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        On the power factor correction electronic ballast discussion of the issue

        Number of visits: Date:2016-03-27

        This paper analyzes the power factor correction electronic ballast issue, focused on the active power factor correction of three modes (peak current control, the fixed opening hours, the average current of fixed frequency continuous conduction mode) works, their advantages and disadvantages and apply other occasions.

        Keywords: passive power factor correction active power factor correction time peak current control fixed frequency clamp opening set before (after) modulation discontinuous conduction along the critical turn, continuous conduction mode transition model

        Usually used in the electronic ballast input circuit shown in Figure 1a, due to the capacity of a large electrolytic capacitor CO, the charge stored a lot of work, only the input voltage exceeds the voltage on the capacitor only when the input current, the current waveform serious distortion, voltage peak only in the vicinity of a current spike will appear (Figure 1b). As a result, the circuit power factor becomes very low, about 0.5 or so, the input current harmonic content is very rich. According to the national standard GB/T17263-2002 and European regulations EN63000-3-2, for more than 25W energy-saving lamps and electronic ballasts of the harmonic content of the proposed strict requirements, many existing circuit simply can not meet this requirement .


         

            In order to reduce the ballast input current harmonic distortion, must take some special measures, often called the power factor correction (PFC Power factor correction) technology to improve its power factor. Generally speaking, the power factor correction, there are two options: Passive Power Factor Correction (Passive PFC) and Active Power Factor Correction (Active PFC), has been a lot of information on the former, not the focus of this paper, we mainly analyze active Power factor correction of three models, how they work, advantages and disadvantages, and other suitable occasions.

        The principle of passive power factor correction and power used

        Passive power factor correction principle is to increase the input current conduction time, the supply current waveform close to sinusoidal waveform voltage, reducing its distortion. The program was originally used by the current circuit.
         

            It with Figure 2 (a) of the circuit instead of the capacitor in Figure 1 CO, power through VD3 for capacitors C1, C2 charge to the input voltage peak, each capacitor voltage peak of up to half the input voltage. This capacitor can be recharged in a 120 range, enter the current time is stretched, the current is zero (dead) time only 33.3%. Power factor can be increased to about 0.9, but the voltage on the capacitor fluctuates very, very high harmonic content, is still unable to meet the national standard GB/T17263-2002 and the European standard EN61000-3-2 harmonic content of each (2 to 39 harmonic) limit requirements, and the lamp current crest factor of a great, great light power fluctuations, human vision and lamp life are unfavorable.

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