Suitable Switching Converter Topologies for Automotive Signal Lamps and Headlamps Using Power LEDs

Since the high rise in luminous flux power LEDs have experienced in the last years, they have become an overcoming alternative to incandescent bulbs for automotive signal lamps, and even an interesting choice for automotive headlamps, as most recent prototypes has shown, since the performance is near to that of HID lamps. This rise in luminous flux is based on both higher efficiency and forward current, being the latter the reason why switching regulators have become interesting for current control. Linear regulators usually work quite well in lamps where the forward current is kept at a low level, whereas the efficiency drops as forward current rises. Another drawback of linear regulators is that the load voltage must be lower than the supply voltage, otherwise the LED lamp does not work The advantages of switching regulators consist of both high efficiency whatever the working point is, and the capability of working in any condition of supply and load voltage. In this paper, three high efficiency-one switch-simple-switching converters such as buck, boost and buck-boost converter are discussed for the use in automotive LED lighting applications, both for 14 V network and 42 V Powernet system, the newest power bus system, consisting of a 14/42 V dual voltage bus.