1. Technical Field
The present disclosure relates to a lighting circuit for a light source that lights the light source, and a lamp system for a vehicle.
2. Description of the Related Art
In the related art, a lighting circuit for a light source (“a light source lighting circuit”) has been known including a first circuit (e.g., a circuit for a stop lamp) that supplies a first driving current (e.g., a constant current) to a light source and a second circuit (e.g., a circuit for a tail lamp) that supplies a second driving current (e.g., a constant current) smaller than the first driving current to the light source (see, e.g., JP 2005-029020 A).
In order to prevent a countercurrent caused by a reverse connection of a battery, a first diode is connected between the first circuit and the light source, and a second diode is also connected between the second circuit and the light source.
When DC power voltage is input only to the first circuit, the first driving current is supplied to the light source from the first circuit by driving only the first circuit. When the DC power voltage is provided to the first circuit and the second circuit, the second driving current is supplied to the light source from the second circuit by driving only the second circuit.
However, in related art as described above, when only the first circuit is driven, the first driving current is larger than the second driving current, so that the first diode needs to have a large maximum rated voltage and thus, an expensive diode is required to be used as the first diode. As a result, the cost of the light source lighting circuit and the lamp system for a vehicle including the same is increased.