High brightness LED to improve family energy efficiency programs

High power LED need to use high drive current level of 350 ~ 1000 ma. Using the latest technology, each LED can produce 40 ~ 80 lumens of luminous flux, general is 1 ~ 3 w. According to the data on the website for the department of energy (doe), the main LED manufacturers with Cree, Philips and Osram, etc. Below the HBLED with the widespread use of white light and fluorescence, compare a family application circuit examples are presented.

compare light

to HBLED ( High brightness LED) Aware of the benefits of consumers will be to find a way to use HBLED as much as possible. By comparison with the data in table 1 can be found, apparently HBLED is brightness top lighting scheme.

light source is similar to the efficiency of energy efficiency. Compared with the calorific value, how many is input into the energy into light bulb? User wants this value higher, apparently HBLED did that. If the drive current fluctuations, incandescent color hue most likely to change.

compared with incandescent lamp, fluorescent lamp and the main advantage is that life of HBLED so incandescent bulbs are being phased out in many countries. Next, HBLED may on the penetration than fluorescent light, because HBLED is solid, Made by silicone material, non-friable) , size is very small and do not contain harmful chemicals ( Don't need to deal with) the use of special environment 。

HBLED lighting design goal

let consumers to switch to HBLED, require HBLED must have a high quality. Consumers are demanding the power factor of at least 90%, the efficiency reached 80% or higher. In dc applications, the maximum input voltage is no more than 40 v. In communication applications, can use 120 v or 240 v ( The largest 270 v) The input voltage. HBLED must work with more than 120 hz frequency of pulse width modulator, driven to minimize annoying visible light blinking. Sometimes, the frequency is variable is required. In addition to these design constraints, but also by the engineer and the application to determine the design scheme using isolation or unfenced. If necessary, the last may also consider using complex dimming circuit.

as you can see, there is not a universal solution. Design considerations are interlinked. Each solution need according to the number of the LED current through the LED and designed. Designers also need according to the different electromagnetic devices, as well as the selection of power devices and to adjust the output capacitor. Application circuit

HBLED price is about 1 ~ 2 $. Because in each design scheme, HBLED is the string to use, therefore, when the design without considering the cost of converter constraint problems.

first introduces controller is ISL6721. ISL6721 is single-ended PWM current mode controller, the peak current mode control can effectively solve the problem of instantaneous power, and provides the built-in over-current protection. There have been a big contract manufacturers use ISL6721, can produce replace T8 circuit products (currently used The starter replace fluorescent lamp in the traditional ballast circuit) 。 ISL6721 can also be set to incandescent lamp replacement plan. Non solid flyback solutions is now in a shopping centre in Asia. The scheme USES 10 HBLED, output 10 w, efficiency is 82%.

to be really competitive in the domestic market, HBLED lighting solution must also provide the dimming function. Intelligent circuit can do this. Remember, the LED is driven by the PWM controller. That is to say, the LED is not always in a state of 'open'. The number of pulses to the LED power supply is controlled by the controller, and is variable. As it happens, the work is done by the 'controller'.

a 6 leds of the adapter and the dimming circuit consisting of a core of shoot the light design of complete circuit diagram ( Of course want to HBLED excluding) Is ISL6745A controller. In the top right corner of the device is composed of a SEPIC controllers, six HBLED drive together. The amplifier around the current adjustments, short circuit protection and over voltage protection. In the lower left corner, you can find the dimming circuit communication. Dimmers amplifier output filtering first, and then used as the reference point of current regulator, feedback to the control loop.

ISL6745A bias voltage VDD range is 6. 5 ~ 20 v, low side ( 低收入 面) FET drive output is 12 v, 1 a, can drive a low side FET ( So in the design of Q1) , high voltage driver IC gate, or gate drive transformer.

in Intersil products ISL6745A HBLED drive is the most popular. In addition to using method as shown in figure 1, you can also switch frequency of ISL6745A adjustments, soft start, over temperature protection, 'dead zone' time can also be precise adjustment. ISL6745A using MSOP - save a space 10 encapsulation. ISL6745A flexibility is also one big characteristics, can work in isolation method can also work in isolation, dimming function is optional. Conclusion

HBLED is the most green consumer lighting alternatives, and technological progress have enough to make it a viable option. Had appeared on the market can replace incandescent and fluorescent lamps. To save energy and prolong the service life and improve security and increase the reliability, please use HBLED.