Voltage regulator
View Patent ↗Provided is a voltage regulator capable of securely preventing a reverse current from an output terminal ( 122 ) with lower current consumption, irrespective of magnitude of a voltage of a VDD terminal ( 121 ). Such a configuration is adopted that the voltage of the VDD terminal ( 121 ) and a voltage of the output terminal ( 122 ) of the voltage regulator are compared with each other with the use of a voltage generated between a transistor and a constant current circuit, to thereby reduce current consumption of a backup battery. Besides, such a configuration is also adopted that a gate of an output transistor is connected with the output terminal ( 122 ) based on an output of a comparator circuit, to thereby prevent the reverse current securely.
1. A voltage regulator, comprising:
an output transistor that is provided between a power supply terminal and an output terminal;
an error amplifier for controlling a gate voltage of the output transistor so that a voltage of the output terminal becomes constant;
a second transistor for connecting a substrate of the output transistor with the power supply terminal;
a third transistor for connecting the substrate of the output transistor with the output terminal; and
a comparator circuit for comparing a voltage of the power supply terminal with the voltage of the output terminal, and performing control of switching the second transistor and the third transistor based on a result of the comparing, wherein:
the comparator circuit comprises:
a fourth transistor having a source connected with the power supply terminal, a gate connected with a drain, and the drain connected with a first constant current circuit; and
a fifth transistor having a source connected with the output terminal, a gate connected with the gate of the fourth transistor, and a drain connected with a second constant current circuit; and
the comparator circuit outputs the result of the comparing based on a voltage of a connection point between the fifth transistor and the second constant current circuit.
2. A voltage regulator according to claim 1 , wherein the comparator circuit is configured to:
turn ON the second transistor when the voltage of the power supply terminal is higher than the voltage of the output terminal; and
turn ON the third transistor when the voltage of the power supply terminal is lower than the voltage of the output terminal.
3. A voltage regulator according to claim 2 , wherein the comparator circuit has a hysteresis function.
4. A voltage regulator according to claim 3 , wherein: the comparator circuit further comprises:
a sixth transistor that is connected in series with the fifth transistor; and
a seventh transistor that is connected in parallel with the fifth transistor; and
the hysteresis function is realized by controlling the seventh transistor based on the output of the comparator circuit.
5. A voltage regulator according to claim 4 , wherein:
the comparator circuit further comprises:
an eighth transistor that is connected in series with the fourth transistor; and
a ninth transistor that is connected in parallel with the fourth transistor; and
the hysteresis function is realized by controlling the ninth transistor based on the output of the comparator circuit.
6. A voltage regulator, comprising:
an output transistor that is provided between a power supply terminal and an output terminal;
an error amplifier for controlling a gate voltage of the output transistor so that a voltage of the output terminal becomes constant;
a second transistor for connecting a substrate of the output transistor with the power supply terminal;
a third transistor for connecting the substrate of the output transistor with the output terminal; and
a comparator circuit for comparing a voltage of the power supply terminal with the voltage of the output terminal, and performing control of switching the second transistor and the third transistor based on a result of the comparing, wherein:
the comparator circuit comprises:
a fourth transistor having a source connected with the power supply terminal, a gate connected with a drain, and the drain connected with a first constant current circuit;
a fifth transistor having a source connected with the output terminal, a gate connected with the gate of the fourth transistor, and a drain connected with a second constant current circuit;
a sixth transistor that is connected in series with the fifth transistor; and
a seventh transistor that is connected in parallel with the fifth transistor, wherein a hysteresis function is realized by controlling the seventh transistor based on the output of the comparator circuit; and
the comparator circuit outputs the result of the comparing based on a voltage of a connection point between the fifth transistor and the second constant current circuit.
7. The voltage regulator according to claim 6 , wherein the comparator circuit is configured to:
turn ON the second transistor when the voltage of the power supply terminal is higher than the voltage of the output terminal; and
turn ON the third transistor when the voltage of the power supply terminal is lower than the voltage of the output terminal.
8. The voltage regulator according to claim 6 , wherein the comparator circuit further comprises:
an eighth transistor that is connected in series with the fourth transistor; and
a ninth transistor that is connected in parallel with the fourth transistor; and
the hysteresis function is realized by controlling the ninth transistor based on the output of the comparator circuit.