Analysis of the latest development trend of the ho

Analysis of the latest development trend of LCD TV power supply

with the advantages of large screen, low waw-d-c series microcomputer controlled electro-hydraulic servo hydraulic universal testing machine, WDS tensile testing machine thickness and high definition, the penetration rate of LCD TV in the market has increased rapidly. Market research predicts that the overall market share of LCD TV will reach 50% in 2009. With the continuous breakthrough of screen size, the power of LCD TV has also increased. Higher power consumption will directly increase consumers' electricity expenditure and deviate from the trend of energy conservation and environmental protection. Therefore, governments and regulatory agencies around the world have issued or updated Energy Efficiency Specifications for television, such as the "Energy Star" version 3.0 television specification issued by the U.S. Environmental Protection Agency (EPA), which has come into force since November 1, 2008

lips solution replaces the traditional LCD TV power supply

in order to reduce the power consumption of large-size LCD TV, make it comply with various energy efficiency specifications, help reduce the system cost and reduce the size of the solution, and make LCD TV more popular with consumers, we can take a variety of ways in terms of LCD TV power supply

Figure 1: block diagram of traditional LCD TV switching power supply using standard DC 24 V inverter

traditional LCD TV power supply mainly includes AC-DC conversion, DC-DC conversion and high-voltage inverter. AC-DC and DC-DC are located on the same circuit board, while the inverter is a separate circuit board, which is usually provided together with the LCD panel. Among them, the AC-DC power supply part, the mains 110 vac/220 VAC voltage is converted into 200 v/400 V DC high voltage through rectification, power factor correction (PFC) and filtering. Since the input voltage of the traditional inverter is required to be 24 V, the output voltage of PFC 200 v/400 V must be reduced and converted to generate multiple output voltages, of which one 24 V voltage is supplied to the inverter, that is, it is converted into a high voltage of more than 1000 V or even up to 2000 V through DC-AC to drive the CCFL backlight of the LCD panel. The functional block diagram of this standard 24 V inverter LCD TV switching power supply is shown in Figure 1

in the current LCD TV power supply on the market, this traditional power supply still accounts for the majority. It is worth mentioning that among LCD TV models of various sizes, LCD TVs larger than 26 inches, especially 32 inches and larger, occupy a dominant position in the market. In recent years, a new inverter concept, LCD integrated power supply (abbreviated as lips), has emerged for 26 inch and above LCD TVs. Unlike the traditional power supply where the inverter is located on an independent circuit board, this lips solution combines AC-DC, DC-DC and inverter on the same circuit board. After rectifying, PFC and filtering the mains power and obtaining a 200 v/400 V DC voltage, 200 v/400 V voltage will be directly used as the input of the inverter, which will be converted into a high voltage of more than 1000 V or even up to 2000 V required by the LCD panel through DC-AC boost. In this way, the 24 V conversion section is eliminated, and a large amount of power loss in the process of reducing the voltage to 24 V first and then greatly increasing the voltage of the backlight with a high voltage of one or two thousand volts is reduced, so as to improve the energy efficiency of the system and reduce the bottom coil. Then, we can find a professional technician to investigate the heat of the experimental equipment and reduce the total cost

Figure 2: functional block diagram of full bridge high voltage lips solution of Anson semiconductor for 32 inch LCD TV

in this regard, Anson semiconductor cooperates with MICROSEMI to provide a complete set of high voltage lips solutions suitable for various power levels by combining their expertise. At present, we have cooperated to develop lips solutions for 32 inch LCD TVs (as shown in Figure 2). In terms of the system motherboard power supply, this solution adopts the ncp1606 PFC controller of Anson semiconductor and the NCP1351 PWM controller as the auxiliary switching power supply; In the part of lips inverter, the lx6503 phase-shifting full bridge driver of MICROSEMI using soft switching technology is adopted, which can conduct zero voltage switching (ZVS) at a fixed working frequency. Compared with the half bridge structure, this full bridge inverter solution has significant advantages, such as reducing electromagnetic interference (EMI) and power loss, while improving the driving current waveform of the backlight. There is no need to use additional power diodes on the bridge. The current specification of the four MOSFETs and transformers used in the full bridge structure is half that of the half bridge structure. It can directly drive the power MOSFET through the isolation transformer, GH2132 alloy overcurrent protection (OCP) and other materials are easier to realize the primary end experiment

in order to better meet the market demand for larger size lips LCD TVs, Anson semiconductor is developing the next generation of lip LCD TV reference design, and plans to launch a 46/47 inch reference design in mid-2009. In the part of lips inverter, the full bridge inverter and backlight controller lx6503, which are the same as the 32 inch scheme, are used, but the output power is greatly increased, which can drive more CCFL lamps. In terms of system motherboard power supply, we can flexibly choose ansenmey semiconductor solutions according to specific design requirements, such as PFC controllers such as ncp1601, ncp1606 or ncp1631, and PWM controllers such as NCP1351 or ncp1379. This new solution uses a dedicated standby switching power supply with relays to support ultra-low standby energy consumption as low as 150 MW. The component height on the circuit board of this solution is less than 16 mm (the total degree of the system is less than 20 mm), supporting a thinner LCD TV design

it is worth mentioning that different regional markets such as the United States/North America and China/European Union have different requirements for power supply. Anson Semiconductor provides corresponding power supply solutions for different power supply requirements in different regions of the world, aiming at optimizing design, reducing system size and reducing costs

different regulator configurations are used for audio and video signal processing power supply according to the output current requirements

for audio and video signal processing, the input voltage is usually + 5 V or + 12 v. in terms of the configuration of voltage regulator or controller, it can be configured according to the output current requirements. Generally speaking, low voltage drop regulator (LDO) is used for low output current, and the range is generally between 0.1 and 1.5 A; The high current LDO, bias input LDO controller and integrated step-down converter are used to provide an output current of 1.5 A to 5 a. In terms of larger current, Synchronous Step-Down Controller with external switch and synchronous rectifier can be used to provide current output greater than 5 a. Ansenmey Semiconductor provides a series of high-performance LDO regulators, such as ncp699/633, ncp5500/5501, ncp3334/3335a, ncp5661/5662/5663, ncp605/606 and ncp3520/3521

from the perspective of development trend, with the increasing integration of more audio and video processing chipsets, a single IC may need multiple output voltages (such as 3.3 V i/o and 1.25 V core), making the choice of linear scheme (LDO) increasing. In addition, as the size of the circuit board tends to be smaller, the board space that can be allocated to LDO power dissipation is reduced. Accordingly, the DFN packaged LDO can be used to improve the power density, and the integrated MOSFET and LDO controller can help reduce the occupied area of PCB

on the other hand, in order to improve the power conversion efficiency and support high current operation and out of phase operation, some outputs need to be converted from LDO to switching regulator. Switching regulators and controllers are tending to adopt higher switching frequencies, such as from 50 kHz to 150 kHz, 350 kHz, 500 kHz and even 700 kHz, which allows the size of external inductors and capacitors to be reduced and facilitates the manufacture of thinner LCD TVs. In order to help reduce the system size and cost, switching regulators tend to integrate multiple outputs, such as dual regulators. In addition, the current requirements on some voltage input terminals are higher and higher, even greater than 5 A, which gives birth to integrated switching regulators with greater current capacity, as well as discrete controller + field effect transistor (FET) combinations with higher switching frequency, and promotes the application of synchronous rectification technology

Anson semiconductor ncp312x series two-way 2 a/2 A and 3 a switching regulators are very suitable for the application of +5 V or +12 V input terminals on the LCD TV signal processing board. Their frequency can be adjusted between 200 kHz and 750 kHz, providing 0.8 V ± 1% voltage reference, and supporting 180 ° out of phase operation, and users can control the automatic tracking and sequencing function

the novel PFC architecture is adopted to support the design of ultra-thin LCD TV

as we all know, the thickness of LCD TV can be thinner now, and the latest trend is that the thickness of electronic modules tends to be less than 10 mm. Such a thin thickness brings more stringent challenges to the power supply design, such as the need to use a low height transformer (which is particularly critical for high-voltage lips that need to consider isolation and leakage) or multiple components (PFC coils) in series, and use a low height heat sink to horizontally install the components, and limit the height of all capacitors vertically inserted to less than 10 mm

Figure 3: functional block diagram of interleaved PFC architecture realized by using two ncp1601 PFC controllers

in terms of PFC, the thickness of LCD TV can be reduced to a low level by using the ncp1606 and ncp1654 PFC controllers of Anson semiconductor. In order to support the extremely thin design as low as 10 mm, two relatively small ncp1601 chips can be used to realize the interleaved architecture, as shown in Figure 3. The main idea of the so-called interleaved PFC is to place two smaller PFCs with half power in parallel where a single larger PFC was originally placed. These two smaller PFCs work alternately with a 180 ° phase shift. When they are added at the input or output, the main part of the current ripple of each phase will be offset

in order to provide customers with more choices, Anson semiconductor also plans to launch a new interleaved PFC controller ncp1631 in 2009. This is a single-chip solution, which replaces two ncp1601s, but can achieve the same extremely low design height, suitable for the design of extremely thin LCD TV with a thickness of 10 mm, and also expand the power range and reduce the current ripple

standby energy consumption tends to be less than 100 MW

the standby energy consumption of LCD TV is another noteworthy point. The standard for standby energy consumption in the "Energy Star" version 3.0 TV specification, which came into effect in November 2008, is less than 1 W. Although this standard is not mandatory, it still has high guiding significance in the market

the standby energy consumption of LCD TV will be further reduced in the future. For example, with the addition of a small dedicated microprocessor, the energy consumption is less than 600 MW when the output power is 50 W, less than 400 MW when using a dedicated standby switching power supply, and less than 200 MW when using a dedicated standby switching power supply and adding relays (thereby disconnecting all PFCs and switching power supplies in standby). If manufacturers want to use more "green" technology to differentiate products, establish a higher brand image and improve profit margins, they need to further improve the design, so that the standby energy consumption of less than 100 MW may become the next important trend

summary:

as the LCD TV market continues to grow, its power consumption has also attracted more attention. An important way for electronic manufacturers to stand out in the market competition is to constantly optimize their LCD TV power supply design to make it conform to the latest energy efficiency specifications and other important development trends, such as using lips scheme to replace the traditional inverter, supporting ultra-thin LCD TV design through innovative PFC architecture, and so on. The transition point of "Hooke zone" and yield zone on the fiber tension curve is called the yield point. This paper emphatically analyzes the influence of these trends on liquid