How a fluorescent tube starter works: the technology explained simply

Fluorescent tubes have been a popular light source in offices, workshops and public buildings for decades. They are more energy-efficient than conventional light bulbs and have a longer service life. However, anyone who has ever switched on a fluorescent tube will be familiar with the typical flickering before it finally starts to light up. This flickering is caused by the so-called starter. But what exactly does the starter do, why is it necessary and how does it actually work? In this blog post, we explain the technology of the fluorescent tube starter in a detailed and understandable way.

What is a fluorescent tube starter and what is it needed for?

A fluorescent tube starter is a small but essential component that is needed to switch on a fluorescent tube. It ensures that the tube ignites and lights up evenly. Fluorescent tubes require a high ignition voltage to start, as they work with a gas discharge. Without a starter, it would not be possible to generate the necessary voltage pulse to ionize the gas in the tube and ignite the arc.

The starter is mainly used in combination with a so-called conventional ballast (CCG). This older technology requires a separate starter to enable the fluorescent tube to be switched on. Modern electronic ballasts (EBs), on the other hand, do not require a separate starter as they generate the necessary ignition voltages themselves. However, the starter is still an important component in many older or inexpensive fluorescent lamps.

The structure of a fluorescent tube starter: the most important components

A classic fluorescent tube starter is a small component that is usually housed in a cylindrical plastic or metal casing. Inside the starter are a number of crucial components that are responsible for its function.

The most important component is a so-called glow starter, which consists of a glass tube filled with gas. This glass tube contains two electrodes that are arranged in such a way that they can generate a gas discharge at a certain voltage. These electrodes usually consist of bimetallic strips that deform when heated.

The starter also contains a capacitor that reduces electromagnetic interference and serves as a radio interference suppression element. Another component may be a resistor, which is used to control the voltage. Together, these components ensure that the fluorescent tube ignites reliably.

The ignition phase: How the starter makes the fluorescent tube light up

When the fluorescent tube is switched on, a voltage is applied between the electrodes of the starter. This voltage is high enough to make the gas in the starter light up, which generates a so-called glow discharge. This discharge causes the bimetal electrodes in the starter to heat up, causing them to bend and eventually make contact. This contact closes the circuit so that a high current flows through the heating coils in the fluorescent tube.

Heating up the heating coils is crucial, as this causes electrons to be emitted, which are necessary for subsequent ignition. As soon as the electrodes in the starter are in contact, the glow discharge goes out and the gas in the starter tube cools down. This causes the bimetallic strips to return to their original shape and reopen the contact.

The electrical switching process: What happens inside the starter?

The sudden opening of the starter contact results in a decisive process: the sudden interruption of the current flow through the heating coils generates a high induction voltage in the choke coil of the ballast. This voltage is sufficient to ionize the gas contained in the fluorescent tube and set the gas discharge in motion.

Once the tube has ignited, the starter is no longer required. The voltage at the fluorescent tube drops so that the gas discharge in the starter can no longer take place. As a result, the starter remains inactive while the tube remains permanently lit.

Why does a fluorescent tube flicker when it is switched on?

The typical flickering when a fluorescent tube is switched on is caused by the repeated opening and closing of the starter. If the first ignition is not successful, the process starts again: the starter closes, the filaments are reheated, the starter opens and a new high voltage is generated. This process can be repeated several times until the tube finally lights up permanently.

This process can take several seconds, especially with old or worn starters. If the starter is defective, it can happen that the tube no longer ignites at all or flickers permanently.

Differences between conventional and electronic starters

While conventional glow starters rely on the principle of bimetallic contacts, there are modern electronic starters that control this process more efficiently and quickly. Electronic starters use semiconductor components to control the switching process more precisely. This eliminates the typical flickering when switching on, as the tube is usually ignited straight away.

Another advantage of electronic starters is their longer service life and greater reliability. They operate wear-free and allow the fluorescent tube to ignite more smoothly. Nevertheless, they are more expensive to purchase than conventional glow starters.

Common problems and troubleshooting tips for fluorescent tubes

Fluorescent tubes can have problems starting for various reasons. One common problem is a defective starter. If a tube no longer ignites at all or flickers continuously, the starter should be replaced first. This is usually the simplest and cheapest solution.

An ageing or defective fluorescent tube can also lead to ignition problems. After several years, the gas in the tube can no longer be sufficiently ionized so that the tube no longer lights reliably despite a functioning starter. In this case, the only solution is to replace the tube.

Another problem can be a defective ballast. If the tube does not work despite a new starter and new fluorescent lamp, the ballast may be defective. In this case, a repair or replacement is necessary.

The fluorescent tube starter is a central component of conventional lighting systems with fluorescent tubes. It ensures that the high voltage required to ignite the tube is provided. Thanks to its clever mechanism with bimetallic contacts and a gas discharge, it enables the typical lighting of the tube after switching on.

Modern electronic starters have several advantages over conventional glow starters, as they make the starting process faster and more reliable. Nevertheless, conventional starters are widespread and are still used in many older lighting systems. If you have problems with a flickering or non-starting tube, you should first check the starter and replace it if necessary. In many cases, this will restore the lighting to working order.