Abstract: A switching power supply device that can reduce switching loss to obtain high efficiency. Additionally, the number of components of control circuits and the cost of switching elements can be reduced, with a transformer made compact and lightweight. In this switching power supply device, one end of a series circuit comprising a primary winding of the transformer, an inductor, and a capacitor is connected to a junction of a first switching circuit and a second switching circuit. The other end of the series circuit is connected to an input power source. A secondary winding of the transformer is connected to a rectifying and smoothing circuit including a rectifying element. In addition, in order to perform a self-excited oscillation, there are arranged first and second control circuits.

Abstract: A switching power supply device that can reduce switching loss to obtain high efficiency. Additionally, the number of components of control circuits and the cost of switching elements can be reduced, with a transformer made compact and lightweight. In this switching power supply device, one end of a series circuit comprising a primary winding of the transformer, an inductor, and a capacitor is connected to a junction of a first switching circuit and a second switching circuit. The other end of the series circuit is connected to an input power source. A secondary winding of the transformer is connected to a rectifying and smoothing circuit including a rectifying element. In addition, in order to perform a self-excited oscillation, there are arranged first and second control circuits.

Abstract: A switching power supply apparatus has a transformer having a primary winding and a secondary winding, a first switching element connected in series with the primary winding, a first control circuit for controlling the on-time of the first switching element whereby the output is controlled, and a rectification circuit for rectifying the output from the secondary winding, whereby input voltage is applied to the first winding when the first switching element is on and causes current to flow therein so that energy is stored in the transformer, and the energy stored in the transformer is released as electric current from the secondary winding when the first switching element is off, and the current is rectified in the rectification circuit to obtain an output.

Abstract: A self-oscillation type converter comprises a transformer and a switching transistor. The switching transistor is connected in series to a primary winding of the transformer. A start current is applied from a power supply line to the switching transistor through a start resistor, so that the switching transistor is rendered conductive. A positive feedback is performed through an application of a constant current from a constant current circuit to a base of the switching transistor in response to a voltage generated from a feedback winding, whereby the switching transistor is turned on rapidly. A CR time constant circuit is connected to an output of the constant current circuit. An output of the CR time constant circuit is applied to the base of the transistor, a transistor Q2 is turned on after a lapse of time determined by a time constant of the time constant circuit, so that the switching transistor is forcibly turned off.