LED Driver ICs
An LED driver is a electronic circuit which serves as an energy source for LEDs changing AC (grid) voltage to DC while optimizing driving current for LEDs
To drive modern types of luminaires with more and more added value (dimming possibility, emergency unit, presence sensor, remote control, etc.) more complex electronic circuitry is required. In some LED applications we understand under the term LED Driver also part of the power management like voltage conversion circuit used between input voltage and required output voltage. For this particualar case we have made a selection according to the type of output where we have three basic groups of drivers (regulators) Constant Current Regulators (CCR), Constant Voltage Regulators (CVR) and combination of both (CCR+CVR). Linear regulators are also called CONSTANT CURRENT REGULATORS (CCR) drive controlled constant current through the LEDs even if the supply voltage varies. However the linear regulators introduce efficiency and thermal drawbacks. Linear regulators have the advantage of simplicity, low part count and very little Electromagnetic Interference (EMI). At currents of 350 mA and above, the linear solution may require a heatsink, adding cost and size to the design.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 two ways how to control LED light source.
Forward Current Control
- Since LED emits light depending on forward current magnitude, the easiest way how to control LED light source intensity is changing bias current value. Change of luminous flux depends on forward-current change nearly linear; therefore control algorithm implementation is very easy.
- Another way how to control LED light source intensity is pulse-width modulation (PWM) method. Principle of PWM lies on biasing LED by constant nominal current which is periodically switched on and off. Ratio between on-state and off-state defines resulting intensity of the LED. Switching frequency is high enough thus human eye perceives light emitted by LED as continuous luminous flux with intensity depending on PWM duty-cycle.
LED Power Management
While incandescent bulbs need a constant voltage to emit a constant amount of light, LED lights require a specific driving circuit
DC/DC converters, AC/DC converters and other SWITCHED-mode POWER SUPPLIES enable the driving of LEDs in a more efficient way as their power losses are minimal. These driving circuits are more complex requiring a higher number of external components. They operate at switching frequencies from the low 100 kHz range up to more than 1 MHz. Sometimes built-in diagnostic features allow for precise monitoring of the devices. Depending on the application, different kinds of switched power supplies are used. For example if input voltage always exceeds the sum of the maximum forward voltages of every LED string, then Buck converters are the right solution. This is the case when driving one LED from a 12 V supply. When the minimum forward voltage of all LEDs in a string exceed the maximum input voltage, a step-up or boost regulator is needed. Driving five LEDs from a 5 V source would be a typical example. The inductive boost converter is the simplest regulator that can drive currents above 350 mA with a varying output voltage. As with linear and buck regulators, a boost converter with a feedback-divider network can be modified to become a constant current source.When the input voltage range overlaps the LED voltage range, a current regulator is needed that can both buck and boost, as required by the input and output conditions. As HB LEDs are adopted into more and more applications, situations will arise when the input voltage varies above and below the forward voltage of the LED string. This typically happens when four LEDs are driven from a 12 V car battery. Your EBV LightSpeed team will consult with you and provide advice about the most suitable driver circuit for your individual application, from their supplier partner companies. All EBV LED driver manufacturers have created detailed brochures with their product offerings including useful application notes.
LED Control and Sensing
The control unit brings the flexibility into your lighting desired feature set
This is in order to create intelligent lighting with high integrated controllability of amount of light with delivery exactly where it is needed. For that purpose you will need digitally controlled lighting control units (based on MCUs) using DALI and DMX512 as most commonly used standards for digital communication networks that are commonly used to control stage lighting and effects.With digital control, designers can scale and easily adjust designs to multiple applications, maximizing reuse and decreasing design time. A digital approach also allows many hardware features, such as soft startup, delay and PWM phase shifting, to be implemented in software, eliminating extra components, cost and complexity. DALI is an International Standard (IEC 62386) for the control of electronic ballasts, transformers, LEDs, emergency lights and exit signs in an easy to manage digital lighting control system. DMX512 employs EIA-485 differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. It is unidirectional. DMX512 does not include automatic error checking and correction, and so is not an appropriate control for hazardous applications.
LED Module Communication
EBV provides latest wired and wireless communication paths to LED module applications
Under the LED communication & control paths we understand either wired or wireless lines. DALI and DMX512 are most commonly used for is a standard for digital communication networks that are commonly used to control stage lighting and effects. EBV offers a variety of power line modems available and dedicated for the data transmission on low- or medium-voltage power lines. These devices offer complete handling of the protocol layers from the physical up to the MAC on different kinds of modulations based either on SFSK or OFDM. On LPRF wireless product portfolio we can offer Zigbee, RF4CE, W Mbus and other solutions. The half duplex S-FSK modemis dedicated for the data transmission on low- or medium-voltage power lines. The device offers complete handling of the protocol layers from the physical up to the MAC. They complies with the EN 50065 CENELEC, IEC 1334-4-32 and the IEC 1334-5-1 standards.
WEBENCH from Texas Instruments
Texas Instruments provides the WEBENCH Design tool tailored to LED designs
With WEBENCH® LED Designer and WEBENCH® LED Architect you will be able to instantly create alternative LED lighting designs and compare them for efficiency, size, and cost for luminous outputs up to 100,000 lumens. WEBENCH LED Architect is easy and powerful, providing a wide range of options to compare, select and optimize for lighting systems. Configure an LED lighting design with up to 60 LEDs in serial or parallel strings. Visually review the detailed parametrics of 450 of the latest LED components from leading manufacturers. With a single keystroke, select a preferred high-brightness LED, match that selection with one of TI’s LED drivers, and easily create an optimized constant-current power supply circuit. Dial-in the size and efficiency requirements using the Optimizer Dial and compare and simulate circuit behavior under dynamic conditions, including start-up, steady state, pulse-width modulation dimming, and line transient.
- Specify a desired light output
- Choose recommended LED/heatsink designs created in seconds
- Leverage a detailed library of 450 of the latest LED components and 30 heatsinks
- Get combinations optimized for thermal management and reliable operation
LIGHTDESK from Infineon
The Infineon Light Desk is an interactive, cloud-based design and verification environment that enables selection and configuration of LED driver ICs in a broad range of applications
Using the Infineon Light Desk, design engineers can identify the LED driver ICs that meet their specific system requirements. For the selected LED driver, the tool creates a custom design displayed in an interactive web schematic. Find out more on following link: https://infineon.transim.com/lightdesk/pages/appfinder.aspx. With the offered redesign functionality users can optimize the proposed LED driver design. Infineon Light Desk offers to download instantly the Bill of Material for the final design as well as a comprehensive design summary report that includes design data, schematic and simulation results. Users can save designs for future reference as well as collaborate on designs with other users within a secure shared workspace. Additionally, the tool has an offline simulator SimT powered by SIMetrix/SIMPLIS: The simulator allows users to run their reference designs offline which enhances the simulation time. Users can directly download the simulator from the Infineon Light Desk. The Infineon Light Desk already supports custom designs for new high power DC/DC LED driver ICs (ILD series) as well as linear LED driver ICs (BCR3x and BCR4x series) for general lighting applications.
Power and Lighting Design Tools from NXP
The tool generates schematic, bill of material and transformer parameters, calculates the design's efficiency, and presents an overview of losses
The isolated LED Driver design tool focuses on creating LED drivers from 2 W up to 25 W. The applications include:
- SSL retro-fit lamps (e.g. GU10, E27)
- LED modules, separate power supplies, e.g. LED spots, down-lights
- LED strings, e.g. retail display
- LED ballasts
- Contour lighting
- Channel letter lighting
- Other lighting applications
- Output power is user-defined and can be fixed, dimmed using pulse width modulation (PWM), or requires mains dimmable solutions.
CompCalc from ON Semiconductor
ON Semiconductor provides CompCalc circuit simulation and design tool for DC-DC power designs
CompCalc is an interactive schematic-based circuit simulator where each components value can be dynamically adjusted, showing the effect on each of the key circuit characheristics like: power stage gain and phase, compensation network gain and phase, loop gain and phase, output impedance, load transient response, ripple voltage or inductor current.