Voltage regulator
View Patent ↗Provided is a voltage regulator capable of stable operation under a light load so as to cover a wide range of load capacitances. The voltage regulator includes a circuit for charging a phase compensation capacitor for the voltage regulator, and a zero due to a resistor ( 104 ) and a capacitor ( 106 ) appears at low frequency.
1. A voltage regulator, comprising:
a first power supply terminal;
a second power supply terminal;
an output terminal;
a reference voltage circuit;
a first resistor and a second resistor that are connected in series between the output terminal and the second power supply terminal;
a first error amplifier circuit for outputting a voltage indicating a comparison result,
the first error amplifier circuit including:
an inverting input terminal connected to an output terminal of the reference voltage circuit; and
a non-inverting input terminal connected to a connection point between the first resistor and the second resistor;
an output transistor having a gate voltage that is controlled by an output of the first error amplifier circuit so that the output terminal has a constant voltage value,
the output transistor being provided between the first power supply terminal and the output terminal;
a phase compensation capacitor including one terminal connected to the output terminal;
a second error amplifier circuit including:
a non-inverting input terminal connected to the connection point between the first resistor and the second resistor; and
an output terminal and an inverting input terminal that are connected to each other; and
a switch circuit configured to:
connect the phase compensation capacitor to an output of the second error amplifier circuit until a predetermined time period elapses after one of power-on and turn-on of the voltage regulator; and
connect the phase compensation capacitor to the connection point between the first resistor and the second resistor after the predetermined time period has elapsed.
2. A voltage regulator according to claim 1 , wherein the non-inverting input terminal of the second error amplifier circuit is connected to the output terminal of the reference voltage circuit.
3. A voltage regulator according to claim 1 , wherein the first resistor and the phase compensation capacitor have a time constant of 1 millisecond or more.
4. A voltage regulator, comprising:
a first power supply terminal;
a second power supply terminal;
an output terminal;
a reference voltage circuit;
a first resistor and a second resistor that are connected in series between the output terminal and the second power supply terminal;
a first error amplifier circuit for outputting a voltage indicating a comparison result,
the first error amplifier circuit including:
an inverting input terminal connected to an output terminal of the reference voltage circuit; and
a non-inverting input terminal connected to a connection point between the first resistor and the second resistor;
an output transistor having a gate voltage that is controlled by an output of the first error amplifier circuit so that the output terminal has a constant voltage value,
the output transistor being provided between the first power supply terminal and the output terminal;
a phase compensation capacitor including one terminal connected to the output terminal;
a second error amplifier circuit including:
a non-inverting input terminal connected to the connection point between the first resistor and the second resistor; and
an output terminal and an inverting input terminal that are connected to each other; and
a switch circuit configured to:
connect the phase compensation capacitor to an output of the second error amplifier circuit as long as an output voltage of the voltage regulator is lower than a predetermined voltage value after one of power-on and turn-on of the voltage regulator; and
connect the phase compensation capacitor to the connection point between the first resistor and the second resistor when the output voltage has the predetermined voltage value or more.
5. A voltage regulator according to claim 4 , wherein the non-inverting input terminal of the second error amplifier circuit is connected to the output terminal of the reference voltage circuit.
6. A voltage regulator according to claim 4 , wherein the first resistor and the phase compensation capacitor have a time constant of 1 millisecond or more.