Simple LED driver with Constant Current Control

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover, this makes the current control so easy. Afterwards, the basic operating principles and analyses are given, particularly for how to derive the effective resistive load from the LED string. Eventually, some experimental results are provided to validate the effectiveness of the proposed LED driver.

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Optimization of a Series Converter for Low-Frequency Ripple Cancellation of an LED Driver

Electronics ◽

10.3390/electronics8060664 ◽

2019 ◽

Vol 8 (6) ◽

pp. 664 ◽

Cited By ~ 2

Author(s):

Jorge Garcia ◽

Sarah Saeed ◽

Pablo Quintana ◽

Jesus Cardesin ◽

Ramy Georgious ◽

...

Keyword(s):

Low Frequency ◽

Current Control ◽

Buck Converter ◽

Constant Current ◽

Led Driver ◽

Original Proposal ◽

Voltage Ripple ◽

Power And Control ◽

Optimization Methodology ◽

And Control

In this paper, the optimization of the power and control stages of a previously proposed topology for an off-line LED electronic driver is presented. The full system avoids the use of electrolytic capacitors at the D C link, therefore increasing the lifespan and reliability of the driver. As a consequence of having a relatively small capacitance, the D C link operates with a large Low-Frequency ( L F ) voltage ripple. This work presents a design optimization for the power and control stages of a current-fed bidirectional buck converter, operating as the LED current control stage. As this block processes only the A C power arising from the L F voltage ripple, it can increase the system efficiency against the typical two-stage solution. In the original proposal, the main drawback was the high inductor losses due to the resulting large inductor currents and large inductance value. The proposed optimization ensures an enhanced design of the inductor while keeping a constant current through the LEDs. A new optimization methodology is proposed and the theoretical results have been validated in a built prototype for a 40 W LED lamp.

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