Author Archives: Esko Väisänen

About Esko Väisänen

Esko is your man if you need help with LED drivers. With a long experience in the field of LED power supplies, Esko will find a solution for your problem.

Different Dimming Types for LED Lighting

You can use several different dimming options to dim LED Lighting. What are the possibilities and what dimming should you look from a LED driver? I’m going to answer these questions in this blog post by going through the different systems.

The goal is to give you the basic understanding of the dimming methods available at moment.

I am grouping the dimming methods in two main groups: analogue and digital.

When you want to control lighting, you have to know some basic issues of your lighting fixtures:

  • Are your fixtures dimmable? If yes, what is the dimming method which works together with your fixtures
  • If your fixtures are non-dimmable, then you can only have on/off – function.

Analogue

Analogue dimming covers all dimming systems that don’t transform the dimming signal into bits and controls the lighting in analogue manner.

Phase dimming

Phase dimming systems dim the lights by altering the supply voltage.

Leading & trailing edge dimming

Before LEDs, we used to dim halogen lamps with wall dimmers.  We can still use these kinds of dimmers.  But dimmer, driver and LED-module must be compatible with each other.

This type of control is accomplished without any need for an additional control wire. It involves connecting a dimmer in series between one of the mains wire and the equipment.

The dimmer cuts part of the mains voltage sinusoidal waveform to a greater or lesser extent in order to dim luminous flux even from 1% to 100%  (this value depends on dimmer and driver).

Depending on how the driver makes the mains voltage cut, it is possible to distinguish between two types of dimming:

Leading-edge dimming

Leading-edge dimming

 

Trailing edge dimming

Trailing edge dimming

Leading-edge dimming:

Dimming cut-off in the wave on its ascending side, from the beginning (phase cut-off at ignition). This is traditionally used in halogen lamps supplied through electromagnetic transformers.

Trailing-edge dimming:

Dimming by cut-off in the wave on its descending side, from the end cutting backwards (phase cut-off at switch off).  And this way of dimming causes less interferences than leading-edge dimming.

There are dimmers and equipment that support both types of dimming, and others that support only one type.

Leading & Trailing-edge dimming LC

Leading & Trailing-edge dimming LC

 

Leading-edge dimming L

Leading-edge dimming L

 

Trailing-edge dimming  C

Trailing-edge dimming  C

1-10V regulation

The 1-10V system enables dimming of the luminous flux from around 1…10% to 100%. This is done by sending an analogue signal to the equipment over an additional, two-wire control line. These control wires have positive and negative polarities respectively and that must be kept in mind when wiring up the system.

The analogue signal has a direct voltage value of 1V to 10V. 1V or short-circuiting the fixture’s input control gives the minimum light level. While 10V or leaving the input control circuit open gives out the maximum light level.

International standard, IEC 60929, defines the regulation curve. The regulation curve represents the relationship between the control line voltage and the luminous flux. It reflects a practically linear relationship in the range of 3V to 10V.

To get a response adapted to that of the human eye it is possible to use logarithmically controlled potentiometers.

Regulation curve by IEC 60929

Regulation curve by IEC 60929

These in light fixtures generate power control with 1-10V dimming.  Driver supplies a current to the controller through equipment control terminals. The controller current must be from 10µA to 2mA. The maximum control line current is obtained with a voltage of 1V and the minimum with a voltage of 10V.

This dimming system is unidirectional, i.e. the information flows in one direction, from the controller to the light fixture. The latter generates no feedback to control. This means that this system can’t be controlled by a software. Groups have to be created by wiring. This system can be integrated into building control systems.

The voltage drop in the control line wiring limits its length. Therefore, the maximum distance is limited by the number of control gears connected. The latter establishes the current per line and the cable diameter used.

Touch Control Push Button  (analogue but can be connected to digital systems)

Touch Control is a system that enables the simple and economic dimming of luminous flux. It uses the mains voltage as a control signal, applying it with a standard push button on a control line, without any need for specific controllers.
The Touch Control system enables you to carry out the basic functions of a regulation system with a power-free pushbutton. Depending on how long the button is pressed it is possible to switch the light on or off or dim it. Switching the light on or off is done by short, sharp pressing or “click”. If the button is pressed for a long time it is possible to dim the luminous flux between the maximum and minimum levels alternately.

Touch Dimming

Touch Dimming

This is a unidirectional interface, i.e. information flows in one direction. The equipment does not generate any type of feedback, so it can’t be controlled with a software. Groups have to be created by wiring. This system cannot be integrated into building control systems.

The length of the wiring and the number of equipment that can be connected, are theoretically unlimited. But in, asynchronism may occur during switching on and dimming, at distances longer than 25 meters, and with a larger number of fixtures connected.
Owing to its characteristics, the use of this dimming method is recommended for individual offices, small meeting rooms or bedrooms, landings and small spaces in general.

Digital

Digital dimming covers all dimming systems that transform the dimming signal into bits and controls the lighting in digital format.

DALI Regulation (digital)

As revealed by the meaning of its acronym, Digital Addressable Lighting Interface, DALI is a digital and addressable communication interface for lighting systems.

This is an international standard system in accordance with IEC 62386, which ensures compatibility and interchangeabil­ity between different manufacturers’ equipment marked with the following logo: DALI controller

DALI-logo

DALI-logo

It is a bi-directional dimming interface with a master-slave structure. The information flows from a controller, which operates as the master, to the control gears that only operate as slaves. The latter carries out the orders or responds to the information requests received.

Digital signals are transmitted over a bus or two-wire control wire. These control wires can be negatively and positively polarized, though the majority control gears are designed polarity free to make connection indifferent.

DALI Dimming

DALI Dimming

You don’t need especially shielded cables. It is possible to wire the power line and DALI bus together with a standard five-wire cable.

Unlike other systems, you don’t need to create wiring groups. Therefore all the pieces of fixtures are connected in parallel to the bus. Without bearing in mind the grouping of these, simply avoiding a closed ring or loop topology.

You don’t require mechanical relays to switch the lighting on or off, given that this is done orders sent along the control line. You don’t need are bus termination resistors either.

Consequently, the DALI interfaces offer wiring simplicity in addition to great flexibility when it comes to designing the lighting installation.

The maximum voltage drop along the control line must not exceed 2V with the maximum bus current of 250mA. Therefore, the maximum wiring distance allowed depends on the cable cross-section, but it must never exceed 300m in any case.

Configuring

After wiring, the DALI lighting system is configured with the software. You can create up to 16 different scenarios, addressing the equipment individually up to a maximum of 64 addresses.  This can be made with groups up to a maximum of 16, or simultaneously by means of a “broadcast” order. You can change the configuration at any time without any need for re-wiring.

The DALI system has a logarithmic regulation curve adjusted to human eye sensitivity, defined in the international standard, IEC 62386. The possible regulation range is set at from 0.1% to 100%. The driver manufacturer determines the minimum.

DALI Regulation Curve by IEC 62386

DALI Regulation Curve by IEC 62386

With the software, you can change the “fade rate”. “Fade rate”is the time needed to go from one light level to another(fade time) and the speed of the change.

The DALI system lies in the fringe between the complex and costly but powerful ones; control systems for buildings that offer total functionality and the most simple and econom­ic regulation systems, for example, the 1-10V one.

You can use this interface in simple applications indepen­dently, to control a luminaire or a small room. You can also use it in high-level applications such as being integrated by gateways into building smart control systems.

These are the most common systems you can use to dim LED. There are a lot of different dimming systems for different driver manufacturers. I can’t cover all of those in a single blog post. I will be writing a different post about wireless dimming options.

If you have anything you would like to know, you can always contact me taru.matikainen@light.fi .

Sources: ELT

How to Choose a Suitable Constant Voltage LED Driver for Your Application

We discussed earlier about general characteristics of LED drivers and how to choose a suitable constant current LED driver for your application.  Now, I’m going to tell you how to choose a right LED driver for your constant voltage application.  As told in the previous posts, LED drivers are divided into two different categories: constant current and constant voltage drivers. But that is not the only thing you have to take into account when selecting the driver. In this post, we are focusing in constant voltage drivers.

Constant voltage drivers are generally used when you need a stabile voltage fed to your LED. You can check the datasheet of your light source whether it needs constant current or constant voltage. If it says for example 12V or 24 V, then it needs constant voltage. And for example 350 mA or 700mA means that you need a constant current driver. Constant voltage driver (power supply) keeps voltage constant (e.g. as 12 V DC), but feeding current varies according to the load (the higher the load the bigger the current)

Datasheet of Constant Current and Constant Voltage LED Module. The circled value tells you does the module need constant current or constant voltage.

Datasheet of Constant Current and Constant Voltage LED Module. The circled value tells you does the module need constant current or constant voltage.

With these easy step-by-step instructions, you will find a suitable driver for your luminaire or signage application.

Step one: What voltage does your LED application need?

As already mentioned, you should find the voltage that your LED needs, from the datasheet or from the product itself.  For example if your LED needs a voltage of 12 V, you should find a driver with 12 V DC output voltage. If LED demands 24V, you should find a driver with 24 V DC output voltage. So that is pretty straightforward.

Step two: How powerful driver do you need?

The power consumption of the LED application can also be found from the datasheet or from the value label in the product.

Remember that if using multiple LED components, you have to find a driver that can feed all the LED components in your luminaire (in parallel connection).

 

GE Lightech 12W, 12V LED driver

GE Lightech 12W, 12V LED driver

Step three: What current range you need from the driver?

Again take a look at the datasheet and check the current of the LED application. If you have multiple LEDs, you should add the current together. Then you should find a driver with a current range that your LEDs fit into.  On the other hand if you have checked well the power you need then your driver will give enough current to get your LED application burn on the right level.

And in some constant voltage LED applications the current is not mentioned at all, only the voltage and the power. Then you can skip this part.

Step four: Do you need dimming? And what type of dimming?

A need for dimming is mainly dependent of the specification of your LED application. If you don’t need dimming, a normal on/off driver is enough for you. If you need dimming, there are many different types of dimming, but that is a topic for another post.  But e.g. in signage applications dimming is not normally required.

Step five: What are the physical dimensions the driver has to fit into?

You should also consider if there are some limitations for the physical dimensions of the driver. These will obviously have an impact on your driver selection. You will generally find the physical dimensions of the driver from its datasheet.

Step six: is the driver placed inside the LED application or outside (built in or independent version)?

If the driver is placed outside the LED application without any fixing the driver should be classified as an independent version. This means that the input and output cables of LED driver have strain reliefs to secure safe cable connections in case of any pulling force.

Step seven: What kind of environment the LED application is used in?

Where is your LED application designed to be used in? If it is designed for indoor use, then you probably won’t need to think about IP-classification so much. Of course if the luminaire is used in a room with a lot of dust or moisture, this has to be taken into account.

And for outdoor use check that the product is approved for min IP67 area.

GE Lightech 200 W 12V, IP67 driver

GE Lightech 200 W 12V, IP67 driver

IP20 class drivers it means that this driver can be used in indoor lighting applications but hardly stands harsh conditions in outdoor lighting unless the luminaire itself is waterproof thus protecting the driver.

But when designing a luminaire to outdoor use, then you should check that that the driver has good enough IP-class.

Usually IP67 drivers are heavier in weight, driver electronics is molded in many cases with plastic (e.g. potted) and the electrical throughputs of the wires both on primary voltage and the secondary voltage side are sealed with required protection against moisture.

Step eight: Approvals, is the driver suited for European or American standards?

Does the driver have any approvals? And are the approvals for Europe (ENEC), America (UL) or for another area? This can generally be found from the datasheet of the driver. In most cases it is the benefit of both the customer and supplier that drivers are certified for that area where they are used.

ROAL Strato CV 24V with ENEC and UL approvals

ROAL Strato CV 24V with ENEC and UL approvals

So there you have it. With these steps you should be able to find a suitable LED driver for your application. If you don’t, please leave a comment or contact me directly.

How to choose suitable Constant Current LED driver for your application

Selection of LED Drivers

Selection of LED Drivers

We discussed earlier about the general characteristics of LED drivers. In this post, I’m going to tell you how to choose a right LED driver for your application. LED drivers are divided into two different categories: constant current and constant voltage drivers. But that is not the only thing you have to take into account when selecting the driver. In this post, we are focusing only in constant current drivers.

Constant current drivers are generally used when you need stabile current fed to your LED. With constant current driver, it is easier to manage the right brightness. You can check the datasheet of your light source whether it needs constant current or constant voltage. If it says for example 350mA, then it needs constant current. 12V or 24V means that you need a constant voltage driver.

In this post, we’ll take a look at constant current drivers.

How to choose a constant current driver for your application?

With these step by step instructions, you will find a suitable driver for your luminaire.

Step one: What forward current does your LED need?

As already mentioned, you should find the forward current your LED needs, from the datasheet. For example if your LED needs a current of 350mA, you should try to find a driver with 350mA output current.

Step two: How powerful driver do you need

The power consumption of the LED can also be found from the datasheet or at least it can be calculated with the data in the datasheet. The power consumption can be calculated by multiplying typical driving current value by typical forward voltage value that both can be found in the LED data sheet. Sometimes you can even find the power consumption directly from the datasheet.

Remember that if using multiple LED components, you have to find a driver that can feed all the LED components in your luminaire.

ELT 10W, 500mA LED driver

ELT 10W, 500mA LED driver

Step three: What output voltage range you need from the driver
Again take a look at the datasheet and check the voltage of the LED. If you have multiple LEDs, you should add the voltages together. Then you should find a driver with a voltage range that your LEDs fit into.

Step four: Do you need dimming? And what type of dimming?

A need for dimming is mainly dependent of the specification of your luminaire. If you don’t need dimming, a normal on/off driver is enough for you. If you need dimming, there are many different types of dimming, but that is a topic for another post.

Step five: What are the physical dimensions the driver has to fit into?

You should also consider if there are some limitations for the physical dimensions of the driver. These will obviously have an impact on your driver selection. You will generally find the physical dimensions of the driver from its datasheet.

Step six: What kind of environment the luminaire is used in?

Where is your luminaire designed to be used in? If it is designed to indoor use, then you probably won’t need to think about IP-classification so much. Of course if the luminaire is used in a room with a lot of dust or moisture, this has to be taken into account.

ELT 60W, 700mA, IP20 driver

ELT 60W, 700mA, IP20 driver

IP20 class drivers it means that this driver can be used in indoor lighting applications but hardly stands harsh conditions in outdoor lighting unless the luminaire itself is waterproof thus protecting the driver.

But when designing a luminaire to outdoor use, then you should check that that the driver has good enough IP-class.

Usually IP67 drivers are heavier in weight, driver electronics is molded with plastic (e.g. potted) and the electrical throughputs of the wires both on primary voltage and the secondary voltage side are sealed with required protection against moisture.

ELT 10W, 350mA, IP67 driver

ELT 10W, 350mA, IP67 driver

Step seven: Approvals, is the driver suited for European or American standards?

Does the driver have any approvals? And are the approvals for Europe (ENEC) or America (UL). This can generally be found from the datasheet of the driver.

So there you have it. With these steps you should be able to find a suitable LED driver for your application. If you don’t, please leave a comment or contact me directly.

You can also use our Light Builder to select a driver.