DC/DC CONVERTER, POWER SUPPLY CIRCUIT, AND SEMICONDUCTOR DEVICE
First Claim
1. A DC-DC converter comprising:
- a power conversion circuit comprising a transistor and a constant-voltage generation circuit,wherein the constant-voltage generation circuit is configured to be input with a first voltage when the transistor is in an ON state,wherein the constant-voltage generation circuit is configured to be input with a second voltage when the transistor is in an OFF state, 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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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.
54 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, wherein the constant-voltage generation circuit is configured to be input with a first voltage when the transistor is in an ON state, wherein the constant-voltage generation circuit is configured to be input with a second voltage when the transistor is in an OFF state, 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; 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 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; 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 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