Abstract: According to this invention, a converter includes a voltage transformer, a switching transistor, a resistor, a control transistor, and a control circuit. The voltage transformer has a primary winding, a secondary winding, and a control winding. The switching transistor is connected in series with the primary winding. The resistor is connected between the switching transistor and one terminal of an input power source. The control transistor has a base connected to a connection point between the resistor and the switching transistor and a collector connected to a control electrode of the switching transistor. The control circuit controls the control transistor on the basis of a control voltage extracted from the control winding.