Patent ID: 7741788

Claim:
A light emitting apparatus comprising: a DC/DC converter to chop, in response to a chopping signal that controls an on/off operation, and transform an output of a DC power supply, to convert a voltage obtained by the transformation into a DC power, and to supply the DC power to a load, at least one semiconductor light source as the load of the DC/DC converter in an output loop of the DC/DC converter, and a current limiting circuit to compare a signal corresponding to a first switching signal with a signal corresponding to a current flowing to the at least one semiconductor light source, to open/close the output loop in accordance with a result of the comparison, and to cause a current to flow to the at least one semiconductor light source so as not to exceed a maximum current while the output loop is closed, wherein the current limiting circuit comprises a resistor connected in series with the at least one semiconductor light source to detect the current flowing to the at least one semiconductor light source, the signal corresponding to a current flowing to the at least one semiconductor light source comprises a voltage across the resistor, and the DC/DC converter is connected to the resistor to receive the voltage across the resistor as a feedback signal, and wherein the apparatus is arranged so that a current defined with an ON duty of the first switching signal is caused to flow as a mean current to the semiconductor light source.