LED driver for VLC

An LED driver for driving a plurality of LEDs or LED groups to transmit light in a VLC mode, wherein the LED driver comprises a control unit that is configured to:

• receive, at an input terminal, a set-point representing a desired illumination characteristic of the plurality of LEDs or LED groups, comprising an intensity set-point and a color set-point, and data that is to be transmitted in the VLC mode;
• determine a current profile for each LED or LED group of the plurality of LEDs or LED groups based on the desired illumination characteristic represented by the set-point, whereby an envelope of a combined current profile of the current profiles is configured to represent one or more code words comprising a plurality of symbols and is modulated in order for a corresponding intensity variation as perceived by a sensor to represent a variable length VLC code representing the data for transmission, the VLC code comprising the one or more code words, a code word comprising the plurality of symbols, whereby each of the plurality of symbols is characterized by both a respective predetermined period and the received set-point of the desired illumination characteristic, and whereby the current profile for each of the LED or LED groups is determined in such a manner that the illumination as generated by the plurality of LEDs or LED groups in the VLC mode corresponds to the desired illumination characteristic;
• and
• generate one or more control signals to drive the plurality of LEDs or LED groups in accordance with the envelop of the combined current profiles in order for the plurality of LEDs or LED groups to transmit the VLC code such that each of the plurality of symbols of the one or more code words transmitted as the data in the envelope of the combined current profiles is identified based only on the duration of the predetermined period and the intensity variation of the plurality of LEDs or LED groups corresponding to the desired illumination characteristic applied during the data transmission,
• wherein the combined current profile has a high current period and a low current period during each predetermined period,
• wherein each predetermined period represents a single symbol.

A control unit for controlling an LED driver to drive a plurality of LEDs or LED groups to transmit light in a VLC mode, the control unit comprising:

• an input terminal configured to receive a set-point representing a desired illumination characteristic of the plurality of LEDs or LED groups, comprising an intensity set-point and a color set-point, and data that is to be transmitted in the VLC mode;
• and
• an output terminal configured to output one or more control signals for controlling the LED driver,
• the control unit being configured to:
• determine a current profile for each LED or LED group of the plurality of LEDs or LED groups to generate the desired illumination characteristic represented by the set-point, whereby an envelope of a combined current profile is configured to represent one or more code words comprising a plurality of symbols and is modulated in order for a corresponding intensity variation as perceived by a sensor to represent a variable length VLC code representing the data for transmission, the VLC code comprising the one or more code words, a code word comprising the plurality of symbols, whereby each of the plurality of symbols is characterized by both a respective predetermined period and the received set-point of the desired illumination characteristic, and whereby the current profile for each of the LED or LED groups is determined in such a manner that the illumination as generated by the plurality of LEDs or LED groups in the VLC mode corresponds to the desired illumination characteristic;
• and
• generate one or more control signals to drive the plurality of LEDs or LED groups in accordance with the envelope of the combined current profiles in order for the plurality of LEDs or LED groups to transmit the VLC code such that each of the plurality of symbols of the one or more code words transmitted as the data in the envelope of the combined current profiles is identified based only on the duration of the predetermined period and the intensity variation of the plurality of LED or LED groups corresponding to the desired illumination characteristic applied during the transmission,
• wherein the combined profile has a high current period and a low current period during each predetermined period,
• wherein each predetermined period represents a single symbol.