This paper presents a dimmable light-emitting diode (LED) driver with adaptive feedback control for low-power lighting applications. An improved pulsewidth modulation dimming technique is studied for regulating the LED current and brightness. Under universal input voltage operation, high efficiency and high power factor can be achieved by a coupled inductor single-ended primary inductance converter power factor correction (PFC) converter with a simple commercial transition-mode PFC controller. The operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility.

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A High-Efficiency Dimmable LED Driver for Low-Power Lighting Applications

This paper presents an LED driver circuit consisting of multiple linear current regulators and a voltage preregulator with adaptive output voltage. In the proposed driver, the output voltage of the preregulator is always self-adjusted so that the voltage across the linear current regulator of the LED string with the highest voltage drop is kept at the minimum value that is required to maintain the desired string current. Because the linear current regulators in this driver operate with the minimum voltages, the driver efficiency is maximized. The performance of the proposed driver was experimentally verified on a four-string LED setup with eight white LEDs in each string. The measured efficiency improvement of the linear current regulators was approximately 15% compared to the corresponding implementation with a constant preregulator voltage.

/pdf/led-driver-with-self-adaptive-drive-voltage-12m7lqq6p0.pdf

LED Driver With Self-Adaptive Drive Voltage

Due to the high rise in luminous efficiency that HB-LEDs have experienced in the last recent years, many new applications have been researched. In this paper, a streetlight LED application will be covered, using the Integrated Buck-Flyback Converter developed in previous works, which performs power factor correction (PFC) from a universal ac source, as well as a control loop using the LM3524 IC, which allows PWM dimming operation mode. Firstly, the LED load will be linearized and modeled in order to calculate the IBFC topology properly. Afterwards, the converter will be calculated, presenting the one built in the lab. Secondly, the converter will be modeled in order to build the closed loop system, modeling the current sensor as well in order to develop an adequate controller. Finally, experimental results obtained from the lab tests will be presented.

A Universal-Input Single-Stage High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck-Flyback Converter

Due to the high rise in luminous efficiency that high-brightness light-emitting diodes (HB-LEDs) have experienced in recent years, many new applications have been researched. This paper covers a streetlight LED application using the offline integrated buck-flyback converter (IBFC) developed in previous works. In this application, the converter is used to provide power-factor correction from a universal ac source. A control loop using the LM3524 IC has been implemented for testing the feasibility of Enabling pulsewidth modulation dimming mode. First, the LED load has been linearized and modeled in order to calculate the IBFC topology properly. Second, the converter has been designed and tested at the laboratory. The converter has also been modeled in order to design a fixed-frequency constant-current control. The dynamics of all the stages involved in the closed loop have been taken into account in order to develop an adequate controller. Finally, the experimental results obtained from the laboratory tests are discussed.

A Universal-Input Single-Stag2e High-Power-Factor Power Supply for HB-LEDs Based on Integrated Buck–Flyback Converter

This paper presents an LED driver circuit consisting of a voltage pre-regulator and multiple linear current regulators with an adaptively-controlled supply voltage. The proposed driver circuit powers all LEDs in a string with a constant current and provides consistent illumination and optimal operating efficiency at low cost. The performance of the proposed driver was verified experimentally.

A novel LED driver with adaptive drive voltage

This paper presents a universal power supply for high-luminance LED lamp test. The proposed power supply is designed and implemented by adopting an improved single-stage Flyback configuration. A constant current control method is used to regulate the lamp current and brightness under different pieces of LED series connection. A laboratory prototype has been built and tested. With the prototype, high efficiency, high power factor, and constant lamp current can be achieved for the performance test of various LED lamps.

Chyng ShihYen

Papers

An Improved Single-Stage Flyback PFC Converter for High-Luminance Lighting LED Lamps