Now in this circuit each led consumes 3 volts if temperature increase each led will consume say 2.8 vdc 2.8*5=14vdc the entire string Now the current in the string is clearly the same as the cureent in the resistor which now will be high due to fact that the voltage across it is high
When tempreture raise each diode will drop much much lower forward drop voltage and there will be high excess voltage across the resistor Still current cant stay constant with this method In this circuit a resistor was put in the serious diode stringĪ resistor will ensure that no manner how the voltage is high across the diode string each diode will only work at its desired forward voltage because the excess voltage will fall across the resistor and remember as I mentioned before forcing higher forward voltage across a led and very high current will pass in it and it will eventually fail The problem is that leds are tempreture sensitive if tempreture increaseĮach led will now ask lower forward voltage and 3vdc now is just too high. It seems that every thing in order right!! However driving led is not that simple
#Drivers for vizio tv series
In this circuit 10 series leds are drivin by 30vdc power source so that each diode have 3vdc across it Lets exam this 3 circuits and see why only the last one will work and why the first two circuits wont work very well in driving leds
#Drivers for vizio tv driver
Why the leds in tv are driven by sophisticated driver board Many people will ask why a led wont work on just normal dc power supplyįor example if one led needs 3vdc why it wont work on 3vdc power supply If current increase in a led beyond predetremind level as recommended by the manufacture the led will just failĬurrent can increase in a led if we operate the leds by forcing voltage higher than the needed forward voltage or by other factors The purpose of led driver board is to keep current constant in the led Leds use dc voltage to work, unlike normal leds the high power leds that used in tv works at 3vdc per led Led tv is the same as lcd tv the only difference is that lcd tv uses ccfl as backlight and inverter as driver board but led tv uses leds as backlight and boost driver board as driver
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