Upowertek New Driver Design to Limit Luminaire Inrush Current

Upowertek New Driver Design to Limit Luminaire Inrush Current

The high inrush current on switching LED power supplies has become an area of concern in the lighting industry. It refers to the input current of a tiny duration that flows into the LED driver which can be regarded as a capacitive device during the power on stage. The figure below shows the typical inrush current with capacitive load from 230Vac 50Hz AC line input.

 

If there are multiple LED Luminaires powered on at the same moment, the max peak inrush current and its duration might trigger the MCB (miniature circuit breaker).

 

A general recommendation for industrial inductive use is to use C or D type MCB which has a bigger volume for inrush. A typical MCB tripping curve showing the amount of time required for a circuit breaker to trip, at a given overcurrent level as below.

These curves differ from manufacturer to manufacturer and from type to type. Typically, the B type MCB curve has the operating range of 3 to 5 In, C type has 5 to 10In and D type has 10-14 In according to the datasheets of most common used ABB S201M series.

 

And the most important curve to calculate how many pieces of LED drivers you could parallel is the one below.

 

A typical example of the inrush current event has been presented below for easier understanding.

 

From the discussion we know that the best way to reduce inrush current is to reduce the Ipeak and or decrease the pulse duration. And the Upowertek solution is to reduce the Ipeak to a very low level and increase the duration so that K factor will not be used for calculating the parallel unit max number.

 

When the inrush period is longer than certain value, for example, 10ms/S201M, K proof factor is not needed to calculate how many pcs of drivers which can be paralleled, but the tripping curve should be used which means the result of the parallel number will be much larger.

 

For example if we use Type C MCB C16 and Upowertek BLD-400 driver which has 2A input current @220Vac input condition, then the max number should be 16x5x0.7/2=28, here 0.7 is for some margin. It is almost 10 times more than standard drivers. Currently Upowertek has released the design with 200-400W drivers, and for lower than 200W driver solution, an external solution of using Upowertek power pack PMS series to enjoy the ZERO inrush current can be used. Please contact with [email protected] for questions and datasheets.

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