The method analysis and protect reason for led

The paper introduction of base concept of led ,the reason of damage and protect electrical circuit.LED base concept (LED is light emitting diode)is semiconductor it put the electrical energy into light energy , it adopt electrical to lit.base on analysis , the character of led is obvious , for example it has long service time, excellent efficiency , no radiation and low power,the optical spectrum almost focus into vision frequency channel , the optical efficiency can reached 80~90%,the high power is light power rate, in generally refer to 0.5W,1W3W5W or upper , lit angel refer to aggregate state of light  led protect,
In specify electrical circuit, we can using the protect circuit as follows,bypass protect, there are many branch is in led serial electrical circuit, we can add a PTC component to protect led in echo branch, this is method as high accuracy and stability
Protect led in generally
Add a PTC component to protect led in generally in echo group led. the advantage of solution is simply , the user was satisfied with the results of the method,
In summary , this paper has been introduction of base concept , the reason of damage and the method of protect led, first we talk about the led concept , then we has analysis that the reason of led damage,
finial we has been refer to some method to protect led. and we introduce electrical circuit of led. wish it is valid information for your led project.

Common LED constant currently

First we recognized LED, because of the led luminous is proportional the led forward currently. and the led structure determine the property of led heat dissipate. the led manufactory will provide detail data shell for user information .fox example Φ5 as 20mA, 1W as 250mA, those parameters not mean that the Led is constant currently device.

Now we start introduce the constant currently , the mainly component
is triode, the withstand voltage of triode should be over 400V, and the power should be over 10W, the radiator is necessary . the electrical circuit can load at least for a few triode. can reached ninety triode.

thought the cost is on the increase, but the affect is best than resister currently . the electrical circuit still output constant currently ,even the input voltage fluctuates largely, so the led have a position of advantage on server time. it can take work currently in constant status,

*The electrical circuit of constant currently
By the way we will talk that which is best way to current limiting both serial connection or parallel connection.
LED electrical circuit adopt serial connection or parallel connection, it is determine by require of design electrical circuit.
in serial connection , one of those led was in open circuit, and other LED will stop lit, one of those led was in short circuit , and other LED is nothing.

in parallel connection, one of those led was in open circuit, and other LED is nothing,
one of those led was in short circuit, whole circuit electrical is break , even the power supply will stop work or damage. the serial connection has certain advantage over the parallel connection.
connection just only to put a low input voltage to led. if each LED has different offset currently , so it will lit different luminous, it may cause uneven luminous.

Essentially, the serial connection can provide the guarantee of consistency currently for LED, but it is necessary of high voltage.
the sum of all led currently is total currently of electrical circuit,
so the sufficient power supply is necessary.

Strict speaking ,there are shortage in serial connection and parallel
connection. there is more to think about design circuit of LED. in fact application, we will adopt the array of serial connection and parallel connection. the resolution can overcome or reduce those shortage.

Furthermore, we also can using serial – parallel – serial connection.
the resolution can reduce influencing surface for a LED , and a few of high power resister become to dozens of low power resister , it is advantage of dissipate heat system, the led device is compactly layer out as a whole.

Using it to drive low power led, it has advantage that not afraid load short circuit, simply electrical circuit. a electrical circuit can drive dozens of led.

The leaking currently only has 100uA, when led can work properly , the led will open circuit ,there are transients in dc power supply .

The typical capacity down back of electrical circuit
We will check the driver electrical, we should carefully check electrically circuit whether correction or not , special check the position poly and negative poly of rectification bridge .

due to the capacity down back is not isolate power supply ,the electrical circuit has withstand high current impulse. also call it’s transients. the withstand high current impulse may damage the LED.
so using the temperature coefficient prevent the withstand high current impulse,
there are PTC(positive temperature coefficient and negative temperature coefficient in mainly device. we also can select transient voltage suppressor(simple to call TVS) using in your prevent electrical circuit.
The work theory of PTC(positive temperature coefficient) is that with temperature of electrical circuit board increase over to Medame curie’s point, the resister increase , it will cause current decrease .

The TVS(transient voltage suppressor) prevent damage of components in overvoltage.

Intelligence led constant current is a instance,

*The typical linear constant current source
We know that the power supply divided to constant voltage source and constant current source , the constant voltage refer to output voltage is stable , this mean is it would never be changed when output load is unalterable. the constant current source is which the output current is stable, this mean is it would never be changed when
output load is unalterable. the led is semiconductor diode , the property of volt-ampere is negative temperature ratio, the bigger input current will damage led when we adopt constant voltage source . so the constant current source will be the led best choice, the constant current source divided into switching power supply and linear power supply, following we will compare the advantage and disadvantage of both switching power supply and linear power supply.
advantage                           disadvantage
switching          High efficient(reach to 90%)         Low reliable , high cost

linear          High reliable , low cost               Low efficient (just only 85%)
*The efficient of linear constant current source
With input voltage increase ,the efficient of linear constant current source will decrease
the input AC as 110v, the efficient just only 85%
But the efficient would be become high when low input voltage normal working ,
The necessity of detail description of structure and property of linear constant current source.
Adopt the normal constant current diode to design linear constant source
We will analysis the led theory from voltage – ampere listing table as follows
Adopt the self-adapter to improvement of efficient of linear constant current source
There are resolution in linear constant current design
Because of the output load is LED , we know that the led is constant current load,
the quantity of led must meet input voltage , for example , suppose the input voltage is 300V,if a led forward voltage is 3v, one hundred led in serial electrical circuit is necessary , when input voltage increase , the forward voltage of led still maintain uncharged , the whole constant current source were to be reducedDo you have any resolution to sole that problem?

Adopt the self-adapter to adjust the quantity of led is best method, add the amount of led to led electrical circuit when input voltage is raise, to decrease the quantity of led when input voltage is fell.
*Character of intelligent led constant current
Self-adaptive input current
As description previous sections, the efficient can reached 99% when adopt the self-adaptive in electrical circuit. the efficient of constant current source still maintain 99% even the range of input voltage in consistent chang.
Self-adaptive temperature
When environment temperature was changed , the power of constant diode will raise ,
fox example the environment temperature raise , as the led forward voltage will fall base on LED voltage – ampere, so the voltage of constant current diode raise, power increase , the intelligent constant current source will add the amount of led to increase total voltage in serial electrical circuit, it can maintain high efficient for whole input voltage,

As see above picture, the environment temperature raise from 35 to 85, but whole efficient of input voltage almost no change , it still maintain over 98%
Self-adaptive of different forward voltage of led
The intelligent led constant current source has other function that it is self-adaptive of different forward voltage. there are different forward voltage of led in electrical circuit , the intelligent led system can automatic switch the amount of led , to guarantee whole efficient in 99%
Chang the amount of led will not change the luminous ,
If the resolution just only change the quantity of led , due to the current of constant current source not change , the total luminous will be change , we considers this problem, we will adopt the self-adaptive to solve the is problem, it can maintain whole power is not change ,

As see above picture , it adopt the self-adaptive after output luminous still maintain no change even in different range of input voltage

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.