lcd panel led backlight voltage supplier

This is a universal LED kit that includes 2 high brightness LED strips, a DC-DC LED driver, and a wire harness.  The LED strips can be easily trimmed in designated increments every 3 LEDs, to fit any size LCD from 10.4"-19". This is known as a cut-to-fit model. This LED bar can be used for LED replacement or CCFL conversion.

Make sure you have an appropriate power supply before installing.  The driver is expecting analog DC voltage.  The driver is designed to operate 2 LED strips at the same time; operating only 1 LED strip may have higher brightness but will reduce the life of the LED strip (to less than 10,000 hours).  If connecting Single LED Strip directly to analog DC source, the recommended input is 10V-11V DC.

NOTE: Plazmo does not have user manuals because every model of LCD power supply board is different.  The customer must have some technical expertise to identify the power source on the monitor power supply board.

This product is commonly used for replacing backlights in a variety of different LCD panels found in gaming machines, POS, ATM and many other applications.

It is possible to buy LCD displays where the LEDs are in parallel and these can be powered from 5V. However series connection is more common since there are plenty of low cost boost ICs you can get to drive them, and these will allow operation from a wide range of supply voltages and incorporate PWM and current regulation brightness control (not always easy to get right, especially if you are worried about colour balance).

LCD Panel are used for TV,Personal Computer, Mobile Phone, Degital Camera etc widely.　LCD　Panel　can not emit light by itself. To emit light, it need the backlight(light source) on the back of LCD Panel. Minebea develops and manufactures the parts used for backlight and backlight using LED light source,for Mobile phone, PC application.

As below picture,Backligt are made with some optical parts.Key parts of Backligtht Unit are light guide plate and housing frame. Minebea"s principal competitive advantages are its ultraprecision machining and mass production technologies. Injection mold die need sub-micron ultraprecision machining and stable injection mold technologies.Minebea has amassed precision ball bearing"s technologies enables it to achieve levels of precision unmatched by its competitors. Minebea also uses these technologies for in-house parts, modl die,tooling and product of Backlight Unit.The function of light guide plate are transforming positional light source to surface light on display uniformly and efficiently.It realize optical design by own optical simulation and independently developed design program. Minebea assembles Backlight Unit by the technologies it put parts into limited space, greatly contributing to the precision and reliability. Minebea put into force exhaustive environmental control at Thai and China factories and enable manufacturing the bulk of Backlight with high quality and stable supply.

As on charts, LED driving Voltage is always higher than controller"s supply voltage (usually 12V) , that way we need driver/inverter, whatever we call step-up converter, it make from regular Vcc (12V) voltage, voltage able to supply and light up LED strings.

Most problem become, because for newer bigger screens are not available any datasheets, so many times I have to test LED backlight parameter by myself.

That is the reason, we must tread LED backlit screens very carefully, normally we must to test each particular screen separately and be sure to NOT overCurrent or overVoltage LED strings, as LEDs will simply burn off.

Some of those universal drivers have on-board places(pads) for I-Sense resistors mount/remove, and/or short-pads to regulate Current for particular LED backlight, this made possible to match LED driver"s Current parameter with particular screen. However such work need some experience and knowledge about DC/DC step-up converters, to avoid any LED burning disaster.

So there is only one I-Sense Resistor for total current, so if we know the driver"s chip reference voltage and proper Current value for particular screen backlight, we can count Sense Resistor for particular current, as from Ohm"s law R=U/I , but we have to know exactly the Current of particular LCD display we use, and reference (feedback threshold) voltage of IC used in driver (usually 150mV to 500mV depend on IC type and manufacturer) .

LED backlight driver ICs control the voltage and current for white LEDs used to illuminate LCD panels. Typical applications include portable appliances such as Smartphones, Tablets, Cameras, Notebook PCs as well as displays such as Computer Monitor and TV.  Kinetic Technologies’ portfolio is one of the largest in the industry and features high efficiency operation with high accuracy at low dimming duty cycles. To enhance reliability, products are designed with several protection mechanisms including, but not limited to, LED short circuit, LED open circuit and over-current.

LED (light emitting diode) backlights are the most popular type of backlight for small and medium LCDs. A new trend has begun where even large displays such as laptops, desktop monitors, and LCD TVs have LED backlights. The advantages of LEDs are its low cost, long life, no EMI interference, low operational voltage, and ease of brightness control. One disadvantage in larger displays is that too many LEDs increase the power consumption and will generate heat as a result. However, this problem will soon be overcome.LED backlights come in several different colors: yellow-green, orange, amber, pure green, blue, and white. There are two basic LED backlight designs: Bottom (array) and edge lit. The bottom (array) lit configuration has several LEDs mounted uniformly behind the display, which provides uniformity and brighter lighting, but also consumes more power and requires thicker LED backlights. The edge-lit configuration consists of LEDs mounted to one side or corner, which offers a thinner package and consumes less power. The edge-lit design occupies 98% of the LED backlight market for small to medium LCD modules.

Electroluminescence Backlight, or EL Backlight, is a solid-state phenomenon which uses colored phosphors, not heat, to generate light. EL backlights are very thin, lightweight and provide an even light. They are available in a variety of colors, with white being the most popular for use with LCDs. While their power consumption is fairly low, they require voltages of 100 VAC @ 400Hz. This is supplied by an inverter that converts a 5, 12 or 24 VDC input to the AC output. EL backlights also have a limited life of 3,000 to 5,000 hours to half brightness. The biggest drawbacks to an EL panel is that it requires an inverter to generate the 100VAC, consistent brightness, and limited life.

Cold Cathode Fluorescent Lamp, or CCFL, backlights offer low power consumption and a very bright white light. The primary CCFL configuration used in LCD backlighting is edge lighting. A cold cathode fluorescent lamp is the light source with a diffuser distributing the light evenly across the viewing area. CCFLs require an inverter to supply the 270 to 300 VAC @ 35KHz used by the CCFL tube. They are used primarily in graphic LCDs and have a longer life – 10,000 to 20,000 hours – than EL backlights do. Their biggest drawbacks are: cold weather will reduce the light output by as much as 60%, they require an inverter to generate the 350VAC please note that the inverters do not function well at low temperatures, the light intensity cannot be varied (it is either on or off), and vibration can reduce the life expectancy of up to 50%.

This article will be limited to character LCD Displays and the three methods available to connect the LED backlight to a power source. All three methods will work, but not all are recommended.

“ Will your LCD display require a backlight?” This is one of the first questions we ask customers when designing a new LCD Display and for good reason. The majority of character (alphanumeric), segment (static) and monochrome graphic (dot matrix) LCD displays operate in low lighting conditions and require a LED (Light Emitting Diode) backlight.

Other Display technologies such as TFT displays contain a built-in backlight that is on when the display is active and OLED Displays generate their own light and do not require a backlight.

The most common method to supply power to the LED backlight is through pins 15 and 16 of the header. This is the preferred method since all power and signal connections can be made through one header/ IDC cable reducing assembly cost. Also the supply voltage for the LED is independent of the Logic voltage of the LCD (VLCD). This is to help eliminate any noise in the circuit.

I would estimate that 50% of the LCD displays equipped with a LED backlight have pin 15 set to positive and pin 16 set to ground, with the reverse being true for the other 50% of the LCD modules. If you power up your LCD and find the display works, but the backlight is dark, then the LCDs backlight polarity is reversed.

The second most popular option to drive the LED backlight is through the A and K pins located on the side of the LCD module. The A stands for Anode and is the positive side of the LED backlight, the K stands for Cathode (yes it’s spelled with a C, but uses the letter K, but that’s an entirely different subject.)

The image below shows the connection pins on the right side of the PCB and are labeled ‘+ ‘and ‘– ‘. Some PCBs (Printed Circuit Boards) will label the ‘+’ (A ) and the ‘-‘ (K) and in some instances: ground.

Many OEMs prefer to add a separate cable to the A and K with the goal of supplying an independent power and ground to the backlight. This is a good method if your backlight voltage is different than your LCD logic voltage, or if you require two independent grounds between the LCD logic and the backlight. Two common methods for connecting the A and K are: through a pigtail as seen in the photo below or with a two position header to mates to the customers PCB.

This is the least popular and least recommended option. Power for the LED backlight is drawn from the same source that supplies the LCD logic. Many times this is done after the design is completed and the LED backlight was an afterthought.

Custom LCD panels offer several advantages for Original Equipment Manufacturers (OEM). These advantages include the ability for engineering to choose: driving voltage of the LCD, operating temperature of the module, and the configuration of the LED back-light.

The Lighting Emitting Diode (LED) used in LCD back-lights can be manufactured in one of two different configurations: Series or Parallel. There are advantages and disadvantage to both options, so let’s review them both.

The backlight attached to a custom LCD panel may contain LEDs wired in series. Take for example that four LEDs are connected in series. Each LED will have the same current (amps) passes through each of them, in other words the current that passes through LED #1 is the same current that passes through LED #2 etc. So if a battery, which is connected in series with your LEDs, provides 3 amps, then the current though each LED will be the same 3 amps.

Voltage behavior for a series circuit used in your custom LCD panel is just the opposite of current. Each LED removes, or decreases, the voltage as it passes through the LED. This is called a ‘voltage drop’ since the voltage decreases, or drops, as it passes through the LED.

A ‘voltage drop’ means that the voltage level goes down for each LED. So if your battery supplies 12 volts and you have 4 LED’s. Then each LED will draw or reduce the voltage by 3 volts(12 volts divided between 4 LEDs). If you reduce the LED count from 4 to 2, the voltage drop for each LED will now be 6 volts. (12 volts divided between 2 LEDs)

In parallel, each LED incorporated on your custom LCD panel, produces a current drop. This means if you have a battery that provides 6 amps and your parallel circuit has 6 LEDs. Then each LED will draw or decrease the current by 1 amp. If you reduce the number of LED’s from 6 to 3. Your current for each LED will now be 2 amps (6 amps divided by 3 LEDs equals 2 amps per LED)

The voltage for each LED in parallel is the same for each LED. If you have a battery that supplies 10 volts, then each LED will have 10 volts supplied to it.

If you have a 10 volt battery and 3 LEDs, each LED will have 10 volts supplied to each LED. If you take the same 10 volt battery and connect it to 100 LEDs. Each one of the one-hundred LEDs will have 10 volts supplied to it. Below is a diagram of a three LEDs wired in parallel.

Each option has its advantages and disadvantages for your custom LCD panel. Contact one of our technical customer support people for help with the design.

LED backlight driver are one of the most commonly used, flashing bright lights at voltage. This allows it to be the brightness of the lights. On the other hand, LED backlight drivers work with luminous lamps that allow a wider range of the lights to be on. The LED backlight drivers also work with a bright source of light, so it is less resistant to be black.

Moreover, the led backlight driver can work with it. The LED backlight driver board has many functions, such as reversing the voltage and the reversed value of the lights. Alibaba.com offers LED driver boards that come with different functions, as well as the backlight driver supply can be different. The LED back supply is an essential power source for many lights.

It appears that the LED has a forward voltage, \( V_f \) of 4.1 V at 100 mA but that there is no current limiting built in. If connected directly to a 5 V supply then excessive current would flow (as predicted by the IV curves), the backlight would be destroyed and the display ruined.

Q1 is a standard NPN switch. If used it will drop about 0.2 V when on and this could be subtracted from the R1 calculation above. If switching is not required then it can be omitted and the LED cathode connected to ground.