Provided is a light source apparatus including semiconductor light sources and a current detection resistor connected in series, a power source circuit that allows current to flow thereto, a current detection circuit that detects current flowing to the current detection resistor and outputs a current detection signal, a control circuit that controls the power source circuit such that a voltage of the current detection signal approaches a target value, a bypass circuit connected in parallel to the semiconductor light sources, and including a clamp element having a clamp voltage higher than a maximum voltage during operation of the semiconductor light sources and a bypass resistor connected in series to the clamp element, and allowing current to flow when an open fault occurs in the semiconductor light sources, and detection circuits that respectively detect an open fault in the semiconductor light sources based on an end-to-end voltage of the bypass resistors.

A display may have display layers that form an array of pixels. The array of pixels may be illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs). The multiple LED strings may be controlled by one or more backlight driver integrated circuits (ICs). In a multi-driver IC architecture, an enable signal may be used to set a desired phase delay between the multiple ICs. One or more of the LED strings may exhibit a short fault. Depending on the number of faulty LED strings, the backlight unit can selectively throttle the maximum brightness of the display. The LED strings may receive an output voltage from a DC/DC converter and may be driven using a current driver. The DC/DC converter may be controlled by a headroom feedforward control circuit to ensure sufficient headroom for the current driver while suppressing acoustic noise.

A display may have display layers that form an array of pixels. The array of pixels may be illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs). The multiple LED strings may be controlled by one or more backlight driver integrated circuits (ICs). In a multi-driver IC architecture, an enable signal may be used to set a desired phase delay between the multiple ICs. One or more of the LED strings may exhibit a short fault. Depending on the number of faulty LED strings, the backlight unit can selectively throttle the maximum brightness of the display. The LED strings may receive an output voltage from a DC/DC converter and may be driven using a current driver. The DC/DC converter may be controlled by a headroom feedforward control circuit to ensure sufficient headroom for the current driver while suppressing acoustic noise.

A bridge circuit (22) includes a first light-emitting element group (102, 110) and a second light-emitting element group (103, 120) connected in series; and a pair of comparison resistors (201, 202) connected in series and generating a voltage (Vref) equivalent to a voltage (VLED) at a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120). A transistor (301, 302) is connected to a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120) and a connecting point between the comparison resistors (201, 202), and operates when the first light-emitting element group (102, 110) or the second light-emitting element group (103, 120) is short-circuited.

A bridge circuit (22) includes a first light-emitting element group (102, 110) and a second light-emitting element group (103, 120) connected in series; and a pair of comparison resistors (201, 202) connected in series and generating a voltage (Vref) equivalent to a voltage (VLED) at a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120). A transistor (301, 302) is connected to a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120) and a connecting point between the comparison resistors (201, 202), and operates when the first light-emitting element group (102, 110) or the second light-emitting element group (103, 120) is short-circuited.

A lighting device circuit comprising: a reference LED string, a mirror LED string coupled in parallel to the reference LED string, an operational amplifier based current mirror circuit coupled to the reference LED string and to the mirror LED string, and a window comparator circuit that includes only a single input that is coupled to a fault sense node. The fault sense node directly connects to a drain node of a transistor within the operational amplifier based current mirror and a LED within the mirror LED string.

A lighting device circuit comprising: a reference LED string, a mirror LED string coupled in parallel to the reference LED string, an operational amplifier based current mirror circuit coupled to the reference LED string and to the mirror LED string, and a window comparator circuit that includes only a single input that is coupled to a fault sense node. The fault sense node directly connects to a drain node of a transistor within the operational amplifier based current mirror and a LED within the mirror LED string.

Devices, methods, and systems for alternating current circuits for airfield lighting are described herein. One system includes a circuit comprising an isolation transformer, a protection hardware circuit coupled to the isolation transformer, wherein the protection hardware prevents a voltage between an electrical contact of the circuit and a ground contact from meeting or exceeding a threshold voltage, and a load coupled to the protection hardware circuit to receive electrical energy from the isolation transformer.

Devices, methods, and systems for alternating current circuits for airfield lighting are described herein. One system includes a circuit comprising an isolation transformer, a protection hardware circuit coupled to the isolation transformer, wherein the protection hardware prevents a voltage between an electrical contact of the circuit and a ground contact from meeting or exceeding a threshold voltage, and a load coupled to the protection hardware circuit to receive electrical energy from the isolation transformer.

Disclosed is a backlight test circuit including N circuit blocks. Each circuit block includes M mini-LED circuits, and each mini-LED circuit includes L mini-LEDs and a switching circuit. The L mini-LEDs are connected in parallel or in serial as a mini-LED set. The switching circuit controls the turning on and the turning off of the mini-LED set according to a control signal. N, M and L are positive integers. During a backlight test, in each circuit block, at least one of the mini-LED sets is turned on. By using this backlight test circuit, the abnormal mini-LED circuit can be found. Thus, a producer can only execute a rework process for the abnormal mini-LED circuit without extra cost.