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...e) boundary. A low input-current harmonic distortion 978-1-4244-4783-1/10/$25.00 ©2010 IEEE 203 can be achieved due to the inherent property of the DCM boost converter to draw a near sinusoidal current if its duty cycle is held relatively constant during a half line cycle. However, voltage VB across bulk capacitor CB is not regulated and at high line it can increase to impractical levels. To reduce the bulk capacitor voltage, one terminal of the boost inductor winding is connected to a tapping point of the primary winding of the flyback transformer, which provides a negative magnetic feedback [7]. However, the tapping of the flyback primary winding also results in a zero-crossing distortion of the line current. In fact, as long as the instantaneous line voltage is lower than the voltage at the tapping point, no current is drawn from the input, which reduces the power factor and increases the line-current harmonics. The single-stage PFC flyback topology shown in Fig. 3 has been successfully applied in adapter/charger applications for the universal line voltage, where the line current harmonics need to meet the IEC 61000-3-2 Class D limits, which are less stringent than the IEC 61000-3-...

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...devices and they carry out an extremely long operating life. The main purpose of this paper consists of presenting a topology for running LED streetlights from an Ac source. In a single-stage approach, input-current shaping, isolation, and high-bandwidth control are performed in a single step, i.e., without creating a transitional dc bus. Among the single-stage circuits, a number of circuits described in seem particularly striking because they can be implemented with only one semiconductor switch and a simple control. All these single stage, single-switch input-current shaping (S41CS) circuits[3] integrate the boostconverter front end with the forward converter or the flyback-converter dc/dc stage. Fig. 1 shows the flyback converter .The two additional primary windings, NI and N2, are employed to keep the voltage of energy-storage (bulk) capacitor below a desired level in the entire line and load ranges. Boost inductor can function either in the discontinuous conduction mode (DCM) or in the continuous conduction mode (CCM). Generally, the CCM operation offers a slightly higher efficiency compared to the DCM operation. However, the DCM operation gives a less total harmonic distortion (...

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...he voltage stress but this may not favour high output current application [2]-[3]. Other solutions solved the problem at the expense of wide switching frequncy range [4], distorting the input current =-=[5]-=--[6] or allowing the line-frequency ripple to be present at the output [7]-[12]. Previous paper [12] reported that the cause of the problem is due to the incapability of controller response to the fas...