Abstract: A switch-type power converter comprising an PET switch operating in a variable duty cycle mode under the control of a Unitrode 3846 integrated circuit controller. Indications of excess input voltage and reverse battery connections are provided by circuits including an element which permanently changes state. A cooling fan mounted on a finned heat sink is operated in a variable speed mode. A single thermistor sensor provides inputs to both the fan speed control and a thermal shutdown circuit connected to shut down the gate drives to the FET switch in the event of a high temperature condition. Another shutdown function is provided in response to an input overvoltage condition by way of an operational amplifier. The converter uses foldback for short circuit protection and is compatible with microprocessor units to selectively provide multiple output voltage levels.

Abstract: A switched power converter for a recreational vehicle includes a housing and a switched power supply. The switched power supply has a switch and at least one energy storage component, the switch controlling the supply of power to the energy storage component. The output of the energy storage component is a regulated DC output voltage. A controller generates a switching control signal for controlling the state of said switch. A protection circuit is connected to the controller for protecting the switched power supply from damage resulting when a reverse battery connection is made. The circuit also includes a controller for controlling the pulse-width of the control signals input to the switch. A fan may be provided on the housing which is selectively enabled to move cooling air over the switched power supply only when a detected temperature exceeds a threshold level. The controller may be disabled when an ambient temperature exceeds a threshold level.

Abstract: A switched power converter for a recreational vehicle includes a housing and a switched power supply. The switched power supply has a switch and at least one energy storage component, the switch controlling the supply of power to the energy storage component. The output of the energy storage component is a regulated DC output voltage. A controller generates a switching control signal for controlling the state of said switch. A protection circuit is connected to the controller for protecting the switched power supply from damage resulting when a reverse battery connection is made. The circuit also includes a controller for controlling the pulse-width of the control signals input to the switch. A fan may be provided on the housing which is selectively enabled to move cooling air over the switched power supply only when a detected temperature exceeds a threshold level. The controller may be disabled when an ambient temperature exceeds a threshold level.

Abstract: A light system is disclosed for controlling the amount of light supplied from a high density light source to a target. A shutter is positioned between the light source and the target, and a motor is coupled to said shutter to control the position of said shutter. Either manual or automatic control of said shutter is provided by electronic means coupled to said motor.

Abstract: A power supply for a gas discharge lamp includes a current regulator for regulating the current supplied to a lamp and current steering means for steering current from the current regulator in alternating directions through an isolation transformer primary winding, the secondary winding of the transformer being connected with a lamp through an arc striking circuit. The frequency of alternating the current through the transformer is controlled as a function of the lamp voltage in order to regulate the volt-second product of the transformer through all portions of a lamp operating cycle including arc striking. This reduces saturation of the transformer and allows a much smaller transformer to be used. In a preferred embodiment, the current regulation and steering functions are performed in a bridge circuit having FET switches in each leg and in which the transformer primary spans the sides of the bridge.

Abstract: A control circuit for fluorescent lamps having gas filled tubes and a pair of discharge electrodes in the tubes includes a transformer, a gated switching device and a control signal generating circuit. The transformer has a secondary winding connected with the lamp discharge electrodes and a primary winding to which power is applied by the switching device when a gating signal is applied to its gating terminal. The control signal generating circuit normally controls the gating of the switching device by alternatingly applying, and then ceasing to apply, a control signal to the gating terminal. The control circuit is capable of continuing a current between the discharge electrodes once the lamp is conducting. The control circuit is further capable of "starting" a lamp by applying a high voltage to the discharge electrodes. The high voltage is generated when the gated switching device is not applying power to the primary winding.

Abstract: A regulation and intensity controller for prolonging the life of an incandescent lamp controls the root mean square voltage across the lamp by converting AC voltage to a DC voltage and by applying the DC voltage to the lamp through a switch and an inductor in series connection with the lamp. The switch is opened and closed according to a duty cycle that will produce a constant average voltage across the lamp. The switch is closed at fixed intervals and is opened by a circuit that is responsive to the instantaneous current through the lamp and to a voltage signal produced by integrating an error signal that represents the difference between the lamp voltage and a reference voltage. In this manner, the average voltage across the lamp is regulated and ripple is kept within a level such that the average voltage is a close representation of root mean square voltage. Additionally, the cycle-by-cycle current through the lamp is closely regulated.

Abstract: A system for producing alternating electromagnetic fields for use in theft detection and surveillance systems, including an arrangement of field-generating inductance coils for disposition on opposite sides of a passage to be monitored by the electromagnetic field produced by such coils. In a preferred such arrangement, upper and lower coils are used on each side of the passage and such coils are mutually distinct from one another and separately energizeable so as to generate separate components of a resulting composite electromagnetic field. The upper and lower coils in each such set are preferably disposed in coplanar alignment with one another but have at least portions of one coil overlapping portions of the other, so as to enhance uniformity in the resulting electromagnetic field. The array of separately-energizeable coils provides for resultant flux vector variation in the magnetic field along three mutually orthogonal axes as a function of coil drive excitation phase variation.

Abstract: Methods and apparatus for producing alternating electromagnetic fields for use in theft detection and surveillance systems include individual series-type electrical drive circuits for separately energizing each of the field-generating coil windings with maximum efficiency and control, and transformer-type coupling between the different field-generating coil drive circuits to effect balanced and equalized current flow in the different coil windings and thereby enhance both drive efficiency and field uniformity. Additionally, a current-sense winding provides for monitoring of field coil current flow, and for feedback control of the magnitude and/or frequency of the coil excitation drive. In a preferred embodiment, the fields are generated by at least two coils on each opposite side of the field, and the coils are separately energized through separate but commonly-coupled drive circuits.

Abstract: This specification discloses an apparatus and method for providing electrically distinguishable signals occurring as a function of the position of a moving element. It is possible to identify a sub group of electrical signals from the remaining electrical signals or from the entire group. The electrical signals can be used altogether to determine a variable such as revolutions per minute of the movable element or, particular ones of the electrically distinguishable signals can be used for initiating a function such as the firing of spark plugs.