Fuji Electric Co., Ltd.

Fuji Electric Device Technology Co., Ltd.

Fuji Electric Systems Co. Ltd.

Kouhei Yamada

Satoshi Sugahara

Kenichi Nishijima

Akira Yamazaki

Tetsuya Kawashima

A selector circuit selects either a class upper-limit voltage or a class lower-limit voltage as a reference voltage of a comparator. A control logic controls the selector circuit, and generates a count-up signal or a count-down signal in accordance with the output of the comparator. An up/down counter counts up upon reception of the count-up signal from the control logic, and counts down upon reception of the count-down signal. A digital-analog converter outputs the class upper-limit voltage and the class lower-limit voltage in accordance with a digital value that is outputted by the up/down counter. A timer circuit is configured to be reset by the count-up signal from the control logic to the up/down counter.

AC input voltage interruption detection method and circuit

The transient response of an output voltage to a load fluctuation is improved, in a switching power source that carries out a PWM control. In a DC-DC converter wherein a switching element of an output stage is controlled by a drive signal, whose pulse width is set at a minimum value, output from a PWM signal generating circuit based on an output voltage output from an error amplifier in accordance with the difference between a feedback voltage in accordance with an output voltage of the output stage and a reference voltage, there is provided a minimum pulse width detector circuit that supplies a current to a phase compensation capacitor when the pulse width of the drive signal is at the minimum value, thus preventing the output voltage from dropping below a value corresponding to the minimum value when the load fluctuates, and improving transient response characteristics of the output voltage.

DC-DC converter control method and DC-DC converter control circuit

A hysteresis control step-up switching power supply includes a switching element. Current flowing through the switching element does not continue to increase indefinitely. The switching element is turned off when a detected value of an output voltage increases to a reference voltage, or when the output of a current detector circuit that detects that a current flowing through the switching element increases to a reference current value.

Step-up switching power supply

A control circuit of a DC-DC converter that has a switching element, including an error amplifier that amplifies a difference between a reference voltage and a feedback voltage corresponding to an output voltage of the DC-DC converter, a voltage reduction comparator that outputs an interrupt signal when the feedback voltage is lower than a voltage reduction threshold that has a value lower than that of the reference voltage, and a pulse-width modulation (PWM) signal generator circuit. The PWM signal generator circuit generates a PWM signal of a predetermined frequency based on the voltage difference when no interrupt signal is generated, or otherwise generates a switch drive signal to activate the switching element for a first period of time corresponding to the difference output by the error amplifier, and to deactivate the switching element for a second period of time after the first period of time has elapsed.

DC-DC converter control circuit and control method

A control system of a DC to DC converter skips switching pulses according to the output of an overvoltage protection circuit. The overvoltage protection circuit includes an overvoltage threshold voltage control section that lowers an overvoltage threshold voltage when the pulse width has a minimum valve. The control system both improves the output voltage accuracy of the DC to DC converter under a light load and promotes a quick return to normal operation after an overvoltage protection operation under a heavy load.

Overvoltage threshold control system of DC to DC converter

A voltage-to-current converter circuit has a differential input unit, and is provided with an input offset voltage, wherein the temperature characteristics of the differential input unit and input offset voltage are substantially flat. A current is supplied wherein a second fixed current having positive temperature characteristics is added to a first fixed current having flat characteristics as a bias current to the differential input unit, to balance the temperature characteristics of the differential input unit and the temperature characteristics of the bias current, thus causing the differential input unit transconductance temperature characteristics to be substantially zero (e.g., substantially flat).

Voltage-to-current converter circuit

A comparator circuit can achieve a reduction in current consumption with a simple configuration, and can suppress an increase in current consumption accompanying a rise in power source voltage. A current mirror circuit is connected to a power source, and gates of MOSFETs of the circuit are interconnected. An input signal is applied to a gate of an NMOSFET of the circuit. By determining the value of the signal with a constant voltage device, the voltage across a tail resistor is constant, even in the event that the power source voltage and the input signal change.

Comparator circuit with current mirror

A DC-DC converter performing pulse frequency modulation (PFM) control with a fixed ON time, having a control circuit performing PFM control of the ON time for a switch, including an error amplifier amplifying the difference between an output voltage and a target voltage, a voltage controlled oscillator increasing and decreasing in frequency and outputting an error signal, and a one-shot circuit generating the ON time based on a trigger signal output from the VCO, where ON time is linked to an input voltage and/or an output voltage. The switching frequency decreases under light loads and current consumption is reduced, and the switching frequency is made to be approximately constant under heavy loads.

DC-DC converter

In a level shift circuit in a high electric potential side driving circuit, a latch circuit and a transmission circuit located at the front stage of the latch circuit are provided. The transmission circuit makes its output impedance high when two inputs Vand Vare detected as low level signals by which erroneous signals due to dv/dt noises can be effectively blocked. In the transmission circuit, since there is no necessity of deliberately increasing delay in part of the circuit for achieving complete blocking, error signals due to dv/dt noises can be blocked with the minimum delay time.

Level shift circuit with noise blocking transmission circuit

A switching power supply system has a control circuit that controls an output voltage by causing a switching device to turn ON and OFF. The control circuit includes a control pulse supplying unit that supplies a pulsed signal that keeps the switching device turned-ON and -OFF. A protection circuit shuts down the switching power supply system upon occurrence of an abnormality. A delay circuit produces a delay signal that delays by a specified time duration the termination of a state of the pulsed signal in which the pulsed signal keeps the switching device turned-ON. The protection circuit is responsive to the pulsed signal or the delay signal to switch between an operation state and a stand-by state.

Switching power supply system with reduced current consumption at light load

An integrated circuit, in which the influence of parasitic capacitance between a semiconductor substrate and a resistor and between the semiconductor substrate and a capacitor can be inhibited, and a DC-DC converter provided with the integrated circuit. A shielding layer of an n-type semiconductor is formed between a p-type semiconductor substrate and a resistor formed thereon and between the semiconductor substrate and a capacitor formed thereon. A point BOOT is connected to the shielding layer, at which an electric potential changes in the same way as a change in the reference potential of a functional circuit carrying out a specified operation by using the resistor and the capacitor.

Integrated circuit and DC-DC converter formed by using the integrated circuit

An overcurrent detection circuit (in FIG.) in a DC-DC converter is connected to a switching control circuit (), and detects an inductor current flowing through an inductor (L) during the ON control of a switching element (Mn), so as to decide whether the inductor current has decreased down to a prescribed value. The switching control circuit () alters the switching timing of a control signal to extend the OFF state of a switching element (Mp) until the decrease of the inductor current to a predetermined magnitude is decided by the overcurrent detection circuit (). Even when a delay is involved in an overcurrent detection operation, the DC-DC converter is still capable of overcurrent limitation.

DC-DC converter and DC-DC power conversion method employing overcurrent protection

A DC-DC converter of a synchronous rectifier type, a control circuit thereof and control method thereof, facilitates detecting and interrupting negative inductor current IL with low power consumption, high accuracy and a simple configuration and facilitates improving the efficiency under a light load. An ON-period decision circuit determines whether an ON-period of the synchronous rectifier switch is too long or too short. An ON-period adjustment circuit generates a signal for adjusting the ON-period, during which the synchronous rectifier switch is ON, based on the decision of the ON-period decision part. A delay circuit adjusts the length of the delay, from the time when a signal changing the ON and OFF states of the synchronous rectifier switch changes to ON, to the time when the synchronous rectifier switch is forcibly turned off based on the adjusting signal.

Control circuit of DC-DC converter with synchronous rectifier adjusting signal to improve efficiency at light loads and control method thereof

A reverse current stopping circuit includes a synchronous rectification device, a comparator for detecting a reverse current of an inductor, the synchronous rectification device being turned off when the reverse current is detected by the comparator, a reverse current detector circuit for detecting a switching terminal voltage after the synchronous rectification device is turned off, thereby determining a value of the inductor current to decide whether the inductor current is flowing in a reverse direction or a forward direction, and a memory unit for receiving a predetermined output signal from the reverse current detector circuit in accordance with a result of the reverse current detector circuit, and outputting a control signal for an offset voltage in accordance with the predetermined output signal. The offset voltage is changed in accordance with the control signal so as to adjust the inductor current to zero when the synchronous rectification device is turned off.

Reverse current stopping circuit of synchronous rectification type DC-DC converter

A DC-DC converter includes a series circuit of a main switch and a choke coil and an output capacitor connected to one end of the series circuit and outputs a DC voltage from the one end of the series circuit. A first MOS transistor is connected in parallel to the series circuit and a second MOS transistor is connected in parallel to the output capacitor. A control circuit controls the gate voltages of the first MOS transistor and/or the second MOS transistor so that the first MOS transistor and/or the second MOS transistor outputs a changed target output voltage, whereby the output voltage is made equal to the target voltage at high speed.

Growing community of inventors

Matsumoto, Japan

Kouhei Yamada