Drivers para leds empregando o conceito de charge-pump para redução do flicker

Abstract

This work aims to study topologies of drives for lighting LEDs based on the charge-pump concept. First of all, a topology with inherent Power Factor Correction (PFC) is proposed. The driver presented a power factor of 0.996. However, it presented a low frequency ripple current ripple of about 59%. In the sequence, the low frequency ripple propagation in LEDs drivers based on signal amplitude modulation theory and resonant tank response is investigated. This investigation demonstrates that, the low frequency current ripple percentage can be lower than the bus voltage ripple percentage, unlike has been found in the literature. Besides, another topology of driver with inherent PFC is proposed, which provides a low current ripple, and consequently a low percent flicker. The second driver presented a power factor of 0.996 and a current ripple of 9.5%. The proposed topologies presented the output power proportional to the switching frequency, which allows the LEDs dimming. Furthermore, the output current can be stabilized in open loop control without needing current sensors. This topology does not utilize electrolytic capacitors, which increases the lifetime of the LED driver and Zero Voltage Switching (ZVS). Prototypes were developed to evaluate the proposals, while the results are presented and discussed accordingly.