Electronic ballast for a luminaire is an electronic starting and regulating device that starts and controls the operation of gas-discharge lighting devices. It is widely used in the device of fluorescent lamps, in which an electric discharge in mercury vapor creates ultraviolet radiation, which is converted by a phosphor into visible light. Unlike an electromagnetic regulating device (choke), the device consists only of electronic elements.
Content
- Device device
- Purpose of the device
- Electronic equipment diagrams
- Operating principle
Device device
A high-quality device contains a built-in protection system against voltage surges in the mains. In addition, it has protection against impulse noise and starting in the absence of a lamp. A typical appliance includes:
-
Noise filter - promotes separation of incoming signals to electronic ballasts and protection from external influences penetrating into the network. - Electrical energy converter - converts incoming alternating current into direct current.
- A device that contributes to the correction of the power factor of the converted current.
- A device for smoothing impulses after changing AC to DC.
- Choke - a device that limits the current in the network.
The electronic ballast circuit for fluorescent lamps is bridge and half-bridge. The first device is used very rarely, since it has a large number of additional elements.
The second type of schemes is used much more often, although it has a low efficiency. To control it, the device is equipped with an inverter with a smooth dimmer, which includes an external dimmer, designed to control the electronic device.
Purpose of the device
Inside the gas discharge lamp, the current rises rather quickly, so there is a sharp drop in resistance. To prevent fluorescent lamps from burning out from excessive heat, an additional load is connected in series to its circuit to limit the current in the circuit, called a ballast or choke.
There are electromagnetic and electronic devices. Electromagnetic is a simple transformer consisting of copper wire and metal plates. Electronic devices include:
- diodes;
- dinistors;
- transistors;
- microcircuits.
An additional device is used in electromagnetic devices - a starter. In electronic equipment, this function is embedded in the circuit itself, which underlies the device of the ballast. It has some advantages:
- light weight;
- smooth switching on of lamps;
- lack of flickering and noise, since the device operates at a high frequency, reaching tens of kilohertz;
- low heat losses.
In addition, electronic ballast for fluorescent lamps has a high efficiency and a number of proven effective protections that help prolong the performance of the devices.
Electronic equipment diagrams
The most budgetary option is considered to be an electronic ballast diode circuit with a step-down transformer. In some models, open transistors are added to smooth out the frequency reduction process. The output voltage is stabilized by two capacitors.
In more modern instrument circuits, operational type dinistors are used, which are gradually replacing simple converters. This allows users to configure the parameters of the output voltage of the devices themselves.
In two-contact circuits of electronic devices, a choke is installed behind the output channels. There are two capacitors in front of the outputsand the step-down transformer is directly above the choke. Stable voltage is regulated by a high-quality dynistor.
The circuit of an electronic device for fluorescent lamps on transistors EN13003A is considered popular. These are fairly simple and cheap devices that are not regulated, but have a long service life.
Operating principle
By means of a diode bridge and a capacitor filter, the voltage becomes constant. Further, thanks to the inverter on two transistors, the constant voltage turns into a high-frequency one. The device operates in three stages:
-
First, the lamp electrodes are warmed up, which provides a faster and smoother start even at low temperatures. - The electronic device raises the voltage to 1.6 kV, making a gas breakdown in the lamp bulb.
- The lamp begins to glow with a small voltage on the electrodes, sufficient to maintain combustion.
All these processes take place thanks to a toroidal transformer with three windings. Two windings, with the help of transistors, control the combustion process, and the third supplies a resonant voltage to the luminaire, which significantly exceeds the indicators of the supply network.
That is, the maximum current heats up the filament of the lamp, and the large resonant voltage created on the capacitor ignites it. As soon as the lamp lights up, the supply of the resonant voltage is interrupted, and the lamp continues to burn.
For this, the strength of the induction current coming from the control part of the electronic device is enough. The start of the fluorescent lamp takes less than 1 second.
