Class D amplifier +LED backlight: Dragon microelectronics launched a new storm black home appliances

Black home appliances usually refers to the audio and video output of home appliances. The main energy consumption of such appliances is located in the terminal display, which is used to watch the screen and speakers to listen to. As the size of the display screen is getting bigger and bigger, the number of Watts audio output is growing, the power problem can not be underestimated. How in the same audio output power and the same size of the screen size, to maximize energy savings, is the key to the black home appliances. In the day before at the IIC 2007 exhibition, dragon vessel microelectronics has demonstrated its filterless class D audio power amplifier PAM8803 and LED driver IC series of the latest, from two angles of audio and video perfect interpretation of the new concept of black appliances such.

Class D amplifier will replace the class AB amplifier

Compared with the ordinary class AB amplifier, the efficiency of class D amplifier can be higher than 3 times. This makes it one of the important measures of energy conservation of black home appliances. Ding Ding, chief scientist pointed out that the micro Bo, audio power amplifier is in the revolutionary period, the trend from analog amplifier to switch amplifier will be unstoppable trend of.

However, one of the major drawbacks of the class D amplifier is the need for an external low pass filter to filter the high frequency switching. Not only increase the cost but also increase the area of the PCB board, while increasing the electromagnetic interference. In the case of the removal of low pass filter to maintain a very low quiescent point current is undoubtedly a challenge to the design of such products. For example, a low pass filter class D amplifier with a quiescent current of about 20-40mA; and when the filter is not used when the quiescent point current will be up to about 200mA.

5-6mA recently launched a class of non filter class D audio power amplifier PAM8803 is the company has a completely independent intellectual property rights of a product, the absence of the filter, the quiescent point current is only one way. Since the output of the amplifier does not need a low pass filter, 4 inductors and 4 capacitors are saved, the area of PCB is reduced by about 75%, and the cost is reduced by about 30%. In the 5V supply voltage, the output can be 3W audio power, when the power supply voltage as low as 2V can also output enough power, which makes it very suitable for battery powered products. When the output power is 1-2W, the THD+N is as low as 0.3%. PAM8803 EMI is very low, in line with the U.S. FCC Class B standard. In addition, the product integrates 64 level digital volume control, eliminating the need for external volume control chip, thereby further reducing the cost.

Mao Yu Hai revealed that this is cheaper than similar products TI company nearly 50%, and therefore has a large cost advantage. At the same time, he said, and now D class amplifier compared to the AB price is still high, only the product shipments on the stairs, the cost can be reduced to a minimum. At present, the dragon has been applied for the patent in the United States, and is about to apply for a patent in china.

LED backlight needs a lot of popularity

On the other hand, for LCD TV, the screen backlight is currently using CCFL (cold cathode fluorescent tube) as a backlight. If you use LED backlight, you can also save a lot of energy. Dragon vessel microelectronics company has developed a series of LED driver IC, has now entered the mass production of the PAM2701 LED LCD screen backlight is used to drive the mobile phone or PMP, this is a charge pump chip, plus the need to 4 ordinary low-cost ceramic capacitors can work. It can drive up to 4 forward current up to 30mA of LED, and to ensure that the current difference of less than 3%, the need to light the LED by the control line to choose from the 3. It can work in the lithium battery voltage higher than the forward voltage of LED, can also work in the lithium battery voltage is lower than LED forward voltage, and can automatically convert its mode. Its maximum efficiency is as high as 91%.

To drive a higher power 3W LED, the dragon also developed a step-up microelectronics PAM2801. This chip can in a battery 1, two batteries, or the use of solar cells, light a 1W or 3W LED, the feedback voltage is only 95mV, and the maximum output current can reach 1A, the highest efficiency can reach 90%.

Mao Yu Hai pointed out that the color of the LED display is closely related to temperature, temperature changes will affect its color display, so there are still many difficulties in the design. But he also admitted that the manufacturer home appliances or in the price competition China low-level competition stage, not to take such measures actively, so the key black energy-saving appliances is to be made by the government to take measures to formulate relevant laws and regulations. "In the long run, environmental protection and energy-saving black home appliances can save energy consumption and cost, will be the future development trend. "

Author: Chen Jinjin

Source: Electronic Engineering album