According to the conventional stabilized DC power supply device, there
is a possibility that the output transistor breaks down by heat when the input
voltage fluctuates. To cope with this, the stabilized DC power supply device embodying
the invention is so configured as to comprise an output transistor for converting
an input voltage to an output voltage and feeding out the output voltage, a control
circuit for controlling the output transistor so as to maintain a value of the
output voltage constant, a current detection circuit for detecting an output current
of the output transistor, a voltage detection circuit for detecting a voltage appearing
between an input side and an output side of the output transistor, a multiplying
circuit for multiplying an output of the current detection circuit and an output
of the voltage detection circuit together, and a protection circuit for restricting
a wattage power of the output transistor according to an output of the multiplying circuit.
