Oita University

Denso Corporation

Taiyo Yuden Co., Ltd.

Ricoh Electronic Devices Co., Ltd.

National University Corporation Oita University

Kimihiro Nishijima

Masaya Takahashi

Eisuke Takahashi

Nobuhisa Yamaguchi

Shohtaroh Sohma

Kosuke Harada

Yuji Takeyama

An overvoltage protection circuit is provided which is connected between a rectifier circuit and a load including an input capacitor element connected to both ends of the load. The overvoltage protection circuit includes a semiconductor switch connected between the rectifier circuit and the load, and a control circuit controls the semiconductor switch. When the rectified voltage exceeds a predetermined value, the control circuit turns off the semiconductor switch, and detects a voltage potential difference between both ends of the semiconductor switch, and then, for an interval when the voltage potential difference is zero or a predetermined minute value, the control circuit generates a control voltage for turning on the semiconductor switch, and outputs the control voltage to a control terminal of the semiconductor switch. The overvoltage protection circuit includes a current change circuit that gradually changes a current flowing through the semiconductor switch.

Overvoltage protection circuit for protecting overvoltage corresponding to wide range of input voltage

In a power converter, switch-off of the synchronous rectification switch while the auxiliary switch is on causes the first capacitance of the main switch and the second capacitance of the synchronous rectification switch to resonate with the inductance of the second magnetic component. A parameter obtainer detects a voltage across a selected one of the main switch and the synchronous rectification switch, and obtains a parameter indicative of a corresponding one of rising and falling waveforms of the voltage across the selected switch while the selected switch is switched. A controller controls a switching control signal for the auxiliary switch to adjust switch-on timing of the auxiliary switch as a function of the parameter obtained by the parameter obtainer.

Power converter with zero-voltage switching control

In a power converter, a first electrical path connects between the series resonant circuit and a selected terminal from the high- and low-side input and output terminals of the power converter. An auxiliary diode is provided on one of the series resonant circuit and the first electrical path. An auxiliary switch, when turned on, causes an inductor current to flow through the auxiliary diode to the resonance inductor, thus storing electromagnetic energy into the resonance inductor, and causes the resonance inductor and the capacitance component of the series resonant circuit to resonate with each other. A second electrical path bypasses the auxiliary switch for flow of the inductor current. A discharge unit is provided on the second electrical path. The discharge unit is activated to discharge the electromagnetic energy stored in the resonance inductor via the second electrical path.

Power converter with resonant circuit

When a commercial power supply E operates normally, converter sections PFC, PFCconnected in parallel to each other can operate to approximate the input current from the commercial power supply E to the waveform and phase of the input voltage to correct a power factor while supplying stabilized output voltages Vo, Voto a load. When the voltage of the commercial power supply E drops, the smoothing capacitor Cooperates as an input power supply to power the converter section PFC, which allows the smoothing capacitor Coto supply the stabilized output voltage Voto the load.

Power factor correction converter with parallel-connected converter sections

To provide a power supply apparatus that can supply a large current and a small current to a load circuit in a switchable manner, with a minimum circuit scale and an efficient use of electronic devices and elements contained in conventionally used power supply apparatuses. The power supply apparatusincludes a power sourcethat supplies power to a load circuitvia one of a first pathand a second path, a switching unitthat switches between the first pathand the second path, a first switchthat controls a supply period that provides a reference for a first level of power supplied via the first path, a driverincluding an open/close switchthat controls timing of opening and closing of the first switch, and a second switchthat controls a supply period that provides a reference for a second level of power supplied via the second path, wherein the first level of power is higher than the second level of power, the first pathruns through outside of the driverwhile the second pathruns through inside of the driver, and the open/close switchand the second switchare a common element.

Power supply apparatus

The number of switches on the primary winding side of a transformer is decreased and ripples contained in the output voltage are greatly reduced. In a state I, Sia and Sib are switched ON, in a state II, Sim and Sia are switched ON, in a state III, Sia and Sib are switched ON, and in a state IV, Sim and Sib are switched ON. As a result, in the states I to III, a transformer Trsa is connected to a capacitor Ci, in the state IV, the transformer Trsa is connected to an input power source Vi supplying an electric current in the direction opposite to that of the capacitor Ci. Further, in states I, III, and IV, the transformer Trsb is connected to the capacitor Ci, and in state II, the transformer Trsb is connected to the input power source Vi supplying an electric current in the direction opposite to that of the capacitor Ci. Further, in states I to III, the electric current generated on the secondary winding side of the transformer Trsa is supplied by a rectifying diode Doa to a load R, and in states I, III, and IV, the electric current generated on the secondary winding side of the transformer Trsb is supplied by a rectifying diode Dob to the load R.

Growing community of inventors

Oita, Japan

Kimihiro Nishijima