What characteristic does the outdoor full-color LED display power supply need to be
Outdoor LED display of the power supply will have what kind of function to meet the demand of LED display demanding power supply?
Here we've collected some professional LED display power features, hope can help to you.
Under certain conditions to keep the LED pixel by constant current drive voltage change caused by screen load change LED group, will affect the current pixel, the change of brightness.
Module in order to guarantee the whole screen brightness uniformity and reduce brightness changes, switching power supply output sampling circuit sampling point from power supply port moved to some point in the display, make that point voltage is kept constant.
Load changes caused by voltage change adjustment by switching power supply, namely load hours, low output voltage;
Large load and high output voltage.
Thus ensures that under the condition of invariable temperature and light, the output to the LED module of voltage constant, pixel drive current constant 2.
By adjusting the voltage to control the display brightness of switch power supply in order to make full use of limited resources in full color screen control system, switching power supply can by adjusting the brightness of the output voltage of full color.
Need, because of the large outdoor illumination change, according to the different climate and time in advance with full color brightness corresponds to the voltage made into tables, stored in a single chip microcomputer.
According to the light sensor sends out the signal of look-up table, it is concluded that numerical control switch power supply output voltage value, to control the display brightness.
Ambient temperature compensation caused by the LED is the change of the pressure drop VF LED the forward voltage drop of VF is along with the rise and fall of the environmental temperature.
All kinds of LED temperature variation coefficient of each are not identical.
At normal operating temperature range, the change of VF can reach 20%.
Under the constant voltage driver, VF decline will lead to the LED current rise, cause temperature rise as a whole.
In the process of this feedback, the working condition of the LED will be more and more worse, seriously affect the quality and life of outdoor screen.
So the outdoor screen switch power supply has temperature compensation function, ensure that the LED drive current does not vary with temperature rising.
Simple method of temperature compensation is in switching power supply, access to the temperature gradient near LEDVF negative temperature coefficient thermistor, and introduction of switch power supply PWM chip reference voltage Vi (
Temperature rises, Vi fell, the output voltage drops, inhibits the LED working current rise.
, because of the large thermal resistance discreteness in order to ensure the consistency of the product, should be selected.
In addition, the resistance of each temperature gradient has independent combination, poor compatibility.
In order to overcome these shortcomings, the use of the numerical control switch power supply output is controlled by digital signal.
According to all kinds of LED temperature drift curve, the need to provide the LED driver voltage under different temperature table, stored in the MCU, for your query.
According to the temperature sensor temperature measured by microcontroller look-up table, they can get the corresponding numerical control switch power supply output voltage.