The hottest switching power supply and UPS revolut

2022-08-21
  • Detail

Switching power supply and UPS revolution

Abstract: the user equipment of UPS is mostly computers and their peripherals. The vast majority of these devices use switching regulated power supply, so AC power supply is no longer necessary, but DC power supply can also eliminate harmonic interference and increase the safety and reliability of data processing and transmission. Inverter free UPS eliminates the inverter in the traditional ups and realizes DC power supply for user equipment. While retaining all external characteristics, other technical performances are also greatly improved, and the cost, volume, weight and power consumption are also reduced to less than 5% of the traditional ups with the same power. The whole machine has no interference with the mains power, the power factor at the input is equal to 1, and the total harmonic distortion thd is equal to zero

key words: switching power supply; UPS revolution; Inverter free UPS

Introduction

the mains power is not stable. It has many power quality problems, such as voltage surge, high voltage sharp pulse, transient overvoltage, voltage sag, line noise, frequency offset, continuous low voltage, power supply interruption, etc. These quality problems can not only cause relatively minor adverse effects such as keyboard locking and hardware aging of the computer, but also cause major accidents such as complete loss of data or burning of the motherboard. Therefore, the computer must be powered by UPS. UPS can improve the power supply quality of municipal power supply and protect the stable and reliable operation of computers

ups is an uninterruptible power supply specially designed for computers. UPS cannot be separated from computers, and computers cannot be separated from UPS. With the wide application of computers, UPS has also been widely used

UPS can be divided into AC UPS and DC UPS according to the different output voltage waveforms. For DC electrical loads such as computers and communication systems, DC UPS has more prominent advantages than AC UPS in terms of power supply reliability, safety and operation efficiency, such as simple circuit, few components, low cost, low power consumption, small volume and weight, high reliability, simple expansion Easy to manufacture and maintain. However, DC UPS also has some disadvantages, such as unable to supply power to the linear regulated power supply through the power frequency transformer, unable to carry AC. many enterprises have not been able to skillfully apply its current load after purchasing the impact testing machine, it is difficult to stabilize the output high-power DC voltage, it is difficult to change the DC voltage, and the isolation between the mains power and the load cannot be achieved. Although DC UPS has more advantages than AC UPS, due to historical reasons and the influence of traditional concepts, AC UPS is still widely used at present. With the increase of juice computer application fields, each field has its own unique characteristics, so the requirements for AC UPS are also different. As a public equipment, AC UPS must have all these functions: at the same time, even for the same field, Due to the needs of continuous development, there are more and more functional requirements for UPS, which makes the circuit of AC UPS more and more complex, more and more components are used, the cost is larger and larger, the maintenance is more and more complex, the volume is larger and larger, and the reliability is worse and worse. In order to improve the reliability of UPS, it is necessary to add various protection circuits or adopt redundant parallel working mode. This snowball development mode leads to the difficulty of production and maintenance technology of AC UPS and the increase of price index. This makes it difficult for ordinary small and medium-sized users to bear, and seriously affects the further promotion and application of AC UPS. When this contradiction develops to a certain extent, it will inevitably trigger a UPS revolution

1 structural characteristics and existing problems of the current UPS

the structural form of the current UPS circuit was determined by the early stage of UPS development in the 1970s. At that time, computers used linear power supply based on power frequency transformer. At the same time, due to the existence of AC motor load, the main purpose of early UPS was to keep power frequency AC uninterrupted. In order to achieve this purpose, inverter must be carried out from the perspective of foreign scientific research level, so inverter has become the core component of ups. The improvement of UPS performance and function is concentrated on the inverter, so everyone makes a big fuss about the inverter, making the inverter the most complex circuit, the most complex process, the most used components, the most stringent requirements, the most difficult to design and manufacture. The largest and most expensive component in UPS, which accounts for more than 90% of the cost, volume, weight and power consumption of the whole UPS, has become a UPS Technology The difficulties of function and manufacturing and maintenance are also the places with the most UPS failures and the worst reliability. Therefore, the ups revolution naturally should be started from the inverter. That is to say, to cancel the inverter is the most thorough revolution for UPS. However, it is not easy to get rid of the inverter before the popularity of switching power supply. There are three difficulties that cannot be solved: first, the DC voltage cannot transmit electric energy to the linear regulated power supply through the power frequency transformer, that is, it cannot realize uninterrupted power supply; Second, it is difficult to stabilize high-power DC voltage, and it is difficult to adopt DC voltage transformation for a variety of low-voltage DC power supplies of computers; Third, it is difficult to isolate electricity from computers

The emergence and wide application of high-frequency switching power supply have created conditions for solving the above three difficulties. The high-frequency switching power supply sprouted in the 1950s, and completed the 20 kHz PWM switching power supply prototype in the 1970s, which is known as the "20 kHz revolution", which is a huge leap in the development history of DC regulated power supply. By the 20th century, the technology of high-frequency switching power supply has been very mature and has been widely used, especially in computer power supply, which has created conditions for UPS to cancel the inverter, because it solves the problems of voltage stabilization and transformation of DC battery voltage and the isolation between mains power and computer

in order to reduce the line voltage drop at low voltage and high current, reduce the influence range of power failure, and improve the reliability of power supply, high-frequency switching power supplies are generally installed in small computers. The specific circuits of these switching power supplies may be different, but their basic structure and components are roughly the same. At present, ATX power supply has replaced the early at power supply in computers, and its principle circuit is shown in Figure L. It is mainly composed of three circuits: anti-interference filter, mains side rectifier and smooth filter, and DC/DC converter composed of high-frequency inverter, high-frequency transformer isolation, high-frequency rectifier, high-frequency filter and control circuit. The output low-voltage DC voltage is ± 12V, ± 5V, 3.3 V, which is used for the internal circuit of the computer. Generally, the allowable input voltage range of high-frequency switching power supply is 165 ~ 275 V AC power frequency, 233.4 ~ 388.9 V DC, and the output voltage accuracy is 0.6 ~ 1%

according to the principle block diagram shown in Figure 1, the three functions of ATX switching power supply are very useful for canceling the inverter in UPS: first, it can input power frequency AC voltage or 2334 ~ 388.9v DC voltage to keep the DC output voltage basically unchanged; Second, the DC/DC converter in ATX has the functions of DC voltage stabilization and transformation; Third, the transformer in the high-frequency transformer isolator has the function of isolation. These three functions meet the requirements of the computer for UPS, and realize the AC/DC compatibility of the computer input power supply, so that the computer no longer has to input 220 V power frequency voltage

2 reform scheme and working principle of UPS

as mentioned above, inverter is the core component that determines the performance and quality of traditional AC UPS. The purpose of the ups revolution is to remove the inverter to reduce the cost of UPS, improve efficiency, reduce production difficulty, reduce volume and weight, simplify operation and maintenance, reduce failure rate, and improve reliability. Therefore, the inverter free UPS without inverter will be a better new UPS scheme

the principle circuit of a single-phase AC UPS supplying power to a computer is shown in Figure 2. The circuit shown in the dotted box on the left in Figure 2 is a traditional AC UPS, which includes rectifier, battery and inverter; The circuit shown in the dotted box on the right in Figure 2 is the ATX power supply in the computer, which includes anti-interference circuit, rectifier and filter circuit on the mains side and DC/DC conversion circuit

in the traditional AC UPS circuit on the left side of Figure 2, the mains 220 V AC voltage is rectified into +300v to float charge the battery through the bridge rectifier with no rise and step-down function, and the +300v DC voltage on the battery is then inverted into 220 V power frequency AC voltage through the inverter to supply power to the computer. In the ATX switching power supply of juice computing machine on the right side of Figure 2, the "rectifier and filter circuit on the mains side" rectifies the 220 V power frequency AC voltage into +300 V DC voltage, and then the DC/DC converter in ATX converts the +300 V DC voltage into ± 12 V, ± 5V and 3.3 V DC voltage to supply power to the computer. From Figure 2, it can be seen that the DC voltage output by the rectifier in the ups on the left, The output voltage of the "mains side rectifier filter circuit" in the right ATX is +300 V, which is the same. This shows that it is unnecessary for the inverter to reverse the battery voltage +300v to 220V power frequency. Therefore, the inverter in the ups can be removed, and the +300v DC voltage of the battery can be directly supplied to the computer through the "mains side rectifier filter circuit" of ATX in the juice computer, as shown in Figure 3. To achieve this, the rectifier in LPS must adopt direct rectification without any voltage rise and fall function

after removing the inverter from the power supply circuit shown in Figure 2 or even a piece of paper that is difficult to find, it becomes the circuit that the inverter free UPS supplies power to the computer as shown in Figure 4. At this time, the inverter free UPS is equivalent to a DC UPS with AC bypass. At this time, the working mode of UPS is that the DC UPS composed of mains power, rectifier and battery supplies uninterrupted power to the computer through the static switch 2. When the DC UPS needs maintenance or fails, the mains power supplies power to the computer through the bypass switch (static switch 1)

compared with figure 2 and Figure 4, the ups circuit is greatly simplified after removing the inverter, leaving r rectifier, battery and static switch. At this time, static switch 2 becomes a DC switch with only one SCR

the three-phase inverter free UPS circuit composed of the single-phase inverter free UPS circuit shown on the left side of Figure 4 is shown in Figure 5. There are two common methods for measuring the extreme pressure performance of the lubricating fluid friction and wear tester of Jinan new era Gold Testing Instrument Co., Ltd., and its working principle and working mode are the same as the single-phase circuit shown in Figure 4

3 two working modes of inverter free ups

there are two working modes of inverter free UPS: one is backup working mode, the other is mode working mode

3.1 backup working mode

the principle circuit of single-phase inverter free UPS supplying power to the computer is shown in Figure 4. When working in the backup mode, when the mains power is interrupted or restored, as the ATX switching power supply in the backup UPS load, the waveforms of the output voltage uh and current IR of the "mains side rectifier filter circuit" are shown in Figure 6. In Figure 6, T1 was powered by mains power before; The mains power is cut off at T1; During T1 ~ T2, the energy storage capacitor inside the ATX switching power supply discharges to maintain the operation of the computer; T2 is powered by the battery in UPS at all times; The mains power is restored at T3

3.2 working mode

as shown in Figure 4, for the working mode, when the UPS is in the mains bypass power supply state (such as when repairing the rectifier or battery) and then resuming the DC power supply, the voltage ur at the output end of the "mains side rectifier filter circuit" of the ATX switching power supply as the ups load

Copyright © 2011 JIN SHI