Optimized Design of a High Input-Voltage-Ripple-Rejection Converter for LED Lighting

Abstract

-The Asymmetrical Half Bridge (AHB) converter has been deeply analysed as second stage in acdc LED drivers. Galvanic isolation, high reliability and high efficiency are their main advantages while a limited duty cycle range (i.e., 0-0.5) and a poor dynamic behaviour are their main disadvantages. As second stage of an LED driver, the most demanding requirement for its control loop is cancelling the low-frequency ripple introduced by the first stage. According to its limited maximum attainable bandwidth, this is normally achieved by implementing a feedforward loop. Nonetheless, the static gain of the standard AHB converter presents a non-linear relation between the output voltage and the duty cycle. As a consequence, the effectiveness of this feedforward loop is limited. In this paper, the use of the Zeta Asymmetrical Half Bridge (ZAHB) converter as second stage of an LED driver is analysed and an optimized design is proposed. Regarding its advantages, it presents an extended duty cycle range (theoretically, 0-1.0). Besides, it presents a linear relation between the output voltage and the duty cycle. Therefore, although its dynamic behaviour is still limited, it can perfectly cancel the low-frequency ripple introduced by the first stage of the LED driver by means of a straightforward feedforward loop. The optimized design proposed in this paper is focused on minimizing the losses in the magnetic components (transformer and inductor) by wisely choosing the value of the two turns ratios of the transformer.

Modular three-phase ac-dc LED driver based on summing the light output of each phase

“…Looking at (15) and (16), it can be seen that both equations are dependent of Iac and Idc which gives a system of two equations and three unknown variables. In order to attain a useful model from an engineering perspective, there is one simplification that can be performed, which is removing Iac from (15).…”

“…In order to attain a useful model from an engineering perspective, there is one simplification that can be performed, which is removing Iac from (15). This is a fine approximation that dramatically decreases the complexity of the solutions.…”

“…Each cell is comprised of a boost converter, able to achieve Power Factor Correction (PFC) followed by a fixed-gain isolated step-down dc-dc converter to adequate voltages and currents to that of the LED string [12]. Similarly to the two-stage single-phase ac-dc solution, the second stage could be implemented by means of an LLC [13], an Asymmetrical Half-Bridge (AHB) [14] or a Zeta AHB [15].…”

Pulse width modulation converter for light‐emitting diode tube light applications

“…In a two‐stage driver circuit, the low‐frequency ripples in the first stage (rectifier) to be cancelled in the second stage to minimize flickering. Such ripple minimization methods were discussed in recent research articles The single‐stage LED driver has been examined for a long time, which comprises of a PFC stage and a dc‐dc converter by sharing dynamic control switches and control circuits .…”

“…Such ripple minimization methods were discussed in recent research articles. 7,8 The single-stage LED driver has been examined for a long time, which comprises of a PFC stage and a dc-dc converter by sharing dynamic control switches and control circuits. [9][10][11][12][13][14][15] Among these single-stage converters, seriesparallel resonant circuit (also known as LLC) is a broadly utilized topology for its delicate exchanging qualities.…”