Panasonic Corporation

Panasonic Intellectual Property Management Co., Ltd.

Naohiko Morota

Kazuhiro Murata

Yoshihiro Mori

Keita Kawabe

Koji Suzuki

Takashi Saji

Tetsuyuki Fukushima

Tatsuya Sakurai

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.

Switching power supply apparatus

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.

Switching power supply device with a switching control circuit

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.

Switching power supply apparatus and semiconductor device

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.

Switching control circuit, semiconductor device and switching power source apparatus

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.

Switching power supply

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.

Switching power supply and regulation circuit

A feedback circuit () 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 (). The peak value of drain current ID passing through a switching element () is controlled by the error amplification signal VEAO and the output voltage Vo is stabilized. Meanwhile, when a load () increases, a reference voltage variable circuit () increases the internal reference voltage of the feedback circuit () based on the error amplification signal VEAO, so that fluctuations in output voltage due to load fluctuations are reduced.

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Hyogo, Japan

Naohiko Morota