The poor performance of certain parameters of the switching power supply may cause EMC to be difficult to pass, standby power consumption is large, and efficiency is not high. How to reduce standby power consumption of switching power supplies and improve the efficiency of switching power supplies is a common concern of the global power supply industry. This article describes the green switching power supply design points. With the development of modern science and technology, the performance of devices has increased, especially energy-efficient power chips have mushroomed. With the mature circuit design, it is not difficult to design energy-saving switching power supplies with high efficiency and low standby power consumption. The matter is that the design of energy-saving switching power supply is to meet the needs of energy-saving emission reduction. In recent years, the implementation of the US Energy Star has played a role in the design and manufacture of high-performance energy-saving switching power supplies. ENERGY STAR-compliant switching power supply is also called green switching power supply. There are several versions of the energy star for switching power supply. With the upgrade of the version, the switching power supply is becoming more and more efficient, and the standby power consumption is getting smaller and smaller. However, the design will be more and more difficult. The efficiency of switching power supply is generally tested at full load output power, but the average efficiency of the design in the CEC (California, USA) and Energy Star specifications is actually measured at the four test points of the load. The four points are: 25%. 50%, 75% and 10%, design is difficult. I now use the circuit diagram of Figure 1 as an example to illustrate the key points of designing a green switching power supply based on the design basis of the U.S. California Energy Star Act (IV level) Table U-2 (implemented in January 2008). The requirements of Table U-2 of the California Energy Star Act (IV level) are as follows: Note 1: In the table, Pn is the standard output power of the external switching power supply, and Ln is the natural logarithm. Note 2: The California Energy Star is enforced and is a California local law. Commodity switching power supplies entering California must comply with this regulation. Many manufacturers in China are designing and producing green switching power supplies according to the California Energy Star Act. Figure 1 shows a parallel-type flyback switching power supply with an output of 12V3A, which is used as a power adapter for 14-inch to 17-inch liquid crystal displays. Green switch power design points The main content of the green switching power supply is high efficiency and low standby power consumption. The efficiency requirement of 36W is greater than 83%, and the standby power consumption is less than 0.5W. Nowadays, power supply chip suppliers generally provide green power chips, and the standby power consumption will generally be very small. However, in addition to the high efficiency of the chip, but also with other devices with current + reverse leakage current Idss × back pressure, with 6N60 plus heat sink to meet the requirements. The secondary rectifier works under high frequency pulse conditions. When outputting at 12V3A, the working voltage is required to be 4 times higher than the output voltage, the working current is more than 3 times of the output current, and the working voltage is 60V and the operating current is 16A. The base diode meets the requirements, but radiators must be added. The smaller the power consumption of the power chip is, the better, because it affects the overall machine's working stability in addition to the overall machine efficiency and standby power consumption. The higher the power consumption, the higher the temperature rise and the more unstable the work. Such as the company's green switching power supply chip 0B2269AP, its normal operating power consumption is less than 30mW, stable operation. The loss of the switching transformer is the bulk of the total loss. It includes copper loss and magnetic loss. Simply copying people's high-quality switching transformers is difficult to make into small lossy switching transformers, because the loss of the switching transformers is a complex relationship, which is related to the core's quality, design, and winding process. Take the design of the flyback switching transformer, it is related to the working frequency, conduction time, winding method, magnetic gap (magnetic core) and so on. The design of the switching transformer is the core of designing the switching power supply. With profound theoretical knowledge and years of experience precipitation, excellent switching power supply design engineers are able to design high efficiency magnetic cores in combination with advanced winding technology. 97% of switching transformers. The core of the switching transformer in Figure 1 is selected from Zhejiang Tiantong's EE-30L, the switching frequency is 65KHz, the conduction time is 0.42T (T is the cycle), the primary 78 turns, the secondary 8 turns, and the chip power supply winding 9 turns The primary inductance is 1.2mH, the leakage inductance is less than 35uH, the efficiency of the transformer can reach 96%, and the temperature rise during operation is lower than 60°C. Damping absorption network consists of R2, C3, D1, D1 with UF4007, C3 with 1000V4700PF high-voltage ceramic capacitors, R2 is 120K2W resistance, R2 and C3 fit well, pulse absorption effect is obvious, R2 and C3 mismatch too much, Not only does the loss increase, but it also radiates electromagnetic waves that make EMC impossible to pass. After testing, the loss of the network is less than 0.4 W. It should be noted that the design of the network is related to the design of the power chip, the operating frequency, and the transformer, and cannot be applied to all the circuits of the switching power supply. Because the secondary rectifier will produce sharp pulses during operation, clutter will be superimposed on the output, and it will also radiate electromagnetic waves to make EMC difficult to pass. Therefore, it is necessary to connect the R8 and C8 pulses at the two ends of the diode in parallel, as shown in Figure 1. C8 is a ceramic capacitor of 22000 PF100V and R8 is a 56 ohm 0.5 W carbon film resistor. This absorption network also has a certain power consumption. The larger the C8 is, the smaller the R8 is, and the greater the loss is. The power loss of the first-pulse pulse-absorbing network is less than 0.25 W. It should also be noted that the design of the absorption network is also related to the power chip, the switching frequency, the characteristics of the Schottky diode, and the design of the transformer. The wave-blocking inductance L2 can reduce the output ripple, which is usually 8 to 16 turns on a 6-mm thick magnet bar with an enameled wire. It should be noted that due to the large current, the enameled wire should be thick and the number of turns should not be too large, so as to avoid excessive pressure drop and increase the loss. The inductance of L2 in Fig. 1 is 12uH, and it is wound with a 0.8 mm thick enameled wire. As for the number of turns, it depends on the magnetic material parameters of the magnetic bar. The design of L2 is related to the operating frequency and output current of the power supply. In particular, it is important to note that the DC output line (not shown in the figure) must meet or exceed 3A, otherwise, due to the large current passing through, the power loss that may be generated on the DC output line is the largest. The price of the DC output line in the power adapter is relatively large, and many manufacturers will reduce their ampacity to reduce the cost. As a result, the efficiency cannot be guaranteed. According to the design of the circuit parameters of a flyback switching power supply, in the domestic standard input voltage (220V50Hz sinusoidal alternating current), in the output power of 25% test, the output ripple is 45mVpp, the efficiency is 83.4%; in the output power In 50% test, the output ripple is 48mVpp, the efficiency is 83.8%; in the 75% output power test, the output ripple is 53mVpp, the efficiency is 84.5%; In the full load output power test, the output ripple is 58mVpp, The efficiency is 84.8%. The standby power consumption is less than 0.4W. It complies with the requirements of the green switch of the CEC (California, USA) Energy Star Act Table U-2 (executed in January 2008). Switching power supply design engineers must have deep theoretical knowledge, rich design experience, and attention to design details to meet the design requirements of the California Energy Star Act IV. However, the green switching power supply that meets the ENERGY STAR is not necessarily a good-quality power supply, but also requires other parameters to be met. The green switching power supply only increases the parameters related to energy efficiency on the original switching power supply parameters. With the demand for low-carbon life, the energy efficiency requirements of switching power supplies will become higher and higher, and the design of switching power supplies will become more and more difficult. This requires switching power supply design engineers to constantly update their knowledge, familiarize themselves with new materials, and learn new technologies. In order to master the new process and improve the technology, we can design a high-quality green switching power supply. Cellular Tower ,Portable Cell Tower,Mobile Cell Tower,Vehicle Mounted Light Tower TIANHEMAST , https://www.robomasts.com