Custom LCD Panels offer Series and Parallel LED Backlight Options
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.
FIGURE BELOW OF PURE GREEN AND BLUE LED
In these examples we will be referring to LEDs, but the concepts of series and parallel are true for other electronic components as well.
Series LED’s in a custom LCD panel
An example of series wiring can be seen in the older sets of Christmas lights. The disadvantage of series configurations is that if one light bulb burns out, or is missing, the entire set will stop working. You may find yourself up on a ladder, in a rain storm, trying to figure out which of the stupid bulbs burned out or came loose.
The LED backlight used on your custom LCD panel can be designed and built in a series configuration.
Current behavior in a series circuit
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.
This is true for one LED or 100 LEDs. The same amount of current passes through each LED.
Voltage behavior in a series circuit
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)
The drawing below shows three LED’s in a series circuit.
Custom LCD panel with Parallel LEDs
If your custom LCD panel contains a backlight with Parallel LEDs, the rules of current and voltage are reversed.
Current behavior in a parallel circuit
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)
Voltage behavior in a parallel circuit
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.