Info!! What Type Of Led Driver Or Ability Provide Produce 1 Need?

Conventional AC-DC might supplies together with DC-DC converters provide an output that is regulated to provide a “constant-voltage.”  However, LEDs move most efficiently together with safest alongside a “constant-current” drive.  As a result, many novel devices bring been developed to provide this type of LED drive.  LED might sources that provide a “constant-current” output bring typically been referred to every bit LED drivers.  In the past, AC-DC might supplies that provided a regulated “constant-voltage” to LEDs were referred to every bit LED might supplies.  Today, the price “LED driver” together with “LED Power Supply” are used interchangeably.  The of import affair to proceed inwards heed is whether the output of the might device provides a “constant-voltage” or a “constant-current.” 

When create I postulate a “constant-voltage” LED driver?
Most commercially available LED “light modules” are constructed past times connecting a reveal of LEDs inwards serial or parallel to shape cluster or string configurations.  In cases where these low-cal modules include a “constant-current” driver every bit purpose of the assembly, an external “constant-voltage” driver or might provide is required.  Some LED circuits command the electrical flow flowing through the LED alongside a uncomplicated resistor.  This is to a greater extent than or less other instance where a constant-voltage might beginning is required.  Other examples where external “constant-voltage” supplies bring been employed include backlit advertizement signs, traffic information signs together with large enshroud high Definition LED displays, such every bit those described inwards this article: http://www.ledsmagazine.com/products/20877.  Constant-voltage drivers come upward inwards many unlike forms.  They tin await similar a conventional might provide or they tin endure enclosed for moisture/environmental protection. 

When create I postulate a “constant-current” LED driver?
In cases where a manufactured cluster or string of LEDs does non include an internal “constant-current” driver, an external LED driver or might provide that provides a “constant-current” is required.  Constant electrical flow LED drivers are available inwards many unlike bundle configurations, ranging from integrated circuits to enclosed moisture-proof packages, depending on the application together with the required output power.  

Series together with Parallel LED Configurations
Depending on the application, LEDs tin endure connected inwards serial and/or parallel configurations.  Obviously, when LEDs are connected inwards serial the forrad voltage drib of each LED inwards the string are additive.  For example, if you lot seat fifteen LEDs inwards serial together with each i has a voltage drib of 3V (at its nominal current), you lot postulate to provide a voltage beginning of 45V (15 x 3V = 45V) to effort the required current.  This is why “constant-current” drivers ever include inwards their specs the output voltage arrive at that it is capable of providing to overcome the LED voltage drops.  In club to boundary the effort voltage to reasonable levels, multiple strings of series-connected LEDs tin endure placed inwards parallel together with driven past times multi-output constant-current drivers.

Below is an excerpt from the datasheet for TDK-Lambda’s ALD6 serial of LED drivers. As you lot tin come across from the diagram, this driver contains upward to vi independent “constant-current” LED drivers.  The 38V output corresponds to combined forrad voltage drib of 10 typical white LEDs connected inwards series.  For high-current applications, upward to 300mA is available to might i series-string of high brightness LEDs.  For applications where the LEDs require upward to 50mA, this device tin might upward to vi strings of LEDs via its multi-output drivers.  These drivers are ideal for LCD display backlighting together with full general LED lighting applications.

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How is LED dimming accomplished?
The low-cal output of LEDs tin endure controlled past times varying the total of electrical flow flowing through the LED (within defined limits) or past times turning the LED on together with off via pulse width modulation (PWM).  LED drivers similar the ALD6 serial bring the capability of providing “dimming” past times both of these pop methods.

The drawing to a higher house shows the 2 methods of low-cal dimming that are included inwards the ALD6 LED driver.  It is permitted to occupation a combination of both of these methods simultaneously.

The “Rbr” is an external variable 10kohm resistor input.  By varying this potentiometer from 1k to 10kohms, an analog dimming command is achieved. In this case, the maximum LED brightness occurs when the pot is prepare to 10k ohms.  This same input tin operate alongside variable analog voltage ranging from 1.6 to 3.8-volts.  In to a greater extent than or less applications this input tin endure connected to a temperature sensing device which could trim back the electrical flow menstruum through the LEDs every bit the temperature rises, so providing a way for temperature compensation.
The “Vpwm” is a “Pulse Width Modulation” input that controls the LED brightness past times varying the duty-cycle of the input indicate from 1% to 100%.  Typical PWM frequencies tin arrive at from 180 to 270 Hz.

More information most LED drivers/supplies tin endure works life at these spider web links:
http://us.tdk-lambda.com/lp/products/ledsigns.htm
http://us.tdk-lambda.com/lp/products/ald-series.htm
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