Driven by more and more emerging demand and green energy conservation trends, the application of power and power management technologies that can improve power efficiency will grow rapidly. Backlighting is a typical application requirement. Although the backlight of LCD TVs is still dominated by traditional cold cathode fluorescent lamps (CCFLs), with the increasing awareness of global energy conservation and environmental protection, new light-emitting diode ( LED ) backlights have received wide attention and become a strong competitor of CCFL. In portable applications, LCD backlight LED driver solutions need to meet the requirements of high energy efficiency, extended battery life, and reduced printed circuit board area. This article will discuss the characteristics and needs of the backlight market and applications in conjunction with ON Semiconductor's solutions.
The needs and challenges of backlight applications
LED has the advantages of high color saturation, environmental protection and durability, and has been widely used in various small and medium-sized LCD panels. It is gradually infiltrating into large and medium-sized LCD backlights such as notebook computers and LCD TVs. In 2009, the proportion of LCD TVs using LED backlights was only 3%. In the next three to four years, it will rapidly climb to 40% to 50%, which has brought huge business opportunities for manufacturers developing LED driver solutions.
Compared to CCFL, the color performance of LED backlights is more advantageous. The LED is driven by a low voltage of 5 V to 24 V, which is very safe, and the drive circuit design is relatively simple and very energy-saving. LEDs do not use mercury that is harmful to the environment, and there are no problems such as mercury leakage. LED technology also faces challenges such as low luminous efficiency, high cost, and high price. As LCD backlights shift to multiple LED technologies, design engineers address new challenges such as power management, thermal management, and color management.
At present, automotive electronics, mobile devices, LCD backlights, addressable signs and general lighting are potential applications of LED technology, and LCD backlighting will become the next major battlefield for LED technology.
In addition, battery-powered portable applications are becoming more and more feature-packed and smaller in size, making these devices more power-hungry. The use of low-power LED drivers helps save power, extend battery life, and give consumers a better experience.
ON Semiconductor's diverse backlight solutions
1. Medium and large size LCD TV LED backlight solution
LED-backlit LCD TVs mainly have two options: side-lit and back-lit. The important requirement of power management is to improve energy efficiency. In addition, because LED-backlit LCD TVs are an important selling point for ultra-thin appearance, their power management solutions must be low. The height to match the slim design, but also to consider heat dissipation, reduce electromagnetic interference, brightness matching of different channels, dimming and fault diagnosis and protection.
(1) Side-light solution: ON Semiconductor's cost-effective multi-channel linear LED side-light solution uses the NCP1397 primary-side controller and the 500 V high-voltage MOSFET NDF05N50 and the 6-channel linear LED driver CAT4026 in the half-bridge conversion stage. The CAT4026 is a cost-effective multi-channel linear LED driver for large-size, edge-lit LED-backlit LCD TVs that can support up to 12 channels in a single IC and easily grade up to 12 or 18 channels (2 or 3 correspondingly) Controller), target energy efficiency is higher than 90%, typical energy efficiency is 94%; provide "±2% excellent current matching accuracy and "1% 400 Hz PWM dimming range, and use external power bipolar junction transistor to achieve more Good heat dissipation.
The solution consists of an LED backlight converter (NCP1397, etc.) and an LED controller (CAT4026, etc.) (see Figure 1). It supports low-height LED-backlit LCD TV design with a board height of less than 8 mm and a total height of less than 12.5 mm. It can also optimize the processing of wide-range dimming, heat dissipation, fault protection, etc., to solve the power supply design challenges.
Figure 1: Large-screen LED-backlit LCD TV side-light solution (yellow background section)
Two mutually perpendicular reflecting surfaces are called ridge surfaces, and prisms with ridge surfaces are called ridge prisms.
The ridge prism is small in volume and can make the objective lens and eyepiece in a straight line, so it is often used for extremely compact binocular lens.
Roof Prism,Roof Penta Prism,Optical Roof Penta Prism,K9 Roof Prism
Hanzhong Hengpu Photoelectric Technology Co.,Ltd , https://www.hplenses.com