2012-10-16

High quality LED lamp

LED manufacturers and their distribution partners are working hard to improve product flux tolerance, at reasonable cost range to provide finer classification. For hope that the product can use 5 or 50000 hours, and in the use of period to maintain overall light output constant designers, even want to meet the most intensive flux classification and set the tolerance of 0.1% current source is also very difficult to achieve. Because the heat and over time and the attenuation performance of two important factors may reduce LED luminous flux, Viribright LED globe lamp dab8d29ck even if the current source tolerance and LED flux tolerance to achieve 0.001% can not solve the problem. To account for these losses, high quality solid-state lighting products designer must find additional feedback loop power, namely, find the heat and light. This requires the dimming control, the output current of the linear control and PWM ( pulse width modulation ) control IC has become the best choice.

The United States National Semiconductor LM3409 and LM3424 is a LED drive IC control, which is applicable to the semiconductor lighting second generation current source. Two products can be through the variable resistor or a voltage source to control the average LED value of current, and can provide PMW (pulse width modulation ) modulation optical signals to provide specialized input signal. In addition to the linear control circuit, LM3409 and LM3424 analogy regulation function also allows a system designer can weigh in the output current accuracy and the size, cost and current detecting resistor between the power to make their own choices.

Need a light control application

Street is a very good source examples, because it has a strict legal standard limit. The road lamp, EU countries set the minimum and maximum light output and lighting model. To conform therewith and provides five year or longer service life of LED lamps, the design must take into account the heat caused by the instant flux loss and longer time to bring down flux loss performance. A natural approach is to use light sensors, such as constituting a linear control circuit of photoelectric diode. The system is enabled on the first day, Viribright LED Bulb Brand shall use only a portion of the overall drive current, this is done by taking into account with the passage of time, the drive current will be increased to a cap, thereby ensuring constant light output. The photodiode bias, and converted to a pulse width modulation signal, which will help in the dimming range of maintain a more constant relative to the color temperature, the linear control circuit is more simple, generally dimming range is relatively small. According to the different time, motion sensors or other measures of saving power consumption, light output control, the PWM control will be more useful. Figure 6 gives a longer life, constant light output LED lamp putative principle diagram.

Output current accuracy evaluation of LED drive only one aspect of performance, but when LED itself flux tolerance remain at far higher than±1% level, even if the current source tolerance and several instruments processor voltage rail tolerance requirements as strict, almost without any meaning, the average LED current tolerance should be about to luminous flux tolerance. In this paper, based on a single classification error of an ideal situation, and gives some practical examples, the examples of the use of two or more classes of LED, its tolerance can also more easily reach± 5%,± 10% or higher. In additional to the control loop, should make money for 1% of the current control, and power in higher detection voltage can be. Some LED exhibit of lanterns emphasizes more simple and practical and low cost, and even using a linear light would be too complex and expensive, but if you want to play LED full performance lighting requires the use of linear control or PWM ( pulse width modulation control ) mode or the two coordination use, hkcar and upgrade the product performance and service life.