【導讀】空氣凈化器，電子冰箱，液晶顯示器，LED燈具，通訊設備，視聽產品，安防，電腦機箱，數碼產品和儀器類等領域。都已廣泛地使用了開關電源，更促進了開關電源技術的迅速發(fā)展。IC和開關器件構成。開關電源和線性電源相比，二者的成本。都隨著輸出功率的增加而增長，但二者增長速率各異。小型化、輕便化。另外開關電源的發(fā)展與應用在節(jié)約能源、節(jié)約資源及保護環(huán)境。方面都具有重要的意義?，F代開關電源有兩種：一種是直流開關電源；另一種是交流開關電源。主要介紹的只是直流開關電源，其功能是將電能質量較差的原生態(tài)電源（粗電），如市電電源或蓄電池電源，轉換成滿足設備要求的質量較高的直流電壓（精電）。也就是說，直流開關電源的分類與DC/DC轉換器的分類是基本相。隔離式DC/DC轉換器也可以按有源功率器件的個數來分類。轉換器有正激式和反激式兩種。四管DC/DC轉換器就是全橋DC/DC轉換器

　　

【正文】 ade a 25kHz switching power supply. At present, the switching power supply to the small, lightweight and high efficiency characteristics are widely used in a variety of puteroriented terminal equipment, munications equipment, etc. Almost all electronic equipment is indispensable for a rapid development of today39。s electronic information industry power mode. Bipolar transistor made of 100kHz, 500kHz power MOSFET made, though already the practical switching power supply is currently available on the market, but its frequency to be further improved. To improve the switching frequency, it is necessary to reduce the switching losses, and to reduce the switching losses, the need for highspeed switch ponents. However, the switching speed will be affected by the distribution of the charge stored in the inductance and capacitance, or 17 diode circuit to produce a surge or noise. This will not only affect the surrounding electronic equipment, but also greatly reduce the reliability of the power supply itself. Which, in order to prevent the switching Kai closed the voltage surge, RC or LC buffers can be used, and the current surge can be caused by the diode stored charge of amorphous and other core made of magic buffer . However, the high frequency more than 1MHz, the resonant circuit to make the switch on the voltage or current through the switch was a sine wave, which can reduce switching losses, but also to control the occurrence of surges. This switch is called the resonant switch. Of this switching power supply is active, you can, in theory, because in this way do not need to greatly improve the switching speed of the switching losses reduced to zero, and the noise is expected to bee one of the highfrequency switching power supply The main ways. At present, many countries in the world are mitted to several trillion Hz converter utility. the principle of Introduction The switching power supply of the process is quite easy to understand, linear power supplies, power transistors operating in the linear mode and linear power, the PWM switching power supply to the power transistor turns on and off state, in both states, on the power transistor V security product is very small (conduction, low voltage, large current。 shutdown, voltage, current) Voltammetric product / power device is power semiconductor devices on the loss. Compared with the linear power supply, the PWM switching power supply more efficient process is achieved by chopping, that is cut into the amplitude of the input DC voltage equal to the input voltage amplitude of the pulse voltage. The pulse duty cycle is adjusted by the switching power supply controller. Once the input voltage is cut into the AC square wave, its amplitude through the transformer to raise or lower. Number of groups of output voltage can be increased by increasing the number of primary and secondary windings of the transformer. After the last AC 18 waveform after the rectifier filter the DC output voltage. The main purpose of the controller is to maintain the stability of the output voltage, the course of their work is very similar to the linear form of the controller. That is the function blocks of the controller, the voltage reference and error amplifier can be designed the same as the linear regulator. Their difference lies in the error amplifier output (error voltage) in the drive before the power tube to go through a voltage / pulsewidth conversion unit. Switching power supply There are two main ways of working: Forward transform and boost transformation. Although they are all part of the layout difference is small, but the course of their work vary greatly, have advantages in specific applications. the circuit schematic The socalled switching power supply, as the name implies, is a door, a door power through a closed power to stop by, then what is the door, the switching power supply using SCR, some switch, these two ponent performance is similar, are relying on the base switch control pole (SCR), coupled with the pulse signal to plete the on and off, the pulse signal is half attentive to control the pole voltage increases, the switch or transistor conduction, the filter output voltage of 300V, 220V rectifier conduction, transmitted through the switching transformer secondary through the transformer to the voltage increase or decrease for each circuit work. Oscillation pulse of negative semiattentive to the power regulator, base, or SCR control voltage lower than the original set voltage power regulator cutoff, 300V power is off, switch the transformer secondary no voltage, then each circuit The required operating voltage, depends on this secondary road rectifier filter capacitor discharge to maintain. Repeat the process until the next pulse cycle is a half weeks when the signal arrival. This switch transformer is called the highfrequency transformer, because the operating frequency is higher than the 50HZ low frequency. Then promote the pulse of the 19 switch or SCR, which requires the oscillator circuit, we know, the transistor has a characteristic, is the baseemitter voltage is is the zoom state, These are the saturated hydraulic conductivity in the oscillatory state, then the operating point after a good tune, to rely on the deep negative feedback to generate a negative pressure, so that the oscillating tube onset, the frequency of the oscillating tube capacitor charging and discharging of the length of time from the base to determine the oscillation frequency of the output pulse amplitude, and vice versa on the small, which determines the size of the output voltage of the power regulator. Transformer secondary output voltage regulator, usually switching transformer, single around a set of coils, the voltage at its upper end, as the