Power source circuit
View Patent ↗A power source circuit adapted to output a first set potential which is set according to a first selection signal, or a second set potential which is set according to a second selection signal and higher than the first set potential, has an output terminal adapted to output the first set potential or the second set potential; a first boosting circuit adapted to boost a voltage supplied from a power source and to output the boosted voltage to the output terminal; a second boosting circuit adapted to boost the voltage supplied from the power source and to output the boosted voltage to the output terminal; a voltage dividing circuit adapted to output a monitor potential by dividing the output potential outputted from the output terminal according to the first selection signal, or to output a monitor potential by dividing the output potential and reducing a voltage dividing ratio of the monitor potential with respect to the output potential according to the second selection signal; a comparison amplifier adapted to compare the monitor potential with a reference potential, and to output a flag signal for activating the boosting circuit when the monitor potential is lower than the reference potential; and a logic circuit adapted to receive the flag signal from the comparison amplifier, and when receiving the first selection signal, to output a first clock signal for making the first boosting circuit perform the boosting operation, and adapted to receive the flag signal from the comparison amplifier, and when receiving the second selection signal, to output a second clock signal for making the second boosting circuit perform the boosting operation, together with the first clock signal.
1. A power source circuit adapted to output a first set potential which is set according to a first selection signal, or a second set potential which is set according to a second selection signal and higher than the first set potential, comprising:
an output terminal adapted to output the first set potential or the second set potential;
a first boosting circuit adapted to boost a voltage supplied from a power source and to output the boosted voltage to the output terminal;
a second boosting circuit adapted to boost the voltage supplied from the power source and to output the boosted voltage to the output terminal;
a voltage dividing circuit adapted to output a monitor potential by dividing the output potential outputted from the output terminal according to the first selection signal, or to output a monitor potential by dividing the output potential and reducing a voltage dividing ratio of the monitor potential with respect to the output potential according to the second selection signal;
a comparison amplifier adapted to compare the monitor potential with a reference potential, and to output a flag signal for activating the boosting circuit when the monitor potential is lower than the reference potential; and
a logic circuit adapted to receive the flag signal from the comparison amplifier, and when receiving the first selection signal, to output a first clock signal for making the first boosting circuit perform the boosting operation, and adapted to receive the flag signal from the comparison amplifier, and when receiving the second selection signal, to output a second clock signal for making the second boosting circuit perform the boosting operation, together with the first clock signal.
2. The power source circuit according to claim 1 , wherein the first boosting circuit has a boosting capability higher than that of the second boosting circuit.
3. The power source circuit according to claim 1 , wherein the first boosting circuit and the second boosting circuit have a same circuit arrangement.
4. The power source circuit according to claim 1 , wherein the logic circuit receives the second selection signal after receiving the first selection signal.
5. The power source circuit according to claim 2 , wherein the logic circuit receives the second selection signal after receiving the first selection signal.
6. The power source circuit according to claim 3 , wherein the logic circuit receives the second selection signal after receiving the first selection signal.
7. The power source circuit according to claim 1 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.
8. The power source circuit according to claim 2 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.
9. The power source circuit according to claim 3 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.
10. The power source circuit according to claim 4 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.
11. The power source circuit according to claim 5 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.
12. The power source circuit according to claim 6 , wherein the voltage dividing circuit comprises:
a first resistor whose one end is connected to the output terminal;
a second resistor whose one end is connected to the other end of the first resistor;
a third resistor whose one end is connected to the other end of the second resistor;
a first switch circuit which is connected between the other end of the second resistor and a ground potential, and is turned on according to an input of the first selection signal; and
a second switch circuit which is connected between the other end of the third resistor and the ground potential, and is turned on according to an input of the second selection signal, and
the voltage dividing circuit outputs a potential at a point between the first resistor and the second resistor as the monitor potential.