LED desk lamp design using adapter

As the fourth generation of new energy-saving light source, LED light source was used as the light source of various lamps since its birth. The incandescent lamp as a light source has a luminous efficiency of only 5%, and the luminous efficiency of the LED light source is almost 90%. LED lighting has become the focus of everyone's attention because of its high energy saving, long life and environmental protection. The desk lamp is an ordinary lamp used by every household. In recent years, the high-brightness LED light source has been leaps and bounds due to its manufacturing technology, and its production cost has been reduced. Now, the table lamp can use the LED light source as high brightness, high efficiency and power saving. A carbon-free lighting source.

LED table lamp working principle

Following the design concept of safety first civil electrical appliances, LED light source is a kind of low-voltage DC constant current source light-emitting device, which can not be directly lit with 100-220V AC high-voltage power. Therefore, the design idea of ​​LED desk lamp scheme is First, the high-voltage AC power is converted into a low-voltage DC constant current source to illuminate the LED light source. The most cost-effective way to step down and perform AC-DC conversion is the primary consideration in design. Today's portable electronic products use AC power AC-DC buck converters - Adapters are both affordable, ready-made, and A good choice.

The output voltage of the adapter is required to be stable at DC12V. The output current should be selected according to the power of the LED light source. Generally, a margin of 30% should be given. Take a 3×1W white LED light source as an example. The standard operating current of a 1W white LED should be It is 350mA, so the current required for the circuit connection of 3 LED light sources is also 350mA. Considering the extension of LED life and reducing the light decay, it can be designed to be 300mA~330mA, which will not obviously affect the brightness of LED illumination, so the output current of the adapter should be Choose 750mA ~ 1A.

A simple and practical LED table lamp scheme is shown in Figure 1. The AC220V provides a stable 12V DC power supply to the LED desk lamp via a safe step-down converter outside the luminaire. A constant current source power supply board is placed in the base of the lamp base to convert the DC voltage into a stable DC constant current source to meet the LED light source. Technical requirements for luminescence. A power switch can be added before the DC constant current source to turn off the DC power when the desk lamp is not used, but the 220V AC power supply cannot be turned off. Therefore, the power plug of the adapter should be removed from the wall when not in use. This is also the practical solution. The only "disadvantage". If you don't want to use mechanical switches and want a more creative selling point, you can use electronic touch switch, such as finger tap to realize the opening of the desk lamp - "full bright, semi-dark, off"; due to the rapid advancement of electronic technology, electronic touch Switches are now a low-cost device.