Mainz, Germany Standard light sources such as bulbs are increasingly replaced by LEDs or LED strings. PREMA Semiconductor offers the new constant current driver PR4130 controlling up to three LEDs in series. Even if one or two LEDs are disconnected or short circuited, the current and the brightness remain constant, thus providing high reliability. The supply voltage of the PR4130 ranges from 10 V up to 14.4 V or a maximum voltage of 21 V for short time. Only one external resistor is necessary for operation, to define the LED current in a range from 5 mA up to 30 mA. Due to the very accurate current control, the brightness of the LEDs is very constant and almost independent of the supply voltage and the number of connected LEDs. The PR4130 circuit is compensating the disadvantage of serial LED circuits, i.e. that a failure in one LED will lead to the disfunction of the whole string. A Zener diode circuit provides a current flow also with a break of one LED and together with the current control the brightness of all connected LEDs stays smooth and constant also with short circuit or break of one or two LEDs. The Zener diode circuit has been defined for forward voltages of the LEDs of up to 2.3V. Prema Semiconductor GmbH , 55129 Mainz, Germany. www.prema.com.