Electronic circuit with a regulated power supply circuit

Abstract

A power supply regulator circuit uses a feedback loop to control current through a first output transistor from a power supply input to a regulated power supply output. The first output transistor is included in an integrated circuit. In order to avoid heating of the integrated circuit in excess of an acceptable level due to permanent supply of a high current through the first transistor, current through a second output transistor in parallel with the first transistor, but outside the integrated circuit is raised when it is detected that the current through the first output transistor exceeds a threshold level. The second output transistor outside the integrated circuit serves to take over supply of a part of the power supply current from first output transistor inside integrated circuit, when long term supply of that part from first output transistor would lead to undesirable heating of the integrated circuit. During a limited time interval a first transistor current above the threshold level is acceptable. During this time interval the current through the second output transistor is raised slowly in order to avoid unpredictable stability problems and the generation of excessive power supply noise.