Abstract: In a switching power supply device, the operating voltage is supplied to the power-factor improvement control circuit when the switching power supply device is operating under normal operating load. Thereby, the booster chopper circuit is controlled by the power-factor improvement control circuit so as to improve the power factor of the device. By contrast, during the non-oscillation period while the switching control circuit is in the intermittent oscillation mode when the power consumption is small, the voltage induced in the auxiliary winding drops. Accordingly, the voltage of the auxiliary power supply also drops. Furthermore, when the driving voltage to be supplied to the power-factor improvement control circuit is reduced below the operating voltage thereof by the voltage reduction circuit, the power-factor improvement control circuit stops functioning, thereby reducing power consumption accordingly.

Abstract: A switching power supply apparatus is provided that is not thermally destroyed even if the load remains short-circuited for a long time when the voltage of the commercially distributed alternating-current power supplied thereto is high. When the load connected between a positive and a negative output terminal is short-circuited, the short-circuited state is detected by an output voltage detection circuit, and a switching control circuit stops operating. At start-up, a current from a bridge rectifier circuit is fed, as a startup current, through a constant current circuit to the switching control circuit. Thus, even when the voltage of the commercially distributed alternating-current power is high, a constant current flows through the switching control circuit. This permits the power consumed with the load short-circuited when the input voltage from the commercially distributed alternating-current power is high to be approximated to that consumed when the input voltage is low.

Abstract: A switching power supply apparatus operates with less power consumption as a whole as a result of reduced power loss suffered while the switching operation of the main switching device is being stopped in burst switching control. Burst switching control is achieved by a signal level checker circuit 15 repeatedly turning on and off a switch circuit 17 provided in the line by way of which a switching controller circuit 19 is supplied with operating power. In burst switching control, when the switching operation of a main switching device 5 is being stopped, the supply of operating power to the switching controller circuit 19 is also stopped. This helps reduce the power loss suffered while the switching operation is being stopped, and thus helps reduce the power consumption of the apparatus as a whole.

Abstract: In a switching power supply device, the operating voltage is supplied to the power-factor improvement control circuit when the switching power supply device is operating under normal operating load. Thereby, the booster chopper circuit is controlled by the power-factor improvement control circuit so as to improve the power factor of the device. By contrast, during the non-oscillation period while the switching control circuit is in the intermittent oscillation mode when the power consumption is small, the voltage induced in the auxiliary winding drops. Accordingly, the voltage of the auxiliary power supply also drops. Furthermore, when the driving voltage to be supplied to the power-factor improvement control circuit is reduced below the operating voltage thereof by the voltage reduction circuit, the power-factor improvement control circuit stops functioning, thereby reducing power consumption accordingly.

Abstract: A switching power supply apparatus is provided that is not thermally destroyed even if the load remains short-circuited for a long time when the voltage of the commercially distributed alternating-current power supplied thereto is high. When the load connected between a positive and a negative output terminal 10 and 11 is short-circuited, the short-circuited state is detected by an output voltage detection circuit 12, and a switching control circuit stops operating. At start-up, a current from a bridge rectifier circuit 4 is fed, as a start-up current, through a constant current circuit 21 to the switching control circuit 14. Thus, even when the voltage of the commercially distributed alternating-current power is high, a constant current flows through the switching control circuit 14. This permits the power consumed with the load short-circuited when the input voltage from the commercially distributed alternating-current power is high to be approximated to that consumed when the input voltage is low.

Abstract: The switching power unit is a switching power unit of PWM system in which, in response to a secondary-side output voltage detected by an output voltage detecting circuit, a control circuit controls a duty of a main switching element so as to stabilize the output voltage. There is provided a filter circuit, preventing EMI, which is constituted of filter capacitors and a filter coil. In relation to the filter circuit, there is provided a discharging resistor which is constituted of two series resistors so as to prevent an accident by discharging electric charges of the filter capacitors quickly. A voltage of a connection point between the series resistors is applied to a power supplying capacitor of the control circuit via an activating resistor.

Abstract: A switching power supply apparatus operates with less power consumption as a whole as a result of reduced power loss suffered while the switching operation of the main switching device is being stopped in burst switching control. Burst switching control is achieved by a signal level checker circuit 15 repeatedly turning on and off a switch circuit 17 provided in the line by way of which a switching controller circuit 19 is supplied with operating power. In burst switching control, when the switching operation of a main switching device 5 is being stopped, the supply of operating power to the switching controller circuit 19 is also stopped. This helps reduce the power loss suffered while the switching operation is being stopped, and thus helps reduce the power consumption of the apparatus as a whole.

Abstract: A switching power supply device is arranged such that a switching of a main switching element is controlled by a control circuit in accordance with output voltage information fed back from the secondary winding side. On this account the switching power supply device has an output voltage being stabilized to be a target value. Moreover, fluctuation of the control is detected only under the light load in accordance with a nonlinear characteristic of a fluctuation detection circuit. A fluctuation in an output of the fluctuation detection circuit is extracted by a differentiating circuit composed of a capacitor and dividing voltage resistors, and the output of the differentiating circuit is superposed on a value of the divided output voltage so as to be fed back. In this manner the fluctuation component, having relatively short change periodicity (like A.C.), of the control fluctuation is superposed on the output voltage information having relatively long change periodicity (like D.C.

Abstract: The switching power unit is a switching power unit of PWM system in which, in response to a secondary-side output voltage detected by an output voltage detecting circuit, a control circuit controls a duty of a main switching element so as to stabilize the output voltage. There is provided a filter circuit, preventing EMI, which is constituted of filter capacitors and a filter coil. In relation to the filter circuit, there is provided a discharging resistor which is constituted of two series resistors so as to prevent an accident by discharging electric charges of the filter capacitors quickly. A voltage of a connection point between the series resistors is applied to a power supplying capacitor of the control circuit via an activating resistor.

Abstract: A switching power supply device is arranged such that a switching of a main switching element is controlled by a control circuit in accordance with output voltage information fed back from the secondary winding side. On this account the switching power supply device has an output voltage being stabilized to be a target value. Moreover, fluctuation of the control is detected only under the light load in accordance with a nonlinear characteristic of a fluctuation detection circuit. A fluctuation in an output of the fluctuation detection circuit is extracted by a differentiating circuit composed of a capacitor and dividing voltage resistors, and the output of the differentiating circuit is superposed on a value of the divided output voltage so as to be fed back. In this manner the fluctuation component, having relatively short change periodicity (like A.C.), of the control fluctuation is superposed on the output voltage information having relatively long change periodicity (like D.C.

Abstract: In a switching power source of the RCC system in which excited energy, accumulated in a transformer during an on-period of a main switching element, is outputted to the secondary side during an off-period, and a ringing pulse, which appears in a control coil of the transformer upon completion of the output, is fed back to the gate of the main switching element through a capacitor used for cutting a dc so that the main switching element is on-driven, a bias resistor is interpolated between the capacitor and the gate, and during the stand-by state, a control transistor is turned on, with the connecting point between them being connected to a main power-source line in a low level through a series circuit consisting of a diode, Zener diode and a resistor. Thus, a higher charge is allowed to accumulate in the capacitor, and the ringing pulse is reversely biased by the charge so as not to cause the re-starting.