Best Design of an adaptive Electronic starter for fluorescent lamps

Design of an adaptive electronic starter for fluorescent lamps - A cost competitive circuit of a fluorescent lamp electronic starter that can provide a single-pulse ignition, adaptive preheating time, fast reset and lower 

voltage working ability is proposed in this paper. In order to analyze the proposed electronic starter, circuit topologies in each working state are derived. 

A prototype for 20 W fluorescent lamps is also designed and implemented to access the performance. Experimental results show that features of a single-pulse 

ignition, adaptive preheating time, fast reset and lower voltage working ability can be achieved what we have predicted.

Fluorescent lights flicker during the ignition phase. The manufacturers are also aware of this problem, which is why they looked for alternatives and found one. Special fast-starting fluorescent lamps. 
However, the relatively high acquisition costs prevent them from catching on everywhere. But it is also possible without new lamps: the electronic starter ensures  that the fluorescent lamp without to torches ignites. A welcome side effect of the new starting system is the longer lamp life.

Figure 1. In addition to the glass tube, the operating circuit of a fluorescent lamp also includes a choke (inductive ballast) and the mechanical starter.

Fluorescent lights flicker during the ignition phase. The manufacturers are also aware of this problem, which is why they looked for alternatives and found one. Special fast-starting fluorescent lamps. 

However, the relatively high acquisition costs prevent them from catching on everywhere. But it is also possible without new lamps: the electronic starter ensures  that the fluorescent lamp without to torches ignites. A welcome side effect of the new starting system is the longer lamp life.

Small but nice! This rightly applies to the circuit presented here for the flicker-free ignition of fluorescent lamps. This only requires a total of 8 components, 

all of which can be accommodated in the plastic housing (!) of a conventional starter. No changes are therefore necessary to the fluorescent lamp itself or to the 

operating circuit for it.  Zero from, so that the magnetic field of the coil is reduced. Now the thyristor blocks. As a result, the negative mains voltage is suddenly across the tube, because  the capacitor C2 has charged up quickly. This capacitor forms an oscillating circuit with L1, which "rocks up" the voltage at the tube far above the mains voltage. 

Figure 2. The conventional starter usually consists of a glow igniter (glow lamp) with a bimetallic contact. A capacitor is also connected in parallel with the starter, which suppresses radio interference caused by the gas discharge in the glass tube

The tube "ignites". With the next positive half-wave of the mains voltage, the thyristor becomes conductive again. This process is repeated 50 times in the second 

After a few periods the tube will be sufficiently warm and will remain burning". This causes the voltage across the starter to drop to the burning voltage of the 

tube.

Figure 3. The electronic starter consists of only 8 components. The circuit ensures that the gas filling is heated and the ignitions take place very quickly one after the other. This eliminates the unpleasant flickering when switched on.

parts list

Resistors:

R1=470k R2=100kaw R3=1k

R4 = 56N/%W

Capacitors:

C1 = 15n (see text) C2 = 100n/630V

Semiconductor:

D1 = Diac ER 900 Th1 = Thyristor TIC 106D

Before the electronic starter takes over its task, it is interesting to know how the fluorescent lamp is constructed and works with the conventional starting device. 

Figure 1 shows the basic circuit diagram for this. The fluorescent lamp consists of an elongated glass tube containing a gas mixture of mercury vapor and argon. 

The pressure inside the tube is very low. If now due to an electric field the

When the gas filling is ignited, a discharge takes place. The discharge mainly produces ultraviolet Light. The inner wall of the glass tube is covered with a layer 

of phosphor, a fluorescent powder. the Fluorescent lights flicker during the ignition phase. The manufacturers are also aware of this problem, which is why they 

looked for alternatives and found one. Special fast-starting fluorescent lamps. However, the relatively high acquisition costs prevent them from catching on everywhere. 

But it is also possible without new lamps: The electronic starter ensures that the fluorescent lamp without to torches ignites. A welcome side effect of the new 

starting system is the longer lamp life. is the ultraviolet radiation now stimulates this layer to glow, visible light is produced. The applied phosphor layer thus 

works as a kind of light transformer that converts short-wave UV light into long-wave visible light. The light properties of the fluorescent lamps depend very much 

on the phosphor layer. They are then also commercially available in different colors and with different light intensities (see also ”’Dimmers for fluorescent lamps’’ 

elsewhere in this issue). The noble gas argon is at the light generator. not directly involved; it just makes ignition easier. The ignition voltage required for gas 

discharge depends very much on the temperature of the gas mixture: at a higher temperature, a lower ignition voltage is sufficient. For this reason, electrodes are 

fitted inside the tube, which heat the gas during the ignition process and thus facilitate the escape of electrons during the gas discharge. If the first ignition 

has taken place, a much lower one is sufficient Voltage to keep the lamp on continuously. The voltage required for this is the so-called "burning voltage". Above the burning voltage, the fluorescent tube behaves like a negative resistance; the resistance decreases, causing the current to increase prevent this, a choke is necessary (it is also known under the term "inductive ballast"). The choke is an inductive resistance; in contrast to the ohmic resistance, only very little electrical power is lost as heat,

The choke is used as an ignition coil and, together with the starter, generates such a high ignition voltage that the fluorescent lamp always ignites. The choke 

takes on another task. It keeps the high-frequency interference caused by the gas discharge away from the mains.

The term "starter" has been used several times. However, not all of its tasks have been discussed. It is not only responsible for a sufficiently high ignition 

voltage together with the choke, but also switches the current through the glow electrodes The starter usually consists of a glow igniter (glow lamp), a bimetal 

contact (thermal switch), an interference suppression capacitor, two connection contacts and a housing (Figure 2). Before the fluorescent lamp is switched on, 

the bimetal contact is open. If you now close the mains switch, the mains voltage via the choke and the glow electrodes also to the starter connections. 

This voltage is sufficient to ignite the gas charge of the glow igniter (usually helium). A relatively low current of about 0.1 A now flows to the glow electrodes. 

Through the gas discharge creates a certain amount of heat in the starter, which after a while causes the bimetallic contacts to close This results in a high 

short-circuit current through the glow electrodes, causing the gas charge in the fluorescent tube to heat up considerably. The short circuit also ends the gas 

discharge in the starter. The bimetallic electrodes now cool down and the contact opens again. The flow of current ends abruptly, so that the magnetic field in 

the choke suddenly collapses. A voltage of several hundred volts is generated, which is sufficient to ignite the fluorescent lamp.

Once ignition has taken place, the lamp voltage drops to around half of the original value; one then speaks of the burning voltage. This voltage is too low to 

close the starter glow igniter again activate. There is therefore no further gas discharge in the starter and the bimetallic contact remains open. An interference suppression capacitor is connected in 

parallel with the starter, which is intended to suppress any interference with radio reception.

That's the theory. In practice, the ignition process looks a little different. Several attempts are always required to ignite a fluorescent lamp. There are two 

reasons for this: 1. The temperature of the gas mixture in the glass tube is still too low at the first ignition attempt; 2. The instantaneous value of the current 

can be zero when the bimetallic switch opens, so that no ignition voltage builds up. Several ignition attempts are therefore always necessary before the fluorescent 

lamp is activated. Due to the mechanical inertia of the starter, the individual ignition processes are separated from one another by short pauses. And that is exactly 

what causes annoying flickering.

In order to suppress the flickering during the starting process, you have to ensure that the gas charge in the glass tube is sufficiently preheated and that the 

individual ignition processes follow each other quickly. The electronic starter takes over this task.

The circuit of the electronic starter is shown in Figure 3. The following initial situations apply to the functional description of the starter: Switch SI closed, 

the anode of the thyristor is positive compared to the cathode. As long as the fluorescent lamp is not ignited, the instantaneous mains voltage is present at the 

starter. The capacitor C1 charges up via the voltage divider R1/R2 until the breakdown voltage of the diac (approx. 30 V) is reached. Now the capacitor can discharge 

and fires the thyristor. A powerful current flows through the choke and the glow electrodes. This current creates a magnetic field. If the mains voltage becomes 

negative (the polarity reverses), then the positive current is initially maintained through the choke. The current picks up

The voltage is then no longer sufficient to fire the diac and thus also the thyristor; the electronic starter is out of order.

The practice

There is not much to write about the assembly of the starter. The circuit board shown in Figure 4 accommodates all components. It is important that there is no 

conductive connection between the connections and the metal cooling surface of the thyristor. If necessary, the thyristor can be glued to the circuit board with 

two-component adhesive. Resistor R4 and capacitor C2 are mounted on the solder side of the circuit board. The photo shows the assembled starter in two different views.

 The circuit board fits exactly into a plastic housing of a conventional starter. For reasons of safety, metal housing must not be used.

Installation in the starter housing is not particularly difficult. After the plastic cap has been removed, the glow starter is detached from the connection contacts. 

The connection wires of the interference suppression capacitor should not be cut too short, as they create the connection between the circuit board and the connection contacts. Once this connection has been established, the electronic starter is fitted with the plastic cap and placed in its place in the fluorescent lamp housing. 

Figure 4. Electronic starter circuit board and assembly diagram. The board dimensions are kept in such a way that the completely assembled board fits into the housing of a mechanical starter. For safety reasons, a metal starter housing must not be used.

The circuit is suitable for fluorescent lamps from 20W to 65W. If a 20 W fluorescent tube does not ignite directly, the value of the capacitor C1 can be reduced down 

to 10 nF. The optimal value of the capacitor depends on the fluorescent tube used; this also applies to the capacitor C2. In the case of fluorescent tubes under 20 W,

 the optimal values ​​for the capacitors must be determined experimentally.

The patent for this circuit is held by the company N.V. Phillips

(NL: Pat. 155707, 30.9.1967;

GB: Pat. 1223733, 12/27/1968).

reference : https://archive.org/details/elektor-1982-06-v-138/page/n55/mode/2up?view=theater