An embodiment device includes a first MOS transistor and a first resistor in series between first node and second nodes, the first resistor being connected to the second node; a second MOS transistor and a second resistor in series between the first and second nodes, the second resistor being connected to the second node and the gates of the first and second transistors being coupled to each other; an operational amplifier including a first terminal connected to a node of connection of the first resistor to the first transistor, a second terminal, and an output terminal coupled to the gate of the first transistor; and a circuit configured to supply a set point voltage to the second terminal of the amplifier.

An LED system includes an LED array, a plurality of driver circuits, a power supply, a bus and a feedback circuit. Each of the plurality of driver circuits is connected to and driving one of a plurality of LED subarrays in the LED array. Each of the plurality of driver circuits includes a comparator circuit, a local voltage register, and a global voltage register. The comparator circuit determines, as a local minimum voltage, a lowest voltage in the corresponding LED subarray. The global minimum voltage is determined by comparing all the local minimum voltages. The feedback circuit provides the power supply with a feedback signal reflecting the global minimum voltage and causes the power supply to adjust the voltage output to the LED array.

An LED driving system with a master-slave architecture. The LED driving system has at least two LED driving circuits which both have a first status detecting circuit, a second status detecting circuit and a first feedback control circuit. The first status detecting circuit receives a plurality of headroom detecting voltages provided by a plurality of LED strings and generates at least one self-status signal. The second status detecting circuit receives a downstream feedback signal and generates at least one downstream status signal. The first feedback control circuit generates a first feedback control signal based on the at least one self-status signal and the at least one downstream status signal. The second status detecting circuit of one LED driving circuit is coupled to the first feedback control circuit of the other LED driving circuit.

A lighting circuit turns on a plurality of semiconductor light sources. Multiple current sources are each coupled to a corresponding semiconductor light source. A switching converter supplies a driving voltage V.sub.OUT across each of multiple series connection circuits each formed of the semiconductor light source and the current source. A converter controller employing a ripple control method turns on a switching transistor of the switching converter in response to a voltage across any one of the multiple current sources decreasing to a bottom limit voltage.

A minimum voltage detector circuit is disclosed. The circuit includes a plurality of LED strings each having a plurality of series-coupled LEDs. The minimum voltage detector circuit is configured to detect a minimum voltage from among the plurality of LED strings, and also to perform open/short detection among the plurality of LED strings. The minimum voltage detector circuit includes a plurality of voltage comparators and correspondingly coupled replica circuits. Each of the voltage comparators includes an amplifier having a first input coupled to a cathode of a last LED of one of the plurality of LED strings, an output, and a second input coupled to the output. Each voltage comparator further includes a replica circuit coupled to the amplifier. The replica circuit is configured to maintain an output transistor of the amplifier in an active state when the amplifier is in an unbalanced state.

A Light Emitting Diode, LED, driver arranged for driving at least one LED, said LED driver comprising a rectifier arranged for receiving an Alternating Current, AC, supply voltage and for providing an output Direct Current, DC, voltage to said at least one LED, a voltage regulating branch arranged for controlling an LED voltage provided to said at least one LED, via a supply line, wherein said voltage regulating branch is arranged for receiving said DC voltage from said rectifier, wherein said voltage regulating branch comprises, a capacitor arranged for providing said LED voltage to said at least one LED, a current limiter, connected in series with said capacitor, and arranged for charging said capacitor thereby providing said LED voltage and a feedback circuit arranged for controlling the charging of said capacitor by said current limiter, and thereby controlling the LED voltage provided to said at least one LED, by regulating a minimum residual headroom voltage present on a LED current limiter coupled in series with said at least one LED.

A Light Emitting Diode, LED, driver arranged for driving at least one LED, said LED driver comprising a rectifier arranged for receiving an Alternating Current, AC, supply voltage and for providing an output Direct Current, DC, voltage to said at least one LED, a voltage regulating branch arranged for controlling an LED voltage provided to said at least one LED, via a supply line, wherein said voltage regulating branch is arranged for receiving said DC voltage from said rectifier, wherein said voltage regulating branch comprises, a capacitor arranged for providing said LED voltage to said at least one LED, a current limiter, connected in series with said capacitor, and arranged for charging said capacitor thereby providing said LED voltage and a feedback circuit arranged for controlling the charging of said capacitor by said current limiter, and thereby controlling the LED voltage provided to said at least one LED, by regulating a minimum residual headroom voltage present on a LED current limiter coupled in series with said at least one LED.

A device comprises a voltage regulator, circuits, a voltage-to-current converter, a control bus, a resistor and a resistor network. Each of the circuits has at least one LED connector and one LED driver. Each of the circuits has a measuring circuit for detecting voltage differences between the potentials of LED terminals and a reference potential. Further, each of the circuits includes a local controller. The local controller withdraws a current from the control bus in dependence on the detected voltage differences. Bias current sources inject bias currents into the control bus in form of a sum current of the injected bias currents. The resistor performs a current-to-voltage conversion of the sum current to a control voltage. The voltage-to-current converter converts the control voltage into a current. The resistor network converts the current into a voltage value. An output voltage of the voltage regulator depends on the voltage value.

A device comprises a voltage regulator, circuits, a voltage-to-current converter, a control bus, a resistor and a resistor network. Each of the circuits has at least one LED connector and one LED driver. Each of the circuits has a measuring circuit for detecting voltage differences between the potentials of LED terminals and a reference potential. Further, each of the circuits includes a local controller. The local controller withdraws a current from the control bus in dependence on the detected voltage differences. Bias current sources inject bias currents into the control bus in form of a sum current of the injected bias currents. The resistor performs a current-to-voltage conversion of the sum current to a control voltage. The voltage-to-current converter converts the control voltage into a current. The resistor network converts the current into a voltage value. An output voltage of the voltage regulator depends on the voltage value.

A lighting arrangement such as a LED lamp comprises a light source and associated current driver, or a set of at least two parallel light sources and associated current drivers, supplied by a DC voltage from a voltage-regulated power converter. A feedback circuit provides a temperature-dependent control input to a control loop of the power converter, such that the DC voltage is adjusted in dependence on a sensed temperature. In this way, the voltage headroom required can be reduced, and efficiency gains are made.