For medium to large-sized LCD TVs, both power consumption and cost are significantly higher than traditional CRTs of the same size. To replace CRTs as the mainstream product, LCD TVs must achieve reasonable power consumption reduction and manufacturing cost reduction, as energy conservation and emission reduction have become the theme of the times. As consumer electronics, price will always be a major factor for users. From a power consumption perspective, to achieve energy conservation and environmental protection, governments and energy agencies around the world have formulated various new energy consumption standards for different power ranges and applications. At the same time, stricter regulations are also being developed. ENERGY STAR (EPA V3.0) has clearly defined the maximum power consumption of television products (Table 1), and this standard will officially take effect on November 1, 2008. [img=598,136]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055001.jpg[/img] Table 1: Definition of maximum power consumption for high-definition televisions in ENERGY STAR V3.0. Furthermore, the maximum allowable power consumption of television products in the EPA V3.0 specification corresponds to their size (Table 2). The maximum power consumption requirement for a 32-inch LCD TV is less than 120W. Currently, the power consumption of LCD TVs on the market generally exceeds the upper limit of the new standard. Therefore, to pass ENERGY STAR certification, design engineers have only two options: fundamentally change the existing power system design to reduce power loss during power conversion; or reduce backlight brightness and decrease the output power of the audio system to reduce the power consumption of the LCD TV. [img=498,165]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055002.jpg[/img][align=center] Table 2: Calculation of maximum allowable power consumption for LCD TVs of various sizes according to the ENERGY STAR V3.0 standard. [img=550,109]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055003.jpg[/img][/align][align=center] Table 3: DisplaySearch's statistics on LCD TV costs in recent years and predictions for future trends. [img=550,233]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055004.jpg[/img][/align][align=center] Table 4: Comparison of the advantages and disadvantages of traditional LCD TV power supply solutions and On-Bright Electronics solutions. [img=550,85]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055005.jpg[/img][/align][align=center] Table 5: Comparison of power consumption between traditional LCD TV power supply solutions and On-Bright Electronics solutions. [/align] Table 6: Comparison of main components between traditional LCD TV power supply solutions and On-Bright Electronics power supply solutions. Clearly, the latter sacrifices the user's visual and auditory experience, while the former is the optimal choice. This presents a major challenge for power supply design engineers: how to reduce the power consumption of LCD TVs without compromising audiovisual effects. [img=582,238]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055007.jpg[/img] Figure 1: On-Bright Electronics' 62W LIPS power supply developed for LCD products under 23 inches. LCD TV Power Supply Solution Analysis: Due to the diversity of loads, the design of LCD TV power supplies has become relatively complex, requiring features such as AC power factor correction, isolated power conversion, non-isolated point-of-load power conversion, and various power monitoring and protection functions. LCD TV products are increasingly relying on technological innovation in the field of power management to establish their competitiveness in the market. Since the total power of an LCD TV is usually less than 75W, it does not require a PFC circuit. The design and manufacturing of its power supply module are relatively mature. The early separate AC/DC main power supply board and DC/AC inverter power supply board have been integrated into a single PCB board to reduce manufacturing costs, which is the current mainstream LCD Integrated Power System (LIPS) structure. On-Bright Electronics has developed several LIPS power supplies for such applications. The AC/DC conversion circuit mainly uses chips such as OB2263, OB2269, and OB2202, while the DC/AC inverter circuit mainly uses chips such as OB3316, OB3318, and OB494P. Small-sized LCD TVs only have two PCBs: a power board and a signal processing motherboard. However, for 32-inch LCD TVs, the internal structure is relatively more complex. Figure 2 shows a traditional 32-inch LCD TV as an example. Its internal components mainly consist of three PCB boards: 1. A signal processing motherboard, used for audio and video processing and system control; 2. An AC/DC power supply board, which converts the 220V@50Hz or 110V@60Hz AC input from the mains into DC voltages such as 24V/18V/12V/5V/3.3V required by the audio, video, and control systems, and performs power factor correction and safety isolation from the input power grid; 3. A DC/AC power supply board, which inverts and boosts the 24V or 12V DC voltage output from the AC/DC power supply board to obtain a 1000V@50kHz AC voltage. This high-voltage, high-frequency sinusoidal AC voltage drives the backlight CCFL lamp and enables backlight brightness adjustment. [img=600,380]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055008.jpg[/img] Figure 2: A traditional LCD TV has three built-in PCB boards: signal processing, AC/DC power supply, and DC/AC power supply. Figure 3 is a structural diagram of a traditional LCD TV power supply, which can usually be divided into three main modules according to function: PFC module; DC/DC main power supply module; and DC/AC inverter power supply module. [img=551,186]http://cms.cn50hz.com/files/RemoteFiles/20081225/405055009.jpg[/img] Figure 3: Structural diagram of a traditional LCD TV power supply system. Offline switching power supplies inevitably generate non-sinusoidal input currents with high harmonic content, which can pollute the power grid and affect other electronic devices connected to the same power line. To meet the EU IEC 61,000-3-2 Class D standard or similar regional harmonic content specifications, a PFC module is usually required in switching power supply designs with an input power greater than 75W. Large-screen LCD TVs have input power far exceeding 75W, therefore, a PFC module is also an indispensable part of LCD TV power supplies. The PFC module uses a boost circuit to convert the AC voltage input from the mains grid into a stable 400V DC voltage to supply the subsequent DC/DC power supply.