Lighting circuit and vehicle lighting tool

A lighting circuit, comprising:

• a power supply line to which power supply voltage is supplied in a first period of time out of a predetermined cycle including the first period of time and a second period of time, the supply of the power supply voltage being stopped in the second period of time;
• a first regulator that supplies first driving current to a first light source based on the power supply voltage across the power supply line;
• a first detection circuit that detects whether there is an abnormality in the first light source;
• a second regulator that supplies second driving current to a second light source based on the power supply voltage across the power supply line;
• a second detection circuit that detects whether there is the abnormality in the second light source;
• a signal output circuit that operates based on the power supply voltage across the power supply line and outputs a signal based on a first detection result of the first detection circuit and a second detection result of the second detection circuit;
• a first control circuit that stops an operation of the first regulator when the signal indicating that there is the abnormality in either of the first light source or the second light source is output;
• and
• a second control circuit that stops an operation of the second regulator when the signal indicating that there is the abnormality in either of the first light source or the second light source is output,
• wherein the signal output circuit holds the signal indicating that there is the abnormality in either of the first light source or the second light source regardless of whether the power supply voltage is supplied to the power supply line when the first detection result indicating that there is the abnormality in the first light source or the second detection result indicating that there is the abnormality in the second light source is input in the first period of time.