Power supply circuit and portable device
View Patent ↗In a power supply circuit, a first switching transistor and a second switching transistor are serially connected between another-side terminal GND and a one-side terminal V CC of an input power supply, and a third switching transistor and a fourth switching transistor are serially connected between the one-side terminal V CC of the input power supply and a boosted output terminal OUT. A shift capacitor is provided between a connection point of the first and second switching transistors and a connection point of the third and fourth switching transistors, and a holding capacitor is connected to the boosted output terminal OUT. A back gate switching circuit for switching a voltage to be applied to the back gate is provided for the third switching transistor.
1. A power supply circuit for boosting a voltage of an input power supply at a predetermined step-up ratio and outputting to a boosted output terminal, comprising:
a plurality of switching transistors for selection connected between another-side terminal and a one-side terminal of the input power supply with a connection relationship predetermined according to a step-up ratio;
a plurality of shift switching transistors connected between the one-side terminal of the input power supply and a boosted output terminal with a connection relationship predetermined according to the step-up ratio;
a shift capacitor connected between one of a plurality of connection points between respective pairs of switching transistors for selection and one of a plurality of connection points between respective pairs of shift switching transistors with a connection relationship predetermined according to the step-up ratio;
a holding capacitor connected to the boosted output terminal; and
a control circuit for turning the respective switching transistors on and off at a time predetermined according to the step-up ratio to hold the voltage of the input power supply in the shift capacitor, and using the voltage held in the shift capacitor, and then making a voltage at both ends of the holding capacitor be a voltage coefficient multiple of the voltage of the input power supply,
wherein
the respective transistors are formed on a semiconductor chip, and
the power supply circuit has a switching circuit for switching a voltage to be applied to a back gate of at least one transistor, in which the voltage to be applied to the back gate is switched between a common isolation voltage determined in accordance with polarity of the transistor and a source voltage of the transistor, according to a time at which to turn the transistor on or off.
2. The power supply circuit according to claim 1 , wherein the switching circuit is provided for each of the transistors other than a transistor directly connected to the boosted output terminal among the plurality of shift switching transistors.
3. A power supply circuit for boosting a voltage of an input power supply at a predetermined step-up ratio and outputting to a boosted output terminal, comprising:
a first transistor and a second transistor serially and sequentially connected between another-side terminal and a one-side terminal of the input power supply;
a third transistor and a fourth transistor serially and sequentially connected between the one-side terminal of the input power supply and a boosted output terminal;
a shift capacitor provided between a connection point of the first transistor and the second transistor and a connection point of the third transistor and the fourth transistor;
a holding capacitor connected to the boosted output terminal; and
a control circuit for turning the first transistor and the third transistor on and turning the second transistor and the fourth transistor off to hold the voltage of the input power supply in the shift capacitor, and then turning the first transistor and the third transistor off and turning the second transistor and the fourth transistor on to add the voltage held in the shift capacitor to the voltage of the input power supply and shifting to the holding capacitor,
wherein
the respective transistors are formed on a semiconductor chip, and
the power supply circuit has a switching circuit for switching a voltage to be applied to a back gate of the third transistor between a voltage at the boosted output terminal and a voltage at the one-side terminal of the input power supply according to a time at which to turn the third transistor on and off.
4. The power supply circuit according to claim 3 , wherein
the input power supply has a voltage +V CC at the one-side terminal and is grounded at the other-side terminal, and
a voltage +2V CC is output to the boosted output terminal.
5. The power supply circuit according to claim 3 , wherein
the input power supply is grounded at the one-side terminal and has a voltage +V CC at the other-side terminal, and
a voltage −V CC is output to the boosted output terminal.
6. The power supply circuit according to claim 3 , wherein the switching circuit sets a period during which the voltage at the one-side terminal of the input power supply is applied to the back gate of the third transistor so as not to overlap a period during which the third transistor remains in an on state.
7. The power supply circuit according to claim 1 , wherein the shift capacitor and the holding capacitor are externally connected to the semiconductor chip having a plurality of transistors formed thereon.
8. The power supply circuit according to claim 2 , wherein the shift capacitor and the holding capacitor are externally connected to the semiconductor chip having a plurality of transistors formed thereon.
9. The power supply circuit according to claim 3 , wherein the shift capacitor and the holding capacitor are externally connected to the semiconductor chip having a plurality of transistors formed thereon.
10. A portable device having a power supply circuit for boosting a voltage of an input power supply at a predetermined step-up ratio and outputting to a boosted output terminal, wherein the power supply circuit comprises:
a plurality of switching transistors for selection connected between another-side terminal and an one-side terminal of the input power supply with a connection relationship predetermined according to a step-up ratio;
a plurality of shift switching transistors connected between the one-side terminal of the input power supply and a boosted output terminal with a connection relationship predetermined according to the step-up ratio;
a shift capacitor connected between one of a plurality of connection points between respective pairs of switching transistors for selection and one of a plurality of connection points between respective pairs of shift switching transistors with a connection relationship predetermined according to the step-up ratio;
a holding capacitor connected to the boosted output terminal; and
a control circuit for turning the respective switching transistors on and off at a time predetermined according to the step-up ratio to hold the voltage of the input power supply in the shift capacitor, and using the voltage held in the shift capacitor, and then making a voltage at both ends of the holding capacitor be a voltage coefficient multiple of the voltage of the input power supply, using the voltage held in the shift capacitor,
wherein
the respective transistors are formed on a semiconductor chip, and
the power supply circuit has a switching circuit for switching a voltage to be applied to a back gate of at least one transistor, in which the voltage to be applied to the back gate is switched between a common isolation voltage determined in accordance with polarity of the transistor and a source voltage of the transistor, according to a time at which to turn the transistor on or off.