VOLTAGE REGULATOR

• US 20130193939A1
• Filed: 01/30/2013
• Published: 08/01/2013
• Est. Priority Date: 01/31/2012
• Status: Active Grant

• Current Assignee: Ablic Inc. (MinebeaMitsumi Inc.)
• Original Assignee: Seiko Instruments Incorporated (Seiko Group)
• Inventors: SAKAGUCHI, Kaoru, SUZUKI, Teruo
• Granted Patent: US 9,459,641 B2
• Time in Patent Office: Days
• US Class Current: 323/277
• CPC Class Codes: G05F 1/56 using semiconductor devices in series with the load as final control devices G05F1/461 takes precedence
• CPC Class Codes: G05F 1/569 for protection
• CPC Class Codes: G05F 1/573 with overcurrent detector
• CPC Class Codes: G05F 1/5735 with foldback current limiting
• CPC Class Codes: H02H 9/02 responsive to excess current current limitation for voltage regulators G05F1/573; disconnection after limiting H02H3/025
• CPC Class Codes: H02H 9/025 Current limitation using field effect transistors
• CPC Class Codes: H02M 1/0025 Arrangements for modifying reference values, feedback values or error values in the control loop of a converter

Abstract

Provided is a variable output voltage regulator capable of reducing heat generation during an overcurrent protection operation even when a setting value of an output voltage is high. The variable output voltage regulator can change an output voltage by trimming a resistor of a voltage dividing circuit in response to a trimming signal output from a trimming signal generation circuit. The trimming signal is used to change a limiting voltage of a fold-back type overcurrent protection circuit.

Claims

1. A voltage regulator, comprising:

an output transistor;

a voltage dividing circuit for dividing an output voltage output from the output transistor to an output terminal;

an amplifier for comparing a divided voltage output from the voltage dividing circuit and a reference voltage so that the output voltage becomes constant;

a drooping type overcurrent protection circuit;

a fold-back type overcurrent protection circuit; and

a trimming signal generation circuit,

the trimming signal generation circuit outputting a trimming signal to trim a resistor of the voltage dividing circuit, thereby being capable of changing the output voltage,

wherein the trimming signal is used to change a limiting voltage of the fold-back type overcurrent protection circuit.

2. A voltage regulator according to claim 1,

wherein the fold-back type overcurrent protection circuit comprises:

a sense transistor having a gate terminal connected to an output of the amplifier;

a variable resistor circuit having one terminal connected to a drain of the sense transistor; and

a control section for controlling a gate of the output transistor in accordance with a voltage generated in the variable resistor circuit, and

wherein the trimming signal is used to change a resistance value of the variable resistor circuit.

3. A voltage regulator according to claim 1,

wherein the fold-back type overcurrent protection circuit comprises:

a sense transistor having a gate terminal connected to an output of the amplifier;

a variable resistor circuit having one terminal connected to a drain of the sense transistor; and

a control section for controlling a gate of the output transistor in accordance with a difference between a voltage generated in the variable resistor circuit and the divided voltage, and

wherein the trimming signal is used to change a resistance value of the variable resistor circuit.

4. A voltage regulator according to claim 3, wherein the fold-back type overcurrent protection circuit comprises an amplifier for detecting the difference between the voltage generated in the variable resistor circuit and the divided voltage.

5. A voltage regulator according to claim 1,

wherein the fold-back type overcurrent protection circuit comprises:

a sense transistor having a gate terminal connected to an output of the amplifier;

a second transistor having a drain connected to a drain of the sense transistor;

a first variable resistor circuit having one terminal connected to a source of the second transistor;

a first amplifier for controlling a gate of the second transistor in accordance with a difference between a voltage generated in the first variable resistor circuit and the divided voltage;

a second variable resistor circuit having one terminal connected to the drain of the sense transistor; and

a second amplifier for controlling a gate of the output transistor in accordance with a difference between a voltage generated in the second variable resistor circuit and the reference voltage, and

wherein the trimming signal is used to change a resistance value of the first variable resistor circuit and a resistance value of the second variable resistor circuit.

6. A voltage regulator according to claims 1, further comprising a non-volatile storage device for storing trimming data input to the trimming signal generation circuit.