Power Supply Circuit, Charge Pump Circuit, and Portable Appliance Therewith
First Claim
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1. A power supply circuit comprising:
- first switching means connected between a first end of a capacitor and an input voltage input terminal and operable to be turned on when the capacitor is charged; and
/or second switching means connected between a second end of the capacitor and a reference voltage input terminal and operable to be turned on when the capacitor is charged, the power supply circuit operable to produce a specified output voltage from an input voltage by charging and discharging the capacitor cyclically, wherein at least one of the first and second switching means comprises a plurality of divided transistors connected in parallel with one another and having different driving capacities and is operable to to yield a minimum driving capacity when the input voltage is high and the output voltage is low and a maximum driving capacity when the input voltage is low and the output voltage is stable.
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Abstract
According to the invention, a charge pump circuit (21) has, as switching means turned on when a capacitor (C1) is charged, transistors (P1 to P3) connected in parallel between one end of the capacitor (C1) and an input terminal (T1). When the capacitor (C1) is charged, a controller (CNT) determines which of the transistors (P1 to P3) to drive based on the results of monitoring of the input and output voltages by first and second detectors (DET1, DET2). Thus, even if the level of the input voltage varies, it is possible to reduce in-rush current at start-up without causing a drop in the output voltage or a loss in efficiency.
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Citations
24 Claims
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1. A power supply circuit comprising:
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first switching means connected between a first end of a capacitor and an input voltage input terminal and operable to be turned on when the capacitor is charged; and
/orsecond switching means connected between a second end of the capacitor and a reference voltage input terminal and operable to be turned on when the capacitor is charged, the power supply circuit operable to produce a specified output voltage from an input voltage by charging and discharging the capacitor cyclically, wherein at least one of the first and second switching means comprises a plurality of divided transistors connected in parallel with one another and having different driving capacities and is operable to to yield a minimum driving capacity when the input voltage is high and the output voltage is low and a maximum driving capacity when the input voltage is low and the output voltage is stable. - View Dependent Claims (10)
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2. A charge pump circuit comprising:
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first switching means connected between a first end of a first capacitor and an input voltage input terminal and operable to be turned on when the capacitor is charged;
second switching means connected between a second end of the first capacitor and a reference voltage input terminal and operable to be turned on when the capacitor is charged;
controlling means to control driving of the first and second switching means;
first monitoring means to monitor an input voltage; and
second monitoring means to monitor an output voltage, the charge pump circuit for producing a specified output voltage from the input voltage by charging and discharging the first capacitor cyclically, wherein at least one of the first and second switching means is divided into a plurality of divided transistors connected in parallel with one another, and wherein the charge pump is operable so that when the first capacitor is charged, the controlling means determines which of the plurality of divided transistors to drive based on a result of monitoring by the first and second monitoring means. - View Dependent Claims (3, 6, 7, 8, 9, 11, 12, 13, 22, 23)
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4. A charge pump circuit comprising:
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a first capacitor;
first switching means connected between a first end of the first capacitor and an input voltage input terminal and operable to be turned on when the first capacitor is charged;
second switching means connected between a second end of the first capacitor and a reference voltage input terminal and operable to be turned on when the first capacitor is charged;
third switching means connected between the first end of the first capacitor and the reference voltage input terminal or between the first end of the first capacitor and an output voltage output terminal and operable to be turned on when the first capacitor is discharged;
fourth switching means connected between the second end of the first capacitor and the output voltage output terminal or between the second end of the first capacitor and the input voltage input terminal and operable to be turned on when the first capacitor is discharged;
a second capacitor connected between the output voltage output terminal and the reference voltage input terminal;
controlling means to control driving of the first to fourth switching means;
first monitoring means connected to the input voltage input terminal to monitor an input voltage; and
second monitoring means connected to the output voltage output terminal to monitor an output voltage, the charge pump circuit for producing a specified output voltage from the input voltage by charging and discharging the first capacitor cyclically, wherein at least one of the first and second switching means is divided into a plurality of divided transistors connected in parallel with one another, and wherein the charge pump circuit is operable so that when the first capacitor is charged, the controlling means determines which of the plurality of divided transistors to drive based on a result of monitoring by the first and second monitoring means. - View Dependent Claims (14, 15, 16, 20)
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5. A charge pump circuit comprising:
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a voltage step-up unit composed of n-stage (where n≧
9) voltage step-up circuits connected one next to another, each voltage step-up circuit comprising;
a first capacitor;
first switching means connected between a first node and a first end of the first capacitor and operable to be turned on when the first capacitor is charged;
second switching means connected between a second node and a second end of the first capacitor and operable to be turned on when the first capacitor is charged;
third switching means connected between a third node and the first end of the first capacitor and operable to be turned on when the first capacitor is discharge; and
fourth switching means connected between a fourth node and the second end of the first capacitor and operable to be turned on when the first capacitor is discharged, wherein either the first node of each of the first to nth voltage step-up circuits is connected to an input voltage input terminal, the second node of the first voltage step-up circuit is connected to a reference voltage input terminal, the second node of each of the second to nth voltage step-up circuits is connected to the fourth node of the preceding voltage step-up circuit, the third node of each of the first to nth voltage step-up circuits is connected to the reference voltage input terminal, and the fourth node of the nth voltage step-up circuit is connected to an output voltage output terminal, or the first node of the first voltage step-up circuit is connected to an input voltage input terminal, the first node of each of the second to nth voltage step-up circuits is connected to the third node of the preceding voltage step-up circuit, the second node of each of the first to nth voltage step-up circuits is connected to a reference voltage input terminal, the third node of the nth voltage step-up circuit is connected to an output voltage output terminal, and the fourth node of each of the first to nth voltage step-up circuits is connected to the input voltage input terminal;
a second capacitor connected between the output voltage output terminal and the reference voltage input terminal;
controlling means to control driving of the first to fourth switching means included in each of the first to nth voltage step-up circuits;
first monitoring means connected to the input voltage input terminal to monitor an input voltage; and
second monitoring means connected to the output voltage output terminal to monitor an output voltage, the charge pump circuit operable to produce a specified output voltage from the input voltage by cyclically charging and discharging the first capacitor included in each of the first to nth voltage step-up circuits, wherein at least one of the first and second switching means included in the first voltage step-up circuit is divided into a plurality of divided transistors connected in parallel with one another, and wherein the charge pump circuit is operable so that when the first capacitor is charged, the controlling means determines which of the plurality of divided transistors to drive based on a result of monitoring by the first and second monitoring means. - View Dependent Claims (17, 18, 19, 21, 24)
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Specification