Patent ID: 7301312

Claim:
An IC for use in a switching power unit, for outputting an output voltage by converting an input voltage to said output voltage in accordance with a switching signal supplied, but for outputting an output voltage close to said input voltage when said switching signal is not supplied, said IC comprising: a switch means that is on-off controlled by said switching signal; a control circuit for outputting said switching signal controlled in association with the voltage difference between a first detection voltage in accord with said output voltage and a first reference voltage such that said first detection voltage becomes equal to said first referenced voltage; and a malfunction detection circuit, adapted to compare a second detection voltage in accord with said output voltage with a second reference voltage; and generate and supply to said control circuit a malfunction detection signal to stop supplying said switching signal when said second reference voltage exceeds said second detection voltage, wherein said switch means is connected in series at one switch terminal thereof with a coil, and wherein said output voltage is obtained by rectifying and smoothing the voltage appearing at said switch terminal, wherein said second reference voltage is set to a level in accord with the input voltage.