LED Backlight Driving System for Large-Scale LCD Panels

Abstract

This paper presents an LED backlight driving system for large-scale liquid crystal display panels. High efficiency, high power factor, circuit simplicity, and low cost can be achieved by using a single-stage charge-pump asymmetrical half-bridge converter. To regulate the LED current and brightness for the LED backlight system, some current sharing methods are presented and compared. The requirements for the current sharing and luminance balance among paralleled LED arrays can be satisfied while current ripple is eliminated significantly. Because of the addition of bypass diodes, an alternative current path can be offered when a single LED fails. The LED array will not be extinguished. Reliability of the LED backlight system can thus be improved effectively. A laboratory prototype has been built and tested. The simulation and experimental results are shown to verify the feasibility of the proposed method.Index Terms-Bypass diode, dimming control, light-emitting diode (LED) backlight, power factor, single-stage charge-pump asymmetrical half-bridge (AHB).

Start-Up Current Spike Mitigation of High-Power Laser Diode Driving Controller for Vehicle Headlamp Applications

“…Figure 7 presents a familiar OPS control circuit that includes the lighting driver, OPSs, and the current regulator (CR). To control the constant driving current in OPSs, a CR comprising an operational amplifier (OPA), a transistor, and a current-voltage (C-V) converter, is the critical circuit because the CR can be considered as a current sink; when the OPS operates in the forward bias, the OPS driving current I f sinks into the transistor, and then I f can be converted by the C-V converter becoming a voltage V If ; therefore, the transistor can be considered as a variable resistance for adjusting the I f because the OPA compares the V If with a CC command to control the transistor's operating region [18,19]. However, the CR is unable to address less steady-state errors and sufficient phase margins.…”

LED Current Balance Using a Variable Voltage Regulator with Low Dropout vDS Control

“…Accordingly, the VVdc can then be synthesized form (14), including NvD, iDSRs, and the specified low-dropout VQ, as shown in Figure 5b. In Figure 5a, the supply vMk for different operation points under constant VQ, can be easily found in (12).…”

“…Final comments are concluded in Section 5. LED current balancing mainly uses a PWM duty cycle control, such as sequential phase-shift duty control [12,13], burst mode [14,15], self-adaptive control [16], and series-connected mode [17], etc. In this case, the LED driven by the pulse to emit luminance for a human is based on the persistence of vision.…”

P‐34: Active Matrix Programmable Monolithic Light Emitting Diodes on Silicon (LEDoS) Displays

“…Backlight units (BLU) are used as light sources of LCD panels, which determine the key performances of LCD such as the brightness, contrast, colors saturation, power consumption and environmental friendliness. Comparing with conventional cold cathode fluorescent lamp (CCFL), light emitting diode (LED) BLU is essential for a high quality LCD because of its superior characteristics such as higher brightness, longer lifetime and lower power consumption [1]. However, most portion of the light is lost on the LCD system.…”