Patent ID: 7642723

Claim:
A vehicular lamp lighting circuit, comprising: a control unit configured to control an electric current that flows to a light source unit, and wherein the control unit includes: an electric current supply section configured to output the electric current to the light source unit; a switching controller; an output current detection section configured to detect the electric current that flows into the light source unit; and a voltage transform circuit configured to transform an electric potential difference that arises from an electric current that flows into the output current detection section into a difference voltage and to output the difference voltage thus converted to the switching controller; wherein the output current detection section is connected to a high electric potential side of the light source unit; and wherein the switching controller compares the reference voltage with the difference voltage, and wherein the switching controller controls, by switching, the electric current that is outputted from the electric current supply section so as to reduce the difference between the reference voltage and the difference voltage.