A control circuit may include a first feedback input terminal which receives the cathode terminal voltage of light-emitting elements from a current driving circuit as a feedback signal. Such an arrangement controls the ON/OFF state of a switching element such that the cathode terminal voltage approaches a predetermined voltage. A second feedback input terminal may be included to receive the anode terminal voltage of the light-emitting elements as a feedback signal. Such an arrangement controls the ON/OFF state of the switching element such that the anode terminal voltage does not exceed a predetermined threshold voltage. A feedback output terminal may be included of the current driving circuit which allows the cathode terminal voltage of the light-emitting elements to be input to a control circuit for the switching regulator as a feedback signal. The control circuit and the current driving circuit may be integrally provided in the form of separate semiconductor chips.