7 Errors that Can Cause Led Driver Failure
Sep. 15, 2020
The LED lighting industry has been developing for several years. As we all know, LED drivers are the key components of LED lighting. Generally, the quality and correct application of the LED driver determine the reliability and service life of the entire lamp. Therefore, it is very important to ensure that the luminaire designer is fully aware of possible failures caused by incorrect use of the LED driver. Today, constant current led driver supplier lists the following possible reasons.
1. The higher Vf is not considered during the cold start of the bulb. The maximum output voltage of the LED driver needs to be higher than Vfmax * N (N is the number of LED chips connected in series). Therefore, when choosing a driver, please pay attention to Vf max instead of Vf typ. Generally, the driver has a 5%-10% output voltage margin from Vomax to the no-load protection voltage to ensure cold start.
2. Do not check the derating curve provided in the drive data sheet. Usually, LED manufacturers provide both Ta and Tc information in the product label or data sheet. If the driver is fully connected to the heat sink, Tc is a key parameter worth paying attention to. Tc must be less than the maximum rating to ensure correct driver output without triggering overheat protection. Moreover, if the driver is independent of and separate from the lighting device, it is usually sufficient to pay attention to the operating environment temperature, which is easier than monitoring Tc. In addition, since the input current is higher under low input conditions, the input voltage will affect the derating curve.
3. Incorrect startup, usually occurs in the laboratory. Generally, a 90-305Vac driver can work at a lower input voltage, even down to 70Vac, but the thermal performance will be poor, triggering overheat protection or undervoltage lockout. Therefore, it is recommended to start the driver after setting the input voltage completely, rather than gradually increasing the input from a low voltage.
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4. Input overvoltage. Need to ensure that the input voltage does not exceed the maximum rating, usually 305Vac or 528Vac. We have encountered such a failure: the fault was caused by improper start in the actual tunnel light application, because the actual tunnel light was powered by the generator, and the operator turned on the power generation after connecting all the lights directly to the generator Machine, and then damaged 1,000 drives. Strong overshoot of the generator. The correct method should be: first turn on the generator, and then connect the light to the power supply through a switch.
5. Connect. L/N/G, the wiring of the output and dimming cables should be correct, for VDE cables, input cables are usually brown, blue and green (green/white), for UL cables, they are usually black, white and green. Most dimming cables are purple/violet and gray. Check the label carefully to avoid this problem.
6. Dimming problem. When the source current from the driver Vdim + is appropriate, the 0-10V dimmer usually outputs a minimum of 1V and a maximum of 9V. If the dimmer cannot reach 9V, the reason may be insufficient source current from Vdim+, and if the dimmer always exceeds 1V, it may be due to the overcurrent of Vdim+ power supply capability. Therefore, the best way to use a 0-10V dimmer is to understand the internal impedance of the driver's dimming circuit and try to use the driver for dimming.
7. Load performance. It is not recommended to use high-power rated drivers in low-power applications. Some light manufacturers want to reduce the purchase of models and increase the number in order to get a better price, but at the expense of drive performance. As we all know, PF, THD and efficiency vary with load, usually the best performance range is 80%-100% of the load. If the load is less than 70%, the performance may be much worse than announced.
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