ZCS Technology

What is Zero Cross Switching?

Zero Cross Switching (ZCS) allows a circuit to detect when the AC waveform has reached the zero-voltage point. Switching ON when the AC source is at zero volts greatly decreases electrical spikes and transients.

 

Why do LED lights have a large In-Rush Current?

A common characteristic of LED lighting is the in-rush current typically seen when turning on the LED luminaire. This is due to the fact that an LED light is more of a Capacitive load (versus the older HID technology which is more of an Inductance load) which requires a period of time to charge up before turning ON. It is during this 'charge up' time when the in-rush of current occurs.

 

Why is ZCS Beneficial to LED Lighting?

Using ZCS technology to apply power precisely at zero volts allows the LED light to charge up as the sine wave is ramping up. This allows for a smooth charge up of the LED circuit which does not require an access of current, thereby minimizing the In-Rush current typically seen without ZCS technology deployed. 


 

Side by Side Comparison

Standard vs. ZCS Power Switching

In the two Voltage / Current plots below, the Line voltage is the blue line, the load voltage is the magenta line and the load current is the green line.  You will see in the left hand plot, that the power was delivered to the load at a peak voltage (no ZCS) which caused a very large spike of in-rush current (green line).  On the right hand plot, the power was delivered at 0 volts (with ZCS) which resulted in the same load pulling virtually no inrush current.  This side by side comparison demonstrates the advantage of using ZCS technology in LED lighting control.

ZCS Plots