Patent ID: 6400545
Filing Date: 2002-06-04
Classification: H02M,H03K

Abstract:
A fuseless DC-DC converter comprising:a load circuit formed including a first overheat self-interruption-type semiconductor switch connected in series between a DC power supply and a load; a reference circuit including a second overheat self-interruption-type semiconductor switch connected in parallel with the first overheat self-interruption-type semiconductor switch, and a reference resistor having one end connected to the source of the second overheat self-interruption-type semiconductor switch and the other end is grounded, said reference circuit inducing, across the drain and source of the second overheat self-interruption-type semiconductor switch, the same voltage as that arising across the drain and source of the second overheat self-interruption-type semiconductor switch when a constant load current flows through the first overheat self-interruption-type semiconductor switch; a comparator circuit comparing the source voltage of the first overheat self-interruption-type semiconductor switch with a reference voltage applied to the source of the second overheat self-interruption-type semiconductor switch, and a power supply controller for deactivating the first overheat self-interruption-type semiconductor switch when said controller judges a current greater than a predetermined value flows through the first overheat self-interruption-type semiconductor switch on the basis of the result of the comparison performed by the comparator circuit, for controlling activation or deactivation of the first overheat self-interruption-type semiconductor switch by a predetermined duty cycle under predetermined conditions, for judging an occurrence of an abnormal condition in the load circuit, when the activation and deactivation of the first overheat self-interruption-type semiconductor switch has continued for a predetermined amount of time, to interrupt the first overheat self-interruption-type semiconductor switch so as to suspend power supply to the load.