DC/DC converter, power supply circuit, and semiconductor device
First Claim
1. A DC-DC converter comprising:
- a power conversion circuit comprising;
a transistor, anda constant-voltage generation circuit comprising;
a coil directly connected to one of a source and a drain of the transistor; and
a diode directly connected to the one of the source and the drain of the transistor,wherein the transistor is configured to control a supply of current to the coil such that induced electromotive force is generated in the coil, andwherein a threshold voltage of the transistor is controlled according to a magnitude of a power output from the constant-voltage generation circuit.
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Accused Products
Abstract
Provided is a DC-DC converter with improved power conversion efficiency. A transistor which is incorporated in the DC-DC converter and functions as a switching element for controlling output power includes, in its channel formation region, a semiconductor material having a wide band gap and significantly small off current compared with silicon. The transistor further comprises a back gate electrode, in addition to a general gate electrode, and a back gate control circuit for controlling a potential applied to the back gate electrode in accordance with the output power from the DC-DC converter. The control of the potential applied to the back gate electrode by the back gate control circuit enables the threshold voltage to decrease the on-state resistance when the output power is high and to increase the off-state current when the output power is low.
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Citations
22 Claims
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1. A DC-DC converter comprising:
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a power conversion circuit comprising; a transistor, and a constant-voltage generation circuit comprising; a coil directly connected to one of a source and a drain of the transistor; and a diode directly connected to the one of the source and the drain of the transistor, wherein the transistor is configured to control a supply of current to the coil such that induced electromotive force is generated in the coil, and wherein a threshold voltage of the transistor is controlled according to a magnitude of a power output from the constant-voltage generation circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A DC-DC converter comprising:
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a constant-voltage generation circuit comprising a coil and a diode; a transistor electrically connected to the constant-voltage generation circuit, the transistor comprising a gate electrode and a back gate electrode with a semiconductor film interposed therebetween; an output voltage control circuit which is configured to control a ratio of an ON time to OFF time of the transistor; and a back gate control circuit configured to control a potential applied to the back gate electrode, wherein the transistor is configured to control a supply of current to the coil such that induced electromotive force is generated in the coil, wherein one of a source and a drain of the transistor is directly connected to the coil and the diode, and wherein the back gate control circuit comprises; a current detection circuit for detecting an amount of current output from the constant-voltage generation circuit; and a power-voltage conversion circuit for determining the potential applied to the back gate electrode from the amount of the current output from the constant-voltage generation circuit and an output voltage from the constant-voltage generation circuit. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. A DC-DC converter comprising:
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a constant-voltage generation circuit comprising a coil and a diode; a transistor electrically connected to the constant-voltage generation circuit, the transistor comprising a gate electrode and a back gate electrode with a semiconductor film interposed therebetween; an output voltage control circuit which is configured to control a ratio of an ON time to OFF time of the transistor; and a back gate control circuit configured to control a potential applied to the back gate electrode, wherein the transistor is configured to control a supply of current to the coil such that induced electromotive force is generated in the coil, wherein one of a source and a drain of the transistor is directly connected to the coil and the diode, and wherein the back gate control circuit comprises; a current detection circuit for detecting an amount of current output from the constant-voltage generation circuit and converting the current into a voltage; and a power-voltage conversion circuit for determining the potential applied to the back gate electrode from the amount of the current output from the constant-voltage generation circuit and an output voltage from the constant-voltage generation circuit. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification