[雙語翻譯]--外文翻譯--作為功率因數(shù)校正的變換器的基本拓撲對比（英文）

1、Comparison of Basic Converter Topologies For Power Factor Correction Huai Wei, IEEE Member, and Issa Batarseh, IEEE Senior Member University of Central Florida Orlando, FL 328 16 Abstract: Basic types of dc-dc convert

2、ers, when operating in discontinuous conduction mode, have self power factor correction (PFC) property, that is, if these converters are connected to the rectified ac line, they have the capability to give higher pow

3、er factor by the nature of their topologies. Input current feedback is unnecessary when these converters are employed to improve power factor. In this paper, basic types of dc-dc converter topologies are studied to

4、investigate their self-PFC capabilities. Their input characteristics will be compared and their input line current waveforms will be predicted. I. Introduction To improve input power factor of power converters, norma

5、lly a power factor correction (PFC) circuit is designed and placed in front end of the converter, which in turn interfaced with the load. This power factor correction circuit may be an independent unit, by which the

6、power supply followed, or an inseparable part of circuit incorporated into the power supply of the load. The line is a voltage source and will not be distorted if the line current is a sinusoidal one. Hence, the b

7、asic idea of doing PFC is straightforward, by certain means, to force the line current to follow the waveform of the line voltage. However, there exists an unbalance of instantaneous power between the input pow

8、er of the PFC circuit, which is an alternative quantity with two times the line frequency, and its dc output power. Therefore, the operation principle of a PFC circuit is to process the input power in certain way th

9、at it stores the excessive input energy when the input power is larger than the dc output power, and releases the stored energy when the input power is less than the dc output power. To accomplish the above process,

10、at least one energy storage element must be included in the PFC circuit. In most PFC circuits, an input inductor has been connected to the bridge rectifier. Because of the current continuity nature of inductor, we us

11、ually call such connection as “current driven”[ 11. The input inductor can operate in either continuous conduction mode (CCM) or discontinuous conduction mode (DCM). In DCM, the input inductor is no longer a state v

12、ariable since its state in a given switching cycle is independent on the value in the previous switching cycle[2]. The peak of the inductor current is sampling the line voltage automatically. This property of DCM inp

13、ut circuit can be called “self- power factor correction” because no control loop is required from its input side. This is also the main advantage over a CCM power factor correction circuit, in which multi-loop contro

14、l strategy is essential. However, the input inductor operating in DCM can not hold the excessive input energy because it must release all its stored energy before the end of each switching cycle. As a result, a bulky

15、 capacitor is used to balance the instantaneous power between the input and output. In addition, if discontinuous conduction mode is applied, the input current is normally a train of triangle pulse with nearly const

16、ant duty ratio. In this case, an input filter is necessary for smoothing the pulsating input current into a continuous one. Obviously, to ensure high power factor, the average current of the pulsating current should

17、follow the input voltage in both shape and phase. The DCM input circuit can be one of the basic dc-dc converter topologies. However, when they are applied to the rectified line voltage, they may draw different shape

18、 of averaged line current. In this paper, basic buck, boost, buck-boost, flyback, forward, Cuk, Sepic and Zeta converter topologies are investigated. Analysis results show that only some of them are suitable for PFC

19、application. 11. Input Voltage-Current Characteristics of Basic Converter Topologies In order to examine the self-PFC capabilities of the basic converters, we first investigate their input characteristics. Because th

20、e input currents of these converters are discrete when they are operating in 0-7803-4391 -3/98/$10.00 1998 IEEE 348 sinusoidal average input current from the line, shown as in Fig. 2(c). f DITS (b) Input current w

21、t(c) Input V-I Characteristics Fig. 2 Input V-I Characteristic of basic boost converter operating in DCM As one might notice from Eq. (2) that the main reason to cause the non-linearity is the existence of D1. Ideall

22、y, if D1 = 0, the input V-I characteristic will be a linear one. In practice, to reduce the discharge period D1, by properly configuring the circuit topology, a higher voltage, instead of V,, can be created to be ap

23、plied to the inductor during D1 to discharge the induct Because of the reasons, boost converter is comparably superior to of the other converters when applied to do . However, it should be noted that boost conv

24、erter can operate properly only when the output voltage is higher than its input voltage. When low voltage output is needed, a step- down dc-dc converter must be cascaded. C. Buck-boost converter Figure 3(a) shows a b

25、asic buck-boost converter. The averaged input current of this converter can be found according to its input current waveform, shown in Fig. 3(b). (a) Buck-boost converter 4 ' 0 DTs T, (b) Input current (c) Inpu

26、t V-I Characteristics Fig. 3 Input V-I Characteristic and input waveforms. Equation (3) gives a perfect linear relationship between i,,u,,dt) and v,(t), which proves that a buck- boost has excellent self-PFC property.