Solution as an environmentally friendly and energy-efficient LED flashlight in a wide range of applications such as cars, homes, office buildings, hotels, airports, and street lights to find their own arena. But its large-scale commercial addition to still need to overcome the cost barriers need to be addressed dimmer flashes, heat, color, uniformity of technical problems. In addition, the concern for clean energy and the decline in the cost of solar panels, has also led to a boom of the commercial solar industry. To help readers better and faster to seize this opportunity, the article takes a special invitation to Linear power expert Tony to share his insights.
Q: using PWM or analog dimming, how to eliminate the LED light flicker?
A: The face of high power, high brightness LED flashlight penetration is increasing, the electronic lighting designers to provide efficient, accurate and simple LED driver solution. Due to the high power lighting (such as car headlamps, or large LCD display backlight) in series with the commercialization of the interchangeability of the LED array, thus making this task more difficult.
Traditionally, the use of accurate and current to drive high-power LED strings to achieve simplicity and high efficiency between the two conflict, usually need some kind of inefficient linear regulator program or a more sophisticated multi- IC switching regulator configuration. In addition, to ensure that each LED has a uniform brightness and does not produce any flicker also become a major design obstacle.
There are two widely accepted LED brightness control, analog dimming and PWM digital dimming. When analog dimming, the LED current adjustment range at a maximum value to the maximum of about 10% (10:1 dimming range). Chromatogram the current of the LED flashlight, so this method is not suitable for some applications. However, PWM digital dimming in some fast enough to cover up the rate of visual flicker (usually higher than 100kHz) switching between zero current and the maximum LED current. The duty cycle changes the effective average current, in order to achieve up to 3000:1 dimming range (limited only by the minimum duty cycle). Either in the maximum LED current or shutdown, the method has to be able to avoid the occurrence of the advantages of LED color cast, while in analog dimming LED color cast is a very common phenomenon.
Q: The cooling of high-power LED flashlight, the question should be how to solve?
A: Both the largest amount of the highest power LED flashlight application is a large-screen LCD TV display backlighting and automotive headlamps. You may wish to look at the Lexus (Lexus SARS), Audi (Audi), and the standard GM (GM) Cadillac Escalade LED headlamp. The overall lighting structure of all these cars is very similar. Each automobile headlamp includes five kinds of LED-powered beam, optimized for a variety of lighting requirements include: nearly light, high beam, turn assist light, daytime running lamps and turn signal indicator.
The standard LED flashlight beam will usually need to supply power from 35W to 50W. This may seem not a lot of power; provided by the LED brightness has reached 10 times the HID halogen, LED light output equivalent to 500W halogen lamp. High beam power required to reach with standard illumination beam generally the same or slightly a little higher, while turning the assist light, daytime running lamps and turn signal lights required power is lower. However, the overall automobile headlamp will consume more than 200W of electricity, which is likely to produce major thermal power dissipation. This is really not a good thing, because with increasing operating temperature, the LED light output and life will be quickly reduced.