Power adapter, also known as external power supply, is the power supply voltage conversion equipment of small portable electronic equipment and electronic appliances. It is common in small electronic products such as mobile phones, liquid crystal displays and laptops.
The power supply circuit of LCD generally adopts the switching circuit mode. This power supply circuit changes the AC 220V input voltage into DC voltage through the rectifier and filter circuit, and then the high-frequency rectangular wave voltage is obtained by switching tube chopping and high-frequency transformer step-down. Finally, the DC voltage required by each module of LCD is output after rectification and filtering.
There is a nameplate on the power adapter, which indicates the indicators such as power, input and output voltage and current. Pay special attention to the range of input voltage. This is the so-called "travel power adapter". This feature is very useful if you go to a country where the mains voltage is only 110V. Some parallel laptops are only sold in the country of origin. There is no such compatible voltage design, or even a single input voltage of 110V, It will burn out if it is plugged in under the 220V mains voltage in China
What does the nominal voltage and current of the power adapter (hereinafter referred to as the power supply) mean? First of all, the nominal voltage of the general power supply refers to the open circuit output voltage, that is, the voltage when there is no load and no current output, so it can also be understood that this voltage is the upper limit of the power supply output voltage.
When active voltage stabilizing elements are used inside the power supply, even if the mains voltage fluctuates, its output is also a constant value. For the power supply equipped with small transformers on the market, such as Walkman, if the mains power fluctuates, the output of the power supply will not fluctuate.
Generally speaking, the real no-load voltage of ordinary power adapter is not necessarily completely consistent with the nominal voltage, because the characteristics of electronic components cannot be completely consistent, so there is a certain error. The smaller the error, the higher the consistency requirements of electronic components, the higher the production cost, so the price is more expensive.
In addition, with regard to the nominal current value, no matter what power supply has a certain internal resistance, when the power supply outputs current, there will be a voltage drop inside, resulting in two things: one is to generate heat, so the power supply will be hot, and the other is to reduce the output voltage, which is equivalent to internal consumption.
Solution: give the formula ICs = 0.2V (0.18v) ÷ (NP * RC5) on site
As a domestic power adapter IC, it can be compatible with the power adapter IC of most similar manufacturers on the market and use domestic power adapter IC. The display power adapter produced has the following advantages over others
1. Small size and light weight. Switching power adapter does not use bulky power frequency transformer. Because the dissipation power on the switching MOS tube is greatly reduced, a large heat sink is omitted. Due to these two reasons, the switching power adapter has small volume and light weight.
2. Low power consumption and high efficiency. In the switching power supply adapter circuit, under the excitation of the excitation signal, the switching MOS tube works alternately in the on-off and off-on switching states. The conversion speed is very fast, and the frequency is generally more than 50KHz. In some advanced switching power supply lines, it can achieve hundreds or nearly megahertz. This makes the power consumption of switching MOS transistor very small, and the efficiency of power supply can be greatly improved, and its efficiency can reach 90%.
3. The efficiency of filtering is greatly improved, and the capacity and volume of filtering capacitor are greatly reduced. At present, the working frequency of switching power supply adapter is basically above 50KHz, which is more than 1000 times that of linear regulated power supply adapter, which almost improves the filtering efficiency after rectification by 1000 times; Even if half wave rectification is adopted and capacitor filtering is added, the efficiency is improved by 500 times. Under the same ripple output voltage, when switching power supply is used, the capacity of filter capacitor is only 1 / 500 ~ 1 / 1000 of that in linear regulated power supply.
4. Wide voltage stabilizing range. The output voltage of the switching power adapter is adjusted by the duty cycle of the excitation signal, and the change of the input signal voltage can be compensated by frequency modulation or width modulation. In this way, when the power frequency power grid voltage changes greatly, it can still ensure a more stable output voltage. Therefore, the voltage stabilizing range of switching power adapter is very wide and the voltage stabilizing effect is very good. In addition, there are two methods to change the duty cycle: pulse width modulation and frequency modulation. The voltage stabilizing method can be selected flexibly according to various types of switching power supply, and has the advantages of wide switching power supply design requirements
