Voltage generating circuit for improving stability of bandgap voltage generator
First Claim
1. A voltage generating circuit, comprising:
- a bandgap voltage generator, having a first operational amplifier, the first operational amplifier receiving a first voltage and a second voltage, generating a bias voltage by comparing the first voltage and the second voltage, wherein the bandgap voltage generator generates a bandgap current according to the bias voltage and generates an output voltage according to the bandgap current; and
a start-up circuit, comprising;
a comparison circuit, comparing the first voltage or the second voltage with a reference voltage to generate a first comparison result, and generating a first current according to the first comparison result, wherein the reference voltage is generated according to the first current; and
a voltage regulator, coupled to the comparison circuit and the bandgap voltage generator, generating a second current according to the first current, comparing the second current and a reference current to generate a second comparison result, and adjusting voltage value of the bias voltage according to the second comparison result, wherein the voltage regulator comprises;
a first transistor, where a first end of the first transistor is coupled to a power voltage end, a control end of the first transistor receives the first comparison result, wherein the first transistor generates the second current according to the first current;
a second transistor, where a first end of the second transistor is coupled to a reference ground end, a second end of the second transistor receives the bias voltage;
a reference current source, coupled between the second end of the first transistor and the reference ground end, generating a reference current, and drawing the reference current from the first transistor; and
a buffer, coupled to the second end of the first transistor, receiving a current difference of the second current and the reference current, and generating the second comparison result according to the current difference,wherein the reference current source comprises;
a third transistor, where a first end of the third transistor is coupled to the power voltage end, a control end of the third transistor is coupled to a first node,wherein a second end of the third transistor generates a third current according to a voltage on the first node;
a fourth transistor, where a first end of the fourth transistor is coupled to the power voltage end, and a control end of the fourth end is coupled to the first node;
a fifth transistor, where a first end of the fifth transistor is coupled to the power voltage end, and a second end and a control end of the fifth transistor are coupled to the first node;
a sixth transistor, where a first end of the sixth transistor is coupled to the reference ground end, a second end and a control end of the sixth transistor are coupled to a second end of the fourth transistor;
a seventh transistor, where a second end of the seventh transistor is coupled to the second end of the fifth transistor, a control end of the seventh transistor is coupled to the control end of the sixth transistor; and
a first resistor, coupled between the first end of the seventh transistor and the reference ground end.
1 Assignment
0 Petitions
Accused Products
Abstract
In a voltage generating circuit, a bandgap voltage generator has a first operational amplifier to receive a first voltage and a second voltage, and generate a bias voltage by comparing the first voltage and the second voltage, wherein the bandgap voltage generator generates a bandgap current according to the bias voltage and generates an output voltage according to the bandgap current. In a start-up circuit, a comparison circuit compares the first voltage or the second voltage with a reference voltage to generate a first comparison result, and generates a first current according to the first comparison result. A voltage regulator generates a second current according to the first current, and compares the second current with a reference current to generate a second comparison result, and adjusts a voltage value of the bias voltage according to the second comparison result.
-
Citations
9 Claims
-
1. A voltage generating circuit, comprising:
-
a bandgap voltage generator, having a first operational amplifier, the first operational amplifier receiving a first voltage and a second voltage, generating a bias voltage by comparing the first voltage and the second voltage, wherein the bandgap voltage generator generates a bandgap current according to the bias voltage and generates an output voltage according to the bandgap current; and a start-up circuit, comprising; a comparison circuit, comparing the first voltage or the second voltage with a reference voltage to generate a first comparison result, and generating a first current according to the first comparison result, wherein the reference voltage is generated according to the first current; and a voltage regulator, coupled to the comparison circuit and the bandgap voltage generator, generating a second current according to the first current, comparing the second current and a reference current to generate a second comparison result, and adjusting voltage value of the bias voltage according to the second comparison result, wherein the voltage regulator comprises; a first transistor, where a first end of the first transistor is coupled to a power voltage end, a control end of the first transistor receives the first comparison result, wherein the first transistor generates the second current according to the first current; a second transistor, where a first end of the second transistor is coupled to a reference ground end, a second end of the second transistor receives the bias voltage; a reference current source, coupled between the second end of the first transistor and the reference ground end, generating a reference current, and drawing the reference current from the first transistor; and a buffer, coupled to the second end of the first transistor, receiving a current difference of the second current and the reference current, and generating the second comparison result according to the current difference, wherein the reference current source comprises; a third transistor, where a first end of the third transistor is coupled to the power voltage end, a control end of the third transistor is coupled to a first node, wherein a second end of the third transistor generates a third current according to a voltage on the first node; a fourth transistor, where a first end of the fourth transistor is coupled to the power voltage end, and a control end of the fourth end is coupled to the first node; a fifth transistor, where a first end of the fifth transistor is coupled to the power voltage end, and a second end and a control end of the fifth transistor are coupled to the first node; a sixth transistor, where a first end of the sixth transistor is coupled to the reference ground end, a second end and a control end of the sixth transistor are coupled to a second end of the fourth transistor; a seventh transistor, where a second end of the seventh transistor is coupled to the second end of the fifth transistor, a control end of the seventh transistor is coupled to the control end of the sixth transistor; and a first resistor, coupled between the first end of the seventh transistor and the reference ground end. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
Specification