The specification for a universal electrical interface between LED lighting modules and their power supplies has been recently released by the Module-Driver Interface Special Interest Group (MD-SIG). The standard released by MD-SIG is supported by industry players like Osram, Panasonic, Philips and Tridonic.
According to the press release, “The standard is called LEDset1 edition1.0 (a three wire interface) power, ‘Iset’ and a return for both. The specification also allows for separate returns for main and set currents to avoid setting errors due to return voltage drops.”
Adding further, the release states that Iset has nothing to do with dimming. It is provided so that the LED module can indicate its maximum working current to the driver. It does this by drawing Imax/1,000 from Iset. The only time any modulation of Iset is allowed is if the LED module is cover-heating, when it is permitted to reduce its own supply current by reducing Iset.
The official names of the three terminals are: LED+, LEDset and LED- as stated in the release. The optional Iset return is ‘GRNset’. Additionally, the LED module and driver must be marked accordingly and recommended wire colours are: red, white, black and black respectively. Although LEDset1 specifies a universal analogue signalling protocol, it does not cover the matching of driver output voltage and current capability with LED module needs.
“The power interface specification describes driving capabilities like voltage, current and power ranges of LED control gears and respective LED module operating requirements,” said the SIG. “It simplifies matching and comparing output and input parameters with harmonised terms and definitions.” It also mentions that Osram has already adopted LEDset edition 1.0 as its own LEDset Gen2 specification. Osram’s first generation LEDset was a similar but incompatible system. The firm is allowing set resistors from 50kΩ to 1kΩ (100mA-5A ILEDmax). Osram’s specification includes NTC and PTC thermistor circuits to implement thermal protection feedback.