voltage filtering.

Internal material design

The strength of the internal design of the power supply can actually be reflected in the conversion efficiency, voltage stability, and ripple mentioned above, but the internal materials can also tell us something else. For example, the margin of power supply materials can reflect the quality and lifespan, and the workmanship details can reflect the craftsmanship level.

PBzone's philosophy is openness and professionalism

The purpose of the PBzone test specification is not to conflict with 80Plus. In fact, 80Plus is positioned on efficiency specifications and will only release power supply test data that meets the requirements. PBzone is different. We will test any power supply products that domestic consumers may come into contact with. We do not rule out not filtering, just to use test data to restore the internal structure of a power supply.

The PBzone test specification is based on our understanding of the power supply industry. In an environment where 90% of DIYers only know rated power and conversion efficiency, popularizing and disseminating power supply common sense is the only valuable thing, and graphical and intuitive test data is the best way for ordinary users to understand power supplies. PBzone not only sets standards, we are more focused on making everything about power supplies clear.