Abstract
In this paper, a dimmable light-emitting diode (LED) driver, along with the low-frequency current ripple decreased and the bipolar junction transistor (BJT) power dissipation reduced, is developed. This driver is designed based on a single-stage flyback converter. On the one hand, the low-frequency output current ripple reduction is based on the physical behavior of the linear current regulator. On the other hand, when the voltage across the LED string is decreased/increased due to dimming or temperature, the output voltage of the flyback converter will be automatically regulated down/up, thereby making the power dissipation in the BJT linearly proportional to the LED current. By doing so, not only the power loss in the linear current regulator will be decreased as the LED current is decreased or the LED temperature rises, but also the output current ripple can be reduced. Furthermore, the corresponding power factor (PF) is almost not changed, and the total harmonic distortion (THD) is improved slightly. In addition, the LED dimming is based on voltage division. Eventually, a 30 W LED driver, with an input voltage range from 85 to 295 Vrms and with 24 LEDs in series used as a load, is developed, and accordingly, the feasibility of the proposed LED driver is validated by experimental results.
Highlights
As generally recognized, the light-emitting diode (LED) is becoming more attractive in the world due to its small size, light weight, and long life [1,2]
A 30 W LED driver, with an input voltage range from 85 to 295 Vrms and with 24 LEDs in series used as a load, is developed, and the feasibility of the proposed LED driver is validated by experimental results
As for the control loop of the single-stage power factor (PF) flyback converter based on the L6561 pulse width modulation (PWM) IC5 [23], of 18 it will have a narrow bandwidth (
Summary
The light-emitting diode (LED) is becoming more attractive in the world due to its small size, light weight, and long life [1,2]. Modulating the light output through an LED’s current is achieved either by pulse width modulation (PWM) switching, or by amplitude control, known as analog or level dimming. The former allows deep deeming but presents low luminous efficiency and a risk of flicker [3]. In this paper, a single-stage AC–DC flyback LED driver, together with a linear current regulator having the bipolar junction transistor (BJT) whose power dissipation is only linearly proportional to the LED current, is employed so as to decrease LED low-frequency flicker significantly with PF and total harmonic distortion (THD) slightly influenced. Amplitude dimming from 100% to 10% is adopted
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