Abstract: A switching power-supply device, in which an input power is applied to a primary winding of a transformer, a pulse voltage is induced in a secondary winding of the transformer by turning on and off a switching element connected to the primary winding of the transformer and an output voltage rectified and smoothed by a secondary-side rectifying-and-smoothing circuit having a rectifier diode and a smoothing capacitor is outputted. The switching power-supply device includes: a transient state detection circuit, which detects a transient state and outputs a soft-drive instruction signal; and a drive circuit which turns on-and-off the switching element in a soft-drive operation, in which a charging speed of a gate voltage at a time of passing a gate threshold voltage is delayed as compared to a normal operation, in a case where the soft-drive instruction signal is inputted.

Abstract: The present invention includes: a series circuit including a reactor and a switching element connected between the rectified-current output terminals of a rectifier; a series circuit including a diode and a smoothing capacitor for obtaining an output voltage, connected in parallel to the switching element; an error amplifier configured to detect the output voltage, amplify the error between the detected output voltage and a reference voltage, and output an error signal; a zero-current detector configured to output a signal when detecting that a reactor current flowing in the reactor has become zero current; a correction signal circuit configured to detect a switching current flowing in the switching element, and generate a correction signal corresponding to the detected switching current; and an ON-period control circuit configured to control the switching element's ON period in accordance with the error signal and correction signal, from when the zero-current detector detects the zero current.

Abstract: A switching power-supply device, in which an input power is applied to a primary winding of a transformer, a pulse voltage is induced in a secondary winding of the transformer by turning on and off a switching element connected to the primary winding of the transformer and an output voltage rectified and smoothed by a secondary-side rectifying-and-smoothing circuit having a rectifier diode and a smoothing capacitor is outputted, the switching power-supply device includes: a transient state detection circuit, which detects a transient state and outputs a soft-drive instruction signal; and a drive circuit which turns on-and-off the switching element in a soft-drive operation, in which a charging speed of a gate voltage at a time of passing a gate threshold voltage is delayed as compared to a normal operation, in a case where the soft-drive instruction signal is inputted.

Abstract: The present invention includes: a series circuit including a reactor and a switching element connected between the rectified-current output terminals of a rectifier; a series circuit including a diode and a smoothing capacitor for obtaining an output voltage, connected in parallel to the switching element; an error amplifier configured to detect the output voltage, amplify the error between the detected output voltage and a reference voltage, and output an error signal; a zero-current detector configured to output a signal when detecting that a reactor current flowing in the reactor has become zero current; a correction signal circuit configured to detect a switching current flowing in the switching element, and generate a correction signal corresponding to the detected switching current; and an ON-period control circuit configured to control the switching element's ON period in accordance with the error signal and correction signal, from when the zero-current detector detects the zero current.

Abstract: A switching power supply includes a first series circuit formed by connecting first and second switching elements in series at both ends of a direct-current power source, a second series circuit formed by connecting a resonant capacitor, a resonant reactor, and a primary winding of a transformer in series at both ends of the switching element, a rectifying-smoothing circuit configured to rectify and smooth a voltage generated on a secondary winding of the transformer, and a control circuit configured to turn the first and second switching elements and on and off alternately based on an output voltage from the rectifying-smoothing circuit. Here, the control circuit sets an on-period of the second switching element to a predetermined time period longer than a half value of a cycle of a resonant current attributable to the resonant reactor and the resonant capacitor, and controls an on-period of the first switching element based on the output voltage from the rectifying-smoothing circuit.

Abstract: A switching power supply includes a first series circuit formed by connecting first and second switching elements in series at both ends of a direct-current power source, a second series circuit formed by connecting a resonant capacitor, a resonant reactor, and a primary winding of a transformer in series at both ends of the switching element, a rectifying-smoothing circuit configured to rectify and smooth a voltage generated on a secondary winding of the transformer, and a control circuit configured to turn the first and second switching elements and on and off alternately based on an output voltage from the rectifying-smoothing circuit. Here, the control circuit sets an on-period of the second switching element to a predetermined time period longer than a half value of a cycle of a resonant current attributable to the resonant reactor and the resonant capacitor, and controls an on-period of the first switching element based on the output voltage from the rectifying-smoothing circuit.