Abstract: A switching transistor is connected to a primary winding of a transformer, an oscillation frequency control circuit is connected to a feedback winding, the oscillation frequency control circuit controls a first controlling transistor, and the first controlling transistor controls the delay time when the switching transistor is turned on. The oscillation frequency control circuit is set in a first operation mode in which the above delay does not take place at the rated load, in a second operation mode in which the oscillation frequency is controlled such that the oscillation frequency becomes constant or slowly decreases at light loading and in a third operation mode in which the oscillation frequency is further decreased while a switch is switched on.

Abstract: An RCC type switching power supply unit with a transformer having a primary winding, a secondary winding, and a feedback winding, a main switching element receiving a feedback signal from the feedback winding and for turning on and off the current of the primary winding, a rectifying and smoothing circuit having a rectifying element and a smoothing element connected to the secondary winding, and a control circuit connected between the feedback winding and the control terminal of the main switching element. A delay circuit by which the turning on of the main switching element is prohibited for a certain period of time after the current of the rectifying element has become zero and a switching circuit by which the delay time of the delay circuit is changed by two or more stages are provided.

Abstract: A switching power supply having two or more DC outputs includes a DC power supply, a transformer having a primary winding, at least two secondary windings, and a feedback winding, a main switching element having an off-state period and an on-state period, connected in series to the primary winding and to be turned on by a voltage generated in the feedback winding, the main switching element having a control terminal and a threshold voltage to turn the main switching element on; and a rectifying circuit connected to each secondary winding, a starting circuit which initially turns on the main switching element at startup of the power supply and a switching circuit provided between the two DC outputs, and wherein, when the switching circuit is turned on, a voltage generated in the feedback winding is lowered during the off-state period of the main switching element and a voltage to be applied to the control terminal of the main switching element is controlled so as to be less than the threshold voltage, and the

Abstract: A switching transistor is connected to a primary winding of a transformer, an oscillation frequency control circuit is connected to a feedback winding, the oscillation frequency control circuit controls a first controlling transistor, and the first controlling transistor controls the delay time when the switching transistor is turned on. The oscillation frequency control circuit is set in a first operation mode in which the above delay does not take place at the rated load, in a second operation mode in which the oscillation frequency is controlled such that the oscillation frequency becomes constant or slowly decreases at light loading and in a third operation mode in which the oscillation frequency is further decreased while a switch is switched on.

Abstract: An RCC type switching power supply unit with a transformer having a primary winding, a secondary winding, and a feedback winding, a main switching element receiving a feedback signal from the feedback winding and for turning on and off the current of the primary winding, a rectifying and smoothing circuit having a rectifying element and a smoothing element connected to the secondary winding, and a control circuit connected between the feedback winding and the control terminal of the main switching element. A delay circuit by which the turning on of the main switching element is prohibited for a certain period of time after the current of the rectifying element has become zero and a switching circuit by which the delay time of the delay circuit is changed by two or more stages are provided.

Abstract: A switching power supply unit includes a DC power supply, a transformer having a primary winding, a secondary winding and a feedback winding, a main switching element connected in series to the primary winding, and a control circuit connected between the feedback winding and the control terminal of the main switching element, so that a DC output can be obtained. In this switching power supply unit, there are provided a voltage generating unit disposed on the primary side of the transformer to output a voltage according to a load power, and a delay circuit for reducing the switching frequency by delaying the turn-on of the main switching element according to a voltage output from the voltage generating unit thereby to prolong the OFF time of the main switching element.

Abstract: A self-oscillation switching power supply apparatus of the ringing choke converter type comprises a transformer T including a primary winding N1, a secondary winding N2, and a feedback winding NB; a switching transistor Q1 which oscillates in a self-oscillating fashion in response to a feedback signal from the feedback winding NB thereby turning on and off the current flowing through the primary winding; a rectifying and smoothing circuit connected to the secondary winding; an oscillation frequency control circuit including a control transistor Q3 for controlling a control signal input to the switching transistor Q1 thereby controlling the control transistor Q3 so as to extend the off-time in the self-oscillation period of the switching transistor Q1; and an oscillation frequency control disabling circuit for disabling the control of the control transistor Q3 in accordance with a remote signal.

Abstract: A switching power supply having two or more DC outputs comprising: a DC power supply, a transformer having a primary winding, at least two secondary windings, and a feedback winding, a main switching element having an off-state period and an on-state period, connected in series to the primary winding and to be turned on by a voltage generated in the feedback winding, the main switching element having a control terminal and a threshold voltage to turn the main switching element on; and a rectifying circuit connected to each secondary winding, a starting circuit which initially turns on the main switching element at startup of the power supply and a switching circuit provided between the two DC outputs, and wherein, when the switching circuit is turned on, a voltage generated in the feedback winding is lowered during the off-state period of the main switching element and a voltage to be applied to the control terminal of the main switching element is controlled so as to be less than the threshold voltage, and t

Abstract: A switching power supply device comprises: a transformer having a primary winding, a secondary winding and a feedback winding; a switching element connected in series with the primary winding; a controlling element connected to a control terminal of the switching element; a controlling circuit provided between the controlling element and the feedback winding; a rectifying circuit connected to the secondary winding; and a frequency limiting circuit including a charging circuit and a kick voltage absorbing circuit. The charging circuit is adapted to be charged by a voltage reverse in polarity, produced in the feedback winding. The kick voltage absorbing circuit absorbs a current developed by a kick voltage in the feedback winding, by discharge of the charging circuit, whereby the frequency limiting circuit reducing the switching frequency of the switching element by prolongation of the off-state time-period of the switching element in correspondence to a light load signal from a load when the load is light.

Abstract: A switching power supply unit containing a DC power supply; a transformer having a primary winding, a secondary winding and a feedback winding, a main switching element connected in series to the primary winding to be turned on by a voltage generated at the feedback winding, and a voltage dropping circuit for dropping the output voltage obtained form the secondary winding to reduce a fly-back voltage so that the voltage of a control terminal of the main switching element is maintained at a lower value than a threshold voltage of the main switching element.

Abstract: A switching power supply apparatus comprises: a transformer having a primary winding, a secondary winding, and a feedback winding; a switching element connected in series with the primary winding; a control circuit provided between a control terminal of the switching element and the feedback winding; and a rectifying circuit connected to the secondary winding. The control element is provided between the control terminal of the switching element and one end of the feedback winding, and a delay circuit is connected to the control terminal of the control element.