【正文】 ound of an interference source or by conduction through mon cabling or wiring connections. In this study conducted emission is considered only. Equipment such as puters, receivers, amplifiers, industrial controllers, etc that are exposed to interference corruption are called victims. The mon connections of elements, source lines and cabling provide paths for conducted noise or interference. Electromagic conducted interference has two ponents as differential mode and mon mode ??9 . A. Differential mode conducted interference 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 32 This mode is related to the noise that is imposed between different lines of a test circuit by a noise source. Related current path is shown in Fig. 1 ??9 . The interference source, path impedances, differential mode current and load impedance are also shown in Fig. 1. B. Common mode conducted interference Common mode noise or interference could appear and impose between the lines, cables or connections and mon ground. Any leakage current between load and mon ground could be modeled by interference voltage source. Fig. 2 demonstrates the mon mode interference source, mon mode currents Icm1 and Ic m2 and the related current paths ??9 . The power electronics converters perform as noise source between lines of the supply work. In this study differential mode of conducted interference is particularly important and discussion will be continued considering this mode only. III. ELECTROMAGNETIC COMPATIBILITY REGULATIONS Application of electrical equipment especially static power electronic converters in different equipment is increasing more and more. As mentioned before, power electronics converters are considered as an important source of electromagic interference and have corrupting effects on the electric works 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 33 ??2 . High level of pollution resulting from various disturbances reduces the quality of power in electric works. On the other side some residential, mercial and especially medical consumers are so sensitive to power system disturbances including voltage and frequency variations. The best solution to reduce corruption and improve power quality is plying national or international EMC regulations. CISPR, IEC, FCC and VDE are among the most famous organizations from Europe, USA and Germany who are responsible for determining and publishing the most important EMC regulations. IEC and VDE requirement and limitations on conducted emission are shown in Fig. 3 and Fig. 4 ??7 ??9 . For different groups of consumers different classes of regulations could be plied. Class A for mon consumers and class B with more hard limitations for special consumers are separated in Fig. 3 and Fig. 4. Frequency range of limitation is different for IEC and VDE that are 150 kHz up to 30 MH z and 10 kHz up to 30 MHz respectively. Compliance of regulations is evaluated by parison of measured or calculated conducted interference level in the mentioned frequency range with the stated requirements in regulations. In united European munity pliance of regulation is mandatory and products must have certified label to show covering of requirements ??8 . 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 34 IV. ELECTROMAGNETIC CONDUCTED INTERFERENCE MEASUREMENT A. Line Impedance Stabilization Network (LISN) 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 35 1Providing a low impedance path to transfer power from source to power electronics converter and load. 2Providing a low impedance path from interference source, here power electronics converter, to measurement port. 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 36 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 37 Variation of LISN impedance versus frequency with the mentioned topology is presented in Fig. 7. LISN has stabilized impedance in the range of conducted EMI measurement ??7 . Variation of level of signal at the output of LISN versus frequency is the spectrum of interference. The electromagic patibility of a system can be evaluated by parison of its interference spectrum with the standard limitations. The level of signal at the output of LISN in frequency range 10 kHz up to 30 MHz or 150 kHz up to 30 MHz is criterion of patibility and should be under the standard limitations. In practical situations, the LISN output is connected to a spectrum analyzer and interference measurement is carried out. But for modeling and simulation purposes, the LISN output spectrum is calculated using appropriate software. 參考文獻(xiàn) [1] Mohan, Undeland, and Robbins, ―Power Electronics Converters, Applications and Design‖ 3rd edition, John Wiley amp。若發(fā)生輸入電流過(guò)大、輸出電壓 過(guò)大或者電路工作環(huán)境過(guò)熱的情況均會(huì)使 LED 指示燈變暗，說(shuō)明逆變電路停止工作。這里取 200Ω。因?yàn)?VT3 截止， 220V 電壓無(wú)法送至輸出。 圖 32 輸入過(guò)壓電路保護(hù)圖 輸出過(guò)壓保護(hù)電路 電路結(jié)構(gòu)如圖 33，當(dāng)輸出電壓過(guò)高時(shí)將導(dǎo)致穩(wěn)壓管 DZ1 擊穿，使TL494 芯片 II 的 4 腳對(duì)地的電壓升高，啟動(dòng) TL494 芯片 II 的保護(hù)電路，切斷輸出。四只整流二極管 D1~D4 接成電橋的形式，稱單相橋式整流電路 [2]。中心器件變壓器 T1，實(shí)現(xiàn)電壓由 12V 脈沖電壓轉(zhuǎn)變?yōu)?220V 脈沖電壓。由于它僅靠半導(dǎo)體中的多數(shù)載流子導(dǎo)電，又稱單機(jī)型晶體管，場(chǎng)效應(yīng)管不但具備雙極型晶體管體積小、重量輕、壽洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 12 命長(zhǎng)等優(yōu)點(diǎn)，而且輸入回路的內(nèi)阻高達(dá) 1071012Ω，噪聲低、熱穩(wěn)定性好、抗輻射能力強(qiáng)，且比后者耗電省，這些優(yōu)點(diǎn)使之從 20 世紀(jì) 60 年代誕生起就廣泛地應(yīng)用于各種電子電路之中。當(dāng)輸出端接地時(shí)，最大輸出占空比為 96%，當(dāng)輸出端接參考電平時(shí)，占空比為 48%。 3. 內(nèi)部有一對(duì)誤差放大器，可做反饋放大及保護(hù)功能，控制非常方便。 逆變電源的主要元器件及其特性 TL494 電流模式 PWM 控制器 TL494 是一種固定頻率脈沖寬度調(diào)制電路 [1]，它包含了開關(guān)電源控制所需的全部功能，廣泛用于單端正激雙管式、半橋式以及全橋式開關(guān)電源。全橋電路以 50Hz 的頻率交替導(dǎo)通，產(chǎn)生 50Hz交流電。圖中S1S4 是橋式電路的 4 個(gè)臂，他們由電力電子器件及其輔助電路組成。值得注意的是，開關(guān)電源的輸出噪聲和紋波一般比線性電源大，所以在需要非常低的噪聲與紋波（如紋波峰峰值要小于 5~10mV）的情況下，仍需要線性電源，由于大功率全功率非常大（ 1MW 以上）時(shí)，仍需采用相控電源。其功率從零點(diǎn)幾瓦到數(shù)十千瓦， 廣泛用于生活、生產(chǎn)、科研、軍事等各個(gè)領(lǐng)域。 洛陽(yáng) 理工學(xué)院畢業(yè)設(shè)計(jì)（論文） 3 第 1 章 簡(jiǎn)介 概述 逆變電源是將直流點(diǎn)逆變成交流電，本設(shè)計(jì)逆變電源工作是的持續(xù)輸出功率為 150W，并且具有輸出過(guò)壓保護(hù)以及過(guò)熱保護(hù)等功能。逆變電路又包括頻率產(chǎn)生電路（ 50KHz 和 50Hz PWM 脈沖寬度調(diào)制電路）、直流變換電路 (DC/DC)將 12V 直流轉(zhuǎn)換成 220V 直流、交流變換電路 (DC/AC)將 12V 直流變換為 220V 交流。 3. 輸出功率：大于 100W。當(dāng)該腳接基準(zhǔn)電壓是，輸出呈推挽型，輸出方波最大占空比為 48％； 當(dāng)該腳 接地是 內(nèi)部二 個(gè)輸出晶 體管并聯(lián) 工作輸出 電流可達(dá)400mA，最大占空比為 96％ 5 14 +5 +5V 基準(zhǔn)電源