Development of Cost Advantageous Designs for Headlight System Using Light Emitting Diodes

So far, the application of LED headlights to the motorcycle has been limited for only high-priced models, because LED light units and the drivers are expensive. In our development, the cost reduction of light source units was examined by implementing multiple medium intensity LEDs. Distributed mounting scheme was created for LEDs placed on the circuit board to meet the heat dissipation requirement without a heat sink, which is usually installed. By new mounting scheme, the requirement of heat dissipation has been successfully fulfilled by only using the copper foil layer. Moreover, by connecting LEDs in series, the driver circuit configuration was made simple while separate circuits are generally required both for a high-beam and a low-beam. By this configuration, the driver cost was reduced. With this circuitry change, some associated issues arose and measures were devised to cope with them. In addition, the method of driver circuitry, established through applications for conventional incandescent light sources, was applied to provide a discrete voltage in half-waves from the ACG apart from the supply from the battery. Using this method, the circuit was made configurable to manage the situation, in which the foreword voltage drop of LED exceeds the output voltage of the battery, without using a booster circuit. With these measures, a significant cost reduction was made feasible. Owing to those achievements, LED headlight system was made applicable to the motorcycle models in low-priced ranges.