Abstract: A device controls current drawn by a solid state lighting (SSL) fixture, including a power converter and an SSL load. The device includes a rapid start/bleeder circuit having a selectable low impedance path, configured to be temporarily activated to form a low impedance connection between a voltage rectifier and the power converter providing power to the SSL load. The low impedance path is temporarily activated during a start-up period to charge the power converter and during times other than the start-up period based on detected improper operation of the SSL fixture.

Abstract: An exemplary light emitting diode (LED) lamp includes a lamp body, an LED module and a switching member. The LED module is mounted on the lamp body and includes a plurality of first LED components emitting a first light with a first color temperature and a plurality of second LED components emitting a second light with a second color temperature. The switching member is mounted around the lamp body and can be operated to cause the LED lamp to work in different modes. In the different modes, different numbers of the first and second LED components are driven to emit light with different color temperatures.

Abstract: The present invention relates to a protection circuit for an alternating current light emitting diode which mainly comprises light emitting diodes placed in series and parallel with loads in a light emitting diode lamp device. When one of the light emitting diodes has been damaged, the current flows through the load in parallel with the light emitting diode and flows to the next light emitting diode. Only the damaged light emitting diode is off to keep from causing an open circuit in the overall circuitry and to prevent the overall lamp device from turning off and not emitting light. In addition to the device being easier to use, finding the damaged light emitting diode for replacement is faster, easier and more convenient when repairing the damaged light emitting diode, thereby greatly enhancing the usefulness and practicability of the protection circuit for an alternating current light emitting diode.

Abstract: An LED driving circuit, adapted to drive an LED module, is disclosed. The LED driving circuit comprises a converting circuit, a converting controller, and a short-circuit protection circuit. The converting circuit, having a capacitor coupled to the LED module, is coupled to an input power source to proceed converting operation to supply an output current for driving the LED module. The converting controller controls the converting circuit to provide a stable current flowing through the LED module. The short-circuit protection circuit is coupled to the LED module in series and cuts the current flowing through the LED module off when detecting that the current higher than a current protection value.

Abstract: An LED drive circuit is an LED dive circuit that receives an alternating voltage to drive an LED, and includes a current remove portion that removes a current from a current supply line that supplies an LED drive current to the LED. If an input current to the LED drive circuit is an unnecessary current, the LED does not light because of current removal by the current remove portion. If the input current to the LED drive circuit turns into the LED drive current from the unnecessary current, the current remove portion decreases the amount of current removed.

Abstract: A terminal and a brightness control method thereof are provided. The terminal includes an illumination sensor for measuring peripheral illumination of the terminal, a proximity sensor for detecting an object within a preset distance, a memory for storing a brightness table including data for controlling brightness of a display unit corresponding to the measured illumination, the display unit for displaying and for changing a brightness of the display unit under control of a controller, and the controller for controlling the display unit to change the brightness according to the measured illumination and the brightness table when the object is not detected. The terminal and brightness control method thereof provide a more suitable screen to a user.

Abstract: An LED driving apparatus that converts input power into direct-current power and feeds the power to an LED unit, includes: a first transistor that turns current flowing to the LED unit between on-and-off; an LED current detector that detects the current flowing to the LED unit; a controller that outputs a control signal controlling power to be fed to the LED unit, based on an error between a detected voltage obtained by the LED current detector and a burst dimming signal to dim the LED unit; and a second transistor that controls the power to be fed to the LED unit, based on the control signal output from the controller, wherein the first transistor is turned on; based on the burst dimming signal, and wherein the first transistor is turned off, based on a delay signal that is delayed at a predetermined time from the burst dimming signal.

Abstract: A driving device of light emitting diode (LED) and a lighting apparatus using the same are provided. The diving device is adapted for receiving an AC power adjusted by a dimmer and a transformer unit, and includes a dimming match circuit, a voltage conversion unit, and a driver IC. The dimming match circuit receives the AC power and equalize the energy of a positive and a negative half cycles of the AC power, so as to produce a symmetrical AC power. The voltage conversion unit is coupled to the dimming match circuit, and receives and converts the symmetrical AC power into a stable DC power. The driver IC is coupled to the voltage conversion unit, and receives the stable DC power to drive and adjust the light intensity of an LED unit, and thus flicking of the light source of the LED unit can be avoided during dimming.

Abstract: A converter for feeding a load via an inductor with a current having a controlled intensity between a maximum level and a minimum level may include: a switch switchable on and off to permit or prevent, respectively, feeding of current towards said inductor; first and second current sensors sensitive to the current flowing through said switch when said switch is on or off, respectively; comparator circuitry to identify if the current intensity detected by said first current sensor and said second current sensor reaches said maximum level and said minimum level, respectively, by generating respective logical signals; and drive circuitry for said switch sensitive to said logical signals and configured to turn off said switch when the current intensity detected by said first sensor reaches said maximum level and turning on said switch when the current intensity detected by said second current sensor reaches said minimum level.

Abstract: The present invention discloses an LED lighting circuit that generates a power supply voltage required to light an LED by boosting a power supply voltage. The LED lighting circuit includes a power supply circuit that is formed integrally with the LED lighting circuit and supplies the power supply voltage. The LED lighting circuit further includes a feedback circuit that detects an LED current flowing to the LED and feeds the LED current back to the power supply circuit. The power supply circuit controls the power supply voltage supplied to the LED lighting circuit so that the LED current converges on a target value.

Abstract: Described is an (organic) light-emitting diode ((O)LED) wherein the light-emitting layer comprises a blend of an electroluminescent semiconducting material with a ferro-electric material. Either of the electrodes forms a modulatable injection barrier with the ferro-electric material, the modulation requiring a voltage Vm serving to polarize or repolarize the ferro-electric material. With Vm being larger than the voltage Ve required for light emission, the (O)LED can be turned “on” or “off” by applying a pulse voltage to (re)polarize the ferro-electric material.

Abstract: The present invention relates to a LED driver that minimizes the driver electronic pin count and integrates the short circuit protection feature. An NPN bipolar transistor is employed in a boost converter configuration to drive a LED string in the backlight display applications. The bipolar transistor is integrated with the driver electronics by two pins. Drive current is injected from the NPN transistor to the LED string to minimizing high voltage connection of each LED string to one.

Abstract: A light emitting diode lamp includes: two first pins which are provided at one side thereof; two second pins which are provided at the other side thereof; a light emitting diode (LED) module which is disposed between the two first pins and the two second pins; a circuit connecting at least two of the two first pins and the two second pins to the LED module; and a protection circuit including a fuse which is disposed at a front end of the LED module to protect the LED module in case of generation of high voltage. The circuit is configured to have a direction from a front end of the LED module to the other end thereof as a forward direction.

Abstract: A portable lighting device, such as a flashlight, with a mechanical power switch and multiple operating modes is provided. The mechanical power switch is disposed in series with the controller for the lighting device and acts as the user interface to the controller to change modes of operation. Because the mechanical power switch is in series with the controller, the portable lighting device does not consume battery power when the mechanical switch is open. A state machine coupled to the controller is polled by the controller each time it is powered up to determine the operational mode of the lighting device.

Abstract: A driving circuit is provided, which is configured to supply a driving voltage and a driving current to an LED string. A first detection resistor is arranged on a path of the LED string. A voltage source outputs a control voltage having a level that corresponds to the target luminance level of the LED string, and a first threshold voltage that is proportional to the control voltage. A controller generates a gate pulse signal having a duty ratio that is adjusted such that the voltage drop across the first detection resistor matches the control voltage. A first driver drives a switching transistor of a DC/DC converter according to the gate pulse signal. When the voltage drop across the first detection resistor exceeds the first threshold voltage, a first comparator stops the switching operation of the switching transistor.

Abstract: A current limiting circuit includes a power input terminal that is connected to an output terminal of a direct current power source to which an output capacitor is connected in parallel; a power output terminal to which an LED is connected; and a current limiting unit that supplies to the LED a load current to which an upper current value is set, supplies to the LED a load current lower than the upper current value at a normal condition, and supplies to the LED a load current higher than the load current of the normal condition and equal to or lower than the upper current value at an abnormal condition.

Abstract: Various apparatuses, methods and systems for dimmably supplying power are disclosed herein. In some embodiments, an apparatus includes an input power terminal, a switch connected to the input power terminal, an inductor connected in series with the switch, a load terminal connected in series with the switch and with the inductor, and a variable pulse generator operable to control the switch to regulate a current to the load terminal based at least in part on a feedback signal from a node in series with the load terminal and at least in part on a voltage reference signal.

Abstract: A full-wave electronic inverter for supplying one or more low-pressure gas discharge or fluorescent lamps, which inverter is protected by a circuit containing a small tubular core saturable transformer which has the inductive reactance necessary and sufficient for deflecting, from the circuit thereof, the asymmetrical waves which are at a frequency higher than the frequencies stipulated by design and are produced by said lamps at the end of the service life thereof, preventing the inverter from burning out, as occurs with inverters of that type which do not have said circuit which also enables the situation in which, although the inverter is still being connected to the supply circuit, the inverter does not consume energy, even though said lamp or lamps is/are connected to the circuit thereof, until said lamps are replaced with new lamps. This inverter has a starting button which is used to deenergize the inverter each time the latter operates for the first time with new lamps.

Abstract: An LED lamp protecting circuit includes an LED lamp, a constant current source and a buffer circuit. The constant current source includes positive and negative input terminals, positive and negative output terminals and a switch. The buffer circuit is connected between the negative output terminal and the LED lamp. The buffer circuit includes a charging capacitor, a first NPN transistor and a second PNP transistor. An emitting electrode of the second transistor is connected to the LED lamp. A collecting electrode of the second transistor is connected to the negative output terminal. The charging capacitor is connected between the emitting electrode of the second transistor and a ground. A collecting electrode and an emitting electrode of the first transistor are respectively electrically connected to a base electrode of the second transistor and the ground.

Abstract: A projection-type display device according to an embodiment of the invention modulates light emitted from a solid-state light source array and projects the modulated light on a screen. The projection-type display device includes a power source device that generates power used for driving the solid-state light source array using power supplied from a power source, an instant interruption detecting circuit that detects an instant interruption of the power source, and a control device that, in a case where the instant interruption of the power source is detected by the instant interruption detecting circuit, performs control of extinguishing the solid-state light source array during at least a part of an instant interruption period until recovery after the detection of the instant interruption of the power source.

Abstract: A dimmable compact fluorescent lighting device includes a safety protection circuit, an electro-magnetic compatibility (EMC) circuit, a rectification and filter circuit, a power factor correction circuit, a trigger circuit, a switching and anti-saturation circuit, a resonant circuit, and a filament pre-heating protection circuit. Alternate current from an electric main is chopped by a thyristor to form a non-sinusoidal voltage that, after passing through the EMC circuit, is subjected to rectification and filtering and fed through the power factor correction circuit for correction of the non-sinusoidal voltage and suppress of high order resonant waves, so as to supply a stable DC working voltage to a subsequent stage. Two transistors are used to alternate conduct so as to generate oscillation, which induces a high frequency sinusoidal AC voltage supplied through an electronic ballast to drive a lighting tube to emit light.

Abstract: An inverter circuit drives a light source module. An input signal circuit provides electrical signals. A power stage circuit converts the electrical signals to square-wave signals. A transformer circuit converts the square-wave signals to alternating current (AC) signals capable of powering the light source module. A voltage detection circuit detects voltage applied on the light source module so as to output a detected voltage signal. A feedback circuit feeds current flowing through the light source module so as to output a current feedback signal. A protection circuit is connected to the voltage detection circuit and the feedback circuit, for outputting a latch signal according to the detected voltage signal or the current feedback signal. A pulse-width modulation control circuit outputs a switch signal to the power stage circuit according to the latch signal. The input signal circuit also provides the electrical signals to the protection circuit.

Abstract: A LED lamp brightness adjusting circuit has a regulating circuit, multiple rectification diodes and filtering capacitors. Each filtering capacitor is connectable to a LED module in parallel. The LED lamp brightness adjusting circuit is connected to an output terminal of a light regulator. Based on the control of light regulator, the regulating circuit produces a regulated AC input voltage. The positive and negative half cycles of the regulated AC input voltage are further rectified and filtered to drive different corresponding LED modules. Therefore, the amplitude of the drive voltages for the LED modules are controllable to adjust the brightness of the emitted light.

Abstract: A semiconductor apparatus includes an input terminal to which an input voltage is applied; an output terminal at which an output voltage is obtained; a power supply circuit unit configured to generate the output voltage from the input voltage, the output voltage having a value corresponding to a duty cycle of a voltage setting signal that is externally applied to the semiconductor apparatus; and a determination circuit unit determining whether the voltage setting signal has a predetermined signal level for the duration of a first predetermined time or longer. The determination circuit unit activates the power supply circuit unit when the voltage setting signal does not have the predetermined signal level for the duration of the first predetermined time or longer. The power supply circuit unit is deactivated when the voltage setting signal has the predetermined signal level for the duration of the first predetermined time or longer.

Abstract: The application relates to a circuit for operating a light-emitting means, having a half-bridge or full-bridge circuit for providing a supply voltage for the at least one light-emitting means, and a control circuit for the closed-loop control of the operation of the light-emitting means and/or fault identification. A measurement signal which represents the current through the bridge circuit and/or a measurement signal which represents the lamp current and a measurement signal which represents the voltage across the at least one light-emitting means are supplied to the control circuit at the same input.

Abstract: A lighting installation comprises (a) a lighting load, powered by an AC power supply, said AC power supply having a cycle having a period; and (b) a dimmer comprising a first semiconductor switch operable by the action of a switching voltage to switch a current to the load on and off. In normal operation, the switch may repeatedly switch the current on and switch the current off. The average power delivered to the load is altered by altering the switching on or the switching off so that the current is on for a longer or shorter portion of the period. A method of protecting the dimmer comprises monitoring the current and, when the current exceeds a threshold value, altering the switching voltage to cause the first semiconductor switch to switch off the current.

Abstract: A light-emitting diode (LED) protection structure includes an LED portion and a protection portion. The protection portion includes a fuse and a Zener diode connected in series. The protection portion is electrically connected to the LED portion in parallel but opposite in direction. As such, the LED protection structure can effectively protect the LEDs and the Zener diode from being damaged to thereby reduce costs.

Abstract: A shut-down circuit configured for use with an electronic ballast coupled to a lamp in a control path includes a device for sensing the electrical energy associated with the control path, and a sensing circuit for shutting down the ballast in the event that the energy does not conform to a predetermined condition. The sensed energy may be current indicative of lamp installation or short circuit, or voltage indicative of arcing or open circuit. The device for sensing the electrical energy associated with the control path may be an isolation transformer, or alternative devices such as optical isolators may be employed. The circuitry may further include electronic componentry to disable the sensing circuit during initial energization of the lamp.

Abstract: Described are circuits and methods for powering one or more loads from an ac source using a capacitive ballast. The circuit comprises a capacitive voltage divider that limits current to the loads, includes a first capacitor that operates as a ballast creating a leading current draw relative to the voltage from an alternating current source, and includes a second capacitor that protects the set of light emitting diodes by suppressing line transients. The circuit is able to compensate for the predominately inductive power factor of typical residential and building loads (e.g., appliances, etc.), because of its leading current draw. As a consequence the circuit can utilize at least part of the inductive current load that would otherwise be reflected back to the source or wasted.

Abstract: Disclosed is a high current radiation system. The system includes a high current radiation source to generate radiation and an analog circuit to generate, based, at least in part, on an input signal representative of the present current level delivered to the high current radiation source and a user-controlled input representative of a desired current level, an output signal to control a current level to be delivered to the high current radiation source. The system further includes a current driver to control the current delivered to the high current radiation source based, at least in part, on the output signal of the analog circuit.

Abstract: An LED lamp includes a rectifier, an integrated circuit and a string of series-connected LEDs. The lamp receives an incoming AC signal such that a rectified version of the signal is present across the LED string. The integrated circuit includes a plurality of power switches. Each power switch is coupled so that it can separately and selectably short out a corresponding one of several groups of LEDs in the string. As the voltage across the string increases the integrated circuit controls the power switches such that the number of LEDs through which current flows increases, whereas as the voltage across the string decreases the integrated circuit controls the power switches such that the number of LEDs through which current flows decreases. LED string current flow is controlled and regulated to provide superior efficiency, reliability, anti-flicker, regulation against line voltage variations, power factor correction, and lamp over-voltage, over-current, and over-temperature protection.

Abstract: A shut-down circuit configured for use with an electronic ballast coupled to a lamp in a control path includes a device for sensing the electrical energy associated with the control path, and a sensing circuit for shutting down the ballast in the event that the energy does not conform to a predetermined condition. The sensed energy may be current indicative of lamp installation or short circuit, or voltage indicative of arcing or open circuit. The device for sensing the electrical energy associated with the control path may be an isolation transformer, or alternative devices such as optical isolators may be employed. The circuitry may further include electronic componentry to disable the sensing circuit during initial energization of the lamp.

Abstract: A brightness adjusting circuit for an LED lamp has a compensating circuit, a bridge rectifier, a filter capacitor and a current limiting circuit. The compensating circuit is connected between an output terminal of a light regulator and an AC wire to output a regulated input voltage. The bridge rectifier is connected to the compensating circuit and converts the regulated input voltage to a DC voltage. The filter capacitor is connected to the bridge rectifier. The current limiting resistor is connected between the bridge rectifier and the LED lamp to limit a current flowing through the LED lamp. When the light regulator is adjusted, the regulated input voltage across is changed accordingly. Therefore, the DC voltage produced by the bridge rectifier is varied to regulate the brightness of the LED lamp.

Abstract: A light emitting apparatus comprises a light emitting element and a switching converter comprising a conversion circuit for converting an operating electric signal to generate the driving electric signal, a feedback circuit having a light detecting element for detecting a luminous intensity of the light emitting element and generating a feedback signal, and a control circuit for receiving the feedback signal, comparing the received feedback signal with a reference electric signal, and controlling the conversion circuit based on comparison results to adjust the driving electric signal. Alternatively, the light detecting element detects ambient light and the control circuit controls the conversion circuit based on comparison results to stop or enable outputting of the driving electric signal.

Abstract: An illumination system has a lighting module, a microcontroller electrically connected to the lighting module and arranged to control the lighting module, and a transistor electrically connected to the lighting module and the microcontroller arranged to allow the microcontroller to monitor a voltage of one of either the transistor or lighting module. A method of controlling a lighting module including powering on the lighting module, providing a current to the lighting module, wherein the current is determined by a global intensity setting for the lighting module, monitoring a voltage provided to the lighting module, and shutting the lighting module down if the voltage reaches a pre-determined level.

Abstract: A lamp control system includes a first driving circuit, an assistance DC power source having an output voltage lower than a working voltage of a lamp and a second driving circuit. The first driving circuit electrically connects the lamp with a utility power source to convert an AC power a DC power and supply the DC power to the lamp. The second driving circuit electrically connects the assistance DC power source with the lamp. The second driving circuit includes a boost circuit, which is connected to the assistance DC power source to promote the output voltage of the assistance DC power source to the working voltage of the lamp and then supply electrical power with the promoted voltage to the lamp when the utility power source is off.

Abstract: A driving circuit suitable for receiving an alternating current (AC) power to drive a light emitting diode (LED) is provided. The driving circuit includes a rectifier circuit, a process unit, an electric energy conversion circuit, and a detection unit. The rectifier circuit rectifies the AC power to output a first operating voltage. The processing unit is coupled to the rectifier circuit and outputs a second operating voltage and a pulse width modulation (PWM) signal. The electric energy conversion circuit is coupled between the rectifier circuit, the processing unit and the LED and drives the LED according to the PWM signal. The detection unit is coupled to the rectifier circuit and the processing unit and detects the first operating voltage. When the first operating voltage is lower than or equal to a threshold voltage, the detection unit outputs a disable signal to the processing unit to disable the PWM signal.

Abstract: A shut-down circuit configured for use with an electronic ballast coupled to a lamp in a control path includes a device for sensing the electrical energy associated with the control path, and a sensing circuit for shutting down the ballast in the event that the energy does not conform to a predetermined condition. The sensed energy may be current indicative of lamp installation or short circuit, or voltage indicative of arcing or open circuit. The device for sensing the electrical energy associated with the control path may be an isolation transformer, or alternative devices such as optical isolators may be employed. The circuitry may further include electronic componentry to disable the sensing circuit during initial energization of the lamp.

Abstract: High-pressure discharge lamps can only be restarted in the hot state at a very high starting voltage. In order to avoid hotstarting, a method for operating high-pressure discharge lamps without hotstarting comprises two high-pressure discharge lamps (12a, 12b) being provided in one luminaire. The two high-pressure discharge lamps are driven as follows: When the luminaire is switched off, the first lamp is switched off, and the second lamp is set to be in a standby state for the period of time for the recovery of the first lamp or remains in such a state, in which it is not switched off. When the luminaire is switched on again during this period of time, the second lamp can assume the operating state again immediately without being started. If the luminaire is not switched on again, the second lamp is likewise switched off once the period of time has elapsed.

Abstract: A light source unit includes a light source which generates light and a light source driver which drives the light source and includes a driving integrated circuit and a resistance device. The driving integrated circuit includes an input terminal which receives an input voltage from an external source, converts the input voltage into a driving voltage which drives the light source. The resistance device is connected between an input terminal of the driving integrated circuit and a ground terminal and supplies the input voltage to the ground terminal by changing a resistance value thereof according to the input voltage when a level of the input voltage exceeds a preset level.

Abstract: A circuit capable of receiving, in series with at least one light-emitting diode, a rectified A.C. voltage, comprising: a first gate turn-off thyristor connected to first and second terminals of the circuit; and a control circuit for turning off the first thyristor when the voltage between the first and second terminals exceeds a threshold.

Abstract: A circuit arrangement for operating a low-pressure discharge lamp may include a voltage source with two terminals; switches; and a series resonant circuit; a controller configured to control the switches such that an AC voltage is applied to the resonant circuit; a PTC thermistor coupled on one side to a circuit point of the resonant circuit and on the other side, at least one of via a diode, to the first terminal of the voltage source and, via a diode to the second terminal of the voltage source; a resistive element connected in series with a diode in the circuit between a terminal of the voltage source and the PTC thermistor; and an evaluation device configured to tap off the voltage drop across the resistive element and being coupled to the controller in order to deactivate the controller.

Abstract: A device that enables “smart” dimmers comprising electronic circuits beyond those found in traditional dimmers to be installed in existing houses with no need for any new electrical wires. In particular, for smart dimmers comprising PLC (power line communication) modems, the device overcomes the large attenuation imposed on power-line communication (PLC) transmissions, introduced by a load electrically connected in series with the smart dimmer, and eliminates the large noise and ringing otherwise introduced by the switching device, found in dimmers. The device enables a fair amount of sustained current to feed a smart dimmer's internal circuitry, and low PLC signal attenuation, in conjunction with undisturbed dimming functionality, with no need for any new wires.

Abstract: A light fixture includes a CCFL and a driving circuit. The driving circuit includes a first voltage converter and a high-voltage inverter. The first voltage converter provides a DC voltage signal according to a power signal. The high-voltage inverter comprises a second voltage converter and a first transformer. The second voltage converter converts the DC voltage signal into an AC voltage signal. The first transformer is corresponding to the first CCFL and includes a first primary winding circuit and a first secondary winding circuit. The first primary winding circuit has a first input voltage signal in response to the AC voltage signal. The first secondary winding circuit is coupled with the first input voltage signal to generate a first output voltage signal for driving the first CCFL. The first primary and secondary winding circuits belong to a primary-side circuit and receive the same ground voltage signal.

Abstract: It is objected to provide a light control apparatus and a lighting appliance using the same which enable to increase luminous efficiency in the light control and to elongate operative life of a light source. The lighting appliance comprises a light source 1 and a light control apparatus 2. The light control apparatus 2 comprises an electric current output circuit 5 which outputs a constant electric current for lighting to a light source configured of an organic electroluminescence device, a light control circuit 6 which performs light control of the light source 1 by intermittently supplying the constant electric current outputted from the electric current output circuit, and an electric discharge prevention circuit (diode) 70 which prevents electric discharge of an electric charge charged in capacitive component of the organic electroluminescence device.

Abstract: The lighting device contains a bridge circuit composed of four diodes. One of the output terminals of an AC source is connected to one of the input terminals of the bridge circuit via a first capacitor for current limiting and stabilization. The other input terminal of the AC source is connected to the other input terminal of the bridge circuit. A second capacitor is connected between the two output terminals of the bridge circuit for filtering ripples. A number of series-connected light emitting diodes are also connected between the two output terminals of the bridge circuit in a forward-biased manner. The major characteristic of the light device lies in the selection of the first capacitor which provides simple yet effective current limiting and stabilization.

Abstract: A circuit for protecting an electronic ballast for use with a remote controller for gas discharge lamps against miswiring to a power source. Depletion mode MOSFETS are employed in both sides of the circuit to the controller and the MOSFETS respond to overvoltage, including polarity reversal to create an open circuit condition in the circuit to the controller.

Abstract: A lighting installation comprises (a) a lighting load, powered by an AC power supply, said AC power supply having a cycle having a period; and (b) a dimmer comprising a first semiconductor switch operable by the action of a switching voltage to switch a current to the load on and off. In normal operation, the switch may repeatedly switch the current on and switch the current off. The average power delivered to the load is altered by altering the switching on or the switching off so that the current is on for a longer or shorter portion of the period. A method of protecting the dimmer comprises monitoring the current and, when the current exceeds a threshold value, altering the switching voltage to cause the first semiconductor switch to switch off the current.

Abstract: A Christmas light string with a resettable fuse, preferably a positive coefficient thermistor, that prevents damage to the string when an overcurrent condition arises. An overcurrent condition in a light string may occur when lights burn out or when too many light strings are placed end to end. When an overcurrent condition exists, the resistance of the resettable fuse rises and reduces the current in the string to prevent damage to bulbs and glass fuses.

Abstract: An illumination source for a camera includes one or more LEDs, and an electrical circuit that selectively applies power from the DC voltage source to the LEDs, wherein the illumination source is suitable for handheld portable operation. In some embodiments, the electrical circuit further includes a control circuit for driving the LEDs with electrical pulses at a frequency high enough that light produced has an appearance to a human user of being continuous rather than pulsed, the control circuit changing a pulse characteristic to adjust a proportion of light output having the first characteristic color spectrum output to that having the second characteristic color spectrum output. Some embodiments provide an illumination source including a housing including one or more LEDs; and a control circuit that selectively applies power from a source of electric power to the LEDs, thus controlling a light output color spectrum of the LEDs.