Rohm Co., Ltd.

Taichi Hoshino

Eitaro Oyama

Hiroki Kikuchi

Hiroaki Ando

Kengo Adachi

Ryouma Matsuo

Isao Yamamoto

Masanori Fujisawa

Masato Kobayashi

Isao Ouchi

A power supply unit, adapted to provide a predetermined output voltage from its output circuit, compares a feedback voltage associated with the output voltage of the output circuit with a reference voltage so as to control the output circuit. The power supply unit is enabled and disabled in response to an externally supplied operation command signal. The reference voltage is generated by a reference voltage generation circuit, which is operable on the voltage of the operation command signal, and is controllably enabled when the voltage of the operation command signal exceeds a predetermined level, but otherwise disabled. Thus, the reference voltage is stabilized to improve the ripple rejection characteristic of the power supply unit without increasing its current consumption.

Power supply unit and portable device

A power supply unit is adapted to automatically switch its operational mode between a light load mode and a heavy load mode depending on the level of its output current. The unit has a first error amplification circuit for controlling a first output circuit in the heavy load mode, and a second error amplification circuit for controlling the second output circuit in the light load mode. The first and the second output circuits are controllably enabled and disabled in the opposite manner based on the level of the output current. Thus, the unit can operate on a reduced consumption current with an improved transient response when operating in the light load mode.

A step-like operation command signal is inputted into a time-constant circuit to generate a gradually rising operation command input voltage, which is supplied to a power supply unit. Enablement and disablement of the power supply unit is controlled on the basis of the operational command input voltage. When the operation command input voltage exceeds a first predetermined voltage level, a detection signal and a reference voltage are generated, and at the same time an error amplification circuit is enabled. On the other hand, when the operation command input voltage exceeds a second predetermined voltage level, a level shift voltage for initiating a soft start is generated, which enables execution of a soft start of the power supply unit without increasing its consumption current and reduction of the number of its terminals.

A switching power supply unit for providing an output voltage that is controlled such that a first detection voltage detected on the basis of the output voltage becomes equal to a first reference voltage. The peak voltage at the node of a serially connected coil and a switch of the switching power supply unit is detected and used as a second detection voltage for over-voltage protection. Thus, over-voltage protection of the switching power supply unit is secured with no additional terminal on the switching control IC for over-voltage protection even if such components as a feedback circuit and a rectifying diode of the power supply unit become open.

Switching power supply unit and electronic apparatus having display

A low-voltage operating block and a high-voltage operating block are controlled at the same soft start voltage as that employed at the time of start-up. At a point in time at which an output DC voltage has reached an expected value, a control signal of the low-voltage operating block is switched to a control signal of the high-voltage operating block. As a result, switching is smoothly performed without involvement of occurrence of a variation in the output voltage before and after switching operation. In a switching power supply unit having a low-voltage operating block and a high-voltage operating block, which are intended for producing a higher DC voltage from a low power supply voltage, it prevents occurrence of a rush current and a start-up failure, which would otherwise be caused by switching operation.

Switching power supply unit and controller IC thereof

In a switching power source apparatus which outputs a DC output voltage converted from a DC power source voltage, the DC output, voltage is compared with a reference voltage to generate a feedback signal which decreases as the DC output voltage increases. A current detecting signal which decreases as the output current increase is also generated. The smaller of the feedback signal and the current detecting signal, as a comparison signal, is compared with a triangular signal in a PWM comparator to produce a PWM signal. A semiconductor switch is on-off controlled by the PWM signal. Therefore, the apparatus can perform a constant voltage control with a current limit function.

PWM switching regulator with current and voltage feedback

Accumulation and emission of energy in and from a coil having an intermediate tap is controlled by switching a DC input voltage from a DC power source on and off. Controlled voltages generated at a plurality of terminals are rectified and smoothed to output a plurality of DC output voltages. Connection to a reference voltage is controlled such that the voltages generated at the plurality of terminals are not dependent on the DC input voltage during the on-off switching. Therefore, a switching power supply unit is provided in which a coil having an intermediate tap is used to allow a simple configuration, to convert a DC input voltage into a plurality of DC output voltages with high efficiency, and to achieve compactness.

Switching power supply unit

A main driver, in which NPN and PNP bipolar transistors are connected in series, is driven by an output of a pre-driver having a first CMOS circuit driven by an input signal. An assist circuit having a second CMOS circuit driven by the input signal and also having a current limit resistor is provided, and an output of the main driver is assisted by an output of the assist circuit. Therefore, it is possible to reduce a short circuit current in a transistor output circuit, to increase and decrease an output signal to an power-supply potential (upper limit) and a ground potential (lower limit), and to smoothly change the output signal near the power-supply potential and the ground potential. Further, an intensity of electromagnetic noise is reduced and a switching output having a sufficiently large amplitude is supplied.

Transistor output circuit, semiconductor device including transistor output circuit, and switching electric power unit having transistor output circuit

An LED drive circuit includes a booster circuit having a first and second capacitors and using a n/m voltage type rectifying switching and a constant current circuit having a MOS transistor as an output transistor. The constant current circuit is connected in series with an LED as a load of the booster circuit to drive the LED with constant current. With this circuit construction, there is substantially no electromagnetic noise generated and it is possible to maintain a terminal voltage of the LED substantially constant according to the diode characteristics of the LED even when voltage ripple appears in an output of the booster circuit due to the n/m voltage boost, by setting the switching frequency at high to absorb the ripple component on the side of the constant current circuit.

LED drive circuit

A voltage drop DC-DC converter includes a switch circuit including a plurality of switches for alternately connecting a first and second capacitors in series and in parallel in response to an output signal of an oscillator circuit oscillating at a constant frequency. An efficient voltage dropping conversion is possible by deriving a voltage divided by the first and second capacitors when the first and second capacitors are connected in series and deriving terminal voltages of the first and second capacitors when the first and second capacitors are connected in parallel. When the derived voltage is increased beyond an aimed reference output voltage, the oscillation of the oscillator circuit is stopped.

Voltage drop DC-DC converter

A semiconductor amplifier circuit comprises a semiconductor substrate of one conductivity type, a well region of the one conductivity type, formed in said semiconductor substrate, a well region defining region of the other conductivity type, including a side wall portion and a bottom portion defining the well region, a first transistor formed in the well region and a second transistor formed on a surface of another portion of the substrate other than a portion on which the well region is formed. When the first and second transistors are in operation, a potential of the substrate is set to a reference potential, a potential of the well region defining region is set equal to the potential of the substrate or set to a value at which a junction between the well region defining region and the substrate is reverse-biased and at least one of the electrodes of the first transistor is set to a potential at which a junction between the well region defining region and the well region is reverse-biased.

Semiconductor amplifier circuit

A DC-DC converter includes an oscillation circuit for oscillating at a predetermined frequency and generating a pulse with a predetermined pulse width, a reference voltage generating circuit for generating a reference voltage, means mounted in the reference voltage generating circuit for slowly rising the reference voltage, a switching circuit for chopping the current inputted from a DC primary electric power source in accordance with the pulse, and feedback control means for stopping/restarting the oscillation of the oscillation circuit on the basis of the voltage that the output of the switching circuit is smoothed and including the reference voltage with a detection voltage upon stopping control, so that the DC-DC converter having a soft starting function is provided with a simple structure and a compact size without utilizing a PWM circuit and a VCO.

DC-DC converter capable of soft starting function by slowly raising reference voltage

A regulated power source circuit is provided with a current output circuit including a drive stage transistor which operates when receiving at the input side thereof an output signal from one of transistor for differential operation in a differential amplifier circuit, a current output stage transistor which is driven by the drive stage transistor and a detection circuit which detects a drive current value of the drive stage transistor, and further a dummy circuit which causes to output from the other transistor forming a pair with the one transistor in the differential amplifier circuit a current the value of which is substantially equal to that of the current outputted from the one transistor in the differential amplifier circuit to the drive stage transistor when a detection signal from the detection circuit is received.

Regulated power supply circuit

The present invention resides in an audio amplifier circuit which includes an output terminal of an IC connected to a power amplifier circuit, a resistor having one end connected to a negative feedback input of the power amplifier circuit and the other end connected to a certain terminal other than the output terminal of the IC, a first capacitor connected between the output terminal and a loud speaker and a second capacitor connected between a wiring connecting the output terminal to the loud speaker and the certain terminal. A reduction of low frequency gain determined by a time constant of the first capacitor and an impedance of the loud speaker is corrected by an increase of of low frequency amplification gain determined by a time constant of the second capacitor and the resistor.

Audio signal amplifier circuit and a portable audio equipment using the

A data conversion circuit has an input terminal for receiving serial data as time-divided multiple signals, a plurality of sample-and-hold circuits each connected to the input terminal, and output terminals each connected to an associated one of these sample-and-hold circuits to output the received signals as parallel data. At least one of these sample-and-hold circuits is formed with a first switch circuit which is connected on one side to the input terminal and is adapted to be switched on according to a first timing, a second switch circuit which is connected on one side to the input terminal and is adapted to be switched on according to a second timing different from the first timing, a first capacitor and a second capacitor connected respectively to the other side of the first and second switch circuits for holding received data, a third switch circuit having a common contact and being adapted to connect the common contact selectively either to the first capacitor or to the second capacitor according to a third timing different from the first timing and the second timing, and an amplifier connected between the common contact of the third switch circuit and the output terminal to output data from selected one of the capacitors.

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Kyoto, Japan

Taichi Hoshino