Clamp circuit to suppress reference voltage variation in a voltage regulator

Patent metadata

Field	Value
Publication number	US-9952610-B1
Application number	US-201715616300-A
Country	US
Kind code	B1
Filing date	Jun 7, 2017
Priority date	Jun 7, 2017
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A semiconductor integrated circuit includes a control transistor, a control circuit, a reference circuit, a current source, and a stabilizing circuit including a first transistor whose base is connected to a node to receive the reference voltage. The reference circuit includes series-connected second transistor and first and second resistors, third and fourth transistors and third and fourth resistors, and fifth and sixth transistors. The fifth transistor has connected base and collector, which base is connected to a base of the third transistor, the second transistor has a base connected to a node between third and fourth transistors, fourth and sixth transistors have bases connected to a first node between first and second resistors or a second node between second transistor and first resistor, a potential at the first or second node is the reference voltage, and a gain is determined depending on a resistance of the first resistor.

First claim

What is claimed is:

1. A semiconductor integrated circuit for a regulator, comprising:
a control transistor connected between an input terminal to which a DC voltage is applied and an output terminal;
a control circuit to control the control transistor such that an output voltage becomes a predetermined voltage depending on a potential difference between a feedback voltage corresponding to the output voltage and a predetermined reference voltage;
a reference voltage circuit to generate the reference voltage;
a current source circuit to feed an operating current for the reference voltage circuit; and
an operating-current stabilizing circuit to prevent a variation in the operating current for the reference voltage circuit regardless of a variation in the voltage input to the input terminal, wherein
the operating-current stabilizing circuit comprises:
a first transistor connected in series between a power supply line through which the operation current is fed to the reference voltage circuit and a ground line leading to a ground potential point, the first transistor including a base terminal connected to a node to which the reference voltage is output,

the reference voltage circuit comprises:
a second transistor, a first resistor, and a second resistor connected in series between the power supply line and the ground line;
a third transistor, a fourth transistor, a third resistor, and a fourth resistor connected in series between the power supply line and the ground line; and
a fifth transistor and a sixth transistor connected in series between the power supply line and a connection node between the third resistor and the fourth resistor, wherein

the fifth transistor has a base terminal and a collector terminal connected to each other to function as a current-voltage converter,
the third transistor has a base terminal connected to the base terminal of the fifth transistor,
the second transistor has a base terminal connected to a connection node between the third transistor and the fourth transistor,
the fourth transistor and the sixth transistor each have a base terminal connected to a connection node between the first resistor and the second resistor or a connection node between the second transistor and the first resistor,
an electric potential at the connection node between the second transistor and the first resistor or at the connection node between the first resistor and the second resistor is taken out as the reference voltage, and
a gain is determined depending on a resistance value of the first resistor.

2. The semiconductor integrated circuit for the regulator according to claim 1 , further comprising:
a low-pass filter disposed between the reference voltage circuit and the control circuit to remove noise from the reference voltage.

3. The semiconductor integrated circuit for the regulator according to claim 1 , further comprising:
a voltage dividing circuit comprising:
resistors connected in series to divide the output voltage into the feedback voltage to be fed to the control circuit, wherein

an output voltage level is changed stepwise by changing the gain by adjusting the resistance value of the first resistor, and
trimming for finely adjusting the output voltage to eliminate a voltage shift caused by a manufacturing variation is achieved by adjusting the resistance value of one of the resistors constituting the voltage dividing circuit.

Assignees

• Yokoyama Katsuhiro
• Takano Yoichi
• Mitsumi Electric Co Ltd

Inventors

• Yokoyama Katsuhiro
• Takano Yoichi

Classifications

• G05F1/468 Primary

  characterised by reference voltage circuitry, e.g. soft start, remote shutdown · CPC title

• G05F1/575

  characterised by the feedback circuit · CPC title

• G05F1/595

  semiconductor devices connected in series · CPC title

• H03K5/08

  by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding (H03K5/07 takes precedence; comparing one pulse with another H03K5/22; providing a determined threshold for switching H03K17/30) · CPC title