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The Study On The LED Display Of Oscillation Problem

Shenzhen Lights Technology Co.,Ltd | Updated: May 30, 2016



LED display effect and life, depends largely on the driver chip performance advantages and disadvantages. LED screen factory during import LED display driver chip, more focus on the display, for example, whether to display a consistent low ash, whether gradual transition uniform, whether oblique sweep dark highlights, a short-circuit conditions, etc. These items will be tested presented to the end customer.

Tests show that the effect is the most important step, but it is also the first step.

Of driver chips have a better understanding, we can make LED display performance and life have a clearer assessment. Now, more and more screen factory engineer, during the driver chips imported, began to focus on the work environment and working mode of the chip itself. For example, the drive current of consistency, REXT voltage consistency chip VDD spikes, drive waveform ports and so on.

LED display driver port oscillations

Driver chip OUT port drive connected directly to the LED lights is the core part of the driver. In view of the oscillation to the LED display for the many hazards, this paper will make some problems for the port driver chip oscillator brief existence, and analyze its causes and ways to improve.

Test Methods

Power supply for the 5V40A with a single module. Normal lighting module with an oscilloscope probe ground connection module ground access port, the contact probe driving IC port.

Test Results

A market-driven mainstream chip interference on larger modules (such as P10 static, etc.), there has been a port oscillation.

Oscillation hazards

Oscillation port, brought a lot of harm:

Shows poor results

Chip constant current feedback loop, under steady-state operation, a constant current to achieve the desired effect. Port oscillation, the chip can not achieve constant. More should be noted that such oscillations chip easily, at low ash, there will still be oscillations occur, seriously affecting low ash effect. Conformance requirements for higher full color, the screen constant current chip factory took the money, and even worse results than with a constant chip.

A significant reduction in LED lamp life

From oscillation waveform, negative LED lamp has been in the voltage difference is 2V, frequency 20MHz sine wave about class work. Large power spikes, transient large current for very high frequency switching will reduce the LED lamp life.

Power fluctuations, reduce power life

If 5V40A power at full load, ie the load current is 40A, then the power supply is concerned, the current changes will be sustained oscillations ampere current level of about 20MHz. DC power output capacitance, high current fluctuations in the higher frequencies, the equivalent heat resistance, reduced life, and cause more modules spikes. Damage not only the power, but all of the drive components and chip modules.

EMI exceeded

Continuous sine wave frequency 20MHz classes, each drive current change of the port at 0mA to 40mA, the power supply current is amps continuous oscillation at 20MHz. This will cause the entire cabinet, dBuV at around 20MHz frequency point value is superimposed, resulting in the EMI frequency points easily exceed the standard.

Abnormal sound module capacitance

Capacitance sound is often due to damage caused by heat capacitance. Similarly in the power supply capacitor, the port will be more likely to cause oscillation capacitor damage and abnormal noise.

Reasons and preventive measures of oscillation

Oscillation Cause

A constant current source driver chip applications as an example to explain OUT port oscillation...

If you want to know more,please visit this web:www.ledtaxitop.cn


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