US Patent 7239041 Light emitting device for vehicles

A light emitting device includes an input node set, a light emitting unit including at least one light emitting element connected across first and second nodes of the input node set, an impedance matching element having a first end connected to the first node, a switch unit connected between a second end of the impedance matching element and the second node, and a control unit connected in parallel to the light emitting unit and connected to the switch unit. The control unit is operable so as to control the switch unit to operate in an ON-state, where the switch unit makes connection between the impedance matching element and the second node when the first node is applied with an AC input power signal, or an OFF-state, where the switch unit interrupts connection between the impedance matching element and the second node when the first node is applied with a DC input power signal for a predetermined period.