Rohm Co., Ltd.

Panasonic Photo & Lighting Co., Ltd.

Kyoichiro Araki

Isao Yamamoto

Yoichi Tamegai

Noboru Kagemoto

Yoshinori Imanaka

Hironori Nakahara

Hisanori Hoshikawa

Youichi Tamegai

A control circuitaccording to the present invention transits to a first current limiter mode when an output current of a DC-DC converter circuit reaches an upper limit current or greater in a normal mode; transits to the normal mode when the output current falls below the upper limit current in the first current limiter mode; transits to a second current limiter mode when a first predetermined period elapses without a transition to the normal mode in the first current limiter mode; and transits to the normal mode when a second predetermined period elapses in the second current limiter mode.

Power control circuit to prevent a malfunction of a protection circuit

A driving apparatus drives a mover arranged for feedback of a touch panel. A reference voltage generation unit generates a reference voltage having a signal waveform to be applied to the mover. A pulse modulator generates a PWM signal of which duty ratio is controlled by feedback so that a feedback voltage corresponding to a drive voltage to be applied to the mover approaches the reference voltage. A switching element of the DC/DC converter is turned ON/OFF by a PWM signal from the pulse modulator, so that an output voltage of the DC/DC converter is controlled, and a drive voltage corresponding to the output voltage is applied to the mover.

Driving apparatus of mover

A control circuit is provided for a separately excited DC/DC converter which directly monitors output voltage to detect a short-circuit state, and performs overcurrent protection. A switching controller of the control circuit controls a switching operation of a switching transistor of the separately excited DC/DC converter. A voltage comparator compares the output voltage and a threshold voltage, to detect the short-circuit state. After a predetermined start-up time has elapsed after beginning start-up of the separately excited DC/DC converter, when the voltage comparator detects the short-circuit state, the switching controller halts the switching operation of the switching transistor, and makes detection of the short-circuit state by the voltage comparator non-operative before elapse of the start-up time. After detecting the short-circuit state and halting the switching operation of the switching transistor for a predetermined halt time, the switching controller begins start-up of the separately excited DC/DC converter once again.

DC/DC converter control circuit, and power supply apparatus, light emitting apparatus and electronic device using the same

A discharging device capable of realizing a proper PWM drive by accurately reflecting, as a strobe device, the secondary-side condition of a separately-excited strobe charging circuit being charged. A charging device which charges a main capacitor () via a separately-excited DC/DC converter and discharges the energy of the main capacitor, wherein a pulse width control circuit () for controlling a conduction pulse width on the primary side of the separately-excited DC/DC converter is provided, and this pulse width control circuit is configured such that a PWM soft start drive is performed that expands a conduction pulse width on the primary side of the separately-excited DC/DC converter stepwise up to a maximum pulse width.

Discharge device

A control circuit for controlling a switching element in a switching power supply by generating a switching signal is disclosed. The control circuit may include a soft start circuit that generates a switching signal so that an output voltage of the switching power supply gradually increases for a period until the output voltage reaches a predetermined reference voltage. The soft start circuit may increase the output voltage at a first limiting speed when the output voltage is lower than a predetermined threshold voltage, and may increase the output voltage at a second limiting speed which is set higher than the first limiting speed when the output voltage is higher than the threshold voltage.

Switching power supply and its control circuit, and electronic apparatus employing such switching power supply

In a soft start period after power-on, a voltage regulating apparatus checks LED by LED to determine whether the LED is mounted on a position to receive a drive voltage. After the soft start period, the voltage regulating apparatus monitors the driving status of each of the plurality of LEDs. When it is determined as a result of monitoring that the driving status of at least one of the LEDs is improper, the voltage regulating apparatus increases the drive voltage. In this process, the monitoring on an LED determined to be unmounted as a result of a mount checking process is invalidated. With this, it is ensured that a result of monitoring on the LED unmounted is prevented from affecting the increasing of the drive voltage.

Voltage regulating apparatus supplying a drive voltage to a plurality of loads

A charge pump circuit boosts a voltage of a battery so as to generate a drive voltage for an LED. A constant current circuit generates a constant current to feed through the LED. A monitoring circuit monitors a cathode potential of the LED, i.e., a voltage across the constant current circuit. A control circuit receives a result of monitoring from the monitoring circuitand increases a step-up ratio of the charge pump circuit when the voltage across the constant current circuit drops below a minimum voltage that guarantees a constant current. The control circuit sets an externally requested constant current value in the constant current circuit. When a change from a large current to a small current is requested, the control circuit returns the step-up ratio of the charge pump circuit to 1.0.

Boost controller capable of step-up ratio control

An input circuit is provided which prevents malfunctioning of a function circuit during a power source voltage rise without the need of a separate Under Voltage Lock Out (UVLO) circuit. The input circuit includes a first transistor which receives an input terminal signal at a gate, a first resistor arranged between the transistor drain and a power source voltage, a second transistor arranged between the first transistor source and a ground potential, a second resistor arranged between the second transistor gate and the power source voltage, a third resistor arranged between the second transistor gate and the ground potential, a third transistor which receives the signal between the first transistor drain and the first resistor at the gate and connects and disconnects the path of the current which flows to the second and third resistors, and a fourth transistor which receives the signal of the input terminal IN at the gate and connects and disconnects the path of the current which flows to the second and third resistors.

Growing community of inventors

Kyoto, Japan

Kyoichiro Araki