Patent ID: 6788513
Filing Date: 2004-09-07
Classification: H02M

Abstract:
A switching power supply circuit comprising:a direct-current power source; an inductive load circuit supplied with electric power from said direct-current power source; a switching element interrupting the electric power supplied from said direct-current power source to said inductive load circuit; a control signal generating circuit generating a control signal periodically bringing said switching element into conduction; an overload detecting circuit generating an overload detection signal when a load current flowing through said switching element exceeds a predetermined current value; a first latch circuit being set by the overload detection signal and being reset in response to a leading edge of the control signal; a timer circuit performing a clocking operation during a period for which said first latch circuit is set, and generating a time-up signal when a predetermined clocking period elapses; a second latch circuit being set in response to the time-up signal of said timer circuit; and an output drive circuit receiving as inputs the control signal and output signals of said first and said second latch circuits, bringing said switching element into conduction in response to the control signal under normal conditions, and shutting off said switching element irrespective of the control signal when at least one of said first and said second latch circuits is set.