The key points of green switching power supply design

It is of great potential to reduce the standby power consumption and improve the efficiency of switching power supply. With the development of modern science and technology, improve the performance of the device, especially energy-saving power chips such as bamboo shoots after a spring rain emerged, and the circuit design of the mature energy-saving switching power supply design with high efficiency and small power consumption is not too difficult, the design of energy-saving switch power supply is to adapt to the demand of energy saving.

In recent years, the United States early switching power supply due to the technology is not mature, the limitations of device performance, some of the parameters do not seem like EMC sad off, standby power consumption, efficiency is not high. For example, the early 36W power adapter standby power consumption has more than 2W, efficiency of about 78%; early computer power standby power consumption of 3 ~ 5W, efficiency of about 72%.

However, it is of great potential to reduce the standby power consumption and improve the efficiency of switching power supply. With the development of modern science and technology, improve the performance of the device, especially energy-saving power chips such as bamboo shoots after a spring rain emerged, and the circuit design of the mature energy-saving switching power supply design with high efficiency and small power consumption is not too difficult, the design of energy-saving switch power supply is to adapt to the demand of energy saving.

In recent years, the implementation of the "Energy Star" in the United States has played an important role in the design and manufacture of high-performance energy-saving switching power supply. In accordance with the "switching power supply energy star" is also called "green switching power supply, switching power supply for the" Energy Star "has multiple versions, along with the upgrade version, more and more high efficiency switching power supply, standby power consumption is more and more small, but the difficulty of the design will be more and more.

The efficiency of switching power supply in full output power test, but the CEC (California) and the "Energy Star" in the specification for the design of the average efficiency is measured in four test points of the load, the four points are: 25%, 50%, 75% and 100%, there is a certain degree of difficulty of the design. Special note: this site reproduced all the comments do not represent the views of this site, such as the need for related products, please contact the site, the copyright belongs to the original author.

I now plan to a circuit diagram, for example, the United States, California Energy Star Act (level IV) TableU-2 (January 2008 implementation) as the basis for the design of green switching power supply design points.

The requirements of the California Energy Star Act (level IV) TableU-2 are as follows: Note 1: table Pn is the standard output power of the external switching power supply, Ln is a natural logarithm.

Note 2: California, "Energy Star" is mandatory, the United States California local regulations. Commodity switching power supply in California must comply with this regulation. Many manufacturers in China are in accordance with the United States, California, "Energy Star" bill to design and production of green switching power supply.

Figure 1 shows the output of the 12V3A parallel flyback switching power supply, as a 14 - to 17 inch LCD power adapter. The main content of green switching power supply is high efficiency, low standby power consumption. The efficiency requirement of 36W is greater than 83%, and the standby power consumption is less than 0.5W.

Now the power supply chip suppliers are generally green power chip, standby power consumption will generally be small. However, in addition to the high efficiency related to the chip, but also with other devices have flow + reverse leakage current Idss * back pressure, with 6N60 and radiator can meet the requirements.

Two rectifier tube in high frequency pulse condition in 12V3A when the output is 4 times the working pressure is greater than the output voltage, the output current is greater than 3 times the working current, working with voltage 60V, current 16A SB1660 Schottky diode can meet the requirements, but must add the radiator.

Power supply chip is as small as possible, because it not only affects the efficiency and stability of the standby power consumption, also relates to the whole machine, the greater the power consumption, high working temperature rise, the more unstable.

If the company's green switching power supply chip 0B2269AP, its normal operating power consumption is less than 30mW, stable. The loss of the switching transformer is the head of the whole machine, which includes copper loss and magnetic loss. It is very difficult to make the transformer with high quality and easy to make the transformer with small loss, because the loss of the transformer is a complicated relation. For the design of flyback transformer, it is related to the working frequency, the turn-on time, the winding method, the magnetic gap (grinding core) and so on.

Switch transformer design is the core design of switching power supply, have profound theoretical knowledge and years of experience in precipitation, switching power supply design engineers in the core, choose the combination of high-quality winding technology advanced, can design a switch transformer efficiency higher than 97%.

The transformer core switch in Figure 1 the selection of Zhejiang day EE-30L, the switch frequency is 65KHz, the turn-on time is 0.042T (T cycle), the primary secondary 78 laps, 8 laps, 9 chip power supply winding circle, primary inductance 1.2mH, leakage inductance of the transformer is less than 35uH, the work efficiency is up to 96%. The temperature is below 60 DEG C.

The damping absorption network composed of R2, C3, D1, D1 UF4007, C3 high voltage ceramic capacitor 1000V4700PF, R2 120K2W and C3 R2 resistance, with good, pulse absorption effect, R2 and C3 mismatch too much, not only will increase the loss, electromagnetic radiation and EMC guobuleguan.

After testing, the network loss is less than 0.4W. It should be noted that the design of the network is related to the power supply chip, operating frequency, transformer design, can not be applied to all switching power supply circuit.

Because the two rectifier tube at work will produce a spike in the output will overlay the clutter, and will radiate electromagnetic waves and make the EMC sad, so in parallel at both ends of the diode sharp pulse absorption network of R8 and C8, in Figure 1 C8 R8 22000PF100V for ceramic capacitors, carbon film resistor of 56 ohms 0.5W and this is also a certain power absorption network, C8 R8 is smaller, the greater the loss.

Fig. the power loss of the pulse absorbing network is less than 0.25W. It is also important to note that the design of the absorption network is related to the power supply chip, the switching frequency, the characteristics of the Schottky diode, and the design of the transformer. Wave resistance inductance L2 can make the output ripple, is wrapped around the 8 to 16 laps in the 6 mm thick magnetic line paint. It should be noted that, due to the high current, so the enameled wire to be thick, not too many laps, so as to avoid excessive pressure loss and increase the loss.

The inductance L2 in Figure 1 is 12uH, wrapped around the wire with 0.8 mm thick paint, as for the number of laps around, magnetic materials and magnetic parameters should be considered. The design of L2 is related to the working frequency and output current of the power supply. Special note is that the DC output line (not drawn in the picture) must reach or exceed 3A, otherwise, due to the current through the large, may be generated in the DC output line power loss is the largest.

DC output line in the power adapter in a larger proportion of the price, many manufacturers to reduce their carrying capacity and reduce costs, the results will not be guaranteed efficiency. I follow the flyback switching power supply diagram of circuit parameter design, in the domestic standard input voltage (220V50Hz AC), the output power of the 25% tests, the output ripple is 45mVpp, the efficiency is 83.4%; in the 50% test output power, output ripple is 48mVpp, the efficiency is 83.8%; the output power the 75% test, the output ripple is 53mVpp, the efficiency is 84.5%; in full power output test, the output ripple is 58mVpp, the efficiency is 84.8%. standby power consumption is less than 0.4W.

Comply with the requirements of the CEC (California) Energy Star act TableU-2 (January 2008 implementation) green switch. Switching power supply design engineer must have a strong theoretical foundation and rich experience in design and attention to design details to achieve the design requirements of the United States, California Energy Star rating.

However, in line with the "green switch power supply energy star is not high quality power, also requires other parameters with green switch power supply only in switching power supply parameters on the original improved parameter standard about energy efficiency.

People with low carbon life demand, switching power supply efficiency will become increasingly high, the difficulty of the design of switching power supply will be more and more, which requires the design of switching power supply engineers constantly update their knowledge, familiar with the new material, learning new skills, master the new technology, for technical excellence, so that we can design the green switch power quality.

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