Patent ID: 8686696

Claim:
A DC-DC converter comprising: a power conversion portion including a switching element; a first resistor, one of terminals of which is electrically connected to the power conversion portion; a second resistor, one of terminals of which is electrically connected to the other of the terminals of the first resistor; a third resistor, one of terminals of which is electrically connected to the other of the terminals of the first resistor; a constant current supply electrically connected to the other of the terminals of the third resistor; and a control circuit electrically connected to the other of the terminals of the third resistor and configured to control the switching element, wherein a resistance R 1 of the first resistor, a resistance R 2 of the second resistor, a resistance R 3 of the third resistor, a reference current I ref output from the constant current supply, and an output voltage V out output from the power conversion portion satisfy a following formula: { ( 1 + R 3 R 2 ) Â· R 1 + R 3 } Â· I ref > - V out .