Murata Manufacturing Co., Ltd.

Shingo Kunii

Naoto Sano

Yasuyuki Morishima

A DC-DC converter achieves a high level of a signal superimposed in an AC manner onto the output of an insulator such as a photocoupler, and there are very few limitations in the aspects of constant design, phase correction, starting characteristics, and short-circuit protection. A secondary-side control circuit detects an output voltage, and feeds back a control signal to a drive control circuit on the primary side via a photocoupler. The photocoupler insulates the primary side of a DC-DC converter from the secondary side thereof, wherein the control signal output from the secondary-side control circuit is transmitted to the primary side. The output signal of an auxiliary power-supply circuit is superimposed in an AC manner onto the control signal via a coupling capacitor. The drive control circuit has a configuration in which a pulse control signal is applied to a switching element in order to stabilize the output voltage of a secondary-side circuit on the basis of the control signal.

DC-DC converter

A power supply converts a first direct-current voltage into a second direct-current voltage and outputs the second direct-current voltage. The power supply includes a reference voltage generating circuit for generating a reference voltage, a control circuit for controlling an output voltage in accordance with the reference voltage, and a short-circuit detecting circuit for performing an output short-circuit protection operation, when short circuiting occurs at the output, by detecting the occurrence of short circuiting and by decreasing the reference voltage so that the output voltage is decreased.

Power supply, electronic device using the same, and output

A multi-output DC-DC converter includes a step-down DC-DC converter circuit which includes a switching device for switching an input DC voltage to convert it to a pulse voltage, a choke coil and a smoothing capacitor for smoothing the pulse voltage to obtain a first output lower than the input DC voltage, and a flywheel rectifying device for causing a current to flow through the choke coil when the switching device is off; and a rectifying circuit for processing and rectifying the pulse voltage in the DC-DC converter circuit to obtain a second output. Since the flywheel rectifying device is a bi-directional synchronous rectifying device which is turned on when the switching device is off, even when the load current of the first output decreases, the amplitude of the source voltage of the switching device is not reduced. Therefore, the second output obtained from the rectifying circuit always maintains a normal value.

Multi-output DC-DC converter and electronic apparatus using the same

A DC-to-DC converter is provided with an astable multivibrator containing a first time constant circuit for setting an ON period of an output and a second time constant circuit for setting an OFF period of the output, and provided with a switching element controlled by the output. The output voltage is controlled by changing the duty ratio of the astable multivibrator in accordance with the output voltage.

DC-to-DC converter and electronic device using the same

A switching power supply which is capable of generating several different output voltages and which can be easily miniaturized by using a transformer with a small number of terminals. For example, using a transformer with four terminals and three windings that are connected in series, a rectifying-smoothing circuit having a diode and a capacitor is connected to a connection point of the collector of a switching transistor and the windings. A further pair of rectifying-smoothing circuits having diodes and capacitors is commonly connected to one end of the windings, according to one example. As a result thereof, three voltages are generated.

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Nagaokakyo, Japan

Shingo Kunii