Voltage regulator with soft-start circuit

摘要

A voltage regulator includes an operational amplifier, a transistor, a first resistor, a second resistor, an output voltage delaying circuit and a selecting circuit. The output voltage delaying circuit receives an output voltage and generates a delayed output voltage. A first input terminal of the selecting circuit receives a reference voltage. A second input terminal of the selecting circuit receives the delayed output voltage. An output terminal of the selecting circuit generates a control voltage to a first input terminal of the operational amplifier. If the reference voltage is larger than the delayed output voltage, the selecting circuit selects the delayed output voltage as the control voltage. If the reference voltage is smaller than the delayed output voltage, the selecting circuit selects the reference voltage as the control voltage.

主权项

1. A voltage regulator, comprising:
an operational amplifier, wherein a first input terminal of the operational amplifier receives a control voltage, a second input terminal of the operational amplifier receives a feedback voltage, and an output terminal of the operational amplifier generates an error signal; a transistor, wherein a gate terminal of the transistor is connected to the output terminal of the operational amplifier and receives the error signal, a first terminal of the transistor receives a power supply voltage, and a second terminal of the transistor is connected to an output terminal of the voltage regulator, wherein the output terminal of the voltage regulator generates an output voltage; a first resistor, wherein a first terminal of the first resistor is connected to the output terminal of the voltage regulator, and a second terminal of the first resistor is connected to the second input terminal of the operational amplifier; a second resistor, wherein a first terminal of the second resistor is connected to the second terminal of the first resistor and generates the feedback voltage, and a second terminal of the second resistor is connected to a ground voltage; an output voltage delaying circuit connected to the output terminal of the voltage regulator, wherein the output voltage delaying circuit receives the output voltage and generates a delayed output voltage; and a selecting circuit, wherein a first input terminal of the selecting circuit receives a reference voltage, a second input terminal of the selecting circuit receives the delayed output voltage, and an output terminal of the selecting circuit generates the control voltage to the first input terminal of the operational amplifier, wherein if the reference voltage is larger than the delayed output voltage, the selecting circuit selects the delayed output voltage as the control voltage, wherein if the reference voltage is smaller than the delayed output voltage, the selecting circuit selects the reference voltage as the control voltage.