Abstract: An expander circuit may be configured to control a plurality of driver circuits for driving light emitting diodes (LEDs). The expander circuit may comprise a bus interface circuit configured to receive control signals from a processor over a communication bus, and a plurality of modulation signal generators configured to generate modulation signals based on the control signals. The expander circuit may be configured to provide the modulation signals to the plurality of driver circuits for driving the LEDs.

Abstract: The present invention provides a power control circuit and a power device using the power control circuit, wherein quasi resonance is performed by the power control circuit using a coil, current flowing in the coil is monitored by a simple configuration, and a zero cross point or a bottom in resonance is detected. The present invention provides a power control circuit and a power device using the power control circuit. The power control circuit includes a detection circuit connected to a drain of MOSFET, the MOSFET serially connected between an inductor connected to an alternating-current wire and a current sensing resistor connected to ground potential; and a quasi resonance control circuit connected to the detection circuit and the MOSFET for performing quasi resonance control to inductor-current at a zero cross point or a bottom point in a time sequence of discharging while conducting the inductor-current of the inductor.

Abstract: The present invention provides a power control circuit and a power device using the power control circuit, wherein quasi resonance is performed by the power control circuit using a coil, current flowing in the coil is monitored by a simple configuration, and a zero cross point or a bottom in resonance is detected. The present invention provides a power control circuit and a power device using the power control circuit. The power control circuit includes a detection circuit connected to a drain of MOSFET, the MOSFET serially connected between an inductor connected to an alternating-current wire and a current sensing resistor connected to ground potential; and a quasi resonance control circuit connected to the detection circuit and the MOSFET for performing quasi resonance control to inductor-current at a zero cross point or a bottom point in a time sequence of discharging while conducting the inductor-current of the inductor.

Abstract: The present invention provides a power control circuit and a power device using the power control circuit, wherein quasi resonance is performed by the power control circuit using a coil, current flowing in the coil is monitored by a simple configuration, and a zero cross point or a bottom in resonance is detected. The present invention provides a power control circuit and a power device using the power control circuit. The power control circuit includes a detection circuit connected to a drain of MOSFET, the MOSFET serially connected between an inductor connected to an alternating-current wire and a current sensing resistor connected to ground potential; and a quasi resonance control circuit connected to the detection circuit and the MOSFET for performing quasi resonance control to inductor-current at a zero cross point or a bottom point in a time sequence of discharging while conducting the inductor-current of the inductor.

Abstract: An amplitude normalization circuit includes: a peak detector that detects a peak value of a full-wave rectified voltage of an AC voltage; a triangular wave oscillator connected to the peak detector generates a triangular wave voltage having the peak value; a comparator connected to the triangular oscillator compares the triangular wave voltage with the full-wave rectified voltage and outputs a pulse width modulation signal; and a waveform converter connected to the comparator converts a waveform of the pulse width modulation signal and outputs an output voltage with constant amplitude.

Abstract: A control circuit of a switching converter includes a current detection comparator for comparing a detection voltage corresponding to a voltage drop of a detection resistor with a reference voltage and generating a peak current detection signal asserted when the detection voltage reaches the reference voltage, a driving logic unit for generating a pulse signal indicating a turn-on/off operation of a switching transistor and changing the pulse signal to an OFF level indicating the turn-off operation of the switching transistor when the peak current detection signal is asserted, a driver for driving the switching transistor based on the pulse signal, and a reference voltage setting unit for measuring time (TRECT) for which a current flows through a secondary coil and a switching period (T) of the switching transistor and adjusting the reference voltage (VREF) according to an equation: VREF=K×T/TRECT where K is a coefficient.

Abstract: An amplitude normalization circuit includes: a peak detector that detects a peak value of a full-wave rectified voltage of an AC voltage; a triangular wave oscillator connected to the peak detector generates a triangular wave voltage having the peak value; a comparator connected to the triangular oscillator compares the triangular wave voltage with the full-wave rectified voltage and outputs a pulse width modulation signal; and a waveform converter connected to the comparator converts a waveform of the pulse width modulation signal and outputs an output voltage with constant amplitude.

Abstract: The present invention provides a power control circuit and a power device using the power control circuit, wherein quasi resonance is performed by the power control circuit using a coil, current flowing in the coil is monitored by a simple configuration, and a zero cross point or a bottom in resonance is detected. The present invention provides a power control circuit and a power device using the power control circuit. The power control circuit includes a detection circuit connected to a drain of MOSFET, the MOSFET serially connected between an inductor connected to an alternating-current wire and a current sensing resistor connected to ground potential; and a quasi resonance control circuit connected to the detection circuit and the MOSFET for performing quasi resonance control to inductor-current at a zero cross point or a bottom point in a time sequence of discharging while conducting the inductor-current of the inductor.

Abstract: A control circuit of a switching converter includes a current detection comparator for comparing a detection voltage corresponding to a voltage drop of a detection resistor with a reference voltage and generating a peak current detection signal asserted when the detection voltage reaches the reference voltage, a driving logic unit for generating a pulse signal indicating a turn-on/off operation of a switching transistor and changing the pulse signal to an OFF level indicating the turn-off operation of the switching transistor when the peak current detection signal is asserted, a driver for driving the switching transistor based on the pulse signal, and a reference voltage setting unit for measuring time (TRECT) for which a current flows through a secondary coil and a switching period (T) of the switching transistor and adjusting the reference voltage (VREF) according to an equation: VREF=K×T/TRECT where K is a coefficient.

Abstract: A main transformer is arranged such that a load is connected to its secondary winding side. A first error amplifier generates a feedback signal that corresponds to the difference between a detection signal which indicates the electrical state of the load and a predetermined first reference voltage. A current generating resistor is arranged between a current generating transistor and a fixed voltage terminal. A second error amplifier is arranged such that the first input terminal receives the electric potential at a node that connects the current generating transistor and the current generating resistor, a predetermined second reference voltage is input to the second input terminal thereof, and the output terminal thereof is connected to the control terminal of the current generating transistor. An adjustment resistor is arranged between the output terminal of the first error amplifier and a node that connects the current generating transistor and the current generating resistor.

Abstract: A reference voltage source generates a reference voltage for adjusting an electric current for a dimming operation. The first current source generates a first current. A first current mirror circuit includes multiple output terminals, duplicates the first current, and outputs multiple first duplicated currents via the multiple output terminals. Multiple first switches are provided on paths for the respective multiple first duplicated currents. A converting resistor, with one terminal set to a fixed electric potential, is provided on a path for the multiple first duplicated currents output from the first current mirror circuit. A decoder circuit receives a control signal from an external circuit, and controls the ON/OFF operations of the multiple first switches. The reference voltage source outputs, as the reference voltage, a voltage that corresponds to a voltage drop that occurs at a converting resistor.

Abstract: A control circuit 10 according 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.

Abstract: A main transformer is arranged such that a load is connected to its secondary winding side. A first error amplifier generates a feedback signal that corresponds to the difference between a detection signal which indicates the electrical state of the load and a predetermined first reference voltage. A current generating resistor is arranged between a current generating transistor and a fixed voltage terminal. A second error amplifier is arranged such that the first input terminal receives the electric potential at a node that connects the current generating transistor and the current generating resistor, a predetermined second reference voltage is input to the second input terminal thereof, and the output terminal thereof is connected to the control terminal of the current generating transistor. An adjustment resistor is arranged between the output terminal of the first error amplifier and a node that connects the current generating transistor and the current generating resistor.

Abstract: The power supply of the present invention is composed of: a charge pump circuit (54) that periodically turns on and off a plurality of charge-transfer switches (Q1 to Q4) according to clock signals (c1 and c2), thereby charges and discharges a charge storage capacitor (C1) and thus produces the desired output voltage (Vo) from an input voltage (Vi) to supply it to a load (LED); an output current detection circuit 57 for detecting an output current Io (a reference current (Im) thereof in FIG. 1) to the load; and means (a frequency conversion circuit 52 in FIG. 1) that varies the frequency of the clock signals c1 and c2 based on the result of the detection of the output current Io. With this configuration, it is possible to achieve high electric power efficiency irrespective of the magnitude of a load.

Abstract: A soft start circuit generates a soft start voltage Vss which changes with time at a starting time of lighting an EEFL. A pulse width modulator generates a PWM signal Vpwm whose duty ratio is feedback-controlled so that a feedback voltage Vfb corresponding to an output voltage Vdrv of an inverter conforms to the soft start voltage Vss. A logical control unit performs switching control of a voltage of a primary coil of a transformer on the basis of the PWM signal Vpwm from the pulse width modulator. The soft start circuit executes at least one striking operation in which the soft start voltage Vss is raised with time, lowered when being reached to a first voltage level VH, and raised again when being lowered to a second voltage level VL lower than the first voltage level VH.

Abstract: A reference voltage source generates a reference voltage for adjusting an electric current for a dimming operation. The first current source generates a first current. A first current mirror circuit includes multiple output terminals, duplicates the first current, and outputs multiple first duplicated currents via the multiple output terminals. Multiple first switches are provided on paths for the respective multiple first duplicated currents. A converting resistor, with one terminal set to a fixed electric potential, is provided on a path for the multiple first duplicated currents output from the first current mirror circuit. A decoder circuit receives a control signal from an external circuit, and controls the ON/OFF operations of the multiple first switches. The reference voltage source outputs, as the reference voltage, a voltage that corresponds to a voltage drop that occurs at a converting resistor.

Abstract: According to the invention, as an input voltage of a certain step-up unit of a plurality of stages of step-up units, a stepped-up output of a step-up unit in a stage preceding the certain step-up unit is inputted. This makes it possible to increase the level of a voltage stepped up by each step-up unit, and reduce the number of units. Furthermore, according to the invention, when an output voltage of a step-up unit that performs stepping-up operation according to a reference constant current is lower than a reference voltage, a reference constant current is produced; when the output voltage thereof exceeds the reference voltage, the reference constant current is stopped. This makes it possible to provide stable output of an output voltage at a predetermined level, and reduce an inrush current during start-up to a predetermined current level.

Abstract: A control circuit 10 according 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.

Abstract: The power supply of the present invention is composed of: a charge pump circuit (54) that periodically turns on and off a plurality of charge-transfer switches (Q1 to Q4) according to clock signals (c1 and c2), thereby charges and discharges a charge storage capacitor (C1) and thus produces the desired output voltage (Vo) from an input voltage (Vi) to supply it to a load (LED); an output current detection circuit 57 for detecting an output current Io (a reference current (Im) thereof in FIG. 1) to the load; and means (a frequency conversion circuit 52 in FIG. 1) that varies the frequency of the clock signals c1 and c2 based on the result of the detection of the output current Io. With this configuration, it is possible to achieve high electric power efficiency irrespective of the magnitude of a load.

Abstract: A soft start circuit generates a soft start voltage Vss which changes with time at a starting time of lighting an EEFL. A pulse width modulator generates a PWM signal Vpwm whose duty ratio is feedback-controlled so that a feedback voltage Vfb corresponding to an output voltage Vdrv of an inverter conforms to the soft start voltage Vss. A logical control unit performs switching control of a voltage of a primary coil of a transformer on the basis of the PWM signal Vpwm from the pulse width modulator. The soft start circuit executes at least one striking operation in which the soft start voltage Vss is raised with time, lowered when being reached to a first voltage level VH, and raised again when being lowered to a second voltage level VL lower than the first voltage level VH.