How does an electronic ballast work?

Electronic ballasts are converters that convert power-frequency AC power into high-frequency AC power.

The basic working principle is: the power frequency power supply becomes a DC power supply after passing through a radio frequency interference (RFI) filter, full-wave rectification, and passive (or active) power factor corrector (PPFC or APFC). Through the DC AC converter, a high-frequency AC power supply of 20K-100kHz is output, and the LC series resonant circuit connected to the lamp is added to heat the filament, and at the same time a resonant high voltage is generated on the capacitor, which is added at both ends of the lamp, but the lamp is made"Discharge"becomes"Conduction"state, and then enter the luminous state, at this time, the high-frequency inductor plays the role of limiting the increase of current, to ensure that the lamp obtains the lamp voltage and lamp current required for normal operation, in order to improve reliability, often add a variety of protection circuits, such as abnormal protection, surge voltage and current protection, temperature protection and so on.

Since the gas discharge lamp (such as fluorescent lamp, neon lamp, halogen lamp, metal halide lamp, etc.) is a negative resistance electric light source (the characteristic curve is shown in Figure 1), in order to make it work normally and stably, a current limiting device needs to be added. This flow limiting device is called a ballast. There are two types of ballasts currently used in gas discharge lamps:

1) Inductive ballast; (2) High-frequency AC electronic ballast. Because the inductive ballast works in the mains frequency, the volume is large, bulky, and it also needs to consume a lot of metal materials such as copper and silicon steel, and the heat dissipation is difficult, the efficiency is low, and there is a strobosis, so now some scientific and technological workers in the field of electric light source have been looking for new ballast methods, and high-frequency AC electronic ballasts are an effective method.

Electronic ballast uses the method of high-frequency switching to transform electronic circuits to achieve ballast, which has the characteristics of no flicker, high efficiency, small size, light weight, dimmable, and does not use a large number of copper and silicon steel materials, so since the 70s of the 20th century, high-frequency AC electronic ballast has come out, due to its small size and high luminous efficiency (the relationship curve between luminous efficiency and working frequency is shown in Figure 2

No flicker effect, a series of advantages of adapting to a wide range of power supply voltage and energy saving, have been welcomed by users.

The working principle of the electronic ballast: 220 volt electric rectification into DC, and then filter the lower wave, and then the OTL oscillation circuit composed of two transistors will turn DC into high-frequency AC and boost, get a 300+V AC 1000+V peak, 30-80kHz or so high-frequency and high-voltage electricity is added to both ends of the lamp, and the light is on. (It is to rectify the voltage and then form a high-frequency alternating current through the oscillation circuit, and the voltage is boosted by the transformer to make the fluorescent lamp shine.)

The working principle of inductive ballast: The equipment that starts and limits the current on the fluorescent lamp and generates instantaneous high voltage should be called a ballast, which is made of enameled wire wrapped on the iron core made of silicon steel, and such a coil with an iron core will induce high voltage when the power is off instantaneously, and it will be added to the electrodes (filaments) at both ends of the fluorescent tube. This action is carried out alternately, when the starter (jumping bubble) is closed, the filament of the lamp is turned on and heated by the current limiting of the ballast; When the starter is open, the ballast will induce high pressure to be added to the filament at both ends of the lamp, and the filament emits electrons to bombard the fluorescent powder on the wall of the tube.

When the lamp emits light normally, the internal resistance becomes smaller, and the starter always maintains an open circuit state, so that the current can stably pass through the lamp and the ballast, so that the lamp emits light normally. Because the ballast always has a current passing through when the fluorescent lamp is working, it is easy to vibrate and heat, so the fluorescent lamp with ballast, especially when the quality of the ballast is not good, will produce a loud sound, and it is easy to burn out after a long time.

Working characteristics of fluorescent lamp: a high voltage is required when the lamp starts to ignite, and only a small current is allowed to pass through when the light is emitted normally, and the voltage at both ends of the lamp is lower than the power supply voltage.

The emitter plays a switching role in the circuit, which is formed by a neon discharge tube and a capacitor in parallel, and the role of the capacitor is to eliminate the electromagnetic interference of the power supply and form an oscillation circuit with the ballast to increase the amplitude of the starting pulse voltage. One of the electrodes in the discharge tube is composed of a bimetal sheet, which is heated by neon bubble discharge, so that when the bimetal sheet is opened and closed, the current of the inductance ballast is abruptly changed and a high-voltage pulse is generated and added to both ends of the lamp.

After the fluorescent lamp is connected to the circuit, the glow discharge begins between the two electrodes of the igniter, so that the bimetal sheet is heated and expands and contacts with the static contact pole, so the power supply, the ballast, the filament and the radiator form a closed loop, the current preheats the filament, when the heating time is 1-3 seconds, the glow discharge between the two electrodes of the ignitor is extinguished, and then the bimetal sheet is cooled and disconnected from the static contact pole, when the two electrodes are disconnected, the current in the circuit suddenly disappears, so the ballast produces a high-voltage pulse, which is superimposed with the power supply. It is added to both ends of the lamp to ionize the inert gas in the lamp and cause arc discharge, and the self-inductance of the ballast also plays a role in stabilizing the current in the circuit during the normal luminescence process.

Function. The ballast is a necessary electrical component for the discharge of light-emitting devices, which can generate instantaneous high voltage when the starter is disconnected, so that the light-emitting device starts to emit light, and then limit the current to control it within the rated range of the light-emitting device.

Energy conservation. The electronic ballast of the lamp uses a frequency of 20 60kHz to supply the lamp, so that the light efficiency of the lamp is about 10% higher than that of the power frequency (according to the length of the 4-foot lamp), and its own power consumption is low, so that the total input power of the lamp is reduced by about 20%, which has a better energy-saving effect.

2.The glow is more stable.

It is conducive to improving visual resolution and improving efficacy; Reduce visual fatigue during continuous work and help protect eyesight.

3.The starting point is more reliable.

After preheating the lamp, the first starting point is successful, avoiding multiple starting points.

4.High power factor.

Fluorescent lamps above 25W that meet the national standard have a higher power factor than that. However, it should be noted that the harmonic limit specified by the national standard for lamps below 25W is so high that its power factor drops to.

5.Stabilize input power and output luminous flux.

High-quality products have good voltage stabilization performance, and can still maintain the constant power of the light source and stabilize the illuminance when the power supply and voltage deviation are large, which is conducive to energy saving.

6.Extend lamp life.

Factors such as constant power and lamp current reduction of high-quality products, as well as reliable starting point, can extend lamp life.

7.Low noise.

The noise of high-quality electronic ballasts can reach less than 35db, and people do not feel the noise.

8.Can be dimmed.

For places that require dimming, such as places that originally use incandescent lamps or tungsten halogen lamps for dimming, they are replaced by high-efficiency fluorescent lamps with dimmable electronic ballast alarms, which can achieve a wide range of dimming at 2% and 100%.

Brand model: Huawei MateBook D15

System: Windows 11

The basic principle of the ballast: the electric ant flows through the ballast, the lamp filament starter heats the filament, when the two electrodes of the starter are close together, because there is no arc discharge, the bimetal sheet is cooled, and the two poles are separated, because the inductive ballast is inductive, when the circuit is suddenly interrupted, an impulse voltage of 600v-1500v lasting about 1ms will be generated at both ends of the lamp, and its exact voltage value depends on the type of lamp, in the case of discharge, the voltage at both ends of the lamp drops immediately, At this time, the ballast limits the lamp current on the one hand, and on the other hand, the phase difference between the power supply voltage and the working current of the lamp is 55° to 65°, so as to maintain the secondary starting voltage of the lamp and make the lamp work more stably.

Inductive ballast due to the simple structure, as the first kind of fluorescent lamp with the work of the ballast, its market share is still relatively large, due to its low power factor, poor low-voltage starting performance, heavy energy consumption, strobe and many other shortcomings, its market is slowly replaced by electronic ballast, inductive ballast energy loss: 40W (lamp power) + 10W (inductive ballast itself heating loss or silver consumption) is equal to the total power consumption of the whole set of lamps and lanterns is 50W. Stuffy.