Abstract
In this paper, a new LLC converter for series-connected, high-voltage LEDs is proposed. The proposed LLC converter consists of two stacked, single-ended rectifiers and one balancing capacitor, to compensate for the current deviation of two individual LED strings. The proposed LLC LED driver can use a diode with low voltage stress, even if the secondary LED is connected in series to have a high driving voltage. In addition, even if several series-connected LEDs are changed into two-stacked structures, the balancing capacitor can compensate for the current deviation of the two separated LEDs, as well as the difference in leakage inductance of the two stacked single-ended rectifiers. The balancing capacitor can be made equal to the voltage tolerance of the stacked, single-ended rectifier diodes. The proposed circuit can be easily extended to a series channel LED driver circuit, without increasing the voltage stress. To verify the characteristics and operation of the proposed LLC LED driver, a 260W high-power LED driver is implemented.
Highlights
Light-emitting diodes (LEDs) have been emerging as the generation of lighting, due to their long lifetime, eco-friendliness and high optical efficiency [1]
If a large number of LEDs are driven in series, the driving voltage becomes high, and if the LEDs are driven in a serial–parallel structure, many circuits for current driving are required for each parallel driving [2]
Large power LED lights over 65 W require AC/DC converters for power factor correction (PFC), along with DC/DC converters to create isolation and DC voltage to drive those LEDs connected in series
Summary
Light-emitting diodes (LEDs) have been emerging as the generation of lighting, due to their long lifetime, eco-friendliness and high optical efficiency [1]. If a large number of LEDs are driven in series, the driving voltage becomes high, and if the LEDs are driven in a serial–parallel structure, many circuits for current driving are required for each parallel driving [2]. The switching LED driver, which is a type of non-isolated DC/DC converter, separately controls the current of each LED string It has higher efficiency compared with the linear. LED driver, but has demerits, such as a large component count and high cost [4,5,6] Both linear and switching LED drivers require a large number of circuits to drive parallel LEDs. The number of the circuits can be reduced by series-connected LED strings.
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