Digital Systems

Technical application guide

Flexible current setting via LEDset (OTi DALI and OTi)

Current setting via LEDset interface

LEDset interface
OTi DALI and OTi window drivers offer the adjustment of the LED module current in small current steps. Therefore, easy adjustment of the required LED module current is done via an external resistor (Rset)

The LEDset interface is a standardized LED module interface for setting the right maximum output current or establishing an easy and low-cost temperature protection for the connected LED modules.

Today, this interface is used by the majority of European manufacturers of LED drivers. The benefits of a common LEDset interface are:

  • Very easy adjustment of LED modules to LED window drivers
  • Plug & play current setting of LED modules
  • Same resistors/resistor values used across vendors
  • Standardized, future-proof solution

Option 1: Typically between LEDset and LEDset-aux

LEDset gives the possibility to manually set the LED current of LED window drivers without the need for additional programming. This multi-vendor interface is suitable for LED modules connected in parallel or series.

LEDset is based on a 3-wire connection between the LED driver and one or more LED modules. Only one additional wire, besides the two LED current supply wires, is used for transferring information from the LED module(s) to the LED driver, provided the Rset is mounted on the LED module. Alternatively, a standard resistor can be put directly into the driver’s LEDset input connector.

Flexible current setting via LEDset mode (resistor)
There are three options to place the resistor:

Option 3: On the LED module

Option 2: Alternatively between LEDset and LED-; LEDset-aux and LED- are connected/one potential

The LEDset interface works with a 5 V constant-voltage source within the LED driver. The LEDset interface measures the current that flows from the 5 V constant-voltage source through the Rset resistor(s). Therefore, the correct LEDset resistor value can be calculated by the following formula:

Rset [Ω] = (5 V/Iout [A]) x 1000

The figure above shows the standardized Iout/Rset curve. Rmin and Rmax depend on the individual LED window driver. The output current Iout, selected via the Rset resistor and within the valid LEDset range, must match the driving current of the LED components in the module and the nominal current range of the used LED driver. In the above condition, the maximum nominal LED driver current Iout_max is set by the minimum Rset value (Rset_min = 5 V/Imax x 1000) and the minimum nominal LED driver current Iout_min is set by the maximum Rset value (Rset_max = 5 V/Imin x 1000). The interface behavior follows the table below.

In case that there is no Rset connected (Rset > Rset_max ), the factory default current is typically 50 % of the minimum nominal current. As soon as the LED driver detects a resistor, the output current is adjusted according to the LEDset resistor coding. The OSRAM Rset calculator, which is integrated into the OSRAM Matchmaker for LED module/LED driver combinations, helps you to find the correct resistor values. For more details, please see the chapter “The OSRAM Matchmaker – LED modules and system compatibilities”.

Ready-to-use resistors are available from electronics distributors as well as BJB. For non-isolated LED window drivers, the terminals of Rset are connected to mains, therefore an additional isolation is required.

Current setting via programmable interface (Tuner4TRONIC)

In the Tuner4TRONIC software, the programming of the current is called “Fixed current mode”.

Fixed current mode (via programmable interface) For OTi DALI LED drivers where additional parameter settings such as the CLO function are to be programmed, current setting is done via a programmable interface to reduce luminaire manufacturing time.

To use the fixed current mode, it has to be selected in the Tuner4TRONIC software. The minimum and maximum rated output currents are displayed according to the selected LED driver. The output current of the LED driver can be set by changing the value in the “Operating Current” field. Current setting is only possible within the specified current range.

Default current setting mode (ex factory)

Window driver (ex factory):
As soon as the LED driver detects a resistor, the output current is adjusted according to the LEDset resistor coding. When the window driver has been programmed in the fixed current mode, the LEDset mode remains disabled even if a resistor is connected.