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Many LEDs are typically required to source sufficient light for automotive exterior applications. Maintaining even illumination requires the drive current to be well controlled for all the LEDs in an array. This can be challenging in the voltage driven automotive environment when dual level operation is desired, such as for combined stop and tail function. A current source in the form of an LED Driver Module (LDM) can be employed to drive the LED array. However, a passive resistor network may be capable of driving the LED array with a reduction in both cost and complexity when compared to an LDM solution. The advantages and disadvantages of various passive resistor network configurations for dual level operation will be examined.

For the current class of available automotive LEDs (Light Emitting Diodes) used in CHMSLs (Center High Mount Stop Lamps), voltage regulation is required for operation at an optimized output light flux. We have built and measured the performance of resistive, voltage reference, and pulse width modulation DC-DC voltage regulators in order to achieve the required dual level control for RCL (rear combination lamps). These three types of driver electronics for dual level operation of a RCL are compared for performance, and efficiency under various operational conditions.