Ricoh Company, Ltd.

Ricoh Electronic Devices Co., Ltd.

Nisshinbo Micro Devices Inc.

Oita University

Ricoh Electronics Devices Co., Ltd.

Shohtaroh Sohma

Masanobu Fukushima

Katsuhisa Furuse

Kimihiro Nishijima

Koichi Hagino

Yasuhiro Ishizaka

Shinichiro Yamada

Toshiya Murota

Yuji Takeyama

Yuuta Ogino

An isolated switching power supply circuit is compact, high-efficiency, and low noise. It includes a transformer Twhich has a primary winding wound with NP turns and a secondary winding wound with NS turns, a drive switch Qand an active clamp switch Qconfiguring a primary side half-bridge, a boost capacitor CBULKthat charges a discharge energy of the transformer, rectifier diodes Dand Dconnected in series, a tank capacitor CT, and an output capacitor COUT. A secondary side winding voltage, when the drive switch Qor the active clamp switch Qis on, is held in the tank capacitor CT, and by superimposing the secondary winding voltage, when the drive switch Qor the active clamp switch Qis off, on the voltage held in the tank capacitor CT, the configuration is such that output voltage VOUT equals boosted voltage VBULK times (NS divided by NP).

Switching power supply circuit

A lighting system is provided with a dimmer apparatus and lighting equipment that are connected to each other via a two-wire power supply line. The dimmer apparatus generates a DC voltage including a dimming PWM signal having a PWM amplitude corresponding to a dimming control signal, and outputs the DC voltage to the lighting equipment. The lighting equipment includes at least one light emitting element that emits light by a DC current based on the DC voltage, and a current control circuit. The second control circuit modulates the dimming PWM signal included in the DC voltage, and controls brightness of the light emitting element, so that a DC current corresponding to a duty ratio of a modulated dimming PWM signal flows through the light emitting element based on the duty ratio of the dimming PWM signal.

Lighting system provided with dimmer apparatus and lighting equipment

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

A power supply apparatus of the present invention has an input terminal and an output terminal, and converts an input voltage at the input terminal into a predetermined output voltage at the output terminal. The power supply apparatus includes first and second power supply circuits and a smoothing capacitor. The first power supply circuit is coupled between the input terminal and the output terminal, and converts the input voltage into a predetermined voltage to output the predetermined voltage. The smoothing capacitor is coupled to the output terminal. The second power supply circuit outputs a predetermined voltage or current to the output terminal via the smoothing capacitor, based on a feedback signal corresponding to the predetermined output voltage.

Power supply apparatus converting input voltage to predetermined output voltage and controlling output voltage based on feedback signal corresponding to output voltage

A switching power supply device includes a first control circuit that turns a first switch on when first and second switches are off and a voltage at a junction node therebetween is increased to decrease a voltage across the first switch to a first threshold voltage, turns off when a first ON-period has elapsed from when the first switch is turned on, and lengthens the first ON-period as an output voltage decreases relative to a reference voltage; and a second control circuit that turns the second switch on when both switches are off and a voltage across the second switch is decreased to a second threshold voltage, turns off when a reverse current flows through the inductor, sufficient to increase the voltage at the junction node to decrease the voltage across the first switch to the first threshold voltage after the second switch is turned off.

Non-insulating type switching power supply device

A step-down switching regulator includes a switching element performing switching in accordance with an input control signal to charge an inductor with an input voltage; a synchronous rectification element performing switching in accordance with an input control signal to discharge the inductor; a power supply circuit part generating and outputting a supply voltage; a capacitor connected to the connection of the switching element and the inductor; a first drive circuit part controlling the switching of the switching element in accordance with an input control signal; a second drive circuit part controlling the switching of the synchronous rectification element in accordance with another input control signal; and a control circuit part generating and outputting the control signals to the first and second drive circuit parts so that the predetermined constant voltage is output from an output terminal, wherein the second drive circuit part is supplied with power from the capacitor.

Step-down switching regulator

Disclosed is a current-mode control switching regulator that steps down or steps up an input voltage input to an input terminal to a predetermined constant voltage and outputs the stepped input voltage from an output terminal as an output voltage. The current-mode control switching regulator includes a switching element, an inductor, a rectifying element, an error amplification circuit unit, an oscillation circuit unit with variable oscillation frequency, a slope voltage generation circuit unit, and a switching control circuit unit.

Current-mode control switching regulator and operations control method thereof

In a step-down switching regulator, a switching element is a high-voltage NMOS transistor, turned on and off based on a control signal generated by a controller, and charges an inductor with an input voltage input to an input terminal. A first drive circuit is a low-voltage MOS transistor and turns on and off the switching element based on the control signal. A voltage generator generates a predetermined first power supply voltage not greater than a withstand voltage of the low-voltage MOS transistor. A capacitor is connected in parallel with the first drive circuit and stores charge from the voltage generator to supply power to the first drive circuit. One end of the capacitor is connected to a junction node between the switching element and the inductor, and the other end of the capacitor is supplied with the first power supply voltage generated by the voltage generator.

Step-down switching regulator capable of providing high-speed response with compact structure

A disclosed switching regulator includes: a switching element switching in accordance with an input control signal; an inductor charged with a supply voltage by the switching of the switching element; a rectifying element discharging the inductor when the switching element is switched off and charging of the inductor is stopped; and a control circuit unit generating an error voltage based on a voltage difference between a proportional voltage and a predetermined reference voltage, generating and outputting a pulse signal with a duty cycle in accordance with the error voltage to a control electrode of the switching element. The control circuit unit generates a feedback voltage from the duty cycle of the pulse signal, generates the pulse signal with the duty cycle from a voltage difference between the generated feedback voltage and the error voltage, and varies the voltage difference from the duty cycle of the pulse signal.

Switching regulator capable of stable operation and improved frequency characteristics in a broad input and output voltage range and method for controlling operation thereof

A switching power supply circuit for generating an output voltage at an output node based on an input voltage at an input node includes a reference voltage generating circuit configured to generate a reference voltage such that during an initial start-up period of the reference voltage a voltage rise rate of the reference voltage within a first predetermined period from a start point of the initial start-up period and a voltage rise rate thereof within a second predetermined period immediately preceding an end point of the initial start-up period are smaller than a voltage rise rate thereof in a period between the first predetermined period and the second predetermined period, a coil disposed between the input output nodes, and a switch circuit configured to switch on and off to control current through the coil in response to comparison between the reference voltage and a voltage proportional to the output voltage.

A current-mode controlled switching regulator and control method therefor. The switching regulator includes input and output terminals, a switching device to switch in accordance with a control signal, an inductor to store charge from an input voltage at the input terminal based on the switching device, a rectifying device to discharge the charge stored in the inductor, an error amplifier to amplify a voltage difference between a divided voltage generated by dividing an output voltage at the output terminal and a predetermined reference voltage, a slope voltage generator to generate and output a slope voltage having a slope angle corresponding to the input voltage, and a switching controller to compare a voltage output from the error amplifier with the slope voltage, generate a pulse signal with a duty cycle corresponding to a comparison result, and control the switching of the switching device according to the pulse signal.

Switching regulator with slope compensation and control method therefor

A control circuit for a synchronous rectification switching regulator including an output terminal, a switching transistor, an inductor, and a synchronous rectification transistor has a control part configured to control switching of the switching transistor to charge the inductor to and set a voltage output from the output terminal to a predetermined voltage, which causes the synchronous rectification transistor to switch reversely to the switching transistor and discharge the inductor, and backflow prevention part configured to block a current flowing in the synchronous rectification transistor to prevent a backflow current that flows in a direction from the output terminal to the synchronous rectification transistor. The backflow prevention part detects a forward current and regulates timing to block the current flowing in the synchronous rectification transistor and to regulate a time period from blocking the current flowing in the synchronous rectification transistor to determining that the forward current is zero.

Synchronous rectification switching regulator, control circuit for synchronous rectification switching regulator, and control method for synchronous rectification switching regulator

A switching regulator is disclosed that is able to operate with low power consumption and able to prevent variation of an output voltage. The switching regulator operates in a PWM control mode and a PFM control mode, and includes a switching unit; an error amplification circuit for amplifying an error voltage between an output voltage and a first reference voltage; a slope circuit for generating a slope signal; a reference voltage generation circuit for generating a second reference voltage for determining a time interval of an ON state in the PFM control mode; a multiplexer for outputting one of the second reference voltage and an output voltage from the error amplification circuit; a comparison circuit for comparing an output voltage from the slope circuit to an output voltage from the multiplexer; and an oscillation circuit for determining a timing of the ON state in the PWM control mode.

Switching regulator

A switching regulator including an inductor and a switching transistor and having a normal operational mode and a light-load operational mode is disclosed. The switching regulator includes an operational mode switching part configured to switch the normal operational mode and the light-load operational mode, and a light-load detection part configured to detect the light-load state of a load. The light-load detection part is configured to detect the light-load state of the load by a change in the voltage at the connection of the switching transistor and the inductor when the switching transistor is OFF. The operational mode switching part is configured to switch the normal operational mode to the light-load operational mode in response to the detection of the light-load state of the load by the light-load detection part.

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Osaka, Japan

Shohtaroh Sohma