Disclosed is a switching-type
constant current power supply, which comprises an alteration circuit 9 provided on the output side of a power conversion circuit 3 together with a
voltage detection circuit 7, and a feedback circuit 8 provided between the
voltage detection circuit 7, a current detection circuit 5 and a
control circuit 4. The alteration circuit 9 is operable, during a current flow period where a load current IL is flowing, to set the
signal level of a second feedback
signal F2 at a value less than a reference
voltage Vref to be supplied to a
common error amplifier EA1 in a
control circuit 4, and operable, during a current
cut-off period where the load current IL is not flowing, to set the
signal level of the second feedback signal F2 at a value greater than the reference voltage Vref During the current
cut-off period, the feedback circuit 8 is operable to supply the second feedback signal F2 to the
control circuit 4 so as to substantially discontinue the operation of the power conversion circuit 3. The switching-type
constant current power supply of the present invention can stabilize the load current even under the condition that a load (e.g. display including LEDs) is repeatedly turned on and off.