When it comes to fluorescent and discharge lighting there are two primary methods to ignite and operate this type of lighting, these are switch start and high frequency.  They are both designed to illuminate a space but their mechanisms and how they operate vary greatly.  It will help to understand these differences when focusing on your next lighting project.

The core difference between these two types of lighting is the ballast used to regulate the electrical flow and operate the lamp at the desired voltage.

Switch Start Lighting

Switch start systems rely on electromagnetic ballasts and have a separate starter component.  Switch start is the most conventional means of igniting for lighting.

1. Electromagnetic Ballast: These operate on standard mains frequency (50Hz - 60Hz) and in these ballasts there is an inductive coil designed to perform two key functions:
   • Limiting Current: Once the lamp is in operation the ballast will regulate current going into the light to avoid an overcharge on the lamp and causing the lamp to fail. 
   • Creating High Voltage: A starter is used within the ballast to send a pulse through the inductor and ignite the lamp.
2. The Starter: This is a small, replaceable component that connects the pre-heat circuitry within the lamp. This is what creates the high-voltage pulse via the ballast.

High Frequency (Electronic) Lighting

High frequency systems use electronic ballasts, which integrate the functions of the electromagnetic ballast and the starter into one circuit.

At these high frequencies, the lamp requires less voltage to ignite meaning it can be made smaller as less parts are required for the igniting process. This type of ballast helps for a smooth ignition process for the light.

Key Performance and Operational Differences

When choosing between high frequency and switch start lighting it is important to know the benefits and downsides to using each one.

When using a switch start setup you may lose 15%-25% of the lamp wattage whilst in a high frequency setup it will only lose around 5-10% of the lamp wattage as there is less of a process involved in the igniting of the lamp.

Electronic ballasts are inherently more efficient. The internal components consume significantly less power than electromagnetic ballasts, translating to lower overall energy costs for the same light output.

Light Quality and Visual Comfort

The 50/60 Hz operation of a switch start system can cause flickering as the light output on average can fluctuate between 100 to 120 cycles per second.  This has been found to lead to eye strain or headaches.  High frequency operation eliminates this flicker as the light starts up providing a stable light.

Lamp Life and Maintenance

High frequency ballasts are usually gentler on fluorescent tubes thanks to their optimised current control and pre-heating conditions reducing wear and tear on the electrodes inside when the lamps are ignited and in operation. This can lead to reduced costs in the long term especially as there is also not a starter that would need replacing within its lifespan.

Dimming Capability

Dimming can be unreliable with conventional electromagnetic ballasts, often requiring specialised components to work.  Because of this a lot of modern electronic ballasts are often designed with integrated dimming (0-10V or DALI for example), allowing for easy installation into lighting systems that require a dimming function.

Conclusion

Switch start technology was the standard for a very long time but it is now becoming obsolete as it has a number of drawbacks compared to high frequency technology. High frequency electronic lighting has been found to have higher energy efficiency, flicker-free light output, quieter operation, and often an extended lamp life. The shift to high frequency lighting also links up well to LED technology which often incorporates similar high-frequency electronic drivers is becoming a clear way forward for lighting technology.