Input overvoltage protection circuit with soft-start function
AssigneeRenesas Electronics Corporation
InventorTakeshi Yoshizawa
Life of this patent
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Abstract
An overvoltage protection circuit includes a PMOS transistor Q1 that is disposed between an input circuit 21, from which an input voltage VIN is supplied, and a system 22 and functions as a switch. A comparator 110 compares the input voltage VIN with a predetermined reference voltage to determine the occurrence of an overvoltage. Further, the comparator 110 outputs a High level as an operation signal when no overvoltage is detected. A soft switching control circuit 130 starts up by using the High level output from the comparator 110 as an enable signal, and gradually turns on the PMOS transistor Q1. A sudden change of the load exerted on the circuit on the input side is suppressed by the soft start function.
Claims13
An overvoltage protection circuit that prevents an overvoltage from flowing into a system and thereby protects the system, comprising:
- a first switch to function as a switch disposed between an input circuit and the system, the input circuit being configured to supply an input voltage, and the first switch being constructed of a semiconductor transistor;
- a comparator that determines an occurrence of an overvoltage by comparing the input voltage with a predetermined reference voltage, and when no overvoltage is detected, outputs an operation signal;
- a soft switching control circuit that starts up by using the operation signal from the comparator as an enable signal, and turns on the first switch gradually by gradually increasing a voltage between a source and a gate of the first switch;
- and
- a second switch provided between the soft switching control circuit and the input circuit, the second switch being configured to cutoff a current path between the input circuit and the soft switching control circuit in response to an overvoltage detection signal output from the comparator.
Dependencies are inferred from the claim text.