Flow of electricity that periodically reverses polarity and direction of travel through a circuit. The number of cycles is referred to as frequency.
A standard unit of measurement of electrical current. Amps = Watts/ Voltage.
A device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current and waveform) for starting and operating; all fluorescent and HID light sources require a ballast for proper operation. Dimmable ballast units are being increasingly used in place of conventional or low-loss ballast units. They not only save energy, but increase vision comfort. Higher lamp light output, flicker-free instantaneous starting, longer lamp life and automatic switch-off of defective lamps and further advantages possessed by dimmable ballast units.
Undesirable condition under which the ballast turns lamps on and off (cycles) due to the overheating of the thermal switch inside the ballast. This may be due to incorrect lamps, improper voltage being supplied, high ambient temperature around the fixture, or the early stage of ballast failure.
The ballast efficiency factor (BEF) is the ballast factor divided by the input power of the ballast. The higher the BEF ( within the same lamp-ballast type) the more efficient the ballast.
The measured ability of a particular ballast to produce light from the lamp(s) it powers; ballast factor is derived by dividing the lumen output of the same lamp(s) on a reference ballast.
Abbreviation for Certified Ballast Manufacturers Association
A measure of the rate of flow of electricity, expressed in amperes (A).
A dimming system controlled by a photocell that reduces the output of the lamps when daylight is present. As daylight levels increase, lamp intensity decreases. An energy-saving technique used in areas with significant daylight contribution.
DC-to-DC converter is an electronic circuit which converts a source of direct current (DC) from one voltage level to another. It is a class of power converter. Most DC to DC converters also regulate the output. Some exceptions include high-efficiency LED power sources, which are a kind of DC to DC converter that regulates the current through the LEDs, and simple charge pumps which double or triple the input voltage.
Lumen value at 40% of rated average life.
Control that varies the output of the light source by reducing the voltage or current to the lamp.
Dimming of lamps means the control of the brightness of an individual light or groups of lights. This allows the amount of light to be adjusted to deal with various uses to which a room is put. Dimming is also used to save energy when using day light dependent regulators, such as those found in offices. Phase angle dimming of normal incandescent lamps and 230V halogen lamps as well as low-voltage halogen lamps operated via magentic transformers. Compact and tube fluorescent lamps must be operated via dimmable ballast units.
The DIN 5035 regulation regualtes lighting by means of artificial light in, among other places, hospitals, outdoors in indoors workplaces and educational premises, includes regulation of emergency lighting and contains noteson the measurement and evaluation of artificial light.
See LED Driver.
In lighting design, 'efficacy' refers to the amount of light (luminous flux) produced by a lamp (a light bulb or other light source), usually measured in lumens, as a ratio of the amount of power consumed to produce it, usually measured in watts.
Lighting efficiency is always a dimensionless ratio of output divided by input which for lighting relates to the watts of visible power as a fraction of the power consumed in watts.
A light source that produces light by passing a current between electrodes through a vapour or gas. Includes fluorescent and high intensity discharge lamps.
A light source technology used in exit signs that provides uniform brightness, long lamp life (approximately eight years), while consuming very little energy (less than one watt per lamp).
A ballast that uses Semiconductor components to increase the frequency of fluorescent lamp operation. Electronic dimmable ballast units are being increasingly used in place of conventional or low-loss ballast units. They not only save energy, but increase vision comfort. Higher lamp light output, flicker-free instantaneous starting, longer lamp life and automatic switch-off of defective lamps and further advantages possessed by dimmable ballast units.
EMI stands for electromagnetic interference. High frequency interference (electrical noise) caused by electronic components. Federal Communication Commission (FCC) has established limits for EMI.
The English unit of measurement of the illuminance (or light level) on a surface when the foot is taken as the unit of length. It is the illuminance on a surface one square foot in area on which there is a uniformly distributed flux of one lumen, or the illuminance produced on a surface all points of which are at a distance of one foot from a directionally uniform point source of one candela. See FC.
Connecting electrical components to earth for safety.
A harmonic is a sinusoidal component of a periodic wave having a frequency that is a multiple of the fundamental frequency. Harmonic distortion from lighting equipment can interfere with other appliances and the operation of electric power networks. The total harmonic distortion (THD) is usually expressed as a percentage of the fundamental line current. THD for 4-foot fluorescent ballasts usually range from 20% to 40%. For compact fluorescent ballasts, THD levels greater than 50% are not uncommon.
A type of fluorescent lamp-ballast circuit designed to start fluorescent lamps instantly with a very high starting voltage. Instant-start circuits were developed to eliminate separate mechanical starter devices.
A dimming switch that allows you to create multiple preset lighting scenes within a room. Scenes can be recalled at the touch of a button from a single wall box or with a hand-held remote control.
A device that controls the current flow and manages power for an LED lighting product. In some LED applications we understand under term Driver also part of the power supply like voltage conversion circuit used between input voltage and required output voltage. According to the type of output we have three groups of drivers : Constant Current (CC) – LEDs are in serial connection and driver delivers precise current value, Constant Voltage (CV)- LEDs are in parallel connection which is ideal for decorative LED strips, this topology is not recommended for dimming and Special Drivers (CC+CV) – which is a bit expensive solution allowing both serial and parallel connections. There are also following LED Driver important parameters like Rated Current/Voltage – predefined output current and voltage, Rated Power – output power of the driver and Efficacy – Ratio between output/input power.
An LED module refers to a combination of multiple LEDs and their control elements on a board.
In order to reach desired lumen output we need to combine LEDs in different kind of LED strings. We know four basic ways how to connect LEDs together:
- LEDs in serial connection (see LED string -Serial)
- LEDs in parallel connection (see LED string - Parallel)
- LEDs in serial/parallel connection (see LED string -Serial/Parallel)
- LEDs in matrix connection (see LED string -Matrix)
Main advantages of matrix connection are high efficacy and ability to drive very high number of LEDs. You will gain also on forward current control and PWM dimming (when constant current LED driver is used) and it will be LED open/short-circuit proof.
LEDs in parallel connection use much cheaper LED driver. Parallel connection is LED open-circuit proof but offering pretty low efficacy. It is unstable when one LED goes to short-circuit and unusable for forward current control.
Using LEDs in serial connection each LED will use same current causing stabilized CCT, CRI and high efficacy without need of balance resistor. This will be LED short-circuit defect-proof connection. This connection is ideal for forward current control and also PWM control. However we risk unstability when one LED goes to open-circuit - whole string will switch-off. Beside that we will need more expensive LED driver
If case you would like to drive very high number of LEDs you have to use LEDs in serial/parallel connection. This connection has LED open/short-circuit proof, but will offer lower efficacy and will be unusable for forward current control.
Devices which give you flexibility, decorative effects and multiple uses from your lighting sources. Today’s sophisticated dimming systems enable you to lower the light level to conserve energy and increase bulb life; vary the mood of a room, etc.
Control that uses passive infrared or ultrasonic detection to sense whether someone is present or not, and to turn a light on or off appropriately.
National Electrical Manufacturers Association. Includes lamp, electrical device and larger fixture manufacturers. NEMA develops consensus ratings and designations for various products.
A scientific law which states that current (amperes) in a circuit depends on resistance (ohms) and applied electromotive force (volts). Current (I) = Voltage (E) / Resistance (R).
Light-sensitive device used to operate fixtures according to available daylight. They are used in solar lighting and to turn outdoor or security lights on and off at dusk and dawn.
The three basic topologies used in switching power supplies are Buck, Boost and Buck-Boost. Based on these other popular topologies are derived; including the Flyback, Forward, Push-Pull, Half-bridge, and Full-bridge converter topologies. These topologies are nonisolated, i.e., the input and output voltages share a common ground. There are, however, isolated derivations of these nonisolated topologies. The power supply topology refers to how the switches, output inductor, and output capacitor are connected. Each topology has unique properties. These properties include the steady-state voltage conversion ratios, the nature of the input and output currents, and the character of the output voltage ripple. Another important property is the frequency response of the duty-cycle-to-output-voltage transfer function.
The boost topology is an indirect converter since the energy is only transferred to the load during the off time at the switching element. It can operate in two states : continuous, where the inductor current never falls to zero and discontinuous where the inductor current falls to zero at the end of each cycle. In the discontinuous state, there are three stages.
- The transistor is on and the inductor current rises from zero to the peak current. The inductor stores energy during this stage (LI2/2) and the load is fed from the output capacitor. The diode isolates the load from the input.
- As the transistor turns off, the inductor voltage reverses and the stored energy causes current to flow through the diode. During this time the inductor current is delivered to the output until the stored energy has been depleted.
- When the inductor has no more energy, the current stops flowing in all elements until the start of the next cycle.
The buck-boost is a popular nonisolated, inverting power stage topology, sometimes calleda step-up/down power stage. Power supply designers choose the buck-boost power stage because the output voltage is inverted from the input voltage, and the output voltage can be either higher or lower than the input voltage. The topology gets its name from producing an output voltage that can be higher (like a boost power stage) or lower (like a buck power stage) in magnitude than the input voltage. However, the output voltage is opposite in polarity from the input voltage. The input current for a buck-boost power stage is discontinuous or pulsating due to the power switch current that pulses from zero to I
L every switching cycle. The output current for a buck-boost power stage is also discontinuous or pulsating. This is because the output diode only conducts during a portion of the switching cycle. The output capacitor supplies the entire load current for the rest of the switching cycle.
The most common and probably the simplest power stage topology is the buck power stage, sometimes called a step-down power stage. Power supply designers choose the buck power stage because the output voltage is always less than the input voltage in the same polarity and is not isolated from the input. The input current for a buck power stage is discontinuous or pulsating due to the power switch current that pulses from zero to Io every switching cycle. The output current for a buck power stage is continuous or nonpulsating because the output current is supplied by the output inductor/capacitor combination; the output capacitor never supplies the entire load current (for continuous inductor current mode operation).
The flyback topology is an indirect converter since the energy is only transferred to the load during the off time of the switching element. It can operate in two states : continuous, where the inductor current never falls to zero and discontinuous where the inductor current falls to zero at the end of each cycle.
In the discontinuous state, there are three stages.
- The transistor is on and the inductor current rises from zero to the peak current. The inductor stores energy during this stage ( LI2/2 ).
- As the transistor turns off, the inductor voltage reverses and the stored energy causes current to flow through the diode. During this time the inductor current is delivered to the output until the stored energy has been depleted. Because the load is connected to the anode of the diode, the voltage across the load is in the opposite direction to the input, i.e inversed.
- When the inductor has no more energy, the current stops flowing in all elements until the start of the next cycle.
Adding a transformer to the basic Buck converter circuit we add some important advantages. When the input is 120 or 230 VAC, the transformer provides isolation. It also allows the input voltage to the buck circuit to be matched to the required output voltage and multiple outputs can easily be achieved. The circuit shown is for a single ended forward converter. The series diode is required to provide a path for the current flowing due to the back emf generated as the transistor switch opens. The main advantage of the buck converter is its simplicity and flexibility. The buck converter is typically used in supplies from 10 to 250 W. A disadvantage is that the voltage stress across the primary switching element is 2 x the input voltage. This can be reduced by a variation on circuit whereby a 2nd switch on the other side of the transformer winding is employed.
SEPIC (Single Ended Primary Inductance Converter) is similar to a traditional buck-boost converter, but has advantages of having non-inverted output (the output voltage is of the same polarity as the input voltage), the primary means of coupling energy from the input to the output is via a series capacitor Cs, and true shutdown mode.The output voltage can be higher or lower than the input voltage. The SEPIC converter uses two inductors, L1 and L2. The two inductors can be wound on the same core since the same voltages are applied to them throughout the switching cycle. Using a coupled inductor takes up less space on the PCB and tends to be lower cost than two separate inductors. The capacitor Cs isolates the input from the output and provides protection against a shorted load.
A type of ballast/lamp circuit that uses a separate starter to heat-up a fluorescent lamp before high voltage is applied to start the lamp.
A fluorescent lamp designed for operation in a circuit requiring a manual or automatic starting switch to pre-heat the electrodes in order to start the arc.
Pulse width modulation (PWM) is a type of modulation where a technical parameter is switched between two values. The duty cycle is modulated at a constant frequency. PWM is used to transmit information or additionally to control energy conversion in a technical system.
A fluorescent lamp-ballast circuit which utilises continuous cathode heating, while the system is energised, to start and maintain lamp light output at efficient levels. Rapid start ballasts may be either electromagnetic, electronic or of hybrid designs. Full-range fluorescent lamp dimming is only possible with rapid start systems.
A measure of resistance to flow of current, expressed in ohms.
A semiconductor is a solid-state device whose electrical conductivity heavily depends on temperature, allowing it to behave both as a conductor and as an insulator.
A device used with a ballast to start pre-heat fluorescent lamps.
Device that turns lights on and off at pre-programmed times.
A circuit used that eliminates the starter and allows for instant starting of pre-heat lamps.
The standard unit of measurement for electrical potential.
The recommended operating voltage for a lamp.