Power supply system and electronic instrument

1. A power supply system, comprising:

a first plurality of power supply units configured to supply working voltages from a battery to a second plurality of loads;

a large-capacitance capacitor configured to charge electric charges from the battery;

a third plurality of switching means for connecting the large-capacitance capacitor to the second plurality of loads selectively;

control means for switching the third plurality of switching means corresponding to at least one load presently in use among the second plurality of loads;

voltage monitoring means for monitoring a voltage of the large-capacitance capacitor; and

discharge means, in a case where an output voltage of the large-capacitance capacitor monitored by the voltage monitoring means is found higher than an operating voltage of the second load when the large-capacitance capacitor is switched from a first load to a second load, for discharging charges stored in the large-capacitance capacitor according to a control by the control means so that a voltage of the large-capacitance capacitor decreases to the operating voltage before connection to the second load.

2. The power supply system according to claim 1 , wherein

at least one of the second plurality of loads is one necessitating anyone of pulse currents and large currents having a constant frequency.

3. The power supply system according to claim 1 , wherein

the first plurality of power supply units include anyone of a direct connection line, a DC/DC convertor, an LDO regulator, and a charge pump circuit.

4. The power supply system according to claim 1 , 2 or 3 , wherein

the large-capacitance capacitor includes anyone of an electric double layer capacitor, a lithium ion capacitor, and a ceramic capacitor.

5. The power supply system according to claim 1 , 2 or 3 , wherein

each of the third plurality of switching means includes an FET configured to connect the first plurality of power supply units selectively with the large-capacitance capacitor, and a voltage conversion means for converting a control voltage from the control means to an output voltage corresponding to a highest voltage among outputs of the first plurality of power supply units, so that an output of the voltage conversion means is subsequently applied to the FET as a control signal.

6. The power supply system according to claim 5 , wherein

each of the third plurality of switching means includes a buffer circuit as the voltage conversion means and the first plurality of diodes, so that anodes of the diodes are respectively connected to output terminals of the first plurality of power supply units, and that cathodes of the diodes are connected in common to a power supply input terminal of the buffer circuit.

7. The power supply system according to claim 5 , wherein

each of the third plurality of switching means includes a buffer circuit as the voltage conversion means

so that an output voltage from a power supply unit is connected in common to a power supply input terminal of the buffer circuit, the power supply unit being specifically identified in advance to supply a highest voltage among the first plurality of power supply units.

8. The power supply system according to claim 1 , 2 , 3 , 6 or 7 , wherein

all the third plurality of switching means are turned off when none of the second plurality of loads operates.

9. An electronic instrument, comprising:

a second plurality of loads configured to be supplied with power from a battery;

a first plurality of power supply units configured to supply working voltages from a battery to the second plurality of loads;

a large-capacitance capacitor configured to charge electric charges from the battery;

a third plurality of switching means for connecting the large-capacitance capacitor to the second plurality of loads selectively;

control means for switching the third plurality of switching means corresponding to at least one load presently in use among the second plurality of loads;

voltage monitoring means for monitoring a voltage of the large-capacitance capacitor; and

discharge means, in a case where an output voltage of the large-capacitance capacitor monitored by the voltage monitoring means is found higher than an operating voltage of the second load when the large-capacitance capacitor is switched from a first load to a second load, for discharging charges stored in the large-capacitance capacitor according to a control by the control means so that a voltage of the large-capacitance capacitor decreases to the operating voltage before connection to the second load.

10. The electronic instrument according to claim 9 , wherein

at least one of the second plurality of loads is one necessitating anyone of pulse currents and large currents having a constant frequency.

11. The electronic instrument according to claim 9 , wherein

the first plurality of power supply units include anyone of a direct connection line, a DC/DC convertor, an LDO regulator, and a charge pump circuit.

12. The electronic instrument according to claim 9 , 10 or 11 , wherein

the large-capacitance capacitor includes anyone of an electric double layer capacitor, a lithium ion capacitor, and a ceramic capacitor.

13. The electronic instrument according to claim 9 , wherein

the electronic instrument is a mobile-phone terminal including a wireless communication unit and a camera unit, and the first load is a power amplifier included in the wireless communication unit and the second load is a flash generation means.

14. The electronic instrument according to claim 9 , 10 , 11 or 13 , wherein

all the third plurality of switching means are turned off when none of the second plurality of loads operates.

15. A power supply system, comprising:

a first plurality of power supply units configured to supply working voltages from a battery to a second plurality of loads;

a large-capacitance capacitor configured to charge electric charges from the battery;

a third plurality of switching mechanisms configured to connect the large-capacitance capacitor to the second plurality of loads selectively; and

a control mechanism configured to switch the third plurality of switching mechanisms corresponding to at least one load in use presently among the second plurality of loads

a voltage monitor to monitor a voltage of the large-capacitance capacitor; and

a discharge mechanism, in a case where an output voltage of the large-capacitance capacitor monitored by the voltage monitor is found higher than an operating voltage of the second load when the large-capacitance capacitor is switched from a first load to a second load, for discharging charges stored in the large-capacitance capacitor according to a control by the control mechanism so that a voltage of the large-capacitance capacitor decreases to the operating voltage before connection to the second load.

16. An electronic instrument, comprising:

a second plurality of loads configured to be supplied with power from a battery;

a first plurality of power supply units configured to supply working voltages from a battery to the second plurality of loads;

a large-capacitance capacitor configured to charge electric charges from the battery;

a third plurality of switching mechanisms configured to connect the large-capacitance capacitor to the second plurality of loads selectively; and

a control mechanism configured to switch the third plurality of switching mechanisms corresponding to at least one load presently in use among the second plurality of loads

a voltage monitor to monitor a voltage of the large-capacitance capacitor; and

a discharge mechanism, in a case where an output voltage of the large-capacitance capacitor monitored by the voltage monitor is found higher than an operating voltage of the second load when the large-capacitance capacitor is switched from a first load to a second load, for discharging charges stored in the large-capacitance capacitor according to a control by the control mechanism so that a voltage of the large-capacitance capacitor decreases to the operating voltage before connection to the second load.