Abstract: The present invention is a method and system for preventing voltage spike feedback with switched inductive loads connected to isolated redundant power supplies. A voltage clamp circuit of the present invention may clamp the voltage spikes caused by inductive loads within a power supply system to a safe voltage level. When the common output voltage of the redundant power supplies becomes too large, the voltage clamp circuit of the present invention may clamp the common output voltage to a safe voltage level at or slightly above the higher voltage of the parallel connected power supplies.

Abstract: A method and apparatus for fire prevention in electronic equipment utilizes infrared imaging technology to monitor a substantial region of an enclosure within the electronic equipment. For example, a shelf within a computer cabinet may have a lens and thermal sensor array placed within to detect changes in temperature. A processor interprets the data from the thermal sensor array to determine whether to send an alert to an operator and/or to shut down a power supply.

Abstract: The present invention is a method and system for actively limiting transient voltages across a voltage bus. Circuitry coupled to a bus may adjust the voltage level of a bus to a voltage within a desired range when transient voltages cause the voltage level on the bus to fall outside of a desired range. Circuitry of the present invention may include active elements that may adjust a voltage level of a bus in a rapid fashion. Additionally, use of the circuitry of the present invention reduces the cost and design limitations associated with stabilizing buses by solely using multiple low ESR/ESL capacitors.

Abstract: Operational transconductance amplifiers (OTAs) are combined at their outputs, yielding a single frequency compensation connection point. In a preferred embodiment, the output of each OTA is asymmetric, i.e., they can only source current and the OTA outputs are tied together to a constant current sink. Consequently, the OTA that sources more current controls the voltage of the merged output. This merged output point provides a voltage output that may be used as a frequency compensation point.

Abstract: A current mode converter with continuously variable optimized slope compensation and improved power factor is disclosed. In the slope compensation circuit, the output voltage of the converter is sensed and a ramp signal is generated with a slope that is determined by the loading of the converter. The ramp signal is combined with a conventional sensed current signal of the converter to generate a composite sensed current signal which is coupled to the comparator of the converter. The other input to the comparator is a conventional error amplifier and the comparator's output is used to control switching of the converter. In an alternate embodiment, the continuously variable slope compensation circuit is operative using an un-filtered full-wave rectified input voltage waveform.

Abstract: An illumination sensing and light level control system for an area of interest includes a light collector to collect and focus light from a relatively large portion of the area of interest, a light-sensitive array including a matrix of light-intensity sensitive elements for receiving light collected and focused by the collector, a multiplexer and signal conditioner for processing and digitizing the light intensity values, a microprocessor for processing the digitized data and controlling the operation and control functions of the system, and a controller for controlling the light level of one or more lamps or sets of lamps associated with the area of interest. A calibration device is used to generate the desired matrix values for comparison.

Abstract: A dimming system for fluorescent lamps is disclosed which includes a first switching means connected to said source terminals and to said load terminals for controlling the supply of power to said load terminals, a switch control connected to switching means for modulating said load terminals to modulate the sinusoidal power on a time ratio variable basis in order to supply a variable amount of power to said load terminals; and an inverting reducing transformer connected to said source terminals between said source terminals and a second switch means.

Abstract: A power-up/power-down safety switch includes a simple, low-cost circuit having one AND gate, which may be a CMOS IC, one voltage-limiting diode and three resistors. The circuit functions in conjunction with a logic control circuit in a manner which assures that the inhibiting voltage to the logic control circuit V.sub.INH is equal to (or slightly less than) the supply voltage, V.sub.CC (t), until V.sub.CC (t) reaches the minimum required supply voltage for the circuit logic to operate properly. V.sub.INH is then rapidly switched to a low state such that the circuit logic operates without interference. Conversely, when the circuit is turned OFF, the value of V.sub.INH is switched to a high state as soon as the supply voltage reaches the minimum value to operate the logic circuit thereby again causing the logic outputs to go low and that all the drive signals to the power switch are in the OFF state.

Abstract: The present invention provides a low-cost switching system that allows very high speed ON and OFF switching of a bipolar power transistor. The switching system of the present invention consists of an FET-bipolar transistor combination which unites the advantages of FET and bipolar power transistors for extremely fast switching applications. The system draws negligible steady-state drive power and still turns the bipolar transistor fast ON and fast OFF.

Abstract: A remotely controlled dimming solid state ballast system for gas discharge lamps adapted to respond to external control signals is disclosed which includes the ballast itself along with integral controls for interfacing with an external addressing control system, which may be a powerline carrier system. The external control system includes a signal receiver for receiving, and recognizing remotely transmitted control signals addressed to said ballast. An output device is provided for generating an output control signal modulated in response to the control signals to provide the desired control setpoint of the lamps controlled by the ballast or to turn the lamps on or off.

Abstract: A two-wire electronic dimming ballast arrangement for one or more gas discharge lamps is disclosed which includes an inverter driven by a variable pulse width electric power and a control system for modulating the pulse width of the variable pulse width square wave electric power driving the inverter. A unique distortion suppression system is provided for suppressing current abberations and achieving substantially a unity power factor.

Abstract: A phase modulated DC-to-AC or a DC-to-DC power converter utilizes input terminals connected to a source of power and output terminals connected to a suitable load. The transfer of power between the power source and the load or from the load back to the power source is accomplished by electronic switching that is phase displaced controlled in all four quadrants.

Abstract: A voltage isolated gate drive circuit for insulated gate semiconductors utilizes a small, inexpensive pulse transformer to provide a rectangular drive wave form. The small pulse transformer can be operated with an input square wave form at relatively low frequencies, such as 60 hertz, and can be operated from a common power supply with the high voltage supplied to the output field effect transistor.

Abstract: A low cost high frequency electronic dimming ballast for gas discharge lamps is disclosed which eliminates the need for external primary inductance or choke coils by employing leakage inductance of the transformer. The system is usable with either fluorescent or high intensity discharge lamps and alternate embodiments employ the push-pull or half-bridge inverters. Necessary leakage inductance and tuning capacitance are both located on the secondary of the transformer. Special auxiliary windings or capacitors are used to maintain necessary filament heating voltage during dimming of fluorescent lamps. A clamping circuit or auxiliary tuned circuit may be provided to prevent component damage due to over-voltage and over-current if a lamp is removed during operation of the system.

Abstract: A low cost, high frequency, solid-state dimmable fluorescent ballast is disclosed which utilizes a resonant bridge inverter to provide high frequency sinusoidal power to the lamps. One embodiment of the invention includes auxiliary windings connected to the filaments of the lamps to be powered which utilize the inductance of the resonant bridge inductor coil to maintain the voltage across the filaments during dimming. A clamping circuit or auxiliary tuned circuit may be provided to prevent damage due to an over-voltage and over-current condition upon removal of a lamp during operation of the system. In an alternative embodiment, the auxiliary windings, are replaced by capacitors across each of the lamps to be powered. This also eliminates the need for the clamping circuit. If desired, a current splitting capacitance system may be used. Pulse width modulation of the inverter drive or variable AC or DC power supply input may be used to accomplish dimming.

Abstract: A two-wire ballast arrangement for fluorescent lamp dimming is disclosed in which a modified transformer utilizing the natural leakage inductance associated with ballast transformers is used to achieve full-range fluorescent tube dimming at substantially constant filament heating voltage. Additional auxiliary secondary windings are disposed in predetermined spaced relationship to the primary winding and the main secondary winding to create a "tapping" effect in the magnetic flux. The mutual leakage inductances of the auxiliary secondaries in relation to the primary and the main secondary is utilized in a manner such that as the voltage is decreased to the primary, the voltage of the auxiliary secondary windings remains substantially constant to hold the filament heating voltage substantially constant. Embodiments are disclosed for use either with conventional 50/60 Hz or at high frequency, i.e. above 400 Hz.