High inrush current for LED drivers

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In summary, ir LED drivers can have high inrush currents that can damage the camera if they are pulled too hard. This can be avoided by using fast-acting fuses or thermal protection.
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Ivan Seeking
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One issue I ran across recently involved 24-volt IR LED drivers for IR cameras, in a factory. The LED units were each rated as 0.5 amp loads. The camera was on the same circuit and only pulled about 250 ma. The engineer had specified 2 amp fast-acting fuses to protect the camera circuit and they were popping all over the factory. I investigated and found that we were pulling over 6 amps on each LED driver circuit, on startup. And that was just what I could catch on a meter. The current then dropped to the nominal value.

This particular manufacturer didn't list the inrush current in the specifications which is why our engineer had missed it. I did a little checking and found that LED driver circuits, and particularly IR LED drivers, have high inrush currents that can be as much as 100 times greater than the nominal load.

Challenge of High Inrush Current
As with any power supply, the LED Driver contains internal capacitors. For the typical LED Driver, the capacitors charge in less than one millisecond after power is turned on. This rapid charging creates https://adlt.com.au/%EF%BB%BFled-driver-inrush-currents/. Compared to older lighting modalities, this is 6 times the inrush current of an incandescent lamp and 4 times the inrush current of the magnetic ballast used in fluorescent lighting.
https://www.ametherm.com/blog/inrush-current/inrush-current-protection-led-lighting-retrofits/

Technologies exist to limit the inrush in LED circuits. In our case, we were able to exchange the drivers for some that had current limiting.
 
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The switching converters used in LED current drivers generate significant EMI unless plenty of reservoir capacitance is employed at the power input. That capacitance results in the higher inrush currents observed.

I expect to find thermistors used in those situations where the product is mass produced. But I have trouble finding one-off thermistors to fix occasional problems. I guess LED drivers without thermistors are at the cheaper end of the product line, and if you are lucky, you get what you pay for.

Semiconductors are notorious for blowing faster than fast fuses. It takes electronic protection to protect electronics. Fuses prevent short circuits from melting insulation, making smoke and starting fires.

I always have the feeling that thermistors must run hot while the equipment is in use, and that waste of thermal energy is inefficient. I guess a thermally well insulated thermistor can be more efficient, but then the fuse can be blown when there is a momentary power outage, shorter than the thermistor thermal recovery time.

Where I have encountered inrush problems in low voltage equipment I have found that replacing the fast-blow fuse with a slow-blow fuse, or with a thermal circuit breaker (manual reset), overcame the problem.
 
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Baluncore said:
Where I have encountered inrush problems in low voltage equipment I have found that replacing the fast-blow fuse with a slow-blow fuse, or with a thermal circuit breaker (manual reset), overcame the problem.

We tried 4 amp slow-blows but they were still popping. And we didn't want to go any bigger on the camera, which had some very small wires. So the manufacturer agreed to send another model. But I did see that they actually make soft starts for LED drivers.
 
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Related to High inrush current for LED drivers

1. What is high inrush current for LED drivers?

High inrush current for LED drivers is a temporary surge of electrical current that occurs when an LED driver is first turned on. This surge can be several times higher than the normal operating current of the driver.

2. What causes high inrush current for LED drivers?

High inrush current for LED drivers is caused by the initial charging of the capacitors in the driver circuit. As the capacitors charge, they draw a large amount of current, resulting in a surge. This surge can also be caused by the high starting voltage of LED drivers.

3. Why is high inrush current a concern for LED drivers?

High inrush current can cause damage to the LED driver and other components in the circuit. It can also cause flickering or dimming of the LED lights, reducing their lifespan and performance. In extreme cases, high inrush current can lead to electrical fires.

4. How can high inrush current for LED drivers be reduced?

There are several ways to reduce high inrush current for LED drivers. One method is to use an inrush current limiter, which is a circuit component that limits the amount of current flowing into the driver. Another method is to use soft-start circuits, which gradually increase the current to the driver over a short period of time.

5. Can high inrush current be completely eliminated for LED drivers?

While it is not possible to completely eliminate high inrush current for LED drivers, it can be significantly reduced through the use of inrush current limiters and soft-start circuits. It is important to properly design and select components for LED driver circuits to minimize the effects of high inrush current.

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