Mitsumi Electric Company Ltd.

Minoru Kado

Takeshi Sato

Takumi Hyugaji

Satoshi Arima

Takashi Inoue

A switching power supply device includes a secondary-side control circuit including a switching control circuit that generates a voltage for ON-OFF control of a switching element for synchronous rectification. The secondary-side control circuit includes an external terminal to which a drain voltage of the switching element is input, a power supply terminal to which a voltage rectified by the switching element is input, a peak hold circuit that holds a peak of the drain voltage input to the external terminal, and an abnormality detection circuit that operates based on the voltage at the power supply terminal or a voltage derived from the voltage at the power supply terminal and a holding voltage of the peak hold circuit, and outputs an abnormality detection signal when detecting an abnormal state in which the voltage at the power supply terminal decreases or no voltage is input to the power supply terminal.

Switching power supply device

Disclosed is a switching power supply device including: a transformer for voltage conversion; a main switching element connected in series to a primary coil; a primary side control circuit that performs on/off control of the main switching element; a synchronous rectification MOS transistor connected in series to a secondary coil; and a secondary side control circuit that performs on/off control of the MOS transistor, wherein the secondary side control circuit includes: an off-timing detection circuit that compares a drain voltage of the MOS transistor with a predetermined threshold voltage, and detects a timing to turn off the MOS transistor; and a threshold voltage setting circuit that sets the threshold voltage, and the threshold voltage setting circuit sets the threshold voltage based on a conduction period of the secondary coil or a period obtained by adding the conduction period to a conduction period of the primary coil.

Switching power supply device having secondary side synchronous rectification element and control circuit therefor

A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, and a secondary side control circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The secondary side control circuit includes a peak period detection circuit and a determination reference voltage generation circuit. The peak period detection circuit detects a peak period of the drain voltage. The determination reference voltage generation circuit generates a reference voltage to be used as a reference for determining the peak period based on a voltage in the peak period. The peak period detection circuit detects the peak period based on the drain voltage and on the reference voltage.

A switching power supply device includes a transformer for voltage conversion, a synchronous rectification MOS transistor, a secondary side control circuit, and a minimum on-time setting circuit. The synchronous rectification MOS transistor is connected in series to a secondary side coil of the transformer. The secondary side control circuit performs on/off control of the synchronous rectification MOS transistor based on a drain voltage of the synchronous rectification MOS transistor. The minimum on-time setting circuit sets a minimum on-time when turning on the synchronous rectification MOS transistor based on a peak period and a bottom period detected by the secondary side control circuit.

A switching power source apparatus includes: a synchronous rectifier switching element for synchronous rectification constituted of an insulated-gate field-effect transistor; and a secondary-side control circuit including a detector circuit and a timer circuit. The secondary-side control circuit performs ON/OFF control of the synchronous rectifier switching element. The detector circuit monitors a voltage of a drain terminal of the synchronous rectifier switching element, and detects an abnormal state in which the voltage of the drain terminal is undetectable. The timer circuit starts up and measures a predetermined time in response to the detector circuit detecting the abnormal state. When the detector circuit detects the abnormal state, and the predetermined time elapses according to the timer circuit, the secondary-side control circuit outputs a detection signal indicating an abnormality to outside.

Switching power source apparatus and direct-current power source apparatus

An insulated power supply device includes: an electric power conversion unit, a rectifier, a filter, a detection unit, a control circuit, and a signal transmission unit. The control circuit generates and outputs a control signal for a switching element that controls a current to be flown through a primary side of the electric power conversion unit. The signal transmission unit transmits, to the control circuit, a detection signal by the detection unit for detecting an output current or an output voltage. An output control pulse signal having control information in a duty ratio can be supplied as an outputted control signal individually to both of the control circuit and a secondary side of the electric power conversion unit. The output current or the output voltage can be thereby controlled.

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Hachioji, Japan

Minoru Kado