Abstract: An up-converter (100) comprises: an inductor (5) and a diode (6) connected in series with an output (3); a capacitor (8) connected in parallel to said output; a controllable switch (7) having one switch terminal coupled to a node between the inductor and the diode. A control method comprises the steps of feeding the inductor with a rectified AC voltage (Vi); and generating a switch control signal (SC) having a pulse width (TH), for switching the switch open and closed; wherein the switch control signal is generated on the basis of the output voltage (Vo) at said output (3). According to the invention, the up-converter comprises a digital processor (110) which samples the output voltage (Vo), and digitally processes the sampled output voltage (Vo) to calculate the pulse width (TH) of the switch control signal (SC) such that the output voltage (Vo) remains substantially constant.

Abstract: A method for measuring a color temperature (TC) of a light source (2) comprises the steps of: measuring the partial intensity of one predefined blue spectral conpponent (B); measuring the luminance (V); and calculating the quotient BN as representing the color temperature (TC). The color temperature (TC) is calculated on the basis of a predetermined relationship between the color temperature (TC) and the quotient BN. Sensor assembly capable of generating a measuring signal containing information regarding the color temperature of a light source. Switch stage for cooperation with a sensor assembly. Driver for during a lamp with variable color temperature properties. Lamp system comprising a lamp, a sensor assembly and a lamp driver.