An overview of ballasts

Ⅰ. What is a ballast?

The ballast interacts with the lighting mechanism to control, regulate and ultimately stabilize the light output of the lamp.

A ballast is a device used with a discharge lamp to obtain the circuit conditions (voltage, current and waveform) required for starting and operation. All fluorescent and HID light sources require ballasts to operate properly. Dimming ballasts are special ballasts that, when used with a dimmer, change the light output of a lamp.

In short, the ballast is the functional heart of a fluorescent or HID light source. Just as the heart regulates blood flow to the body, ballasts ensure the lamp stays on by managing the distribution of energy throughout the lamp. The heart distributes blood through channels, or arteries, in the body to keep the body active and alive. Ballasts do what fluorescent, HID, and plug-and-play linear LEDs do in buildings, only with energy as their lifeblood.

The diagram below shows how a ballast in a fluorescent lamp works.

Ⅱ. The origin and development of ballasts

There was a worldwide energy crisis in the 1970s. The sense of urgency to save energy has led many companies to devote themselves to the research of energy-saving light sources and electronic ballasts for fluorescent lamps. With the rapid development of semiconductor technology, various high back-voltage power switching devices are emerging, which provides conditions for the development of electronic ballasts.

In the late 1970s, foreign manufacturers took the lead in launching the first generation of electronic ballasts, which was a major innovation in the history of lighting development. Because it has many advantages such as energy saving, it has aroused great attention and interest all over the world. It is considered an ideal product to replace magnetic ballasts. Subsequently, some well-known enterprises have invested considerable manpower and material resources for higher-level research and development.

The rapid development of microelectronic technology has promoted the development of electronic ballasts in the direction of high performance and high reliability. Many semiconductor companies have introduced families of dedicated power switching devices and control integrated circuits. In 1984, Siemens developed active power factor correction electrical ICs such as TPA4812, with a power factor of 0.99.

Subsequently, some companies launched integrated electronic ballasts one after another. In 1989, Finland Hervalli Company successfully launched a dimmable monolithic integrated circuit electronic ballast. Electronic ballasts have been popularized and applied all over the world, especially in developed countries.

Ⅲ. Types of ballasts

There are 6 types of ballasts, namely inductance ballast, resistance ballast, capacitor ballast, electronic ballast, LC ballast and flux leakage transformer ballast.

1. Inductance ballast

Inductance ballasts, also known as reactors and choke coils, are lagging ballasts, that is, the phase of the lamp current lags behind the phase of the power supply voltage. It regulates the lamp current by the voltage across the inductor proportional to the time rate of change of the current. It is mainly used in the gas discharge light source circuit with AC power supply. 

Compared with resistance ballast, it consumes less power and can improve the lamp current waveform and the stability of lamp operation. Inductance ballast is composed of iron core made of ferromagnetic material, coil made of enameled wire and related insulating materials. The processing technology is similar to that of ordinary transformers. Inductance ballasts are designed according to the power supply voltage, lamp voltage and lamp current, mainly to ensure the electrical parameters of the lamp, and also consider other parameters such as loss and temperature rise. In practical applications, magnetic ballasts are stable and reliable, but bulky and noisy.

2. Resistance ballast

Resistance ballast is to regulate the lamp current through the voltage on the resistor which is proportional to the current. In the gas discharge light source circuit equipped with DC power supply, the application of resistance ballast is relatively simple in design and processing, but the power consumption is large and the efficiency is low. In the gas discharge light source circuit equipped with AC power supply, resistive ballasts are also used. For example, in self-ballasted high-pressure mercury lamp circuits, tungsten wires are used as resistive ballasts. But in general, the application of resistive ballasts in AC circuits will affect the lamp current waveform, and reduce the luminous efficiency and stability of the lamp, but it can improve the power factor of the circuit.

3. Capacitor ballast

It refers to the use of capacitors as ballasts in gas discharge light source circuits equipped with AC power. It does not limit the instantaneous current of the lamp, only the total amount of charge that passes through the circuit in each half cycle. In the low-frequency AC circuit, the waveform of the lamp current will be seriously distorted, forming a very high pulse peak current (the effective value is not large), which will have a very harmful effect on the electrodes of the lamp, resulting in a greatly reduced lamp life. Therefore, capacitors are rarely used as ballasts in low-frequency AC circuits. In higher frequency (20 ~ 100kHz) AC circuits, capacitors can be used as ballasts to achieve satisfactory results, with low power consumption, small current waveform distortion, small size, light weight, and no noise.

4. Electronic ballast

Electronic ballast is a new type of ballast composed of electronic components. Its loss, volume, weight, circuit power factor, flicker and other parameters are superior to the above-mentioned various ballasts. Electronic ballasts and the lamp tubes of the above-mentioned various ballasts all work at the power frequency (usually 50Hz or 60Hz) except the direct power supply. The electronic ballast makes the lamp work at a frequency of 20-100kHz. It is essentially a power converter, and the lamp tube is in a working state of 20-100kHz. At present, there are two types of electronic ballasts in practical application: circuits powered by low-voltage DC power supply (voltage lower than 250V), called transistor ballasts, also known as inverters. A circuit powered by grid (AC 220V) DC is called an electronic ballast.

5. LC ballast

A ballast consisting of an inductor and capacitor connected in series. Usually, the capacitive reactance is designed to be about twice the inductive reactance, and the total impedance is capacitive. It belongs to the leading ballast, that is, the phase of the lamp current is ahead of the phase of the power supply voltage. 

Compared with resistance ballasts and inductance ballasts, the power consumption is small, especially it has good steady current characteristics, and the short-circuit characteristics when the lamp is started are also good. It can greatly improve the power factor of the circuit when used in conjunction with a hysteresis type inductive ballast. However, when the power supply voltage is reversed, the voltage of repeated ionization every half cycle is low, and the ability of repeated ignition is poor.

6. Flux leakage transformer ballast

Flux leakage transformer ballast is a ballast that can obtain a higher open circuit voltage (greater than the power supply voltage). Utilizing the magnetic leakage performance of the transformer is equivalent to being used as an inductance ballast, which belongs to the hysteresis ballast. Its advantage is that it makes it easy to start the lamp, but its disadvantage is that it consumes more power than an inductive ballast, and it is also bulkier and noisier.

Ⅳ. Ballast factor

The ballast factor is calculated by dividing the lumen output of the lamp-ballast combination by the lumen output of the same lamp on the reference ballast. A ballast factor <1 means that your fluorescent system will produce less light (lumens) than the reference ballast, while a factor >1 means it will produce more light.

The ballast factor also affects the energy use of the luminaire. This can be an important consideration if you want to calculate the return on investment of your lighting upgrades.

Ⅴ. The role of ballasts

1. Limit the starting current of the lamp to an appropriate range

The starting current refers to the current passing through the lamp within 30 seconds after the lamp is energized or during the lamp warm-up process. Generally (especially in the state of the lowest temperature), the starting current is much larger than the working current of the lamp, so each lamp has a maximum starting current. If the starting current is too high, the service life of the lamp will be shortened. If the current is too low, the lamp will not warm up to normal starting condition or complete the process from glow discharge to arc discharge. The starting current provided by the ballast must be able to start the lamp in a short time without affecting the normal service life of the lamp.

2. The open circuit voltage provided is sufficient to make the lamp start smoothly

When the open-circuit peak voltage of the ballast is used as the start-up voltage of the lamp, it must be sufficient to ionize the gas in the gas discharge lamp, that is, to generate a transitional discharge between the electrodes that causes the peak current of the glow arc to make the lamp start to work. High-pressure mercury lamps and metal halide lamps are difficult to start at low temperatures, and the open-circuit peak voltage provided by the ballast must be high enough.

3. Prevent large changes in lamp power

Although the lamp is designed and delivered with a certain range of voltage values, the voltage value of the lamp will change during actual use and throughout its lifetime. This requires the matching ballast to be adjusted within a certain range so that the lamp power does not change significantly. An ideal ballast should have a lamp wattage similar to that of a new lamp and a lamp nearing the end of its life.

4. Working current of automatic control lamp

Stable impedance within a certain voltage range is the basic condition for the impedance ballast to control the working current of the lamp. The ballast uses the time rate of change of voltage and current proportional to the time to regulate the operating current of the lamp. When the open circuit voltage within a certain period of time causes the lamp operating current to increase, the inductive effect of the ballast will limit the rate at which the current increases; when the current begins to decrease, the inductive effect will prevent the rate at which the current decreases.

Ⅵ. How to replace the ballast?

1. How to tell if the lamp is broken or the ballast is broken?

(1) Fluorescent lamps need ballasts to meet the voltage required for fluorescent lamps to start and work. If the lamp is broken, you can try to replace the lamp to troubleshoot the lampshade. If the fluorescent light works, the lamp is bad, and if the fluorescent light still does not light, the ballast is bad.

(2) It can also be judged by measuring the filament breakage with a multimeter: measure both ends of the fluorescent lamp with a multimeter. If the resistance value is not zero, it means that the fluorescent lamp is broken and the lamp can be short-circuited. According to the method, if the two components of the lamp tube and the luminous body are checked, it means that the ballast is broken.

2. Symptoms of ballast failure

(1) The shell of the lamp or ballast is black.

(2) Check the ballast with a pencil. No power going in or out.

(3) Check with an electric pen, if there is electricity at the incoming terminal, but there is no electricity at the outgoing terminal, it means that there is a disconnection inside the ballast.

(4) If the ballast casing is electrified with an electric pen, it means that there is a leakage problem in the ballast.

(5) Use an electric pen to check whether there is electricity at the inlet and outlet. The house has no electricity, but the lights are out. After changing the trigger, the light still goes off.

(6) Measure the resistance of the coil with a multimeter with a resistance range of 200. Its resistance is infinite.

3. Replacement program

(1) Open the lampshade: There are three rotatable clips around the lampshade. Use a screwdriver to turn the clips open and remove the lampshade. Place the removed clips in place for reinstallation.

(2) Observe the position of each component

(3) Check whether the old lamp is damaged. Generally speaking, the longer part of the ring light will appear gray. We should know that this situation is caused by the sublimation of a certain substance inside the lamp tube in a high temperature environment.

(4) Remove the lamp: After opening the lamp cover, remove it, and you can see that there is a wire slot on the ring lamp. The wire extending from the light socket in the center goes into this slot. This line is plug-in, just unplug it! The inner ring tube is clamped by three bent metal plates. The metal is flexible and can be split with a screwdriver. You can remove the ring light, pay attention to the wiring inside.

(5) Replace the ballast: the ballast of the ring light, the two white wires are 220V power lines, there is no positive and negative poles. The four small round holes on the box are sockets for the lamp pins. Remove the case, unplug the power cord, drop the ballast, and replace it with a new one.

(6) Ring light installation: the steps are just opposite to those of disassembly. To secure the new lamp, use three bent metal clips to secure the lamp. Use a screwdriver to tighten. Then connect the wires. Tape and secure. At the same time, clamp the wire slot on the ring light.

(7) Install the lampshade: Put the three clips just removed back to their original places. Fix lampshade. Turn on the power. You can test whether the light is on. If it's on, it's a good replacement light.

4. Preventive measures:

(1) Be sure to cut off the main power switch before operation;

(2) When removing the lampshade, small parts such as cards and screws must be put away. In order to eventually reinstall it.

Ⅶ. The difference between starter and ballast

Starters and ballasts are common electronic components in the lighting field, they are used to control and stabilize the current and voltage of lighting equipment. They all play an important role in the performance and reliability of lighting equipment.

In the lighting world, we often hear the terms starter and ballast. They are two different electronic components used to control and stabilize the current and voltage of lighting equipment. While they function similarly, there are some important differences in their design and working principles.

Although both starters and ballasts are used in lighting equipment, there are some important differences in their design and operating principles. Here are a few key differences between starters and ballasts:

1. Different functions

The main function of the starter is to provide a high enough voltage to start the gas discharge tube, and gradually reduce the voltage after starting to stabilize the current. 

The main function of the ballast is to limit and stabilize the flow of current to ensure that the lighting equipment works at a stable voltage.

2. Different scope of application

The starter is mainly used in the starting process of gas discharge lamps (such as fluorescent lamps, high-intensity gas discharge lamps, etc.). 

The ballast is suitable for various types of lighting equipment, including LED lamps, high-intensity gas discharge lamps, etc.

3. Different working principle 

The starter activates the gas discharge tube by generating high-frequency high-voltage pulses, and gradually reduces the voltage after starting to stabilize the current. 

The ballast controls the flow of current by adjusting the impedance and voltage in the circuit and ensures a constant current supply to the lighting device.

4. Different lighting effects

Since starters are designed to start gas discharge tubes for a short period of time, they may produce some flickering or temporary brightness changes. 

The ballast can provide a stable current supply, so uniform and bright lighting effects can be obtained.

Although starters and ballasts are different in function, scope of application, working principle and lighting effects, they both play an important role in the performance and reliability of lighting equipment. Correct selection and use of appropriate starters and ballasts can prolong the life of lighting equipment, improve lighting effects, and reduce energy consumption. When planning and designing a lighting system, it is important to understand the differences and advantages between them in order to make the best choice.