Recently, it is widely noticed that replacing conventional incandescence lights with light emitting diodes as light sources is beneficial in terms of their low power consumption, longer life and larger degree of freedom in designing. That is also the case in automobile industry and light emitting diodes are increasingly used as light sources. Applying light emitting diodes to light sources of the headlights, which consume a large amount of electric power, is highly advantageous for overall reduction of consumed energy in a vehicle resulting in a good fuel economy. Moreover, if light emitting diodes are applied to headlights of motorcycles sold in a large number in affordable price range, a significant contribution is expected to the reduction of the total amount of carbon dioxide emission. However, up to the present, the use of light emitting diodes for headlights of motorcycles has been limited to only certain models in high price range. This is mainly because the headlight systems using high power light emitting diodes and their driver units are expensive. Based on these backgrounds, we adopted a configuration with a multiple use of medium intensity light emitting diodes. In addition, heat dissipation configuration that fulfills the thermal requirements was devised without using a heat sink that was a causal factor of high cost. The cost was further reduced through the employment of a single constant current regulation circuit. It was made possible by the serial connection of high-beam and low-beam light sources. This development made it possible to employ headlights using light emitting diode for motorcycles in low price ranges as well.
Article of Honda R&D Technical Review Vol.27 No.1 (62 - 70)