“control signal lam-current signal IL” ramps doWn at and after the time T0 as the current signal IL rises. For the Waveform of “ramp signal Ramp3+ramp signal Ramp11”,
its peak value increases at and after the time T0 With the rising of the ramp signal Ramp11. Therefore, the difference betWeen these tWo values gradually becomes smaller as time elapses. Then, “ramp signal Ramp3+ramp signal Ramp11” becomes larger than “control signal lam-current signal IL” at a time T1. When such a state is detected, the comparator 12 outputs H. Namely, the comparator 12 outputs a reset pulse to the latch circuit 5.