A load control device coupled between an AC power source and an electrical load may operate in a three-wire mode or a two-wire mode based on whether the load control device is connected to a neutral side of the AC power source. The load control device may further comprise first and second zero-cross detect circuits to be respectively used in the two-wire mode or the three-wire mode, and a neutral wire detect circuit configured to generate a neutral-wire detect signal indicating whether the load control device is connected to the neutral side of the AC power source. A control circuit of the load control device may determine whether the load control device should operate in the two-wire mode or in the three-wire mode in response to the neutral-wire detect signal.

System and method for controlling one or more light emitting diodes. For example, the system includes: a power supply controller configured to receive a cathode voltage from a cathode of a diode, the diode including an anode configured to receive a rectified voltage generated by a rectifying bridge, the power supply controller being further configured to generate a first signal based at least in part on the cathode voltage; and a driver configured to receive the first signal and generate a second signal based at least in part on the first signal, the driver being further configured to output the second signal to a gate terminal of a transistor, the transistor including a source terminal coupled to the driver and a first resistor, the transistor further including a drain terminal coupled to the one or more light emitting diodes and an output capacitor connected to the cathode of the diode.

A load control device for controlling power delivered from an alternating-current power source to an electrical load may comprise a controllably conductive device, a control circuit, and an overcurrent protection circuit that is configured to be disabled when the controllably conductive device is non-conductive. The control circuit may be configured to control the controllably conductive device to be non-conductive at the beginning of each half-cycle of the AC power source and to render the controllably conductive device conductive at a firing time during each half-cycle (e.g., using a forward phase-control dimming technique). The overcurrent protection circuit may be configured to render the controllably conductive device non-conductive in the event of an overcurrent condition in the controllably conductive device. The overcurrent protection circuit may be disabled when the controllably conductive device is non-conductive and enabled after the firing time when the controllably conductive device is rendered conductive during each half-cycle.

An electrical circuit for providing led light bulb drivers with the necessary electrical load for most triac and digital dimmer switches and provide dimming control to mimic incandescent light bulbs is described herein. The electrical circuit includes a non-linear electrical load circuit that is electrically coupled to a rectified alternating current (AC) input power source and providing the necessary load current to initiate and maintain activation of triac and digital dimmer switches. A phase sense and amplifier circuit is also coupled to the rectified AC input power source and it senses the AC input voltage phase, then transmits a control signal to the light emitting diode (LED) driver to adjust the current level of the power being delivered to the LEDs in a manner to mimic the dimming of incandescent light bulbs.

A lighting device, such as a two-wire lighting control device, may include a controllably conductive device and a control circuit. The controllably conductive device may supply an AC line voltage to a load in response to a dive signal such that the controllable conductive device is non-conductive for a first duration of time and conductive for a second duration of time within a half-cycle of the AC line voltage. The control circuit may receive a signal from the controllably conductive device that represents a voltage developed across the controllable conductive device during the first duration of time. The control circuit may generate a sine-wave-shaped signal that complements the voltage developed across the controllably conductive device during the second duration of time. The control circuit may also filter the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time.

A lighting device, such as a two-wire lighting control device, may include a controllably conductive device and a control circuit. The controllably conductive device may supply an AC line voltage to a load in response to a dive signal such that the controllable conductive device is non-conductive for a first duration of time and conductive for a second duration of time within a half-cycle of the AC line voltage. The control circuit may receive a signal from the controllably conductive device that represents a voltage developed across the controllable conductive device during the first duration of time. The control circuit may generate a sine-wave-shaped signal that complements the voltage developed across the controllably conductive device during the second duration of time. The control circuit may also filter the signal from the controllably conductive device during the first duration of time and the sine-wave-shaped signal during the second duration of time.

A light fixture of a light system is configured to be dimmable using a dimming signal that is either a direct-current (DC) dimming signal or an alternating-current (AC) dimming signal. For example, a 0-10 volt DC dimming signal could be used, or a 120 volt AC dimming signal could be used. A dimming controller in the light fixture is configured to receive both a DC and an AC dimming signals and adjust a brightness and/or color of a light based on the dimming signal.

A 2-Wire LED dimming system and method re-purposes existing 120V AC architecture and hardware to carry low voltage PWM gradient DC power to the LED lamps provides a consistent gradation over a 0-100% dimming range. An LED Driver is electrically connected to an AC power source and connect to at least one LED lamp. The AC power source is electrically connected to an AC to DC converter where the AC power is converted to filtered and regulated DC power for the control unit and the power switch. The power switch is electrically connected to the AC to DC converter DC power output. The control unit is electrically connected to the power switch which is turned ON or OFF according to the pulse width modulation PWM signal from the control unit in order to connect or disconnect the DC power from the AC to DC converter.

Timing adjustment for accurate zero-crossing determination includes obtaining time offset(s) representing amounts of time between (i) zero-crossings of an input signal waveform, representative of an input AC waveform, input to a zero-crossing detector circuit and (ii) corresponding transitions of an output signal from an output of the circuit to a microcontroller, and determining times of the zero-crossings of the input AC waveform, which includes determining times of the corresponding transitions as detected by the microcontroller and adjusting the determined times using the time offset(s) to produce the times of the zero-crossings of the input AC waveform. In another aspect, input AC frequency is determined by determining pulse width(s) of pulse(s) of the output signal, and adjusting a half-cycle time corresponding to the pulse width(s) using the time offset(s) to provide a duration of half-cycles of the input AC waveform and inform a frequency of the input AC waveform.

A load control device for controlling an amount of power delivered from an alternating-current (AC) power source to an electrical load may be configured to determine if a miswire condition exists at the load control device. For example, a control circuit of the load control device may be configured to detect a hot-to-dimmed-hot miswire condition in which a dimmed-hot terminal may be coupled to a hot side of the AC power source and a hot terminal may be coupled to the electrical load. In addition, the control circuit may be configured to detect a neutral-to-accessory-terminal miswire condition in which the hot terminal may be coupled to the hot side of the AC power source and an accessory terminal may be coupled to a neutral side of the AC power source. The control circuit may maintain a controllably conductive device non-conductive in response to determining that one of the miswire condition exists.