Using high brightness LED to improve the energy efficiency of the family

High power LED with high driving current level 350~1000mA. Using the latest technology, each LED can produce 40~80 lumens luminous flux, power is generally 1~3W. according to the U.S. Department of energy website information, the major LED manufacturers have Cree, Philips and Osram. The following will be HBLED with a wide range of white paper lamps and fluorescent used to do a comparison, and gives a family application circuit examples.

Source comparison

Of HBLED (high brightness LED) the benefits that consumers will try as much as possible the use of HBLED. through the contrast table of 1 data can be found, HBLED is apparently the highest brightness lighting scheme.

Let us carefully look at the table of the 1 light source is similar to the energy efficiency. How much of the energy input into the bulb becomes light compared to the amount of heat? Users want this value to be higher, apparently HBLED did it. If the drive current fluctuates, the color tone of the incandescent lamp is most likely to change.

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Compared with incandescent lamp, fluorescent lamp and the main advantage of HBLED is life, so in many countries are being phased out incandescent bulbs. Next, HBLED may be more than the fluorescent lamp in the penetration rate, because HBLED is a solid state (manufacturing, by silicon material is not fragile), very small size, and does not contain harmful chemicals (without the use of special environmental treatment).

The design goal HBLED lighting

Allows consumers to switch to HBLED, HBLED must have high quality requirements. Consumers require a power factor of at least 90%, efficiency of up to 80% or higher. In DC applications, the maximum input voltage should not exceed 40V. in AC applications, which may be 120V or 240V (max 270V) input voltage. HBLED must be driven by a pulse width modulator operating at frequencies exceeding 120Hz in order to reduce annoying visible light. Sometimes, the frequency needs to be variable. In addition to these design constraints, engineers and applications will be able to decide whether to use isolated or non isolated design. If necessary, it may be possible to consider the use of complex dimming circuit.

As you can see, not a universal solution. Design considerations should be linked. Each scheme is designed according to the number of LED and the current flowing through the LED. Designers also need to be adjusted according to different electromagnetic devices, as well as the selected power devices and output capacitors.

Application circuit

HBLED price is about $1~2. Because in each design scheme, HBLED is used in the design of clusters, therefore, without considering the cost constraints of the converter.

The controller was first introduced by ISL6721.ISL6721 is a single ended PWM current mode controller, the peak current mode control can effectively solve the problem of instantaneous power, and provide built-in overcurrent protection. There is already a large contract manufacturer that uses ISL6721 to produce products that replace the currently used T8 circuit (replacing the traditional ballast circuit in the fluorescent starter). ISL6721 can also be set as an alternative to incandescent lamps. A shopping center of non solid flyback scheme has now been used in asia. The program uses 10 HBLED, output up to 10W, efficiency of 82%.

To be really competitive in the domestic market, HBLED lighting solutions must also provide dimming function. Intelligent circuit can do this. Remember, LED is driven by a pulse width modulation controller. In other words, LED is not always in the "open" state. The number of pulses supplied to the LED is controlled by the controller and is variable. It happens that the work is done by the controller.

Figure 1 shows the complete circuit composed of a 6 LED adapter and the lamp dimming circuit scheme. The core of design (of course, the HBLED is excluded from the ISL6745A controller). The upper right corner of the device is composed of a SEPIC controller that drives the amplifiers that are strung together around 6 HBLED. for current regulation, short circuit protection and overvoltage protection. In the lower left corner, you can find the AC dimming circuit. The amplifier output is first filtered and then used as a reference point for the current regulator and fed back to the control loop.

The range of bias voltage VDD ISL6745A is 6.5~20V (10w-side), low side output FET driver for 12V and 1A, can drive a low side PET (so in the design of Q1), high voltage driver IC gate or gate drive transformer.

In Intersil products, ISL6745A is one of the most popular HBLED driver. In addition to the use of the method shown in Figure 1, you can also adjust the switching frequency of the ISL6745A, soft start, over temperature protection, dead time can also be adjusted accurately. ISL6745A uses a space saving MSOP-10 package. The flexibility of ISL6745A is also one of the most important features, which can be operated either in isolation or in a non isolated manner.

Conclusion

HBLED is the green alternative consumer lighting, and technical progress has been sufficient to make it feasible. There are alternatives to incandescent and fluorescent lamps on the market. Save energy, prolong service life, improve safety and increase reliability, please use HBLED.