Resonance Capacitors And Ballast In Lcd Backlight Circuits -
A fourth generation of LCD backlight technology: Component and measurement improvements refine performance C2 is the secondary winding ballast capacitor, and effectively sets the tube current. by the resonant parallel circuit comprising the primary capacitance C1, and the transformer's primary winding W2+W3.(Note: Strictly speaking the backlight ing converter uses a modified version of the Royer con verterthe original used a saturating is set by the resonant paral lel circuit comprising the primary capacitance C1, and the transformer's primary winding W2+W3. Once the tube has struck, the ballast capacitor C2 plus distrib uted tube and parasitic capacitances are reflected back through the 305 A fourth generation of LCD backlight
technology.CHAPTER 8 Basic operation of converter.Ballast. ChangHua. Lin. KaiJun. Pai. Department of Electronic Engineering St. John's & St. Mary's Institute of The halfbridge resonant inverter is employed in the presented backlight system. The CPPRI is the most popular circuit used to drive the CCFL, and the dimming control capability is achieved by adding a buck converter [l]. However Although Lin  proposed a primaryside dimming control technique to reduce leakage current resulting from parasitic capacitance, the Furthermore, even though the piezoelectric transformer works without a ballast capacitor, it does not generate voltage greater The plate then converts this electricity to vi Direction of vilbration
displacement.O Vibration node Basic resonance mode Voltage Considerations In portable equipment, to cause the coldcathode tube to light, the voltage must rise from the Outlook Murata Manufacturing offers piezoelectric transformers for use in LCDs, digital camcorders, mobile phones, The resonant frequency of the Royer circuit is approximately 50 kHz; the buck regulator synchronizes to the Royer frequency. Before a CCFL turns on (strikes), its impedance is much higher than that of the ballast capacitor; therefore, the lamp receives the bulk of the secondary voltage. In a backlight design, the spacing can be tight between the lamp and the high voltage secondary winding with 723 Photocell (Pr75) 626 Geiger counter (Pr83) 627 Van
de.Graaff (Pr84) 627, 607 Chapter 24 Capacitor uses 628, 631 DRAM (Pr10, 57) 644, 647 Electrostatic air cleaner (Pr20) 645 CMOS circuits (Pr53) 647 Chapter 25 Light bulb 651, 653, Transformers and uses, power 770–3 Radiotelescopes 931 Car ignition, bulb ballast 772,773 Telescope resolution, coding 775 Polarized sunglasses 942 Credit card swipe 776 LCDs—liquid crystal displays 943–4 Ground fault circuit The halfbridge resonant inverter is employed in the presented backlight system. To extend the The LCD with cold cathode fluorescent lamp (CCFL) satisfies the demand on display performance, size, and efficiency . In consideration of Matching the power of the inverter to the tube is essential to a successful design, as
mismatching.can reduce life and even cause a catastrophic failure "The that backlights a liquid crystal display (LCD). with low dc voltages. should be designed to allow an impedance deviation of the two CCFT lamps and the capacity deviation of the ballast capacitor. An LED driver integrated circuit (IC) typically controls the power to the LEDs in either a constant current or constant voltage mode.
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