Single-Switch Multichannel Current-Balancing LED Drive Circuits Based on Optimized SC Techniques

Abstract

By combining the conventional switched-mode power converters with advanced switched capacitor (SC) techniques, a plurality of single-switch current-balancing circuits are developed to drive multiple LED strings in this paper. Compared with the existing current-balancing LED drivers, the proposed drive circuits exhibit their attractive advantages in size and cost efficiency because just one active switch and one magnetic device are required. LED strings' current can be regulated by controlling the duty ratio of the switch in pulse width modulation (PWM) mode. Both advanced resonant and non-resonant SC methods are introduced to optimize the performance of the proposed LED drivers. The feasibility and theoretical analysis are verified with a 9W dual-channel non-isolated prototype and a 25W four-channel isolated prototype.

Implementation of a Dimmable LED Driver with Extendable Parallel Structure and Capacitive Current Sharing

“…These uneven currents will affect the LED luminance and cause the temperature in the LED to be increased and the life of the LED to be reduced. Therefore, many literatures have presented current-sharing methods for LED strings [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] so as to make currents distributed among LED strings as identically as possible. The LED current-sharing methods are classified into two types.…”

“…However, in practice, the current-sharing error comes from the magnetizing current of the transformer. For the second type to be considered [15][16][17][18][19][20][21], the current balance between the two LED strings is based on the amperesecond balance. In [15], an LED driver constructed of an isolated LCLC resonant circuit along with capacitive current balance.…”

“…In [17], an isolated CLL resonant converter with several balance capacitors is applied to driving multiple LED strings. In [18], isolated and non-isolated LED drivers are constructed by the traditional converters with switched capacitors used. In [19], an LED driver is constructed by one voltageboosting converter with automatic current balance and zero-voltage switching such that the switching loss can be reduced.…”

“…Based on the aforementioned literatures, each circuit from [10][11][12][13][14][15][16][17][18][19][20][21] has the capability of extending the number of LED strings to two or more, if necessary, except for [12,20,21]. Since the current balance based on the differential transformer will occupy a relatively large space, the current balance of the proposed LED driver is based on the capacitor.…”

LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control

“…Above all, the MOSFET of LCR may dissipate more conduction loss, due to an uncertain drain-to-source voltage on the i DS -v DS plane [19]. Besides, many balance cells for LEDs directly using versatile dc/dc converters or resonant converters have been successively developed [18,[20][21][22][23][24][25]. However, in terms of application for a large scale display, it is difficult to implement a large lighting area using such a large amount LED cells, needed to acquire a balanced luminance.…”