A load control device for controlling power delivered from an AC power source to an electrical load may have a closed-loop gate drive circuit for controlling a semiconductor switch of a controllably conductive device. The controllably conductive device may be coupled in series between the source and the load. The gate drive circuit may generate a target signal in response to a control circuit. The gate drive circuit may shape the target signal over a period of time and may increase the target signal to a predetermined level after the period of time. The gate drive circuit may receive a feedback signal that indicates a magnitude of a load current conducted through the semiconductor switch. The gate drive circuit may generate a gate control signal in response to the target signal and the feedback signal, and render the semiconductor switch conductive and non-conductive in response to the gate control signal.

A load control device for controlling power delivered from an AC power source to an electrical load may have a closed-loop gate drive circuit for controlling a semiconductor switch of a controllably conductive device. The controllably conductive device may be coupled in series between the source and the load. The gate drive circuit may generate a target signal in response to a control circuit. The gate drive circuit may shape the target signal over a period of time and may increase the target signal to a predetermined level after the period of time. The gate drive circuit may receive a feedback signal that indicates a magnitude of a load current conducted through the semiconductor switch. The gate drive circuit may generate a gate control signal in response to the target signal and the feedback signal, and render the semiconductor switch conductive and non-conductive in response to the gate control signal.

In response to a measured value of temperature of a stator by a thermometer exceeding a first temperature threshold, an overheat signal may be output to a rotor of a rotary connector via a communication device. In response to the measured value of the temperature exceeding a second temperature threshold higher than the first temperature threshold, power supply to a transmission coil that transmits power to a receiving coil of the rotor in a non-contact manner is stopped. In response to the overheat signal being received or a measured value of temperature of the rotor by a thermometer exceeding a third temperature threshold, a limit signal for limiting current flowing through a load circuit is output. In response to the measured value of the temperature by the thermometer exceeding a fourth temperature threshold higher than the third temperature threshold, output of power received from the stator is stopped.

A method for reducing current ripple at an output of a power supply includes sensing an alternating current (AC) input voltage waveform; determining a correction factor for a switching frequency of the power supply based on the sensed AC input voltage; and applying the correction factor to the switching frequency of the power supply to modify the power supply switching frequency. A modification of the switching frequency synchronizes the switching frequency of the power supply to the AC input voltage waveform.

A method for reducing current ripple at an output of a power supply includes sensing an alternating current (AC) input voltage waveform; determining a correction factor for a switching frequency of the power supply based on the sensed AC input voltage; and applying the correction factor to the switching frequency of the power supply to modify the power supply switching frequency. A modification of the switching frequency synchronizes the switching frequency of the power supply to the AC input voltage waveform.

System and method for current control. As an example, the system for current control includes: a transistor including a drain terminal, a gate terminal, and a source terminal, the drain terminal being coupled to one or more light emitting diodes; a resistor coupled to the source terminal of the transistor and configured to generate a resistor voltage related to a current flowing through the one or more emitting diodes; a voltage detector configured to receiver a first input voltage related to a second input voltage received by the one or more light emitting diodes; and a voltage controller coupled to the voltage detector, the resistor, and the gate terminal of the transistor; wherein the voltage detector is further configured to: detect the first input voltage; and generate a control signal based at least in part on the first input voltage.

System and method for current control. As an example, the system for current control includes: a transistor including a drain terminal, a gate terminal, and a source terminal, the drain terminal being coupled to one or more light emitting diodes; a resistor coupled to the source terminal of the transistor and configured to generate a resistor voltage related to a current flowing through the one or more emitting diodes; a voltage detector configured to receiver a first input voltage related to a second input voltage received by the one or more light emitting diodes; and a voltage controller coupled to the voltage detector, the resistor, and the gate terminal of the transistor; wherein the voltage detector is further configured to: detect the first input voltage; and generate a control signal based at least in part on the first input voltage.

A method for operating clocked and regulated electronic power converters may be contained in operating devices for light-emitting diodes. An associated regulating circuit may include at least one regulating amplifier having at least two regulating inputs, from the output of which a negative feedback network runs to one of its regulating inputs, a first input for the signal for a target value of the average of the output power to be regulated, and a second input which forwards a signal for the target value of a waveform or of a pulse pattern for the output power to be regulated to one of the regulating inputs via a DC current-blocking high-pass filter.

A method for operating clocked and regulated electronic power converters may be contained in operating devices for light-emitting diodes. An associated regulating circuit may include at least one regulating amplifier having at least two regulating inputs, from the output of which a negative feedback network runs to one of its regulating inputs, a first input for the signal for a target value of the average of the output power to be regulated, and a second input which forwards a signal for the target value of a waveform or of a pulse pattern for the output power to be regulated to one of the regulating inputs via a DC current-blocking high-pass filter.

A two-wire load control device (such as, a dimmer switch) for controlling the amount of power delivered from an AC power source to an electrical load (such as, a high-efficiency lighting load) includes a thyristor coupled between the source and the load, a gate coupling circuit coupled between a first main load terminal and the gate of the thyristor, and a control circuit coupled to a control input of the gate coupling circuit. The control circuit generates a drive voltage for causing the gate coupling circuit to conduct a gate current to thus render the thyristor conductive at a firing time during a half cycle of the AC power source, and to allow the gate coupling circuit to conduct the gate current at any time from the firing time through approximately the remainder of the half cycle, where the gate coupling circuit conducts approximately no net average current to render and maintain the thyristor conductive.