LED driver with compensation of thermally induced color drift

A circuit arrangement comprising:

• a temperature sensing circuit configured to provide a temperature signal representing temperature(s) of a plurality of light emitting diodes emitting light of different colors arranged adjacent to each other for additive color mixing to provide a desired color;
• a current source for each light emitting diode of the plurality of light emitting diodes, current sources configured to provide the light emitting diodes with respective load currents in accordance with corresponding control signals received by the current sources;
• a first modulator unit and a second modulator unit configured to generate the control signals which are modulated such that a time average value of each control signal corresponds to the value of a corresponding input signal of the respective modulator unit;
• and
• a calibration circuit configured to provide the input signals dependent on a color signal defining the desired color and dependent on the temperature signal, wherein the calibration circuit includes a lookup table unit including color calibration data for different discrete temperature values, the lookup table unit is configured to provide a set of calibration data selected dependent on the temperature signal, the input signals of the modulator units being responsive to the selected set of calibration data.

A method for driving a multi-color LED arrangement including a plurality of light emitting diodes emitting light of different colors and arranged adjacent to each other for additive color mixing to provide a desired color, the method comprising:

• generating a temperature signal representing temperature(s) of the light emitting diodes, wherein generating the temperature signal comprises
• providing a sense signal representing temperature(s) of one or more light emitting diodes, and
• sigma-delta modulating the sense signal thus generating a stream of bits or digital words, whose time average represents the sensed temperature(s), to provide the temperature signal;
• supplying, to each light emitting diode, load currents regulated in accordance with corresponding control signals;
• generating modulated signals as the control signals which are modulated such that a time average value of each control signal corresponds to a value of a corresponding input signal;
• and
• providing the input signals dependent on a color signal defining the desired color and dependent on the temperature signal using a look-up table, wherein the look-up table includes color calibration data for different discrete temperature values, and wherein a set of calibration data is selectable dependent on the temperature signal, the input signals for the sigma-delta modulation being responsive to a selected set of calibration data.

A method for driving a multi-color LED arrangement including a plurality of light emitting diodes emitting light of different colors and arranged adjacent to each other for additive color mixing to provide a desired color, the method comprising:

• generating a temperature signal representing temperature(s) of the light emitting diodes;
• supplying, to each light emitting diode, load currents regulated in accordance with corresponding control signals;
• generating modulated signals as the control signals which are modulated such that a time average value of each control signal corresponds to a value of a corresponding input signal;
• and
• providing the input signals dependent on a color signal defining the desired color and dependent on the temperature signal using a look-up table, wherein the look-up table includes color calibration data for different discrete temperature values, and wherein a set of calibration data is selectable dependent on the temperature signal, the input signals being responsive to a selected set of calibration data.