Abstract: The present invention discloses a separately excited inverter circuit whose switching circuit having a plurality of switching elements and which is capable of minimizing the damage of other switching elements even if any of the plurality of switching elements is short circuited and damaged.

Abstract: The separately-excited inverter circuit for performing the protecting operation upon the rise in the output voltage caused by the contact failure includes a switching circuit 26b which applies the AC to a primary coil of a pressure-rising transformer 26e, a control circuit C1 which starts a switch control of the switching circuit 26b upon an input of a command signal to set an oscillation state ON from a transmission line for the command signal to command to set the oscillation state ON and OFF, an output voltage monitor circuit 51 which allows a comparator 51a to compare an output voltage of the separately-excited inverter circuit with a predetermined voltage, and to output a predetermined reference voltage when the output voltage is higher than the predetermined voltage, and a thyristor circuit 52 which is turned ON to set the transmission line of the command signal into an oscillation OFF state upon the input of the reference voltage to the gate to stop a switch control of the control circuit C1.

Abstract: The present invention discloses enabling readily determining which circuit, among a plurality of circuits including an optical source lighting circuit and a power supply circuit, has a failure and repairing the circuits easily in a short period.

Abstract: A cold-cathode tube driving circuit for driving a plurality of substantially-C-shaped cold-cathode tubes, includes: a first transformer 2 having primary windings which induce voltages, and secondary windings which apply voltages of opposite polarities (?V, +V) to respective ends of the respective substantially-C-shaped cold-cathode tubes; and a second transformer 3 having third and fourth primary windings which respectively induce voltages, and third and fourth secondary windings which apply voltages of opposite polarities (?V, +V) to respective ends of the respective substantially-C-shaped cold-cathode tubes. In the cold-cathode tube driving circuit, the first and second transformers 2, 3 apply an in-phase voltage to adjacent ends of the substantially-C-shaped cold-cathode tubes.

Abstract: The present invention discloses enabling readily determining which circuit, among a plurality of circuits including an optical source lighting circuit and a power supply circuit, has a failure and repairing the circuits easily in a short period.

Abstract: The present invention discloses a separately excited inverter circuit whose switching circuit having a plurality of switching elements and which is capable of minimizing the damage of other switching elements even if any of the plurality of switching elements is short circuited and damaged.

Abstract: The separately-excited inverter circuit for performing the protecting operation upon the rise in the output voltage caused by the contact failure includes a switching circuit 26b which applies the AC to a primary coil of a pressure-rising transformer 26e, a control circuit C1 which starts a switch control of the switching circuit 26b upon an input of a command signal to set an oscillation state ON from a transmission line for the command signal to command to set the oscillation state ON and OFF, an output voltage monitor circuit 51 which allows a comparator 51a to compare an output voltage of the separately-excited inverter circuit with a predetermined voltage, and to output a predetermined reference voltage when the output voltage is higher than the predetermined voltage, and a thyristor circuit 52 which is turned ON to set the transmission line of the command signal into an oscillation OFF state upon the input of the reference voltage to the gate to stop a switch control of the control circuit C1.

Abstract: This backlight light source drive device includes a plurality of backlight light source drive circuits which drive a plurality of respective backlight light sources, and a control circuit which turns those drive circuits ON and OFF. Each of the drive circuits includes a protection signal output circuit which, when its corresponding tube electrical current decreases, outputs to the control unit a protection signal for stopping the operation of all of the drive circuits. This protection signal output circuit includes an LED illumination circuit which, when the tube electrical current thus decreases, illuminates an LED to indicate the anomalous state, and an LED power supply circuit which always supplies power to the LED illumination circuit. And the control circuit stops the operation of all of the plurality of backlight light source drive circuits, when it receives a protection signal from any one or more of the protection signal output circuits.

Abstract: This backlight light source drive device includes a plurality of backlight light source drive circuits which drive a plurality of respective backlight light sources, and a control circuit which turns those drive circuits ON and OFF. Each of the drive circuits includes a protection signal output circuit which, when its corresponding tube electrical current decreases, outputs to the control unit a protection signal for stopping the operation of all of the drive circuits. This protection signal output circuit includes an LED illumination circuit which, when the tube electrical current thus decreases, illuminates an LED to indicate the anomalous state, and an LED power supply circuit which always supplies power to the LED illumination circuit. And the control circuit stops the operation of all of the plurality of backlight light source drive circuits, when it receives a protection signal from any one or more of the protection signal output circuits.

Abstract: A secondary winding W2 of a step-up transformer of a self-excited inverter 2 is grounded at the midpoint thereof. High-frequency voltages differing in polarity from each other are outputted from both terminals OT1 and OT2 of the secondary winding W2. Two U-shaped cold-cathode tubes L1 and L2 series-connected to each other are provided directly below a liquid crystal panel. One of terminals of the secondary winding W2 is connected to the terminal OT1 through the ballast capacitor C1. The other terminal thereof is connected to the terminal OT2 of the ballast capacitor C2. The connecting point P between the two U-shaped cold-cathode tubes L1 and L2 is ungrounded. Thus, electric currents flowing through the cold-cathode tubes are equal in value to each other.

Abstract: A cold-cathode tube driving circuit for driving a plurality of substantially-C-shaped cold-cathode tubes, includes: a first transformer 2 having primary windings which induce voltages, and secondary windings which apply voltages of opposite polarities (?V, +V) to respective ends of the respective substantially-C-shaped cold-cathode tubes; and a second transformer 3 having third and fourth primary windings which respectively induce voltages, and third and fourth secondary windings which apply voltages of opposite polarities (?V, +V) to respective ends of the respective substantially-C-shaped cold-cathode tubes. In the cold-cathode tube driving circuit, the first and second transformers 2, 3 apply an in-phase voltage to adjacent ends of the substantially-C-shaped cold-cathode tubes.

Abstract: A secondary winding W2 of a step-up transformer of a self-excited inverter 2 is grounded at the midpoint thereof. High-frequency voltages differing in polarity from each other are outputted from both terminals OT1 and OT2 of the secondary winding W2. Two U-shaped cold-cathode tubes L1 and L2 series-connected to each other are provided directly below a liquid crystal panel. One of terminals of the secondary winding W2 is connected to the terminal OT1 through the ballast capacitor C1. The other terminal thereof is connected to the terminal OT2 of the ballast capacitor C2. The connecting point P between the two U-shaped cold-cathode tubes L1 and L2 is ungrounded. Thus, electric currents flowing through the cold-cathode tubes are equal in value to each other.