Analyze of some important property of LED
LED color
The led color is terrible important property ,echo led will indicate correspond color, there are red ,green , blue , yellow , white , warm – white in led color, we should tight remember those color when design , because of the different color will result in vary change for design work

* LED currently
LED currently The led forward limit currently as 20mA,the luminous decay can’t be over IF/3, about 15mA or 18mA. the forward currently is proportional to luminous intensity in a certain scope. the luminous will not increase when the forward currently over 20 mA, the reliable input currently is in 17~19mA, those value only suitable for common low power LED（0.04-0.08W）, the rated power of high power led as 40mA.
With technology development gradually , various high power led was appeared on LED market, such as 0.5WLED（IF=150MA），1WLED（IF=350MA），3WLED（IF=750MA）there are more property in product datasheet , please refer to correspond product manual.
*LED voltage the connect way of led forward voltage is that led positive pole connect to positive pole of power , negative pole connect to negative pole of power. the led color relate to input voltage, for example red ,yellow and green of voltage between in 1.8—2.4v, white ,blue of voltage between in 3.0—3.6v, there are some different even from same bitch,
* led reverse voltage
The reverse voltage of led over limit reverse voltage will breakdown LED.
*led intensity
How may Intensity does the led have?
*Luminous Flux
Luminous Flux The stream of photons coming from a light source,the value of luminous is define by human , there are different result between the human and animal , the human has different feeling through saw the different color ,the yellow green light is sensitive color for human’ eyes. the red light is not sensitive color for human’ eyes.
* LED service time The LED can met to 50,000 hours in general datasheet Some professor put out a report ,they talk about the high quality led working for 50,000 hours before it still has 60% luminous , the led is not quit work, the luminous decay will appear with time is fly.
*Led lit angle,
the light scattering agents were blended with led that the LED light -emitting adjusted to met variety of angle needs.

LED design solution base on H bridge
LED design solution base on H bridge is classics driver electrical circuit for DC motor. the simply work theory of H bridge driver is that via PWM(pulse width modify) to switch four MOSFET, it is widely use for mechanic or power electrical device. this instance is newly solution for full wave current limiting . The H bridge can driver LED array directly,thereby the solution achieved that soiled state LED with no flash and high efficiency .it will AC transform to DC and output constant currently.new solution with fast response and without rippe .improvement output power rate.

The COB packing is more reasonable than traditional SMD packing. the COB packing is that single or various led chip pacing in to aluminum substrate.aluminum substrate for heat dissipation. the COB packing is low heat resister, the low heat resister lit well-distributed is the advantage .so the COB widely applicable to the lighting field

Attentions in use:
The COB afraid static electrical, so ant-static electrical is necessary , especially the static electrical is bigger that max specified value. it will damage the cob. the user must adopted a resolution for ant-static electrical,

Welding
The power of welding machine be lower 20W and work temperature of welding machine is not higher than 300℃, the welding time no more than three seconds.
Clean COB
After welding please using ultrasonic to clean the COB

White light led
Any one know that the wavelength range of visible light between 380nm～760nm，human eyes can saw seven kind of color in 380nm～760nm. the seven kind of color is red, yellow ,orange, green, glen , blue and ultraviolet respectively , they are signal color, for example green led lit that wavelength is 565nm. so there are not white light in optical spectrum of visible light. the white light is not signal color light. fox example the blue light and yellow light mix to white light, and mix up the blue light and green light with red light produce white light. the key step of white production is blue light.

Let’s summarize what is important note
*The engineer utilized bright of red green and blue to producing white light, in general the ratio of luminous of red green and blue is 3：6：1.
*The blue light (InGaN) LED to stimulate the yellow phosphor to producing
white light.
*The blue light (InGaN) LED to stimulate the RGB (red,green,blue )phosphor to producing white light

Talk about dual-color LED

The dual-color LED can lit light of two kind color
In general, there are three type of dual-color LED,

* Dual-color led with three pin
The dual-color led has three pin, the middle pin is common pin.
other pin correspond two color respectively
* Dual-color led with four pin
Echo side output one color respectively

*Dual color led with two pin
It just only has two pin, the follows are work status of dual color led with two pin
The positively of power lead to short ping and negative connect to long pin will generated one kind of color.
The positively of power lead to long ping and negative connect to short pin will generated other kind of color.

High temperature will cause low light output
The drift of led wavelength due to a variety of output color

Forward voltage will fall down
persistent herd for long time will cut down server time or cause luminous decay.

The currently effect
The drift of instable current due to a variety of color output
If the currently is beyond its normal range value will decrease server time.

LED driver IC

With the continuous development of led lighting, the led lighting system are increasingly being applied to all led lighting areas .there are not any advantage if the inappropriate led driver is selective. so   the led driver IC(integrated chip)   is important for led lighting design on led lighting field. followings we will talk about technology detail of led drivers.

*The voltage input range should be in DC8-40V, the wide input voltage adapt to various design. the suppose voltage was fluctuations as grid
voltage change. at moment the fluctuations voltage will damaged led.we’ve got to get the wide input voltage on your design.

* The require output currently of led driver as 1.2-1.5A , the input currently of 1W led source as 350mA , the input currently of 3W led source as 700mA . the high power led driver can support high power led source.
so we will require sufficient output currently to driver led source. by the way, the led driver don’t output currently with full energy ,the work status of output currently is best as output rage at 70-90%. the solution can increased led server time.
*The led source will require constant output current and the led source can lit constant bright. the output currently should be as small as possible on same batch of led driver. this best way for discrete control . and it can keep the finial production consistent.
*LED encapsulation help the led chip dissipate heat rapidly.*The key conditional of comply with CE and UL certification is that
the led drive ic has capability of anti nose and anti EMI. it is necessary to select appropriate construct and production technology for your project.
* The work power of led driver should be less than 0.5W, and the work frequency should be big than 120Hz, to avid interference from power frequency noise. the led lighting can not do without led drive ic, so the led source will require multi – function led drives.

Intelligent led system

In pass year, the fluorescent lamp is mainly lighting device in business

lighting areas. thought it can saved a lot of cost than the filament lamp.
but some problem was exist with fluorescent lamp, for example
* server time is shorter
* color temperature has different
* random shining and random noise
* it cat not validly adjust light level to save electrical energy
* which effect server time as frequency switch ON/OFF

Base on those problems , the human thought that how to improve led lit system. include that add a intelligence controller . the controller also is network device. this is corner stone of led network lighting .
The new solution of led lighting design provided high efficiency element .it’s can save 90% electrical energy than traditional lamp.

In summary, this is new trend in the development of led lighting system.

How to selecting the suitable led for your project

LED is a solid state semiconductor device. it can transform electrical energy to light energy directly. The led is a most popular light device. the follow topic will introduces parameters of led and the skill in selecting led.

LED characters

*Voltage- The input value of led is in low voltage, the range of input voltage between 2v to 4v, this is safety voltage for user, so it is appropriate for public place.
*Currently-Work currently from 0mA to 15mA, as the work currently increase gradually , and led has more bright
*Efficiency- the consumer energy was decrease eighty percent than tradition lamp.
*Appropriate- the led sharp is square with 3mm or 5mm, so the led appropriate for complex environment.
*Responsible time, The responsible time of tradition lamp is m second , the led responsible time is n second.
*Friend environment – The led has not harmful metals

The selecting in led skills

* The price is different when led bright is different
* Anti-static electrical capacity – The led has strange capacity for anti static electrical, so it has long server time. The led can use for lighting design when the anti static electrical reached to 700V
*Wavelength – The standard wavelength require . the price as growth when the customer is going to buy some led with same color
*Leak current ,The led woke at fore-ware voltage, it will make leak currently when the led woke at reveres voltage, the leak currently will effects server time of led.

The safety requirement of LED lighting
The safety requirement of LED lighting means to the led lighting can meet safety parameters in design and product,The standards can prevent dangerous

For production safety, The following step of quality check is necessary
* identifying rated voltage，frequency, power, color temperature
* lit test / function test
* voltage withstand test and insulativity test(Inspection led lighting wiring and insulativity is whether good)
* test for continuous connect to ground