Design Of LED Display Control Circuit

  • LED control part is the core part to decide the display effect and the control circuit built-in high-performance single micro-type control chip. The controller sends control signals and data to the LED driver chip through the internal control program, and the LED driver chip receives the signal and generates the corresponding action, so as to realize individual control for each way of red, green, and blue LED emitting chips.

    LED Display

    Driver System Of LED Display

    The function of the LED driver part is to receive color data and drive the LED display according to the brightness value indicated by the data, usually, there are 3 ways of constant current, voltage regulation, and constant voltage - constant current.

    Constant current driver circuit output current is constant, the output DC voltage changes with the load resistance value, the whole circuit is not afraid of the load short circuit, but the load is strictly prohibited completely open circuit.

    The output voltage of the voltage regulator circuit is fixed, and the output current changes with the increase or decrease of the load, so the whole circuit is not afraid of the open circuit of the load, but the complete short circuit of the load is strictly prohibited.

    Constant voltage and then constant current is the most ideal drive circuit, both to detect the LED current, but also to control the LED voltage, is conducive to improving the LED life, and reducing power consumption, and is generally used in high-end LED products.

    Control System Of LED Display

    The display effect of LED depends on the size of the current and voltage through it, time, and other factors, so the control system is mainly to control the power output of LED. At present, the PWM (pulse modulation) control method design of LED power supply, the conversion efficiency of up to 80% ~ 90%, and the output voltage or current is very stable, is a highly reliable power supply.

    PWM can control the time ratio of LED on and off, by dividing the time ratio into a number of levels, so that the LED displays the corresponding number of gray levels (grayscale). The product of the gray levels of the three base colors is the theoretical number of colors that the display can reproduce, generally 256 levels, and the number of colors reaches 16.7M, it can display 24-bit true color information. The general PWM frequency is greater than 100Hz, otherwise, there will be display flicker and scan lines when viewing. Now the gray level of a 10-bit large screen, refresh frequency is mostly 800 ~ 1000 Hz, the LED industry's highest refresh rate of 6800Hz. in the normal camera framing and rotation, LED screen display stable flicker-free, and in the highest refresh rate of grayscale over smooth, no color crosstalk.

    Combination Of LED Display Drive System And Control System

    LED is the load of the circuit, and the drive system and control system circuit connection is related to the stability of the entire display, there are generally series, parallel, and mixed connections in 3 ways. Series connection is not a highly reliable connection, often used in low-end products, in the voltage regulator driver circuit, when a short-circuit LED, the voltage assigned to the other LED will rise, easily causing more damage.

    The parallel connection method is suitable for products with lower power supply voltage, and constant current drive circuits, when a LED is disconnected, the current allocated in another LED will increase, easily damaging all the LEDs on the circuit. currently, in order to improve the reliability of the product, generally use the mixed connection method, the number of LEDs in series and parallel is equally distributed, grouped in parallel, and then connect each group in series together, so that the voltage allocated on a string of LED is the same, though each one LED current is also basically the same, the LED brightness is the same, while it is best to increase the LED temperature negative feedback in the constant current output to prevent the LED temperature is too high.

    The entire LED display is spliced by multiple module units, in order to ensure the reliability of the power supply and data, must also adopt a mixed connection to achieve the loop backup function, when an abnormal failure of a power supply, other power supplies will automatically carry out intelligent even flow, so as not to affect the normal use of the system, more effectively enhance the system's trouble-free operation time, reduce the time of maintenance failure.

    As technology continues to improve, the design of LED control circuits will become more and more sophisticated.