Boosting circuit and boosting method
View Patent ↗A boosting circuit includes a boosting capacitor to which an input voltage is applied; a smoothing capacitor to which a boosted voltage is applied; a discharging MOS transistor configured to connect said boosting capacitor and said smoothing capacitor in a discharging operation during a boosting operation period such that charge stored in said boosting capacitor is discharged to said smoothing capacitor; and a charging MOS transistor configured to apply the input voltage to said boosting capacitor in a charging operation during the boosting operation period to charge up said charging capacitor. A back gate of said charging MOS transistor and a back gate of said discharging MOS transistor are connected to a common node, and said common node is connected to different voltages in the charging operation and the discharging operation.
1. A boosting circuit comprising:
a boosting capacitor to which an input voltage is applied;
a smoothing capacitor to which a boosted voltage is applied;
a discharging MOS transistor configured to connect said boosting capacitor and said smoothing capacitor in a discharging operation during a boosting operation period such that charge stored in said boosting capacitor is discharged to said smoothing capacitor; and
a charging MOS transistor configured to apply the input voltage to said boosting capacitor in a charging operation during the boosting operation period to charge up said charging capacitor;
wherein a back gate of said charging MOS transistor and a back gate of said discharging MOS transistor are connected to a common node, and
said common node is connected to different voltages in the charging operation and the discharging operation.
2. The boosting circuit according to claim 1 , further comprising:
a first connection switch configured to connect said common node to said boosting capacitor in the discharging operation; and
a second connection switch configured to connect said common node to said smoothing capacitor in the charging operation.
3. The boosting circuit according to claim 1 , wherein said charging MOS transistor and said discharging MOS transistor are formed on a same well layer.
4. The boosting circuit according to claim 1 , further comprising:
a supplying circuit configured to supply the input voltage to said common node when a voltage of said common node is lower than the input voltage by a predetermined voltage in the initial charging period.
5. The boosting circuit according to claim 4 , wherein said supplying circuit comprises a schottky-barrier diode.
6. The boosting circuit according to claim 4 , wherein said supplying circuit comprises:
a first transistor switch which is turned on immediately when a start signal is supplied in the initial charging period; and
a second transistor switch which is turned on a predetermined time after a time when said start signal is supplied in said initial charging period,
wherein said first transistor switch and said second transistor switch are connected in parallel as a parallel circuit, the parallel circuit is supplied with the input voltage and is connected to said common node, and
when one of said first and second transistor switches is turned on, the input voltage is supplied to the back gate.
7. The boosting circuit according to claim 1 , further comprising:
a first logic circuit configured to control said charging MOS transistor to be turned on in an initial charging period prior to the boosting operation period, such that the input voltage is applied to said boosting capacitor; and
a second logic circuit configured to control said discharging MOS transistor to be turned on in the initial charging period, such that the input voltage is applied to said smoothing capacitor via said charging MOS transistor.
8. The boosting circuit according to claim 7 , further comprising:
a first switch configured to make said smoothing capacitor to discharge in response to a standby signal during a standby period prior to the initial charging period; and
a second switch configured to make said boosting capacitor to discharge in response to the standby signal during the standby period.
9. The boosting circuit according to claim 8 , further comprising:
a logic circuit configured to control said second switch to be turned off while a voltage of said smoothing capacitor is higher than a predetermined voltage regardless of the standby signal and to be turned on in response to the standby signal when the voltage of said smoothing capacitor becomes equal to or lower than the predetermined voltage.
10. A boosting method comprising:
charging a boosting capacitor with an input voltage through a charging MOS transistor in a charging operation during a boosting operation period to charge up said charging capacitor;
discharging charges stored in said boosting capacitor to a smoothing capacitor through a discharging MOS transistor; and
connecting a common node to different voltages in the charging operation and the discharging operation, wherein said common node is connected to a back gate of said charging MOS transistor and a back gate of said discharging MOS transistor.
11. The boosting method according to claim 10 , wherein said connecting comprising:
connecting said common node to said boosting capacitor in the discharging operation; and
connecting said common node to said smoothing capacitor in the charging operation.
12. The boosting method according to claim 10 , wherein said charging MOS transistor and said discharging MOS transistor are formed on a same well layer.
13. The boosting method according to claim 10 , further comprising:
supplying the input voltage to said common node when a voltage of said common node is lower than the input voltage by a predetermined voltage in the initial charging period.
14. The boosting method according to claim 13 , wherein said supplying comprises
supplying the input voltage to said common node through a schottky-barrier diode.
15. The boosting method according to claim 13 , wherein said supplying comprises
supplying the input voltage to said common node through a transfer gate.
16. The boosting method according to claim 10 , further comprising:
charging said boosting capacitor with the input voltage through said charging MOS transistor in an initial charging period prior to the boosting operation period; and
charging said smoothing capacitor with the input voltage through said charging MOS transistor said discharging MOS transistor in the initial charging period.
17. The boosting method according to claim 16 , further comprising:
making said smoothing capacitor to discharge through a first switch in response to a standby signal during a standby period prior to the initial charging period; and
making said boosting capacitor to discharge through a second switch in response to the standby signal during the standby period.
18. The boosting method according to claim 17 , further comprising:
controlling said second switch to be turned off while a voltage of said smoothing capacitor is higher than a predetermined voltage regardless of the standby signal and to be turned on in response to the standby signal when the voltage of said smoothing capacitor becomes equal to or lower than the predetermined voltage.