Abstract: A control circuit of a driving circuit of a backlight LED is provided. The driving circuit includes a DC/DC converter that supplies a driving current to the backlight LED. The control circuit includes a pulse signal generating circuit configured to switch between a quasi-resonant mode and a continuous current mode to generate a pulse signal based on a selected mode and a driver configured to drive the DC/DC converter based on the pulse signal.

Abstract: A control circuit of a driving circuit of a backlight LED is provided. The driving circuit includes a DC/DC converter that supplies a driving current to the backlight LED. The control circuit includes a pulse signal generating circuit configured to switch between a quasi-resonant mode and a continuous current mode to generate a pulse signal based on a selected mode and a driver configured to drive the DC/DC converter based on the pulse signal.

Abstract: A current driving circuit is connected to an LED terminal LEDi, and generates an intermittent driving current ILEDi that corresponds to a dimming pulse signal PWMi. An error amplifier generates a feedback voltage VFB that corresponds to the difference between a detection voltage VLEDi and a predetermined reference voltage VREF. A pulse modulator generates a pulse signal having a duty ratio that corresponds to the feedback voltage VFB. A fault detection comparator COMP_OPENi generates a fault detection signal OPEN_DET which is asserted when the detection voltage VLEDi is lower than a predetermined threshold voltage VOPEN—DET. A forced turn-off circuit instructs the current driving circuit to suspend the generation of the driving current ILEDi during a predetermined period after a switching power supply starts to operate. The fault detection circuit detects whether or not the fault detection signal OPEN_DETi has been asserted in a predetermined period.

Abstract: A current driving circuit is connected to an LED terminal LEDi, and generates an intermittent driving current ILEDi that corresponds to a dimming pulse signal PWMi. An error amplifier generates a feedback voltage VFB that corresponds to the difference between a detection voltage VLEDi and a predetermined reference voltage VREF. A pulse modulator generates a pulse signal having a duty ratio that corresponds to the feedback voltage VFB. A fault detection comparator COMP_OPENi generates a fault detection signal OPEN_DET which is asserted when the detection voltage VLEDi is lower than a predetermined threshold voltage VOPEN—DET. A forced turn-off circuit instructs the current driving circuit to suspend the generation of the driving current ILEDi during a predetermined period after a switching power supply starts to operate. The fault detection circuit detects whether or not the fault detection signal OPEN_DETi has been asserted in a predetermined period.

Abstract: A pulse modulator generates a first pulse signal having a duty ratio which is adjusted such that a detection voltage which indicates the electrical state of an LED string to be driven matches a predetermined reference voltage. A first pulse signal is applied to a primary coil of a pulse transformer. A DC/DC converter includes a switching element the ON/OFF operation of which is controlled according to a signal that originates at a secondary coil of the pulse transformer. The DC/DC converter stabilizes an input voltage Vdc, and supplies the input voltage Vdc thus stabilized to the anode of the LED string.

Abstract: A current driving circuit may include a reference voltage input terminal; a resistor connection terminal; an output terminal via which the light emitting element is connected; a reference voltage generating unit; a transistor arranged such that one terminal thereof is connected to the resistor connection terminal; and an operational amplifier including first and second non-inverting input terminals and a single inverting input terminal, and arranged such that the output terminal thereof is connected to a control terminal of the transistor, the internal reference voltage is input to the first non-inverting input terminal, the external reference voltage is input to the second non-inverting input terminal, and the inverting input terminal thereof is connected to the resistor connection terminal. When the external resistor is connected between the resistor connection terminal and a ground terminal, a driving current is output via the output terminal.

Abstract: A current mirror circuit duplicates an input current that flows through an input terminal, and outputs an output current via an output terminal. A first transistor, a second transistor, and a diode are sequentially arranged in series between a power supply terminal to which a fixed voltage is applied and an input terminal. A third transistor and a fourth transistor are sequentially arranged in series between the power supply terminal and the output terminal. The gate of the first transistor and the gate of the third transistor are connected to the drain of the second transistor. The gate of the second transistor and the gate of the fourth transistor are connected to the input terminal.

Abstract: A pulse modulator generates a first pulse signal having a duty ratio which is adjusted such that a detection voltage which indicates the electrical state of an LED string to be driven matches a predetermined reference voltage. A first pulse signal is applied to a primary coil of a pulse transformer. A DC/DC converter includes a switching element the ON/OFF operation of which is controlled according to a signal that originates at a secondary coil of the pulse transformer. The DC/DC converter stabilizes an input voltage Vdc, and supplies the input voltage Vdc thus stabilized to the anode of the LED string.

Abstract: A first transistor is provided on a current path for a phototransistor. A first resistor is provided between one terminal of the first transistor and the power supply line. A second transistor forms a current mirror circuit in cooperation with the first transistor, which amplifies with a predetermined amplification factor the current that flows through the first transistor. A charge capacitor, one terminal of which is connected to a fixed electric potential, is charged with the current thus amplified. A second resistor is provided between one terminal of the second transistor and the power supply line.

Abstract: A power supply circuit includes a standard voltage generator; a regulator to control an output voltage, and to be capable of being switched ON/OFF; a capacitor in parallel between the standard voltage generator and the regulator; a discharging circuit including a first switch and a second switch configured to discharge electrical charges from the capacitor via the second switch while the regulator is in an OFF state; and a starting controller configured to transmit a signal for controlling the first switch and the second switch. The first switch is connected in series between the standard voltage generator and the regulator. The second switch has one end connected to a connection node between the first switch and the regulator, and has another end connected to a ground. When the first switch is in OFF state, the second switch is turned to ON state while the regulator is in OFF state.

Abstract: A first transistor is provided on a current path for a phototransistor. A first resistor is provided between one terminal of the first transistor and the power supply line. A second transistor forms a current mirror circuit in cooperation with the first transistor, which amplifies with a predetermined amplification factor the current that flows through the first transistor. A charge capacitor, one terminal of which is connected to a fixed electric potential, is charged with the current thus amplified. A second resistor is provided between one terminal of the second transistor and the power supply line.

Abstract: A power supply circuit includes a standard voltage generator; a regulator to control an output voltage, and to be capable of being switched ON/OFF; a capacitor in parallel between the standard voltage generator and the regulator; a discharging circuit including a first switch and a second switch configured to discharge electrical charges from the capacitor via the second switch while the regulator is in an OFF state; and a starting controller configured to transmit a signal for controlling the first switch and the second switch. The first switch is connected in series between the standard voltage generator and the regulator. The second switch has one end connected to a connection node between the first switch and the regulator, and has another end connected to a ground. When the first switch is in OFF state, the second switch is turned to ON state while the regulator is in OFF state.

Abstract: A power supply circuit includes a standard voltage generator, a regulator, a capacitor and a discharging circuit. The standard voltage generator is configured to generate a standard voltage. The regulator is configured to control an output voltage by use of a reference voltage based on the standard voltage outputted from the standard voltage generator, and to be capable of being switched ON/OFF. The capacitor is connected in parallel to the regulator between the standard voltage generator and the regulator. The discharging circuit is configured to discharge electrical charges from the capacitor while the regulator is in an OFF state.

Abstract: A power supply circuit includes a standard voltage generator, a regulator, a capacitor and a discharging circuit. The standard voltage generator is configured to generate a standard voltage. The regulator is configured to control an output voltage by use of a reference voltage based on the standard voltage outputted from the standard voltage generator, and to be capable of being switched ON/OFF. The capacitor is connected in parallel to the regulator between the standard voltage generator and the regulator. The discharging circuit is configured to discharge electrical charges from the capacitor while the regulator is in an OFF state.