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Voltage generating circuit for improving stability of bandgap voltage generator

  • US 10,423,188 B1
  • Filed: 07/09/2018
  • Issued: 09/24/2019
  • Est. Priority Date: 04/10/2018
  • Status: Active Grant
First Claim
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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.

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