LED display device fluctuation hazards and preventive measures

The OUT drive port of the LED display driver chip is directly connected to the LED light and is also the core part of the driver chip. Lianhuiye Technology will analyze the hazards and preventive measures for everyone. First, the test method: the power supply is 5V40A power supply, with a single LED module. The module is normally on, use an oscilloscope probe, connect the ground terminal to the ground wire inlet of the module, and connect the probe to the driver port of the driver chip. Second, the harm caused by vibration: 1. The display effect is poor. The constant current feedback loop inside the chip can achieve the ideal constant current effect only in a stable working state. The port oscillates, and the chip cannot achieve constant current. What needs to be explained is that this kind of easily oscillating chips will still oscillate when the gray is low, which seriously affects the low gray effect. For full-color screens with high consistency requirements, screen manufacturers spend money on constant current chips, which is even worse than using constant voltage chips. 2. The power supply fluctuates greatly, reducing the life of the power supply. If the 5V40A power supply is working at full load, that is, 40A current load, then for the power supply, the current change will be that the ampere-level current continues to oscillate around 20MHz. The capacitor at the output end of the DC power supply, under the high frequency fluctuation of the current, the equivalent internal resistance heats up, which reduces the life span and causes a larger module peak. It is not only the power supply that is damaged, but all the components and driver chips on the module. 3. The service life of LED lights is greatly reduced. It can be seen from the oscillation waveform that the negative electrode of the LED lamp has been working under a sine-like wave with a voltage difference of 2V and a frequency of about 20MHz. Larger power spikes, high transient currents, and continuous extremely high-frequency switching will reduce the service life of LED lights. 4. Abnormal sound of module capacitor. Capacitor noise is often caused by heat damage to the capacitor. Similar to power supply capacitors, port oscillations are more likely to cause damage to the capacitors and make abnormal noises. 5. EMI exceeds the standard. A sine wave with a continuous frequency of 20MHz, the current of each drive port varies from 0mA to 40mA, and the power supply is an ampere-level current that oscillates continuously at about 20MHz. This will cause the whole cabinet to superimpose the dBuV value at the frequency point of about 20MHz, and eventually cause EMI to easily exceed the standard at this frequency point. Third, preventive measures: 1. Driver chip stability: Replace the driver chip with better stability to avoid oscillation from the source. 2. Increased module capacitance: it will increase the cost. 3. Optimize the wiring of LED modules to reduce parasitic inductance: try to use ground wires and power wires to lay copper, but limited by the space on the board, there is little room for improvement. 4. Try to use a driver chip with high stability to avoid port oscillation problems. .