Class D amplifier and LED backlight are key technologies

TV screens are getting bigger, speakers are getting bigger, and black appliances are consuming more power. Energy conservation is becoming more and more prominent. Home appliances account for 15% of the country's total energy consumption, so energy conservation is a very important issue. However, most of the energy conservation targets for home appliances at home and abroad are white appliances (air conditioners, refrigerators, washing machines, microwave ovens, etc.), while few people mention energy conservation for black appliances (televisions, speakers, and other audio and video products). Only manufacturers advertise "energy-saving air conditioners", but no manufacturer advertises "energy-saving televisions". Does this mean that black appliances do not need to be energy-efficient?

The problem of energy saving of black electricity is becoming increasingly prominent

In fact, energy saving of black appliances during operation is a very important energy-saving link, because the daily working hours of black appliances are usually longer than those of white appliances.

The main energy consumption of black home appliances is located in the terminal output part, that is, the display screen for the eyes to see and the speaker for the ears to hear. In principle, the larger the display screen is, the more power it consumes, and the louder the speaker is, the more power it consumes. In recent years, TVs with screens larger than 29 inches have become the best-selling TV products, and speakers with wattages higher than 20 watts are also popular with users. Whether it is a CRT (cathode ray tube) display terminal or an LCD display terminal, the larger the screen, the more power it consumes. Similarly, in audio products, high-power audio amplifiers, home theaters, etc. consume considerable power.

At present, the number of television sets in China has exceeded 410 million. If each television set can save 10 watts of electricity, assuming 3 hours of viewing per day, 4.5 billion kilowatt-hours of electricity can be saved each year. This is a very impressive figure. In addition, in recent years, the performance of black home appliances has become higher and higher, TV screens have become larger and larger, and the wattage of stereos has become larger and larger. The power consumption of black home appliances has also increased, and the issue of energy saving has become increasingly prominent.

How can black appliances save electricity without reducing their performance?

CRT Energy Saving: Using Class D Amplifier

In 2007, my country produced 88.07 million television sets, 70% of which were CRT TVs, and there are about 60 million CRT monitors in use in my country. Therefore, energy saving of CRT is still the most important issue.

The power consumption of CRT is mainly determined by the size of the screen. The larger the screen, the higher the anode voltage and the more power it consumes. At the same time, the larger the screen, the greater the deflection current required. In the circuit that generates the scanning sawtooth wave, there is still great potential for energy-saving measures.

Although the sawtooth current required for vertical deflection is completely determined by the deflection angle, the power required to generate the same size of sawtooth wave can be saved. At present, almost all vertical deflection amplifiers use class AB amplifiers to amplify the power of vertical deflection sawtooth wave. However, this class AB deflection amplifier works in a linear state and has a very low efficiency. Usually, it has an efficiency of only 20%-30% at low output. Therefore, the class AB amplifier requires a large heat sink to dissipate heat.

A new type of Class D amplifier has now appeared on the market. This amplifier allows the final power transistor to work only in the switching state, which can amplify the analog signal and achieve an efficiency of 80%-90%.

When this amplifier is applied to the vertical deflection amplifier, a lot of energy can be saved. For example, a class AB deflection amplifier originally required 6.94 watts, but after using the class D deflection amplifier, it only needs 2.94 watts, saving 4 watts of power. Another vertical deflection circuit of a larger screen originally required 10.8 watts, but after using the class D amplifier, it only needs 4.6 watts, saving 6.2 watts. Therefore, on average, after using the class D amplifier in the vertical deflection of a TV, about 5 watts can be saved.

Although 5 watts is not a very large number, there are currently 400 million CRT TV sets in China. Assuming an average of 3 hours of use per day, 2.19 billion kWh of electricity can be saved each year. There are 60 million CRT computer monitors. Assuming they are used 8 hours a day, 876 million kWh of electricity can be saved each year. The sum of the two is as high as 3.066 billion kWh, which is a very impressive number.

LCD energy saving: Start with display backlight

my country produced 26 million LCD TVs in 2007, of which more than 8 million were sold domestically. The largest energy consumption of LCD TVs is in the backlight of the display.

Currently, most LCD TVs use cold cathode fluorescent tubes (CCFL) as backlights. CCFL has a high luminous efficiency, but because its light is emitted in all directions, a reflector is needed to reflect the light emitted backwards, which will result in a lot of loss. Moreover, its color performance is relatively poor, usually only 70%-80% of the NTSC (National Television System Committee, which is the color television broadcasting standard stipulated by the International Television Standards Committee, expressed in percentage. This indicator indicates the saturation of various colors that the display device can display) standard. And its bigger problem is the environmental problem - it contains mercury. The EU's RoHS standard has stipulated that related electronic products are not allowed to contain mercury. It has not been allowed to be imported since July 1, 2006. If it is imported, a hazardous waste disposal fee of US$10 will be paid.

Currently, the luminous efficiency of LED is relatively low, only 2/3 of CCFL. However, this situation will change as the luminous efficiency of LED increases.

Recently, the "field sequential" technology has been used to reduce the light loss of the color filter, which has doubled the total luminous efficiency. This "field sequential" technology is impossible for CCFL. In 2006, Samsung developed a 32-inch LCD TV with "field sequential" color filter-free LED backlight, with a resolution of 1366×768, a brightness of 500cd/m2, a contrast ratio of 1000:1, a color representation of 110% of NTSC, and a power consumption of 82 watts, which is 60% of the traditional method. Another 40-inch LCD TV, LE40M91, has a contrast ratio of 10000:1 and a color representation of 110% of NTSC. If a 40-inch LCD TV uses CCFL, it consumes 170 watts of power, while using LED backlight, it consumes only 100 watts of power, which makes its power consumption much lower than CCFL backlight.

Recently, some manufacturers have also introduced a "regional brightness control" technology that can control the brightness according to the content of the picture. This technology can only be realized by using LED backlight. After adopting this technology, energy can be further saved by more than 50%. Recently, someone in China has proposed a technology called "color LED display based on blue backlight", which can save power by eliminating color filters.

In short, assuming that each LCD TV can save 50 watts of electricity on average, and there are about 20 million LCD TVs in China, if they are turned on for an average of 3 hours a day, 1.095 billion kilowatt-hours of electricity can be saved each year.

Audio energy saving: Applying Class D amplifier

There are about 10 million mini speakers in my country, with an average power output of 40 watts x 2. Mini speakers are mainly used to play music, so the efficiency can be increased by 6 times after using Class D amplifiers. Assuming that they are turned on for an average of 3 hours per week, 55 million kWh of electricity can be saved each year. There are more than 10 million home theaters in my country. The average power output is 200 watts x 2 (including the average value of 5.1 channels). Assuming that they are turned on for 5 hours per week, 458.6 million kWh of electricity can be saved each year after using Class D amplifiers.

Of course, this is still a very incomplete estimate in terms of audio. There are a large number of KTV (karaoke) rooms and cinemas in my country, and the power of their audio is no less than the total power of household audio. In addition, there are car audio, broadcasting in various public places (train stations, bus stations, airports, etc.), and even more than 500 million mobile phones, tens of millions of learning machines, millions of game consoles, hundreds of thousands of walkie-talkies, etc., which can all use Class D amplifiers. In addition, by reducing the standby power consumption of various electronic devices and charging equipment, the prospect of energy saving is extremely impressive.

There is a lot of room for energy saving in black-and-white appliances

Nowadays, the world is beginning to pay attention to the standby power consumption of all electrical equipment (including black appliances). For example, the US Environmental Protection Agency has introduced the "Energy Star" standard, which stipulates that the standby power consumption of televisions is only 3W. The International Energy Agency (IEA) and the European Union have successively formulated a more stringent "1W plan", which is to reduce the standby power consumption level of all products to below 1W by 2010. The European Union also proposed that the standby power consumption of chargers should be less than 0.1W, and now follows the IEA's 0.3W recommendation. However, most countries do not yet have energy-saving regulations on the average power consumption of black appliances when they are turned on.

The energy saving of black appliances mainly comes from the use of Class D amplifiers and LED backlights. If all black appliances are replaced with high-efficiency Class D amplifiers, it is estimated that a total of about 5.6724 billion kWh of electricity can be saved each year. Similarly, if all LCD screen backlights are replaced with high-efficiency LED backlights, about 1.3037 billion kWh of electricity can be saved. The sum of the two is 6.8761 billion kWh.

Of course, to achieve such energy conservation, we must first formulate energy conservation standards for black home appliances. Now, although we already have the "Energy Efficiency Label Management Measures" jointly formulated by the National Development and Reform Commission and the General Administration of Quality Supervision, Inspection and Quarantine, it has not yet been implemented in black home appliances. Black home appliances have not yet been affixed with energy efficiency rating marks certified by the state. This is the first problem to be solved.

At the same time, all black home appliance manufacturers must also take the energy conservation of black home appliances seriously. Users must also enhance their energy conservation awareness and quality and resist black home appliances without energy conservation labels.

Energy conservation of black appliances requires joint efforts from the government, manufacturers, and consumers. It is hoped that in the near future, black appliances will be able to make energy conservation issues deeply rooted in the hearts of the people like white appliances and achieve energy-saving effects to the greatest extent possible.