Controller and self-oscillation DC-DC converter including the controller

A controller, comprising:

• a first input terminal;
• a second input terminal;
• a third input terminal;
• an output terminal;
• a switching element circuit, including a first depletion type field effect transistor and at least one field effect transistor containing a gate connected to a gate of the first depletion type field effect transistor, a source connected to a source of the first depletion type field effect transistor, and a drain, the at least one field effect transistor including a second depletion type field effect transistor and at least one enhancement type field effect transistor;
• a first connector, including each terminal respectively connected to a drain of the first and second depletion type field effect transistors included in the switching element circuit;
• a second connector, including each terminal respectively connected to a drain of the at least one enhancement type field effect transistor included in the switching element circuit;
• a first rectifying element, connected between the first input terminal and the second input terminal with a direction from the second input terminal to the first input terminal as a forward direction;
• a second rectifying element, connected between a connection point between the first input terminal and the first rectifying element and the output terminal with a direction from the connection point to the output terminal as a forward direction;
• a resistor, having a first end connected to a gate of the first depletion type field effect transistor and the third input terminal and a second end connected to the second input terminal;
• and
• a clamp circuit, clamping a voltage of the third input terminal to a predetermined voltage.