Abstract: A switching power supply apparatus of the present disclosure is a device connection state detection circuit that detects a connection state in a load device connection terminal in a power supply system having the load device connection terminal. The device connection state detection circuit includes a transformer, a switching element, a pulse generator, and a waveform detection circuit. The waveform detection circuit detects a voltage or a current generated in a primary winding wire or a secondary winding wire of the transformer in accordance with operation of a pulse signal, compares the detected voltage or current with a preset reference value, and outputs an output signal in accordance with a comparison result, to an OFF terminal.

Abstract: A switching power supply apparatus of the present disclosure is a device connection state detection circuit that detects a connection state in a load device connection terminal in a power supply system having the load device connection terminal. The device connection state detection circuit includes a transformer, a switching element, a pulse generator, and a waveform detection circuit. The waveform detection circuit detects a voltage or a current generated in a primary winding wire or a secondary winding wire of the transformer in accordance with operation of a pulse signal, compares the detected voltage or current with a preset reference value, and outputs an output signal in accordance with a comparison result, to an OFF terminal.

Abstract: A switching power supply device including: a power transformer including a primary winding, a secondary winding, and an auxiliary winding; a switching element which is connected to the primary winding; an output voltage generation circuit which converts, into a direct-current voltage, a voltage induced in the secondary winding; a secondary-side on-time signal generation circuit which generates a secondary-side on-time signal indicating a secondary-side on-time; and a switching control circuit which controls a switching operation of the switching element so that the second direct-current voltage falls within a specified range, wherein the switching control circuit controls the switching operation so that the direct-current voltage becomes equal to or below an overvoltage specified value when the secondary-side on-time becomes smaller than a set value.

Abstract: The switching power supply apparatus includes a transformer including a primary winding, a secondary winding, an auxiliary winding, a switching device connected to the primary winding, an output voltage generation circuit which is connected to the secondary winding and generates an output voltage, and an auxiliary power voltage generation circuit which is connected to the auxiliary winding and generates an auxiliary power voltage. The switching power supply apparatus also includes a control circuit, which operates using the auxiliary power voltage and controls a driver circuit so that an intermittent oscillation is performed when the output voltage is higher than a first output voltage, and which controls a peak of a current flowing through a switching device is lower than a peak in a normal mode, when the auxiliary power voltage is lower than a first auxiliary power voltage in the intermittent oscillation.

Abstract: At the starting time and an overload time in which the output voltage of the switching power source apparatus is low, if an overcurrent state, in which the ON period of the switching device becomes short and a current not less than the current limit value of the switching device flows through the switching device, occurs, this overcurrent state is detected. The blanking period of a blanking pulse signal is made shorter than the blanking period that is obtained during steady operation, and the ON period of the switching device is made shorter. Hence, the device current flowing through the switching device can be made small in each pulse for the switching operation, and, at the same time, the device current is suppressed from increasing each time a pulse for the switching operation is generated.

Abstract: A switching power supply apparatus that can precisely control the overload protection voltage is provided.

Abstract: A switching power supply device including: a power transformer including a primary winding, a secondary winding, and an auxiliary winding; a switching element which is connected to the primary winding; an output voltage generation circuit which converts, into a direct-current voltage, a voltage induced in the secondary winding; a secondary-side on-time signal generation circuit which generates a secondary-side on-time signal indicating a secondary-side on-time; and a switching control circuit which controls a switching operation of the switching element so that the second direct-current voltage falls within a specified range, wherein the switching control circuit controls the switching operation so that the direct-current voltage becomes equal to or below an overvoltage specified value when the secondary-side on-time becomes smaller than a set value.

Abstract: A switching power supply device including: a switching element which performs a switching operation; an output voltage generation circuit; a transformer reset detection circuit which generates a transformer reset signal; a secondary-side on-time signal generation circuit; a feedback control circuit which generates a feedback signal; a switching element drive circuit which controls the switching operation of the switching element according to the feedback signal; and an output voltage correcting signal generation circuit which generates an output voltage correcting signal from the feedback signal and a secondary-side on-time signal, and supplies the output voltage correcting signal to the feedback control circuit.

Abstract: The present invention has as an object to introduce a switching power supply device having a simple circuit structure and controlling a secondary-side output voltage in a highly-accurate and stable manner. The switching power supply device includes: an auxiliary winding resetting detecting circuit which is connected to the auxiliary winding, monitors an auxiliary winding voltage pulse signal generated on the auxiliary winding, and generates an auxiliary winding reset signal indicating timing of which a secondary-side current finishes flowing into the secondary winding and the auxiliary winding voltage signal drops; and an auxiliary winding voltage sample hold circuit which holds the auxiliary winding voltage signal. The auxiliary winding voltage sample hold circuit includes a delaying circuit which delays the auxiliary winding voltage signal, and holds the auxiliary winding voltage pulse signal delayed by the delaying circuit with the timing indicated by the auxiliary winding reset signal.

Abstract: A switching element driving control circuit includes: a regulator circuit which generates a power supply voltage having an amplitude; a capacitor which smoothes the power supply voltage generated by the regulator circuit to remove a high frequency component; a circuit power supply line to which the smoothed power supply voltage is supplied; an oscillation circuit which generates a periodic signal according to an oscillation of the power supply voltage supplied from the circuit power supply line; a control circuit which generates a control signal for controlling the switching operation of the switching element, based on the periodic signal; and a driver circuit which supplies the switching element with the control signal.

Abstract: The switching power supply apparatus according to the present invention includes: a transformer including a primary winding, a secondary winding, and an auxiliary winding; a switching device connected to the primary winding; an output voltage generation circuit which is connected to the secondary winding and generates an output voltage; an auxiliary power voltage generation circuit which is connected to the auxiliary winding and generates an auxiliary power voltage; and a control circuit which operates using the auxiliary power voltage and controls a driver circuit so that an intermittent oscillation is performed when the output voltage is higher than a first output voltage and controls a peak of a current flowing through a switching device is lower than a peak in a normal mode, when the auxiliary power voltage is lower than a first auxiliary power voltage in the intermittent oscillation.

Abstract: A switching power supply is provided which keeps constant, even when the oscillation frequency of a switching element increases, the on duty of secondary current passing through a secondary winding, thereby achieving a constant current drooping characteristic with high accuracy. To be specific, a secondary current on-period detection circuit generates a signal indicating the off timing of the secondary current, based on a flyback voltage generated on an auxiliary winding. A secondary-current detection delay time correction circuit generates a signal indicating a time when a predetermined period has elapsed since the switching element is turned off. A secondary current on-duty control circuit generates a clock signal for turning on the switching element so as to keep constant the on duty of the secondary current, based on the signal generated by the secondary current on-period detection circuit and the signal generated by the secondary-current detection delay time correction circuit.

Abstract: The present invention provides a switching power supply that enables a reduction in noise without the need for an anti-noise component such as a filter circuit. A secondary current on period detecting circuit detects a first period during which a secondary current flows, the secondary current starting to flow through a secondary winding after a switching element is turned off. A secondary current on duty control circuit oscillates a clock signal set turning on the switching element so as to maintain, at a constant value, an on duty ratio of the first period to a third period made up of the first period and a second period during which the secondary current does not flow. A secondary current on duty modulating circuit applies a modulation component to the on duty ratio to periodically modulate the on duty ratio and thus the oscillation frequency of the switching element.

Abstract: According to the present invention, when a secondary current on period T2on reaches a predetermined maximum secondary current on-period, an overload is detected and an output power is controlled to decrease. Further, a maximum secondary current on-period signal is set so as to correspond to a secondary current on-period when constant voltage control is performed on an output voltage.

Abstract: A switching power supply of the present invention includes: an oscillator circuit for oscillating a signal for turning on a switching element; an error signal generating circuit for generating an error signal having a signal level corresponding to a difference between the signal level of a feedback signal and a reference level; a switching control circuit for turning on the switching element at a time in response to the signal oscillated by the oscillator circuit and turning off the switching element at a time in response to the signal level of the error signal; and a reference level control circuit for controlling the reference level according to a time period during which the switching operation of the switching element is stopped.

Abstract: At the starting time and an overload time in which the output voltage of the switching power source apparatus is low, if an overcurrent state, in which the ON period of the switching device becomes short and a current not less than the current limit value of the switching device flows through the switching device, occurs, this overcurrent state is detected. The blanking period of a blanking pulse signal is made shorter than the blanking period that is obtained during steady operation, and the ON period of the switching device is made shorter. Hence, the device current flowing through the switching device can be made small in each pulse for the switching operation, and, at the same time, the device current is suppressed from increasing each time a pulse for the switching operation is generated.

Abstract: The present invention reliably reduces output power during an overload, due to overload protection in which an on-time of a switching element 1 is reduced or the peak value of a switching current is lowered by reducing the minimum value of the on-period of the switching element 1.

Abstract: A feedback circuit (3) generates an error amplification signal VEAO for stabilizing an output voltage Vo at the reference voltage. The reference voltage is set beforehand in the feedback circuit (3). The peak value of drain current ID passing through a switching element (1) is controlled by the error amplification signal VEAO and the output voltage Vo is stabilized. Meanwhile, when a load (132) increases, a reference voltage variable circuit (13) increases the internal reference voltage of the feedback circuit (3) based on the error amplification signal VEAO, so that fluctuations in output voltage due to load fluctuations are reduced.

Abstract: A switching power supply is provided which keeps constant, even when the oscillation frequency of a switching element increases, the on duty of secondary current passing through a secondary winding, thereby achieving a constant current drooping characteristic with high accuracy. To be specific, a secondary current on-period detection circuit generates a signal indicating the off timing of the secondary current, based on a flyback voltage generated on an auxiliary winding. A secondary-current detection delay time correction circuit generates a signal indicating a time when a predetermined period has elapsed since the switching element is turned off. A secondary current on-duty control circuit generates a clock signal for turning on the switching element so as to keep constant the on duty of the secondary current, based on the signal generated by the secondary current on-period detection circuit and the signal generated by the secondary-current detection delay time correction circuit.

Abstract: The present invention provides a switching power supply that enables a reduction in noise without the need for an anti-noise component such as a filter circuit. A secondary current on period detecting circuit detects a first period during which a secondary current flows, the secondary current starting to flow through a secondary winding after a switching element is turned off. A secondary current on duty control circuit oscillates a clock signal set turning on the switching element so as to maintain, at a constant value, an on duty ratio of the first period to a third period made up of the first period and a second period during which the secondary current does not flow. A secondary current on duty modulating circuit applies a modulation component to the on duty ratio to periodically modulate the on duty ratio and thus the oscillation frequency of the switching element.