【導(dǎo)讀】備的種類也越來越多，電子設(shè)備與人們的工作、生活的關(guān)系日益密切。傳統(tǒng)的晶體管串聯(lián)調(diào)整穩(wěn)壓電源是連續(xù)控制的線性穩(wěn)壓電源。模塊，具有穩(wěn)定性能好、輸出波紋電壓小、使用可靠等優(yōu)點。都需要體積大且笨重的工頻變壓器與體積和重量都很大的濾波器。在近半個世紀(jì)的發(fā)展過程中，開關(guān)電源因具有重。算機(jī)等許多領(lǐng)域的電子設(shè)備中得到了廣泛的使用。計算機(jī)全面實現(xiàn)了開關(guān)電源化，率先完成計算機(jī)的電源換代。用，開關(guān)電源技術(shù)進(jìn)入快速發(fā)展期。此外，大規(guī)模集成電路技術(shù)的迅。傳統(tǒng)的開關(guān)電源一般均采用分立的高頻功率開關(guān)管和多引腳的。一起，已成為開關(guān)電源IC發(fā)展的主流。開關(guān)電源，可使電路簡化，體積進(jìn)一步縮小，成本也明顯降低。變換器的開關(guān)頻率將上升到MHz。數(shù)，減少對電網(wǎng)的諧波污染。適應(yīng)微處理器和便攜式電子設(shè)備的供電要求。故仍需在這一領(lǐng)域開展大量的工作，以使得該項技術(shù)得以實用化。中國特色的產(chǎn)學(xué)研聯(lián)合發(fā)展之路，為我國民經(jīng)濟(jì)的高速發(fā)展做出貢獻(xiàn)。

　　

【正文】 cle longer, make Uo 390v decreases, and reduction. PFM type of switch power supply output voltage range is very wide, output terminal don39。t meet dummy loads. PWM way and way of PFM respectively modulating waveform is shown in figure 1 (a), (b) shows, tp says pulse width (namely power switch tube conduction time tON), T represent cycle. It can be easy to see the difference between the two. But they have something in mon: (1) all use time ratio control (TRC) on voltage stability principle, whether change tp, finally adjustment or T is pulse 390v. Although adopted in different ways, but control goals, is all rivers run into the sea. (2) when load by light weight, or input voltage respectively, from high changed by increasing the pulse width, higher frequency method to make the output voltage remained stable. 3) mix modulation mode, it is to point to the pulse width and switching frequency is not fixed, each other can change, it belongs to the way the PWM and PFM blend mode. It contains a pulse widthomdulatros and pulse frequency modulator. Because and T all can adjust alone, so occupies emptiespared to adjust the most wide range, suitable for making the output voltage for laboratories that use a wide range of can adjust switching power supply. Above 3 work collectively referred to as Time Ratio Control (as a Control, from TRC) way. As noted, pulse width omdulatros either as a independent IC use (for example UC3842 type pulse width omdulatros), can also be integrated in DC/DC converter (for example LM2576 type switching voltage regulators integrated circuit), still can integration in AC/DC converter (for example TOP250 type monolithic integrated circuit switching power supply. Among them, the switching voltage regulators belong to DC/DC power converter, switching power supply general for AC/DC power converter. The typical structure of switch power as figure2shows, its working principle is: the first utility into power rectifier and filtering into high voltage dc and then through the switch circuit and highfrequency switch to high frequency low pressure pulse transformer, and then after rectification and filter circuits, finally output low voltage dc power. Meanwhile in the output parts have a circuit feedback to control circuit, through the control PWM occupies emptiespared to achieve output voltage stability. Switching power supply by these four ponents: 1) the main circuit: exchange work input, from the main circuit to dc output. Mainly includes input filter, rectifier and filtering, inverter, and output rectifier and filtering. (1) input filter: its effect is the power grid existing clutter filtering, also hinder the machine produces clutter feedback to public power grid. (2) rectifier and filter: the power grid ac power directly for a smooth dc rectifier, for the next level transformation. (3) inverter: will the dc after rectifying a highfrequency ac, this is the core of high frequency switching power supply, the higher the frequency, the volume, weight and the ratio of power output and smaller. (4) output rectifier and filter: according to load needs, providing stable and reliable dc power supply. 2) control circuit: on the one hand, from the output by sampling with set standards to pare, and then to control inverter, changing its frequency or pulse width, achieve output stability, on the other hand, according to data provided by the test circuit, the protection circuit differential, provide control circuit to the machine to various protection measures. Including the output feedback circuit and sampling circuit, pulse width modulator. 3) the detection and protection circuit: detection circuit had current detection, overvoltage detection, owe voltage detection, overheat detection, etc.。 Protection circuit can be divided over current protection, overvoltage protection, owe voltage protection, the groundclamp protection, overheating protection, automatic restart, soft start, slow startup, etc. Various types. 4) other circuit: if the sawtooth wave generator, offset circuit, optical coupler, etc.