POWER SUPPLY DEVICE
A power supply device includes: a first transistor that switches a first current flowing between a first terminal and a second terminal of the first transistor; a second transistor that has a first terminal connected to the first terminal of the first transistor and a control terminal connected to a control terminal of the first transistor and is formed in a chip in which the first transistor is formed; a current source that supplies a second current between the first and second terminals of the second transistor; and a control part that performs a turn-on and turn-off control of the first transistor on the basis of voltages of the second terminals of the first and second transistors.
1 . A power supply device comprising:
a first transistor that switches a first current flowing between a first terminal and a second terminal of the first transistor;
a second transistor that has a first terminal connected to the first terminal of the first transistor and a control terminal connected to a control terminal of the first transistor and is formed in a chip in which the first transistor is formed;
a current source that supplies a second current between the first and second terminals of the second transistor; and
a control part that performs a turn-on and turn-off control of the first transistor on the basis of voltages of the second terminals of the first and second transistors.
2 . The power supply device according to claim 1 , wherein the control part turns off the first transistor on the basis of a ratio of the voltages of the second terminals of the first and second transistors.
3 . The power supply device according to claim 1 , comprising a shutdown circuit that shuts down a voltage applied to the control part from the second terminal of the first transistor or clamps the voltage applied to the control part from the second terminal of the first transistor at a voltage lower than that of the second terminal of the first transistor, when the control part turns off the first transistor.
4 . The power supply device according to claim 2 , comprising a shutdown circuit that shuts down a voltage applied to the control part from the second terminal of the first transistor or clamps the voltage applied to the control part from the second terminal of the first transistor at a voltage lower than that of the second terminal of the first transistor, when the control part turns off the first transistor.
5 . The power supply device according to claim 1 , further comprising a third transistor cascaded between the first transistor and a power supply.
6 . The power supply device according to claim 2 , further comprising a third transistor cascaded between the first transistor and a power supply.
7 . The power supply device according to claim 1 , further comprising a peak hold circuit that holds a peak of a voltage applied to the control part from the second terminal of the first transistor.
8 . The power supply device according to claim 2 , further comprising a peak hold circuit that holds a peak of a voltage applied to the control part from the second terminal of the first transistor.
9 . The power supply device according to claim 4 , further comprising a delay circuit that causes the shutdown circuit to shut down or clamps the voltage applied to the control part before the first transistor is turned off and to release the shutdown circuit from shutting down or clamping the voltage applied to the control part after the first transistor is turned on.
10 . The power supply device according to claim 5 , further comprising a delay circuit that causes the shutdown circuit to shut down or clamps the voltage applied to the control part before the first transistor is turned off and to release the shutdown circuit from shutting down or clamping the voltage applied to the control part after the first transistor is turned on.
11 . The power supply device according to claim 1 , wherein the first and second transistors include GaN.
12 . The power supply device according to claim 1 , wherein the first transistor is a main switch of a step-up power supply circuit.
13 . The power supply device according to claim 1 , further comprising an inductor connected between the second terminal of the first transistor and a power supply terminal.
14 . The power supply device according to claim 1 , further comprising a transformer connected between the second terminal of the first transistor and a power supply terminal.
15 . The power supply device according to claim 1 , wherein the second transistor has a size smaller than that of the first transistor.