VOLTAGE REGULATOR

• US 20120194947A1
• Filed: 01/23/2012
• Published: 08/02/2012
• Est. Priority Date: 01/28/2011
• Status: Abandoned Application

• Current Assignee: Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: Nakashimo, Takao
• Application Number:
  US13/355,746
• Publication Number:
  US 20120194947A1
• Time in Patent Office: Days
• US Class Current: 361/18
• CPC Class Codes: G05F 1/573 with overcurrent detector

Abstract

Provided is a voltage regulator capable of providing overcurrent protection without increasing current consumption even when an output current increases. An overcurrent protection circuit includes: a sense resistor provided to a drain of an output transistor, for sensing an output current; an offset comparator for comparing voltages at both terminals of the sense resistor; and a first transistor including a gate connected to an output of the offset comparator. A current path between a detection transistor and the sense resistor is eliminated, and hence a current for detection does not increase even when an output current is large.

Claims

1. A voltage regulator, comprising:

an error amplifier circuit for amplifying and outputting a difference between a reference voltage and a divided voltage obtained by dividing a voltage output by an output transistor, to thereby control a gate of the output transistor; and

an overcurrent protection circuit for monitoring an output current of the output transistor to protect the voltage regulator from an overcurrent,

wherein the overcurrent protection circuit comprises;

a sense resistor provided to a drain of the output transistor, for sensing the output current;

an offset comparator including an input terminal provided with an offset voltage, for comparing voltages at both terminals of the sense resistor; and

a first transistor including a gate connected to an output terminal of the offset comparator, and a drain connected to the gate of the output transistor.

2. A voltage regulator according to claim 1, wherein the sense resistor uses one of a wiring resistor and a bonding resistor.

3. A voltage regulator according to claim 1, wherein the offset comparator comprises an adjustment circuit for adjusting an offset amount based on a magnitude of the divided voltage.